Programs & Examples On #Mongodb

MongoDB is a scalable, high-performance, open source, document-oriented NoSQL database. It supports a large number of languages and application development platforms. Questions about server administration can be asked on

How to filter array in subdocument with MongoDB

Using aggregate is the right approach, but you need to $unwind the list array before applying the $match so that you can filter individual elements and then use $group to put it back together:

    { $match: {_id: ObjectId("512e28984815cbfcb21646a7")}},
    { $unwind: '$list'},
    { $match: {'list.a': {$gt: 3}}},
    { $group: {_id: '$_id', list: {$push: '$list.a'}}}


  "result": [
      "_id": ObjectId("512e28984815cbfcb21646a7"),
      "list": [
  "ok": 1

MongoDB 3.2 Update

Starting with the 3.2 release, you can use the new $filter aggregation operator to do this more efficiently by only including the list elements you want during a $project:

    { $match: {_id: ObjectId("512e28984815cbfcb21646a7")}},
    { $project: {
        list: {$filter: {
            input: '$list',
            as: 'item',
            cond: {$gt: ['$$item.a', 3]}

Find MongoDB records where array field is not empty

If you also have documents that don't have the key, you can use:

ME.find({ pictures: { $exists: true, $not: {$size: 0} } })

MongoDB don't use indexes if $size is involved, so here is a better solution:

ME.find({ pictures: { $exists: true, $ne: [] } })

Since MongoDB 2.6 release, you can compare with the operator $gt but could lead to unexpected results (you can find a detailled explanation in this answer):

ME.find({ pictures: { $gt: [] } })

MongoDB query multiple collections at once

Here is answer for your question.

    {$match : {admin : 1}},
    {$lookup: {from: "posts",localField: "_id",foreignField: "owner_id",as: "posts"}},
    {$project : {
            posts : { $filter : {input : "$posts"  , as : "post", cond : { $eq : ['$$post.via' , 'facebook'] } } },
            admin : 1



Or either you can go with mongodb group option.

    {$match : {admin : 1}},
    {$lookup: {from: "posts",localField: "_id",foreignField: "owner_id",as: "posts"}},
    {$unwind : "$posts"},
    {$match : {"posts.via":"facebook"}},
    { $group : {
            _id : "$_id",
            posts : {$push : "$posts"}

Spring Boot and how to configure connection details to MongoDB?

In a maven project create a file src/main/resources/application.yml with the following content:

spring.profiles: integration
# use local or embedded mongodb at localhost:27017
spring.profiles: production mongodb://<user>:<passwd>@<host>:<port>/<dbname>

Spring Boot will automatically use this file to configure your application. Then you can start your spring boot application either with the integration profile (and use your local MongoDB)

java -jar your-app.jar

or with the production profile (and use your production MongoDB)

java -jar your-app.jar

return query based on date

You can also try:

    "dateProp": { $gt: new Date('06/15/2016').getTime() }

Mongod complains that there is no /data/db folder

I got over this exact same problem by creating the /data/db folders with my window manager. I tried doing it though the terminal at first, and in order to create a folder in the root directory, I had to use sudo.

I just went to the root directory using Finder and created a new folder using 'New Folder'. Totally worked for me.

Note: I'm using OSX.

MongoDB: Server has startup warnings ''Access control is not enabled for the database''

You need to delete your old db folder and recreate new one. It will resolve your issue.

How can I rename a field for all documents in MongoDB?

You can use:{}, {$rename:{"name.additional":"name.last"}}, false, true);

Or to just update the docs which contain the property:{"name.additional": {$exists: true}}, {$rename:{"name.additional":"name.last"}}, false, true);

The false, true in the method above are: { upsert:false, multi:true }. You need the multi:true to update all your records.

Or you can use the former way:

remap = function (x) {
  if (x.additional){{_id:x._id}, {$set:{"name.last"}, $unset:{"name.additional":1}});

In MongoDB 3.2 you can also use

db.students.updateMany( {}, { $rename: { "oldname": "newname" } } )

The general syntax of this is

db.collection.updateMany(filter, update, options)

MongoDb query condition on comparing 2 fields

In case performance is more important than readability and as long as your condition consists of simple arithmetic operations, you can use aggregation pipeline. First, use $project to calculate the left hand side of the condition (take all fields to left hand side). Then use $match to compare with a constant and filter. This way you avoid javascript execution. Below is my test in python:

import pymongo
from random import randrange

docs = [{'Grade1': randrange(10), 'Grade2': randrange(10)} for __ in range(100000)]

coll = pymongo.MongoClient().test_db.grades

Using aggregate:

%timeit -n1 -r1 list(coll.aggregate([
        '$project': {
            'diff': {'$subtract': ['$Grade1', '$Grade2']},
            'Grade1': 1,
            'Grade2': 1
        '$match': {'diff': {'$gt': 0}}

1 loop, best of 1: 192 ms per loop

Using find and $where:

%timeit -n1 -r1 list(coll.find({'$where': 'this.Grade1 > this.Grade2'}))

1 loop, best of 1: 4.54 s per loop

MongoDB Show all contents from all collections

This way:


Update MongoDB field using value of another field

You should iterate through. For your specific case:

    function (elem) {
                _id: elem._id
                $set: {
                    name: elem.firstname + ' ' + elem.lastname

Mongoose, Select a specific field with find


Below code will retrieve all fields other than password within each document:

const users = await UserModel.find({}, {
  password: 0 


    "_id": "5dd3fb12b40da214026e0658",
    "email": "[email protected]"


Below code will only retrieve email field within each document:

const users = await UserModel.find({}, {
  email: 1


    "email": "[email protected]"

Failed to start mongod.service: Unit mongod.service not found

I got the same error for a long while, tried almost all installation isntruciton on google but could not find te answer...

I followed the instructions from but keep getting the error Failed to start mongod.service: Unit mongod.service not found

I firstly installed using: sudo apt-get install -y mongodb-org Then noticed that wher I run:

$ sudo apt-get install -y mongodb-org
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  mongodb-org-mongos mongodb-org-shell mongodb-org-tools
The following NEW packages will be installed
  mongodb-org mongodb-org-mongos mongodb-org-shell mongodb-org-tools
0 to upgrade, 4 to newly install, 0 to remove and 46 not to upgrade.
Need to get 0 B/40.1 MB of archives.
After this operation, 178 MB of additional disk space will be used.
Selecting previously unselected package mongodb-org-shell.
(Reading database ... 379307 files and directories currently installed.)
Preparing to unpack .../mongodb-org-shell_4.0.3_amd64.deb ...
Unpacking mongodb-org-shell (4.0.3) ...
Selecting previously unselected package mongodb-org-mongos.
Preparing to unpack .../mongodb-org-mongos_4.0.3_amd64.deb ...
Unpacking mongodb-org-mongos (4.0.3) ...
Selecting previously unselected package mongodb-org-tools.
Preparing to unpack .../mongodb-org-tools_4.0.3_amd64.deb ...
Unpacking mongodb-org-tools (4.0.3) ...
Preparing to unpack .../mongodb-org_4.0.3_amd64.deb ...
Unpacking mongodb-org (4.0.3) ...
Setting up mongodb-org-shell (4.0.3) ...
Setting up mongodb-org-mongos (4.0.3) ...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
Setting up mongodb-org-tools (4.0.3) ...
Setting up mongodb-org (4.0.3) ...

$ mongod --version
db version v2.6.12
2018-10-26T12:03:12.362+0200 git version: d73c92b1c85703828b55c2916a5dd4ad46535f6a

The db version was 2.6.12 instead of the latest one 4.0.3. So make sure you dont have mongodb-org-server already installed, if yes, then make sure you uupdate it to your target version (as indicated @ -> Step 4 - Install a specific release of MongoDB.)

target_version = 4.0.3

sudo apt-get install -y mongodb-org=target_version mongodb-org-server=target_version mongodb-org-shell=target_version mongodb-org-mongos=target_version mongodb-org-tools=target_version

$ sudo apt-get install -y mongodb-org=4.0.3 mongodb-org-server=4.0.3 mongodb-org-shell=4.0.3 mongodb-org-mongos=4.0.3 mongodb-org-tools=4.0.3
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following NEW packages will be installed
  mongodb-org mongodb-org-mongos mongodb-org-shell mongodb-org-tools
The following packages will be upgraded:
1 to upgrade, 4 to newly install, 0 to remove and 45 not to upgrade.
Need to get 15.7 MB/55.8 MB of archives.
After this operation, 217 MB of additional disk space will be used.
Get:1 bionic/mongodb-org/4.0/multiverse amd64 mongodb-org-server amd64 4.0.3 [15.7 MB]
Fetched 15.7 MB in 2s (6,289 kB/s)                 
Selecting previously unselected package mongodb-org-shell.
(Reading database ... 379306 files and directories currently installed.)
Preparing to unpack .../mongodb-org-shell_4.0.3_amd64.deb ...
Unpacking mongodb-org-shell (4.0.3) ...
**Preparing to unpack .../mongodb-org-server_4.0.3_amd64.deb ...
Failed to stop mongod.service: Unit mongod.service not loaded.
invoke-rc.d: initscript mongod, action "stop" failed.
dpkg: warning: old mongodb-org-server package pre-removal script subprocess returned error exit status 5
dpkg: trying script from the new package instead ...
dpkg: ... it looks like that went OK
Unpacking mongodb-org-server (4.0.3) over (2.6.12) ...**
Selecting previously unselected package mongodb-org-mongos.
Preparing to unpack .../mongodb-org-mongos_4.0.3_amd64.deb ...
Unpacking mongodb-org-mongos (4.0.3) ...
Selecting previously unselected package mongodb-org-tools.
Preparing to unpack .../mongodb-org-tools_4.0.3_amd64.deb ...
Unpacking mongodb-org-tools (4.0.3) ...
Preparing to unpack .../mongodb-org_4.0.3_amd64.deb ...
Unpacking mongodb-org (4.0.3) ...
Processing triggers for ureadahead (0.100.0-20) ...
Setting up mongodb-org-shell (4.0.3) ...
Setting up mongodb-org-mongos (4.0.3) ...
Processing triggers for systemd (237-3ubuntu10.3) ...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
Setting up mongodb-org-tools (4.0.3) ...
Setting up mongodb-org-server (4.0.3) ...
Installing new version of config file /etc/mongod.conf ...
Setting up mongodb-org (4.0.3) ...

and after doing this its all working for me :D

How to join multiple collections with $lookup in mongodb

First add the collections and then apply lookup on these collections. Don't use $unwind as unwind will simply separate all the documents of each collections. So apply simple lookup and then use $project for projection. Here is mongoDB query:

        $lookup: {
           from: "userRole",
           localField: "userId",
           foreignField: "userId",
           as: "userRole"
        $lookup: {
            from: "userInfo",
            localField: "userId",
            foreignField: "userId",
            as: "userInfo"
    {$project: {
        } ])

Here is the output:

/* 1 */ {
    "userId" : "AD",
    "phone" : "0000000000",
    "userRole" : [ 
            "userId" : "AD",
            "role" : "admin"
    "userInfo" : [ 
            "userId" : "AD",
            "phone" : "0000000000"
    ] }


How to use Elasticsearch with MongoDB?

Here how to do this on mongodb 3.0. I used this nice blog

  1. Install mongodb.
  2. Create data directories:
$ mkdir RANDOM_PATH/node1
$ mkdir RANDOM_PATH/node2> 
$ mkdir RANDOM_PATH/node3
  1. Start Mongod instances
$ mongod --replSet test --port 27021 --dbpath node1
$ mongod --replSet test --port 27022 --dbpath node2
$ mongod --replSet test --port 27023 --dbpath node3
  1. Configure the Replica Set:
$ mongo
config = {_id: 'test', members: [ {_id: 0, host: 'localhost:27021'}, {_id: 1, host: 'localhost:27022'}]};    
  1. Installing Elasticsearch:
a. Download and unzip the [latest Elasticsearch][2] distribution

b. Run bin/elasticsearch to start the es server.

c. Run curl -XGET http://localhost:9200/ to confirm it is working.
  1. Installing and configuring the MongoDB River:

$ bin/plugin --install com.github.richardwilly98.elasticsearch/elasticsearch-river-mongodb

$ bin/plugin --install elasticsearch/elasticsearch-mapper-attachments

  1. Create the “River” and the Index:

curl -XPUT 'http://localhost:8080/_river/mongodb/_meta' -d '{ "type": "mongodb", "mongodb": { "db": "mydb", "collection": "foo" }, "index": { "name": "name", "type": "random" } }'

  1. Test on browser:


Node.js Mongoose.js string to ObjectId function

Just see the below code snippet if you are implementing a REST API through express and mongoose. (Example for ADD)

exports.AddSomething = (req,res,next) =>{_x000D_
  const newSomething = new SomeEntity({_x000D_
 _id:new mongoose.Types.ObjectId(), //its very own ID_x000D_
  theForeignKey: mongoose.Types.ObjectId(req.body.theForeignKey)// if you want to pass an object ID_x000D_

Hope it Helps

Dump Mongo Collection into JSON format

Here's mine command for reference:

mongoexport --db AppDB --collection files --pretty --out output.json

On Windows 7 (MongoDB 3.4), one has to move the cmd to the place where mongod.exe and mongo.exe file resides => C:\MongoDB\Server\3.4\bin else it won't work saying it does not recongnize mongoexport command.

mongodb, replicates and error: { "$err" : "not master and slaveOk=false", "code" : 13435 }

I got here searching for the same error, but from Node.js native driver. The answer for me was combination of answers by campeterson and Prabhat.

The issue is that readPreference setting defaults to primary, which then somehow leads to the confusing slaveOk error. My problem is that I just wan to read from my replica set from any node. I don't even connect to it as to replicaset. I just connect to any node to read from it.

Setting readPreference to primaryPreferred (or better to the ReadPreference.PRIMARY_PREFERRED constant) solved it for me. Just pass it as an option to MongoClient.connect() or to client.db() or to any find(), aggregate() or other function.

const { MongoClient, ReadPreference } = require('mongodb');
const client = await MongoClient.connect(MONGODB_CONNECTIONSTRING, { readPreference: ReadPreference.PRIMARY_PREFERRED });

Mongoose, update values in array of objects

There is a mongoose way for doing it.

const itemId = 2;
const query = {
  item._id: itemId 
Person.findOne(query).then(doc => {
  item = );
  item["name"] = "new name";
  item["value"] = "new value";;

  //sent respnse to client
}).catch(err => {
  console.log('Oh! Dark')

How can you remove all documents from a collection with Mongoose?

DateTime.remove({}, callback) The empty object will match all of them.

E: Unable to locate package mongodb-org

For those who use Ubuntu 18.04 can run this command:

Create the /etc/apt/sources.list.d/mongodb-org-4.2.list file for Ubuntu 18.04 (Bionic):

echo "deb [ arch=amd64,arm64 ] bionic/mongodb-org/4.2 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-4.2.list

Checking if a field contains a string

If your regex includes a variable, make sure to escape it.

function escapeRegExp(string) {
  return string.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'); // $& means the whole matched string

This can be used like this

new RegExp(escapeRegExp(searchString), 'i')

Or in a mongoDb query like this

{ '$regex': escapeRegExp(searchString) }

Posted same comment here

how to set mongod --dbpath

Create a directory db in home, inside db another directory data

mkdir db
cd db
mkdir data

then type this command--

mongod --dbpath ~/db/data

How to get the last N records in mongodb?

You may want to be using the find options :

db.collection.find({}, {sort: {createdAt: -1}, skip:2, limit: 18}).fetch();

Referencing another schema in Mongoose

It sounds like the populate method is what your looking for. First make small change to your post schema:

var postSchema = new Schema({
    name: String,
    postedBy: {type: mongoose.Schema.Types.ObjectId, ref: 'User'},
    dateCreated: Date,
    comments: [{body:"string", by: mongoose.Schema.Types.ObjectId}],

Then make your model:

var Post = mongoose.model('Post', postSchema);

Then, when you make your query, you can populate references like this:

Post.findOne({_id: 123})
.exec(function(err, post) {
    // do stuff with post

What's a clean way to stop mongod on Mac OS X?

If you have installed mongodb community server via homebrew, then you can do:

brew services list

This will list the current services as below:

Name              Status  User          Plist
mongodb-community started thehaystacker /Users/thehaystacker/Library/LaunchAgents/homebrew.mxcl.mongodb-community.plist

redis             stopped

Then you can restart mongodb by first stopping and restart:

brew services stop mongodb
brew services start mongodb

MongoDB logging all queries

I made a command line tool to activate the profiler activity and see the logs in a "tail"able way: "mongotail".

But the more interesting feature (also like tail) is to see the changes in "real time" with the -f option, and occasionally filter the result with grep to find a particular operation.

See documentation and installation instructions in:

How to export all collections in MongoDB?

I found after trying lots of convoluted examples that very simple approach worked for me.

I just wanted to take a dump of a db from local and import it on a remote instance:

on the local machine:

mongodump -d databasename

then I scp'd my dump to my server machine:

scp -r dump [email protected]:~

then from the parent dir of the dump simply:


and that imported the database.

assuming mongodb service is running of course.

Is mongodb running?

I know this is for php, but I got here looking for a solution for node. Using mongoskin:

mongodb.admin().ping(function(err) {
    if(err === null)
        // true - you got a conntion, congratulations
    else if(err.message.indexOf('failed to connect') !== -1)
        // false - database isn't around
        // actual error, do something about it

With other drivers, you can attempt to make a connection and if it fails, you know the mongo server's down. Mongoskin needs to actually make some call (like ping) because it connects lazily. For php, you can use the try-to-connect method. Make a script!


$dbIsRunning = true
try {
  $m = new MongoClient('localhost:27017');
} catch($e) {
  $dbIsRunning = false

Retrieve only the queried element in an object array in MongoDB collection

db.test.find( {"shapes.color": "red"}, {_id: 0})

Mongodb service won't start

Delete the .lock file from the C:\mongodb\data\ path and then restart the mongodb service.

How do I connect to mongodb with node.js (and authenticate)?

With the link provided by @mattdlockyer as reference, this worked for me:

var mongo = require('mongodb');
var server = new mongo.Server(host, port, options);
db = new mongo.Db(mydb, server, {fsync:true});, db) {
    if(!err) {
        console.log("Connected to database");
        db.authenticate(user, password, function(err, res) {
            if(!err) {
            } else {
                console.log("Error in authentication.");
    } else {
        console.log("Error in open().");

exports.testMongo = function(req, res){
    db.collection( mycollection, function(err, collection) {
        collection.find().toArray(function(err, items) {

How do I start Mongo DB from Windows?

Step 1

Download the mongodb

Step 2

  • Follow normal setup instructions

enter image description here

enter image description here

enter image description here

enter image description here

enter image description here

enter image description here

Step 3

  • Create the following folder


Step 4

  • cd to C:\Program Files\MongoDB\Server\3.2\bin>
  • enter command mongod
  • by default, mongodb server will start at port 27017

enter image description here

Step 5

  • (optionally) download RoboMongo and follow normal setup instructions

enter image description here

enter image description here

enter image description here

enter image description here

enter image description here

enter image description here

Step 6

  • Start RoboMongo and create a new connection on localhost:27017

enter image description here

Your MongoDB is started and connected with RoboMongo (now Robo 3T) - a third party GUI tool

Query Mongodb on month, day, year... of a datetime

If you want to search for documents that belong to a specific month, make sure to query like this:

// Anything greater than this month and less than the next month
db.posts.find({created_on: {$gte: new Date(2015, 6, 1), $lt: new Date(2015, 7, 1)}});

Avoid quering like below as much as possible.

// This may not find document with date as the last date of the month
db.posts.find({created_on: {$gte: new Date(2015, 6, 1), $lt: new Date(2015, 6, 30)}});

// don't do this too
db.posts.find({created_on: {$gte: new Date(2015, 6, 1), $lte: new Date(2015, 6, 30)}});

How to print out more than 20 items (documents) in MongoDB's shell?

You can use it inside of the shell to iterate over the next 20 results. Just type it if you see "has more" and you will see the next 20 items.

MongoDB not equal to

Use $ne -- $not should be followed by the standard operator:

An examples for $ne, which stands for not equal:

use test
switched to db test
db.test.insert({author : 'me', post: ""})
db.test.insert({author : 'you', post: "how to query"})
db.test.find({'post': {$ne : ""}})
{ "_id" : ObjectId("4f68b1a7768972d396fe2268"), "author" : "you", "post" : "how to query" }

And now $not, which takes in predicate ($ne) and negates it ($not):

db.test.find({'post': {$not: {$ne : ""}}})
{ "_id" : ObjectId("4f68b19c768972d396fe2267"), "author" : "me", "post" : "" }

Cannot authenticate into mongo, "auth fails"

You can also try this :-

mongo localhost:27017/admin -u admin -p SECRETPASSWORD

Found it in this post

Here obviously the localhost can be some other host and the /admin can be some other database on which authentication has been applied

db.collection is not a function when using MongoClient v3.0

I did a little experimenting to see if I could keep the database name as part of the url. I prefer the promise syntax but it should still work for the callback syntax. Notice below that client.db() is called without passing any parameters.

    { useNewUrlParser: true}
.then(client => {

    // The database name is part of the url.  client.db() seems 
    // to know that and works even without a parameter that 
    // relays the db name.
    let db = client.db(); 

    console.log('the current database is: ' + db.s.databaseName);
    // client.close() if you want to

.catch(err => console.log(err));

My package.json lists monbodb ^3.2.5.

The 'useNewUrlParser' option is not required if you're willing to deal with a deprecation warning. But it is wise to use at this point until version 4 comes out where presumably the new driver will be the default and you won't need the option anymore.

show dbs gives "Not Authorized to execute command" error

There are two things,

1) You can run the mongodb instance without username and password first.

2) Then you can add the user to the system database of the mongodb which is default one using the query below.

  user: "myUserAdmin",
  pwd: "abc123",
  roles: [ { role: "userAdminAnyDatabase", db: "admin" } ]


MongoNetworkError: failed to connect to server [localhost:27017] on first connect [MongoNetworkError: connect ECONNREFUSED]

mongoose.connect('mongodb://localhost:27017/').then(() => {
console.log("Connected to Database");
}).catch((err) => {
console.log("Not Connected to Database ERROR! ", err);

Better just connect to the localhost Mongoose Database only and create your own collections. Don't forget to mention the port number. (Default: 27017)

For the best view, download Mongoose-compass for MongoDB UI.

Mongodb: failed to connect to server on first connect

I was trying to connect mlab with my company wifi connection and it was giving this error. But when I switched to personal network it worked and got connected.

Check the current number of connections to MongoDb

In OS X, too see the connections directly on the network interface, just do:

$ lsof -n -i4TCP:27017

mongod     2191 inanc    7u  IPv4 0xab6d9f844e21142f  0t0  TCP (LISTEN)
mongod     2191 inanc   33u  IPv4 0xab6d9f84604cd757  0t0  TCP> (ESTABLISHED)
stores.te 18704 inanc    6u  IPv4 0xab6d9f84604d404f  0t0  TCP> (ESTABLISHED)
  • No need to use grep etc, just use the lsof's arguments.

  • Too see the connections on MongoDb's CLI, see @milan's answer (which I just edited).

Delete everything in a MongoDB database

Also, from the command line:

mongo DATABASE_NAME --eval "db.dropDatabase();"

mongodb group values by multiple fields

Using aggregate function like below :

{$group: {_id : {book : '$book',address:'$addr'}, total:{$sum :1}}},
{$project : {book : '$', address : '$_id.address', total : '$total', _id : 0}}

it will give you result like following :

            "total" : 1,
            "book" : "book33",
            "address" : "address90"
            "total" : 1,
            "book" : "book5",
            "address" : "address1"
            "total" : 1,
            "book" : "book99",
            "address" : "address9"
            "total" : 1,
            "book" : "book1",
            "address" : "address5"
            "total" : 1,
            "book" : "book5",
            "address" : "address2"
            "total" : 1,
            "book" : "book3",
            "address" : "address4"
            "total" : 1,
            "book" : "book11",
            "address" : "address77"
            "total" : 1,
            "book" : "book9",
            "address" : "address3"
            "total" : 1,
            "book" : "book1",
            "address" : "address15"
            "total" : 2,
            "book" : "book1",
            "address" : "address2"
            "total" : 3,
            "book" : "book1",
            "address" : "address1"

I didn't quite get your expected result format, so feel free to modify this to one you need.

MongoDB: Is it possible to make a case-insensitive query?

Keep in mind that the previous example:

db.stuff.find( { foo: /bar/i } );

will cause every entries containing bar to match the query ( bar1, barxyz, openbar ), it could be very dangerous for a username search on a auth function ...

You may need to make it match only the search term by using the appropriate regexp syntax as:

db.stuff.find( { foo: /^bar$/i } );

See for syntax help on regular expressions

mongo - couldn't connect to server

For Windows

Instead of






To find your computer/laptop name write in the search bar View your PC name and the name near Device name is the name you are looking for.

Note: I read somewhere that using localhost keyword in Windows OS for MongoDB is not recommended (most probably here).

Mongoose.js: Find user by username LIKE value

Just complementing @PeterBechP 's answer.

Don't forget to scape the special chars.

function escapeRegExp(string) {
  return string.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');

var name = 'Peter+with+special+chars';

model.findOne({name: new RegExp('^'+escapeRegExp(name)+'$', "i")}, function(err, doc) {
  //Do your action here..

Mongodb: Failed to connect to, reason: errno:10061

Change file permission to 755 for the file:


How to secure MongoDB with username and password

Wow so many complicated/confusing answers here.

This is as of v3.4.

Short answer.

1) Start MongoDB without access control.

mongod --dbpath /data/db

2) Connect to the instance.


3) Create the user.

use some_db
    user: "myNormalUser",
    pwd: "xyz123",
    roles: [ { role: "readWrite", db: "some_db" },
             { role: "read", db: "some_other_db" } ]

4) Stop the MongoDB instance and start it again with access control.

mongod --auth --dbpath /data/db

5) Connect and authenticate as the user.

use some_db
db.auth("myNormalUser", "xyz123"){x:1})
use some_other_db{})

Long answer: Read this if you want to properly understand.

It's really simple. I'll dumb the following down

If you want to learn more about what the roles actually do read more here:

1) Start MongoDB without access control.

mongod --dbpath /data/db

2) Connect to the instance.


3) Create the user administrator. The following creates a user administrator in the admin authentication database. The user is a dbOwner over the some_db database and NOT over the admin database, this is important to remember.

use admin
    user: "myDbOwner",
    pwd: "abc123",
    roles: [ { role: "dbOwner", db: "some_db" } ]

Or if you want to create an admin which is admin over any database:

use admin
    user: "myUserAdmin",
    pwd: "abc123",
    roles: [ { role: "userAdminAnyDatabase", db: "admin" } ]

4) Stop the MongoDB instance and start it again with access control.

mongod --auth --dbpath /data/db

5) Connect and authenticate as the user administrator towards the admin authentication database, NOT towards the some_db authentication database. The user administrator was created in the admin authentication database, the user does not exist in the some_db authentication database.

use admin
db.auth("myDbOwner", "abc123")

You are now authenticated as a dbOwner over the some_db database. So now if you wish to read/write/do stuff directly towards the some_db database you can change to it.

use some_db
// stuff like{x:1})
// remember that the user administrator had dbOwner rights so the user may write/read, if you create a user with userAdmin they will not be able to read/write for example.

More on roles:

If you wish to make additional users which aren't user administrators and which are just normal users continue reading below.

6) Create a normal user. This user will be created in the some_db authentication database down below.

use some_db
    user: "myNormalUser",
    pwd: "xyz123",
    roles: [ { role: "readWrite", db: "some_db" },
             { role: "read", db: "some_other_db" } ]

7) Exit the mongo shell, re-connect, authenticate as the user.

use some_db
db.auth("myNormalUser", "xyz123"){x:1})
use some_other_db{})

How do I remove documents using Node.js Mongoose?

I prefer the promise notation, where you need e.g.

    .then( doc => .... )

Formatting ISODate from Mongodb

MongoDB's ISODate() is just a helper function that wraps a JavaScript date object and makes it easier to work with ISO date strings.

You can still use all of the same methods as working with a normal JS Date, such as:


// Note that getHours() and getMinutes() do not include leading 0s for single digit #s

Connection refused to MongoDB errno 111

Try the following:

sudo rm /var/lib/mongodb/mongod.lock
sudo service mongodb restart

MySQL vs MongoDB 1000 reads

man,,, the answer is that you're basically testing PHP and not a database.

don't bother iterating the results, whether commenting out the print or not. there's a chunk of time.

   foreach ($cursor as $obj)
        //echo $obj["thread_title"] . "<br><Br>";

while the other chunk is spend yacking up a bunch of rand numbers.

function get_15_random_numbers()
    $numbers = array();
        $numbers[] = mt_rand(1, 20000000) ;

    return $numbers;

then theres a major difference b/w implode and in.

and finally what is going on here. looks like creating a connection each time, thus its testing the connection time plus the query time.

$m = new Mongo();


$db = new AQLDatabase();

so your 101% faster might turn out to be 1000% faster for the underlying query stripped of jazz.


Difference between MongoDB and Mongoose

One more difference I found with respect to both is that it is fairly easy to connect to multiple databases with mongodb native driver while you have to use work arounds in mongoose which still have some drawbacks.

So if you wanna go for a multitenant application, go for mongodb native driver.

mongodb: insert if not exists

Sounds like you want to do an "upsert". MongoDB has built-in support for this. Pass an extra parameter to your update() call: {upsert:true}. For example:

key = {'key':'value'}
data = {'key2':'value2', 'key3':'value3'};
coll.update(key, data, upsert=True); #In python upsert must be passed as a keyword argument

This replaces your if-find-else-update block entirely. It will insert if the key doesn't exist and will update if it does.


{"key":"value", "key2":"Ohai."}


{"key":"value", "key2":"value2", "key3":"value3"}

You can also specify what data you want to write:

data = {"$set":{"key2":"value2"}}

Now your selected document will update the value of "key2" only and leave everything else untouched.

MongoDB: How to query for records where field is null or not set?

If the sent_at field is not there when its not set then:

db.emails.count({sent_at: {$exists: false}})

If its there and null, or not there at all:

db.emails.count({sent_at: null})

Refer here for querying and null

When to use CouchDB over MongoDB and vice versa

The answers above all over complicate the story.

  1. If you plan to have a mobile component, or need desktop users to work offline and then sync their work to a server you need CouchDB.
  2. If your code will run only on the server then go with MongoDB

That's it. Unless you need CouchDB's (awesome) ability to replicate to mobile and desktop devices, MongoDB has the performance, community and tooling advantage at present.

How to drop a database with Mongoose?

If you modify @hellslam's solution like this then it will work

I use this technique to drop the Database after my integration tests

mongoose = require "mongoose"
conn = mongoose.connect("mongodb://localhost/mydb")


var conn, mongoose;
mongoose = require("mongoose");
conn = mongoose.connect("mongodb://localhost/mydb");


HTH at least it did for me, so I decided to share =)

Auto increment in MongoDB to store sequence of Unique User ID

The best way I found to make this to my purpose was to increment from the max value you have in the field and for that, I used the following syntax:

maxObj = db.CollectionName.aggregate([
    $group : { _id: '$item', maxValue: { $max: '$fieldName' } } 
fieldNextValue = maxObj.maxValue + 1;

$fieldName is the name of your field, but without the $ sign.

CollectionName is the name of your collection.

The reason I am not using count() is that the produced value could meet an existing value.

The creation of an enforcing unique index could make it safer:

db.CollectionName.createIndex( { "fieldName": 1 }, { unique: true } )

Understanding MongoDB BSON Document size limit

I have not yet seen a problem with the limit that did not involve large files stored within the document itself. There are already a variety of databases which are very efficient at storing/retrieving large files; they are called operating systems. The database exists as a layer over the operating system. If you are using a NoSQL solution for performance reasons, why would you want to add additional processing overhead to the access of your data by putting the DB layer between your application and your data?

JSON is a text format. So, if you are accessing your data through JSON, this is especially true if you have binary files because they have to be encoded in uuencode, hexadecimal, or Base 64. The conversion path might look like

binary file <> JSON (encoded) <> BSON (encoded)

It would be more efficient to put the path (URL) to the data file in your document and keep the data itself in binary.

If you really want to keep these files of unknown length in your DB, then you would probably be better off putting these in GridFS and not risking killing your concurrency when the large files are accessed.

Find objects between two dates MongoDB

You can also check this out. If you are using this method, then use the parse function to get values from Mongo Database:

    createdOn: {
        $gt: ISODate("2020-01-01T00:00:00.000Z"),
        $lt: ISODate("2020-03-01T00:00:00.000Z")

Mongodb find() query : return only unique values (no duplicates)

I think you can use db.collection.distinct(fields,query)

You will be able to get the distinct values in your case for NetworkID.

It should be something like this :


How to remove a field completely from a MongoDB document?

{ name: 'book', tags: { words: ['abc','123'], lat: 33, long: 22 } }



Which SchemaType in Mongoose is Best for Timestamp?

I would like to use this field in order to return all the records that have been updated in the last 5 minutes.

This means you need to update the date to "now" every time you save the object. Maybe you'll find this useful: Moongoose create-modified plugin

MongoDB vs Firebase

Firebase is designed for real-time updates. It easily integrates with angular. Both are NoSQL databases. MongoDB can also do this with Angular through integration. Meteor.js also makes use of MongoDB with an open socket connection for real-time updates.

MongoDB can be run locally, or hosted on many different cloud based providers. Firebase, in my opinion is great for smaller apps, very quick to get up and running. MongoDB is ideal for more robust larger apps, real-time integration is possible but it takes a bit more work.

Failed to connect to, reason: errno:111 Connection refused

For those with Windows. I had the same problem on Windows. Restarting Mongodb service solves this.

Following are the steps to restart on Windows:

i). Go To "Services" on Windows.

ii). Search for "MongoDB" in the list of services.

iii). Right click "start"/"restart" depending on your status.

iv). After the status turns to "running" check if issue is resolved by running "Mongo" or connecting your Mongo client.

Query for documents where array size is greater than 1

There's a more efficient way to do this in MongoDB 2.2+ now that you can use numeric array indexes in query object keys.

// Find all docs that have at least two name array elements.
db.accommodations.find({'name.1': {$exists: true}})

You can support this query with an index that uses a partial filter expression (requires 3.2+):

// index for at least two name array elements
    {'name.1': 1},
    {partialFilterExpression: {'name.1': {$exists: true}}}

MongoDB running but can't connect using shell

Not so much an answer but more of an FYI:I've just hit this and found this question as a result of searching. Here is the details of my experience:

Shell error

markdsievers@ip-xx-xx-xx-xx:~$ mongo
MongoDB shell version: 2.0.1
connecting to: test
Wed Dec 21 03:36:13 Socket recv() errno:104 Connection reset by peer
Wed Dec 21 03:36:13 SocketException: remote: error: 9001 socket exception [1] server [] 
Wed Dec 21 03:36:13 DBClientCursor::init call() failed
Wed Dec 21 03:36:13 Error: Error during mongo startup. :: caused by :: DBClientBase::findN: transport error: query: { whatsmyuri: 1 } shell/mongo.js:84
exception: connect failed

Mongo logs reveal

Wed Dec 21 03:35:04 [initandlisten] connection accepted from #6612
Wed Dec 21 03:35:04 [initandlisten] connection refused because too many open connections: 819

This perhaps indicates the other answer (JaKi) was experiencing the same thing, where some connections were purged and access made possible again for the shell (other clients)

Foreign keys in mongo?

We can define the so-called foreign key in MongoDB. However, we need to maintain the data integrity BY OURSELVES. For example,

  _id: ObjectId(...),
  name: 'Jane',
  courses: ['bio101', 'bio102']   // <= ids of the courses

  _id: 'bio101',
  name: 'Biology 101',
  description: 'Introduction to biology'

The courses field contains _ids of courses. It is easy to define a one-to-many relationship. However, if we want to retrieve the course names of student Jane, we need to perform another operation to retrieve the course document via _id.

If the course bio101 is removed, we need to perform another operation to update the courses field in the student document.

More: MongoDB Schema Design

The document-typed nature of MongoDB supports flexible ways to define relationships. To define a one-to-many relationship:

Embedded document

  1. Suitable for one-to-few.
  2. Advantage: no need to perform additional queries to another document.
  3. Disadvantage: cannot manage the entity of embedded documents individually.


  name: 'Kate Monster',
  addresses : [
     { street: '123 Sesame St', city: 'Anytown', cc: 'USA' },
     { street: '123 Avenue Q', city: 'New York', cc: 'USA' }

Child referencing

Like the student/course example above.

Parent referencing

Suitable for one-to-squillions, such as log messages.

    _id : ObjectID('AAAB'),
    name : '',
    ipaddr : ''

    time : ISODate("2014-03-28T09:42:41.382Z"),
    message : 'cpu is on fire!',
    host: ObjectID('AAAB')       // Reference to the Host document

Virtually, a host is the parent of a logmsg. Referencing to the host id saves much space given that the log messages are squillions.


  1. 6 Rules of Thumb for MongoDB Schema Design: Part 1
  2. 6 Rules of Thumb for MongoDB Schema Design: Part 2
  3. 6 Rules of Thumb for MongoDB Schema Design: Part 3
  4. Model One-to-Many Relationships with Document References

How to use mongoose findOne

In my case same error is there , I am using Asyanc / Await functions , for this needs to add AWAIT for findOne

Ex:const foundUser = User.findOne ({ "email" : });

above , foundUser always contains Object value in both cases either user found or not because it's returning values before finishing findOne .

const foundUser = await User.findOne ({ "email" : });

above , foundUser returns null if user is not there in collection with provided condition . If user found returns user document.

Find document with array that contains a specific value

There is no $contains operator in mongodb.

You can use the answer from JohnnyHK as that works. The closest analogy to contains that mongo has is $in, using this your query would look like:

PersonModel.find({ favouriteFoods: { "$in" : ["sushi"]} }, ...);

MongoDB vs. Cassandra

I'm probably going to be an odd man out, but I think you need to stay with MySQL. You haven't described a real problem you need to solve, and MySQL/InnoDB is an excellent storage back-end even for blob/json data.

There is a common trick among Web engineers to try to use more NoSQL as soon as realization comes that not all features of an RDBMS are used. This alone is not a good reason, since most often NoSQL databases have rather poor data engines (what MySQL calls a storage engine).

Now, if you're not of that kind, then please specify what is missing in MySQL and you're looking for in a different database (like, auto-sharding, automatic failover, multi-master replication, a weaker data consistency guarantee in cluster paying off in higher write throughput, etc).

How can I save multiple documents concurrently in Mongoose/Node.js?

This is an old question, but it came up first for me in google results when searching "mongoose insert array of documents".

There are two options model.create() [mongoose] and model.collection.insert() [mongodb] which you can use. View a more thorough discussion here of the pros/cons of each option:

Mongoose (mongodb) batch insert?

How do you put an image file in a json object?

Use data URL scheme:

In this case you use that string directly in html : <img src="data:image/png;base64,iVBOR....">

Ways to implement data versioning in MongoDB

The first big question when diving in to this is "how do you want to store changesets"?

  1. Diffs?
  2. Whole record copies?

My personal approach would be to store diffs. Because the display of these diffs is really a special action, I would put the diffs in a different "history" collection.

I would use the different collection to save memory space. You generally don't want a full history for a simple query. So by keeping the history out of the object you can also keep it out of the commonly accessed memory when that data is queried.

To make my life easy, I would make a history document contain a dictionary of time-stamped diffs. Something like this:

    _id : "id of address book record",
    changes : { 
                1234567 : { "city" : "Omaha", "state" : "Nebraska" },
                1234568 : { "city" : "Kansas City", "state" : "Missouri" }

To make my life really easy, I would make this part of my DataObjects (EntityWrapper, whatever) that I use to access my data. Generally these objects have some form of history, so that you can easily override the save() method to make this change at the same time.

UPDATE: 2015-10

It looks like there is now a spec for handling JSON diffs. This seems like a more robust way to store the diffs / changes.

How to select a single field for all documents in a MongoDB collection?

 var collection = db.collection('appuser');
      { $project : { firstName : 1, lastName : 1 } },function(err, res){
        res.toArray(function(err, realRes){
          console.log("response roo==>",realRes);
  • it's working

how can I connect to a remote mongo server from Mac OS terminal

With Mongo 3.2 and higher just use your connection string as is:

mongo mongodb://username:[email protected]:10011/my_database

mongodb how to get max value from collections

Folks you can see what the optimizer is doing by running a plan. The generic format of looking into a plan is from the MongoDB documentation . i.e. Cursor.plan(). If you really want to dig deeper you can do a cursor.plan(true) for more details.

Having said that if you have an index, your db.col.find().sort({"field":-1}).limit(1) will read one index entry - even if the index is default ascending and you wanted the max entry and one value from the collection.

In other words the suggestions from @yogesh is correct.

Thanks - Sumit

How to query nested objects?

The two query mechanism work in different ways, as suggested in the docs at the section Subdocuments:

When the field holds an embedded document (i.e, subdocument), you can either specify the entire subdocument as the value of a field, or “reach into” the subdocument using dot notation, to specify values for individual fields in the subdocument:

Equality matches within subdocuments select documents if the subdocument matches exactly the specified subdocument, including the field order.

In the following example, the query matches all documents where the value of the field producer is a subdocument that contains only the field company with the value 'ABC123' and the field address with the value '123 Street', in the exact order:

db.inventory.find( {
    producer: {
        company: 'ABC123',
        address: '123 Street'

Comparing mongoose _id and strings

The accepted answers really limit what you can do with your code. For example, you would not be able to search an array of Object Ids by using the equals method. Instead, it would make more sense to always cast to string and compare the keys.

Here's an example answer in case if you need to use indexOf() to check within an array of references for a specific id. assume query is a query you are executing, assume someModel is a mongo model for the id you are looking for, and finally assume results.idList is the field you are looking for your object id in.

   var array ={ return v.toString(); });
   var exists = array.indexOf(someModel._id.toString()) >= 0;

Uninstall mongoDB from ubuntu

Sometimes this works;

sudo apt-get install mongodb-org --fix-missing --fix-broken
sudo apt-get autoremove mongodb-org --fix-missing --fix-broken

MongoDB query with an 'or' condition

MongoDB query with an 'or' condition


MongoDB query with an 'or', 'and', condition combined.


How to install mongoDB on windows?

I realize you've already accepted an answer for this, but I wrote this short howto article to install mongodb into the c:\wamp directory and run it as a service. Here is the gist of it.

Create these directories

mkdir c:\wamp\bin\mongodb\mongodb-win32...2.x.x\data
mkdir c:\wamp\bin\mongodb\mongodb-win32...2.x.x\data\db
mkdir c:\wamp\bin\mongodb\mongodb-win32...2.x.x\logs
mkdir c:\wamp\bin\mongodb\mongodb-win32...2.x.x\conf

Download and extract win32 binaries into c:\wamp directory along side mysql, apache.

mongodb download page

Create a mongo.conf file


# mongodb.conf

# data lives here

# where to log

# only run on localhost for development
bind_ip =                                                             

port = 27017
rest = true

Install as a service

mongod.exe --install --config c:\wamp\bin\mongodb\mongodb-win32...2.x.x\conf\mongodb.conf --logpath c:\wamp\bin\mongodb\mongodb-win32...2.x.x\logs\mongodb.log

Set service to automatic and start it using services.msc

Add path to mongo.exe to your path

Need more details? Read the full article here...

Installing MongoDB on Windows the WAMP way

Unable to connect to mongodb Error: couldn't connect to server at src/mongo/shell/mongo.js:L112

Same error here, this worked for me:

sudo mongod --repair

followed by

sudo mongod

(forget about service and start)

Then on a different tab/terminal:


Mongoose limit/offset and count query

Instead of using 2 separate queries, you can use aggregate() in a single query:

Aggregate "$facet" can be fetch more quickly, the Total Count and the Data with skip & limit


      //{$sort: {...}}



        "stage1" : [ {"$group": {_id:null, count:{$sum:1}}} ],

        "stage2" : [ { "$skip": 0}, {"$limit": 2} ]
     {$unwind: "$stage1"},
      //output projection
        count: "$stage1.count",
        data: "$stage2"


output as follows:-

     count: 50,
     data: [

Also, have a look at

How to stop mongo DB in one command

Starting and Stopping MongoDB is covered in the MongoDB manual. It explains the various options of stopping MongoDB through the shell, cli, drivers etc. It also details the risks of incorrectly stopping MongoDB (such as data corruption) and talks about the different kill signals.

Additionally, if you have installed MongoDB using a package manager for Ubuntu or Debian then you can stop mongodb (currently mongod in ubuntu) as follows:

  • Upstart: sudo service mongod stop

  • Sysvinit: sudo /etc/init.d/mongod stop

Or on Mac OS X

Or on Red Hat based systems:

  • service mongod stop

Or on Windows if you have installed as a service named MongoDB:

  • net stop MongoDB

And if not installed as a service (as of Windows 7+) you can run:

  • taskkill /f /im mongod.exe

To learn more about the problems of an unclean shutdown, how to best avoid such a scenario and what to do in the event of an unclean shutdown, please see: Recover Data after an Unexpected Shutdown.

TypeError: ObjectId('') is not JSON serializable

As a quick replacement, you can change {'owner': objectid} to {'owner': str(objectid)}.

But defining your own JSONEncoder is a better solution, it depends on your requirements.

Add new field to every document in a MongoDB collection

Same as the updating existing collection field, $set will add a new fields if the specified field does not exist.

Check out this example:

{ "_id" : ObjectId("4e93037bbf6f1dd3a0a9541a"), "test" : "a" }
> item =
{ "_id" : ObjectId("4e93037bbf6f1dd3a0a9541a"), "test" : "a" }
>{"_id" :ObjectId("4e93037bbf6f1dd3a0a9541a") },{$set : {"new_field":1}})
{ "_id" : ObjectId("4e93037bbf6f1dd3a0a9541a"), "new_field" : 1, "test" : "a" }


In case you want to add a new_field to all your collection, you have to use empty selector, and set multi flag to true (last param) to update all the documents

  { $set: {"new_field": 1} },


In the above example last 2 fields false, true specifies the upsert and multi flags.

Upsert: If set to true, creates a new document when no document matches the query criteria.

Multi: If set to true, updates multiple documents that meet the query criteria. If set to false, updates one document.

This is for Mongo versions prior to 2.2. For latest versions the query is changed a bit

                          {$set : {"new_field":1}},

Is there a way to 'pretty' print MongoDB shell output to a file?

Since you are doing this on a terminal and just want to inspect a record in a sane way, you can use a trick like this:

mongo | tee somefile

Use the session as normal - db.collection.find().pretty() or whatever you need to do, ignore the long output, and exit. A transcript of your session will be in the file tee wrote to.

Be mindful that the output might contain escape sequences and other garbage due to the mongo shell expecting an interactive session. less handles these gracefully.

How to populate a sub-document in mongoose after creating it?

This might have changed since the original answer was written, but it looks like you can now use the Models populate function to do this without having to execute an extra findOne. See: You'd want to use this inside the save handler just like the findOne is.

Couldn't connect to server

so first you have to remove the mongod.lock file by below command

sudo rm /var/lib/mongodb/mongod.lock

and then restart the mongo service by issuing below command

sudo service mongod restart 

Avoid "current URL string parser is deprecated" warning by setting useNewUrlParser to true

The complete example for Express.js, API calling case and sending JSON content is the following:

app.get('/api/myApi', (req, res) => {
  MongoClient.connect('mongodb://user:[email protected]:port/dbname',
    { useNewUrlParser: true }, (err, db) => {

      if (err) throw err
      const dbo = db.db('dbname')
        .find({}, { _id: 0 })
        .sort({ _id: -1 })
          (errFind, result) => {
            if (errFind) throw errFind
            const resultJson = JSON.stringify(result)
            console.log('find:', resultJson)

Create an ISO date object in javascript

Try using the ISO string

var isodate = new Date().toISOString()

See also: method definition at MDN.

How to sort mongodb with pymongo

You can try this:


How to Import .bson file format on mongodb

You have to run this mongorestore command via cmd and not on Mongo Shell... Have a look at below command on...

Run this command on cmd (not on Mongo shell)

>path\to\mongorestore.exe -d dbname -c collection_name path\to\same\collection.bson

Here path\to\mongorestore.exe is path of mongorestore.exe inside bin folder of mongodb. dbname is name of databse. collection_name is name of collection.bson. path\to\same\collection.bson is the path up to that collection.

Now from mongo shell you can verify that database is created or not (If it does not exist, database with same name will be created with collection).

Printing Mongo query output to a file while in the mongo shell

If you invoke the shell with script-file, db address, and --quiet arguments, you can redirect the output (made with print() for example) to a file:

mongo localhost/mydatabase --quiet myScriptFile.js > output 

ECONNREFUSED error when connecting to mongodb from node.js

Use this code to setup your mongodb connection:

var mongoose = require('mongoose');

var mongoURI = "mongodb://localhost:27017/test";
var MongoDB = mongoose.connect(mongoURI).connection;
MongoDB.on('error', function(err) { console.log(err.message); });
MongoDB.once('open', function() {
  console.log("mongodb connection open");

Make sure mongod is running while you start the server. Are you using Express or just a simple node.js server? What is the error message you get with the above code?

How do I update a Mongo document after inserting it?

According to the latest documentation about PyMongo titled Insert a Document (insert is deprecated) and following defensive approach, you should insert and update as follows:

result = mycollection.insert_one(post)
post = mycollection.find_one({'_id': result.inserted_id})

if post is not None:
    post['newfield'] = "abc"

How to get the Mongo database specified in connection string in C#

In this moment with the last version of the C# driver (2.3.0) the only way I found to get the database name specified in connection string is this:

var connectionString = @"mongodb://usr:[email protected],,";
var mongoUrl = new MongoUrl(connectionString);
var dbname = mongoUrl.DatabaseName;
var db = new MongoClient(mongoUrl).GetDatabase(dbname);

The server response was: 5.7.0 Must issue a STARTTLS command first. i16sm1806350pag.18 - gsmtp

**this is first  part of program**
<head runat="server">
    <form id="form1" runat="server">

            <div class="style1">
                <table class="style2">
                       <td colspan="2"><h1 class="style4">Sending Email</h1></td>
                       <td><asp:TextBox ID="txtto" runat="server" Height="20px" Width="250px" placeholder="[email protected]"></asp:TextBox><asp:RequiredFieldValidator ForeColor="Red" runat="server" ErrorMessage="Required" ControlToValidate="txtto" Display="Dynamic"></asp:RequiredFieldValidator><asp:RegularExpressionValidator runat="server" ForeColor="Red" ControlToValidate="txtto" Display="Dynamic" ErrorMessage="Invalid Email_ID" ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*"></asp:RegularExpressionValidator> </td>
                       <td><asp:TextBox ID="txtfrom" runat="server" Height="20px" Width="250px" placeholder="[email protected]"></asp:TextBox> <asp:RequiredFieldValidator ForeColor="Red" Display="Dynamic" runat="server" ErrorMessage="Required" ControlToValidate="txtfrom"></asp:RequiredFieldValidator>
                           <asp:RegularExpressionValidator Display="Dynamic" runat="server" ErrorMessage="Invalid Email-ID" ControlToValidate="txtfrom" ForeColor="Red" ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*"></asp:RegularExpressionValidator>
                       <td><asp:TextBox ID="txtsubject" runat="server" Height="20px" Width="250px" placeholder="Demonstration on Youtube"></asp:TextBox><asp:RequiredFieldValidator ForeColor="Red" runat="server" ErrorMessage="Required" ControlToValidate="txtsubject"></asp:RequiredFieldValidator> </td>
                       <td><asp:TextBox ID="txtbody" runat="server" Width="250px" TextMode="MultiLine" Rows="5" placeholder="This is the body text"></asp:TextBox><asp:RequiredFieldValidator ForeColor="Red" runat="server" ErrorMessage="Required" ControlToValidate="txtbody"></asp:RequiredFieldValidator> </td>
                       <td colspan="2"><asp:Button CssClass="style3" BackColor="Green" BorderColor="green" ID="send" Text="Send" runat="server" Height="30px"  Width="100px" OnClick="send_Click"/></td>
                        <td colspan="2"><asp:Label ID="lblmessage" runat="server"></asp:Label> </td>


**this is second part of program**

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Net.Mail;

namespace WebApplication6
    public partial class sendingemail1 : System.Web.UI.Page
        protected void Page_Load(object sender, EventArgs e)


        protected void send_Click(object sender, EventArgs e)
                MailMessage message = new MailMessage();
                message.Subject = txtsubject.Text;
                message.Body = txtbody.Text;
                message.From = new MailAddress(txtfrom.Text);
                SmtpClient client = new SmtpClient("", 587);
                client.EnableSsl = true;
                client.Credentials = new System.Net.NetworkCredential(txtfrom.Text, "Sunil@123");
                for(int i=1;i<=100;i++)
                lblmessage.Text = "Mail Successfully send";
            catch (Exception ex)
                lblmessage.Text = ex.Message;

How to hide Android soft keyboard on EditText

There seems to be quite a variety of ways of preventing the system keyboard from appearing, both programmatically and in xml. However, this is the way that has worked for me while supporting pre API 11 devices.

// prevent system keyboard from appearing
if (android.os.Build.VERSION.SDK_INT >= 11) {
} else {

How to change the background-color of jumbrotron?

The easiest way to change the background color of the jumbotron

If you want to change the background color of your jumbotron, then for that you can apply a background color to it using one of your custom class.

HTML Code:

<div class="jumbotron myclass">   
    <h1>My Heading</h1>
    <p>Lorem Ipsum is simply dummy text of the printing and typesetting industry.</p>

CSS Code:

        background-color: red;

Remove characters from NSString?

If you want to support more than one space at a time, or support any whitespace, you can do this:

NSString* noSpaces =
    [[myString componentsSeparatedByCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]

Command output redirect to file and terminal

In case somebody needs to append the output and not overriding, it is possible to use "-a" or "--append" option of "tee" command :

ls 2>&1 | tee -a /tmp/ls.txt
ls 2>&1 | tee --append /tmp/ls.txt

Bold black cursor in Eclipse deletes code, and I don't know how to get rid of it

You might have pressed 0 (also used for insert, shortcut INS) key, which is on the right side of your right scroll button. To solve the problem, just press it again or double click on 'overwrite'.

Java Generate Random Number Between Two Given Values

One can also try below:

public class RandomInt { 
    public static void main(String[] args) { 

        int n1 = Integer.parseInt(args[0]);
        int n2 = Integer.parseInt(args[1]);
        double Random;

        if (n1 != n2)
            if (n1 > n2)
                Random = n2 + (Math.random() * (n1 - n2));
                System.out.println("Your random number is: " + Random);
                Random = n1 + (Math.random() * (n2 - n1));   
                System.out.println("Your random number is: " +Random);
        } else {
            System.out.println("Please provide valid Range " +n1+ " " +n2+ " are equal numbers." );

What is the meaning of prepended double colon "::"?

The :: operator is called the scope-resolution operator and does just that, it resolves scope. So, by prefixing a type-name with this, it tells your compiler to look in the global namespace for the type.


int count = 0;

int main(void) {
  int count = 0;
  ::count = 1;  // set global count to 1
  count = 2;    // set local count to 2
  return 0;

setState() inside of componentDidUpdate()

I had a similar problem where i have to center the toolTip. React setState in componentDidUpdate did put me in infinite loop, i tried condition it worked. But i found using in ref callback gave me simpler and clean solution, if you use inline function for ref callback you will face the null problem for every component update. So use function reference in ref callback and set the state there, which will initiate the re-render

Overriding the java equals() method - not working?

the instanceOf statement is often used in implementation of equals.

This is a popular pitfall !

The problem is that using instanceOf violates the rule of symmetry:

(object1.equals(object2) == true) if and only if (object2.equals(object1))

if the first equals is true, and object2 is an instance of a subclass of the class where obj1 belongs to, then the second equals will return false!

if the regarded class where ob1 belongs to is declared as final, then this problem can not arise, but in general, you should test as follows:

this.getClass() != otherObject.getClass(); if not, return false, otherwise test the fields to compare for equality!

Simple C example of doing an HTTP POST and consuming the response

After weeks of research. I came up with the following code. I believe this is the bare minimum needed to make a secure connection with SSL to a web server.

#include <stdio.h>
#include <openssl/ssl.h>
#include <openssl/err.h>
#include <openssl/bio.h>

#define PORT "443"

int main() {

    //  Initialize the variables
    BIO* bio;
    SSL* ssl;
    SSL_CTX* ctx;

    //   Registers the SSL/TLS ciphers and digests.
    //   Basically start the security layer.

    //  Creates a new SSL_CTX object as a framework to establish TLS/SSL
    //  or DTLS enabled connections
    ctx = SSL_CTX_new(SSLv23_client_method());

    //  -> Error check
    if (ctx == NULL)
        printf("Ctx is null\n");

    //   Creates a new BIO chain consisting of an SSL BIO
    bio = BIO_new_ssl_connect(ctx);

    //  Use the variable from the beginning of the file to create a 
    //  string that contains the URL to the site that you want to connect
    //  to while also specifying the port.
    BIO_set_conn_hostname(bio, HOST ":" PORT);

    //   Attempts to connect the supplied BIO
    if(BIO_do_connect(bio) <= 0)
        printf("Failed connection\n");
        return 1;

    //  The bare minimum to make a HTTP request.
    char* write_buf = "POST / HTTP/1.1\r\n"
                      "Host: " HOST "\r\n"
                      "Authorization: Basic " APIKEY "\r\n"
                      "Connection: close\r\n"

    //   Attempts to write len bytes from buf to BIO
    if(BIO_write(bio, write_buf, strlen(write_buf)) <= 0)
        //  Handle failed writes here
            // Not worth implementing, but worth knowing.

        //  -> Let us know about the failed writes
        printf("Failed write\n");

    //  Variables used to read the response from the server
    int size;
    char buf[1024];

    //  Read the response message
        //  Get chunks of the response 1023 at the time.
        size = BIO_read(bio, buf, 1023);

        //  If no more data, then exit the loop
        if(size <= 0)

        //  Terminate the string with a 0, to let know C when the string 
        //  ends.
        buf[size] = 0;

        //  ->  Print out the response
        printf("%s", buf);

    //  Clean after ourselves

    return 0;

The code above will explain in details how to establish a TLS connection with a remote server.

Important note: this code doesn't check if the public key was signed by a valid authority. Meaning I don't use root certificates for validation. Don't forget to implement this check otherwise you won't know if you are connecting the right website

When it comes to the request itself. It is nothing more then writing the HTTP request by hand.

You can also find under this link an explanation how to instal openSSL in your system, and how to compile the code so it uses the secure library.

click or change event on radio using jquery

$( 'input[name="testGroup"]:radio' ).on('change', function(e) {_x000D_
     return false;_x000D_

This syntax is a little more flexible to handle events. Not only can you observe "changes", but also other types of events can be controlled here too by using one single event handler. You can do this by passing the list of events as arguments to the first parameter. See jQuery On

Secondly, .change() is a shortcut for .on( "change", handler ). See here. I prefer using .on() rather than .change because I have more control over the events.

Lastly, I'm simply showing an alternative syntax to attach the event to the element.

How can I get the current class of a div with jQuery?

if you want to look for a div that has more than 1 class try this:


<div class="class1 class2 class3" id="myDiv">


var check = $( "#myDiv" ).hasClass( "class2" ).toString();



How to retrieve data from sqlite database in android and display it in TextView

First cast your Edit text like this:

TextView tekst = (TextView) findViewById(;

And after that close the DB not befor this line...


How to POST using HTTPclient content type = application/x-www-form-urlencoded

I was using a .Net Core 2.1 API with the [FromBody] attribute and I had to use the following solution to successfully Post to it:

_apiClient =  new HttpClient();
_apiClient.BaseAddress = new Uri(<YOUR API>);
var MyObject myObject = new MyObject(){
    FirstName = "Me",
    LastName = "Myself"

var stringified = JsonConvert.SerializeObject(myObject);
var result = await _apiClient.PostAsync("api/appusers", new StringContent(stringified, Encoding.UTF8, "application/json"));

How to check if any flags of a flag combination are set?

I created a simple extension method that does not need a check on Enum types:

public static bool HasAnyFlag(this Enum value, Enum flags)
        value != null && ((Convert.ToInt32(value) & Convert.ToInt32(flags)) != 0);

It also works on nullable enums. The standard HasFlag method does not, so I created an extension to cover that too.

public static bool HasFlag(this Enum value, Enum flags)
    int f = Convert.ToInt32(flags);

        value != null && ((Convert.ToInt32(value) & f) == f);

A simple test:

enum Option
    None = 0x00,
    One = 0x01,
    Two = 0x02,
    Three = One | Two,
    Four = 0x04

public void HasAnyFlag()
    Option o1 = Option.One;
    Assert.AreEqual(true, o1.HasAnyFlag(Option.Three));
    Assert.AreEqual(false, o1.HasFlag(Option.Three));

    o1 |= Option.Two;
    Assert.AreEqual(true, o1.HasAnyFlag(Option.Three));
    Assert.AreEqual(true, o1.HasFlag(Option.Three));

public void HasAnyFlag_NullableEnum()
    Option? o1 = Option.One;
    Assert.AreEqual(true, o1.HasAnyFlag(Option.Three));
    Assert.AreEqual(false, o1.HasFlag(Option.Three));

    o1 |= Option.Two;
    Assert.AreEqual(true, o1.HasAnyFlag(Option.Three));
    Assert.AreEqual(true, o1.HasFlag(Option.Three));


How to modify WooCommerce cart, checkout pages (main theme portion)

You can use function: wc_get_page_id( 'cart' ) to get the ID of the page. This function will use the page setup as 'cart' page and not the slug. Meaning it will keep working also when you setup a different url for your 'cart' on the settings page. This works for all kind of Woocommerce special page, like 'checkout', 'shop' etc.


if (wc_get_page_id( 'cart' ) == get_the_ID()) {
  // Do something.

python tuple to dict

>>> dict([('hi','goodbye')])
{'hi': 'goodbye'}


>>> [ dict([i]) for i in (('CSCO', 21.14), ('CSCO', 21.14), ('CSCO', 21.14), ('CSCO', 21.14)) ]
[{'CSCO': 21.14}, {'CSCO': 21.14}, {'CSCO': 21.14}, {'CSCO': 21.14}]

grep without showing path/file:line

Just replace -H with -h. Check man grep for more details on options

find . -name '*.bar' -exec grep -hn FOO {} \;

Decrementing for loops

a = " ".join(str(i) for i in range(10, 0, -1))
print (a)

How to convert password into md5 in jquery?

Download and include this plugin

<script src=""></script>

and use like

if(CryptoJS.MD5($("#txtOldPassword").val())) != oldPassword) {


//Following lines shows md5 value
//var hash = CryptoJS.MD5("Message");

Connect to SQL Server 2012 Database with C# (Visual Studio 2012)


SqlConnection myConnection = new SqlConnection("Database=testDB;Server=Paul-PC\\SQLEXPRESS;Integrated Security=True;connect timeout = 30");

How to assign colors to categorical variables in ggplot2 that have stable mapping?

For simple situations like the exact example in the OP, I agree that Thierry's answer is the best. However, I think it's useful to point out another approach that becomes easier when you're trying to maintain consistent color schemes across multiple data frames that are not all obtained by subsetting a single large data frame. Managing the factors levels in multiple data frames can become tedious if they are being pulled from separate files and not all factor levels appear in each file.

One way to address this is to create a custom manual colour scale as follows:

#Some test data
dat <- data.frame(x=runif(10),y=runif(10),
        grp = rep(LETTERS[1:5],each = 2),stringsAsFactors = TRUE)

#Create a custom color scale
myColors <- brewer.pal(5,"Set1")
names(myColors) <- levels(dat$grp)
colScale <- scale_colour_manual(name = "grp",values = myColors)

and then add the color scale onto the plot as needed:

#One plot with all the data
p <- ggplot(dat,aes(x,y,colour = grp)) + geom_point()
p1 <- p + colScale

#A second plot with only four of the levels
p2 <- p %+% droplevels(subset(dat[4:10,])) + colScale

The first plot looks like this:

enter image description here

and the second plot looks like this:

enter image description here

This way you don't need to remember or check each data frame to see that they have the appropriate levels.

What does `set -x` do?

set -x enables a mode of the shell where all executed commands are printed to the terminal. In your case it's clearly used for debugging, which is a typical use case for set -x: printing every command as it is executed may help you to visualize the control flow of the script if it is not functioning as expected.

set +x disables it.

android:layout_height 50% of the screen size

This is easy to do in xml. Set your top container to be a LinearLayout and set the orientation attribute as you wish. Then inside of that place two linearlayouts that both have "fill parent" on width and height. Finally, set the weigth attribute of those two linearlayouts to 1.

How can I show an element that has display: none in a CSS rule?

I can see that you want to write you own short javascript for this, but have you considered to use Frameworks for HTML manipulation instead? jQuery is my prefered tool for such a task, eventhough its an overkill for your current question as it has SO many extra functionalities.

Have a look at jQuery here

CSS Float: Floating an image to the left of the text

I almost always just use overflow:hidden on my text-elements in those situations, it often works like a charm ;)

.post-container {
 margin: 20px 20px 0 0;
 border:5px solid #333;
.post-thumb img {
 float: left;
.post-content {

Get the second largest number in a list in linear time

You can find the 2nd largest by any of the following ways:

Option 1:

numbers = set(numbers)

Option 2:


How to POST JSON Data With PHP cURL?

Please try this code:-

$url = 'url_to_post';

$data = array("first_name" => "First name","last_name" => "last name","email"=>"[email protected]","addresses" => array ("address1" => "some address" ,"city" => "city","country" => "CA", "first_name" =>  "Mother","last_name" =>  "Lastnameson","phone" => "555-1212", "province" => "ON", "zip" => "123 ABC" ) );

$data_string = json_encode(array("customer" =>$data));

$ch = curl_init($url);

curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string);

curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type:application/json'));

curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

$result = curl_exec($ch);


echo "$result";

Difference between HttpModule and HttpClientModule

There is a library which allows you to use HttpClient with strongly-typed callbacks.

The data and the error are available directly via these callbacks.

A reason for existing

When you use HttpClient with Observable, you have to use .subscribe(x=>...) in the rest of your code.

This is because Observable<HttpResponse<T>> is tied to HttpResponse.

This tightly couples the http layer with the rest of your code.

This library encapsulates the .subscribe(x => ...) part and exposes only the data and error through your Models.

With strongly-typed callbacks, you only have to deal with your Models in the rest of your code.

The library is called angular-extended-http-client.

angular-extended-http-client library on GitHub

angular-extended-http-client library on NPM

Very easy to use.

Sample usage

The strongly-typed callbacks are


  • IObservable<T>
  • IObservableHttpResponse
  • IObservableHttpCustomResponse<T>


  • IObservableError<TError>
  • IObservableHttpError
  • IObservableHttpCustomError<TError>

Add package to your project and in your app module

import { HttpClientExtModule } from 'angular-extended-http-client';

and in the @NgModule imports

  imports: [

Your Models

//Normal response returned by the API.
export class RacingResponse {
    result: RacingItem[];

//Custom exception thrown by the API.
export class APIException {
    className: string;

Your Service

In your Service, you just create params with these callback types.

Then, pass them on to the HttpClientExt's get method.

import { Injectable, Inject } from '@angular/core'
import { RacingResponse, APIException } from '../models/models'
import { HttpClientExt, IObservable, IObservableError, ResponseType, ErrorType } from 'angular-extended-http-client';

export class RacingService {

    //Inject HttpClientExt component.
    constructor(private client: HttpClientExt, @Inject(APP_CONFIG) private config: AppConfig) {


    //Declare params of type IObservable<T> and IObservableError<TError>.
    //These are the success and failure callbacks.
    //The success callback will return the response objects returned by the underlying HttpClient call.
    //The failure callback will return the error objects returned by the underlying HttpClient call.
    getRaceInfo(success: IObservable<RacingResponse>, failure?: IObservableError<APIException>) {
        let url = this.config.apiEndpoint;

        this.client.get(url, ResponseType.IObservable, success, ErrorType.IObservableError, failure);

Your Component

In your Component, your Service is injected and the getRaceInfo API called as shown below.

  ngOnInit() {    
    this.service.getRaceInfo(response => this.result = response.result,
                                error => this.errorMsg = error.className);


Both, response and error returned in the callbacks are strongly typed. Eg. response is type RacingResponse and error is APIException.

You only deal with your Models in these strongly-typed callbacks.

Hence, The rest of your code only knows about your Models.

Also, you can still use the traditional route and return Observable<HttpResponse<T>> from Service API.

Java using enum with switch statement

If whichView is an object of the GuideView Enum, following works well. Please note that there is no qualifier for the constant after case.

switch (whichView) {
    case SEVEN_DAY:
    case NOW_SHOWING:

How do I run PHP code when a user clicks on a link?

Well you said without redirecting. Well its a javascript code:

<a href="JavaScript:void(0);" onclick="function()">Whatever!</a>

<script type="text/javascript">
function confirm_delete() {
    var delete_confirmed=confirm("Are you sure you want to delete this file?");

    if (delete_confirmed==true) {
       // the php code :) can't expose mine ^_^
    } else { 
       // this one returns the user if he/she clicks no :)
       document.location.href = 'whatever.php';

give it a try :) hope you like it

How to get all subsets of a set? (powerset)

I have found the following algorithm very clear and simple:

def get_powerset(some_list):
    """Returns all subsets of size 0 - len(some_list) for some_list"""
    if len(some_list) == 0:
        return [[]]

    subsets = []
    first_element = some_list[0]
    remaining_list = some_list[1:]
    # Strategy: get all the subsets of remaining_list. For each
    # of those subsets, a full subset list will contain both
    # the original subset as well as a version of the subset
    # that contains first_element
    for partial_subset in get_powerset(remaining_list):
        subsets.append(partial_subset[:] + [first_element])

    return subsets

Another way one can generate the powerset is by generating all binary numbers that have n bits. As a power set the amount of number with n digits is 2 ^ n. The principle of this algorithm is that an element could be present or not in a subset as a binary digit could be one or zero but not both.

def power_set(items):
    N = len(items)
    # enumerate the 2 ** N possible combinations
    for i in range(2 ** N):
        combo = []
        for j in range(N):
            # test bit jth of integer i
            if (i >> j) % 2 == 1:
        yield combo

I found both algorithms when I was taking MITx: 6.00.2x Introduction to Computational Thinking and Data Science, and I consider it is one of the easiest algorithms to understand I have seen.

Writing JSON object to a JSON file with fs.writeFileSync

I don't think you should use the synchronous approach, asynchronously writing data to a file is better also stringify the output if it's an object.

Note: If output is a string, then specify the encoding and remember the flag options as well.:

const fs = require('fs');
const content = JSON.stringify(output);

fs.writeFile('/tmp/phraseFreqs.json', content, 'utf8', function (err) {
    if (err) {
        return console.log(err);

    console.log("The file was saved!");

Added Synchronous method of writing data to a file, but please consider your use case. Asynchronous vs synchronous execution, what does it really mean?

const fs = require('fs');
const content = JSON.stringify(output);

fs.writeFileSync('/tmp/phraseFreqs.json', content);

Where does error CS0433 "Type 'X' already exists in both A.dll and B.dll " come from?

This may also happen if you have duplicate TagPrefix in your ASPX file.

This would cause this error...

<%@ Register Src="Control1.ascx" TagName="Control1" TagPrefix="uc1" %>

<%@ Register Src="Control2.ascx" TagName="Control2" TagPrefix="uc1" %>

You can fix this by simply changing the 2nd "uc1" to "uc2"


<%@ Register Src="Control1.ascx" TagName="Control1" TagPrefix="uc1" %>

<%@ Register Src="Control2.ascx" TagName="Control2" TagPrefix="uc2" %>

setup android on eclipse but don't know SDK directory


The Eclipse ADT plugin is no longer supported, as per this announcement in June 2015.

The Eclipse ADT plugin has many known bugs and potential security bugs that will not be fixed.

You should immediately switch to use Android Studio, the official IDE for Android.

For help transitioning your projects, read Migrate to Android Studio.

Javascript: set label text

InnerHTML should be innerHTML:

document.getElementById('LblAboutMeCount').innerHTML = charsleft;

You should bind your checkLength function to your textarea with jQuery rather than calling it inline and rather intrusively:

$(document).ready(function() {
    $('textarea[name=text]').keypress(function(e) {
    }).focus(function() {

You can neaten up checkLength by using more jQuery, and I wouldn't use 'object' as a formal parameter:

function checkLength(obj, maxlength, label) {
    charsleft = (maxlength - obj.val().length);
    // never allow to exceed the specified limit
    if( charsleft < 0 ) {
        obj.val(obj.val().substring(0, maxlength-1));
    // I'm trying to set the value of charsleft into the label

So if you apply the above, you can change your markup to:

<textarea name="text"></textarea>

How can I remove or replace SVG content?

Here is the solution:"svg").remove();

This is a remove function provided by D3.js.

How can I call a function using a function pointer?

Initially define a function pointer array which takes a void and returns a void.

Assuming that your function is taking a void and returning a void.

typedef void (*func_ptr)(void);

Now you can use this to create function pointer variables of such functions.

Like below:

func_ptr array_of_fun_ptr[3];

Now store the address of your functions in the three variables.

array_of_fun_ptr[0]= &A;
array_of_fun_ptr[1]= &B;
array_of_fun_ptr[2]= &C;

Now you can call these functions using function pointers as below:


Checkout subdirectories in Git?

As your edit points out, you can use two separate branches to store the two separate directories. This does keep them both in the same repository, but you still can't have commits spanning both directory trees. If you have a change in one that requires a change in the other, you'll have to do those as two separate commits, and you open up the possibility that a pair of checkouts of the two directories can go out of sync.

If you want to treat the pair of directories as one unit, you can use 'wordpress/wp-content' as the root of your repo and use .gitignore file at the top level to ignore everything but the two subdirectories of interest. This is probably the most reasonable solution at this point.

Sparse checkouts have been allegedly coming for two years now, but there's still no sign of them in the git development repo, nor any indication that the necessary changes will ever arrive there. I wouldn't count on them.

Convert a JSON string to object in Java ME?

Jackson for big files, GSON for small files, and JSON.simple for handling both.

javascript: optional first argument in function

You will get the un passed argument value as undefined. But in your case you have to pass at least null value in the first argument.

Or you have to change the method definition like

my_function = function(options, content) { action }

Using setImageDrawable dynamically to set image in an ImageView

You can try to use this code:

ImageView ImgView = (ImageView)findViewById(;

How to specify the download location with wget?

-O is the option to specify the path of the file you want to download to:

wget <uri> -O /path/to/file.ext

-P is prefix where it will download the file in the directory:

wget <uri> -P /path/to/folder

How to replace text of a cell based on condition in excel

You can use the Conditional Formatting to replace text and NOT effect any formulas. Simply go to the Rule's format where you will see Number, Font, Border and Fill.
Go to the Number tab and select CUSTOM. Then simply type where it says TYPE: what you want to say in QUOTES.

Example.. "OTHER"

SQL Network Interfaces, error: 50 - Local Database Runtime error occurred. Cannot create an automatic instance

I have solved above problem Applying below steps

enter image description here

And after you made thses changes, do following changes in your web.config

 <add name="DefaultConnection" connectionString="Data Source=(LocalDb)\v12.0;AttachDbFilename=|DataDirectory|\aspnet-Real-Time-Commenting-20170927122714.mdf;Initial Catalog=aspnet-Real-Time-Commenting-20170927122714;Integrated Security=true" providerName="System.Data.SqlClient" />

Make column fixed position in bootstrap

Use this, works for me and solve problems with small screen.

<div class="row">
    <!-- (fixed content) JUST VISIBLE IN LG SCREEN -->
    <div class="col-lg-3 device-lg visible-lg">
       <div class="affix">
           fixed position 
    <div class="col-lg-9">
    <!-- (fixed content) JUST VISIBLE IN NO LG SCREEN -->
    <div class="device-sm visible-sm device-xs visible-xs device-md visible-md ">
           NO fixed position
       Normal data enter code here

Google Chrome: This setting is enforced by your administrator

In my case, the setting was HKEY_CURRENT_USER\Software\Policies\Google\Chrome

I deleted Chrome and everything is fine now.

How to get row number in dataframe in Pandas?

df.index[df.LastName == 'Smith']


df.query('LastName == "Smith"').index

Will return all row indices where LastName is Smith

Int64Index([1], dtype='int64')

What is Unicode, UTF-8, UTF-16?

ASCII - Software allocates only 8 bit byte in memory for a given character. It works well for English & adopted (loanwords like façade) characters as their corresponding decimal values falls below 128 in the decimal value. Example C program.

UTF-8 - Software allocates 1 to 4 variable 8 bit bytes for a given character. What does mean by variable here? Let us say you are sending the character 'A' through your HTML pages in the browser (HTML is UTF-8), the corresponding decimal value of A is 65, when you convert it into decimal it becomes 01000010. This requires only 1 bytes, 1 byte memory is allocated even for special adopted English characters like 'ç' in a word façade. However, when you want to store European characters, it requires 2 bytes, so you need UTF-8. However, when you go for Asian characters, you require minimum of 2 bytes and maximum of 4 bytes. Similarly, Emoji's require 3 to 4 bytes. UTF-8 will solve all your needs.

UTF-16 will allocate minimum 2 bytes and maximum of 4 bytes per character, it will not allocate 1 or 3 bytes. Each character is either represented in 16 bit or 32 bit.

Then why exists UTF-16? Originally, Unicode was 16 bit not 8 bit. Java adopted the original version of UTF-16.

In a nutshell, you don't need UTF-16 anywhere unless it has been already been adopted by the language or platform you are working on.

Java program invoked by web browsers uses UTF-16 but the web browser sends characters using UTF-8.

Getting the encoding of a Postgres database

A programmatic solution:

SELECT pg_encoding_to_char(encoding) FROM pg_database WHERE datname = 'yourdb';

How can I prevent the textarea from stretching beyond his parent DIV element? (google-chrome issue only)

I'm hoping you are having the same problem that I had... my issue was simple: Make a fixed textarea with locked percentages inside the container (I'm new to CSS/JS/HTML, so bear with me, if I don't get the lingo correct) so that no matter the device it's displaying on, the box filling the container (the table cell) takes up the correct amount of space. Here's how I solved it:

<table width=100%>
    <tr class="idbbs">
        <textarea id="bsinpt"></textarea>

Then CSS Looks like this...

    color: gainsboro;
    float: none;
    background: black;
    text-align: left;
    font-family: "Helvetica", "Tahoma", "Verdana", "Arial Black", sans-serif;
    font-size: 100%;
  position: absolute;
  min-height: 60%;
  min-width: 88%;
  max-height: 60%;
  max-width: 88%;
  resize: none;
    border-top-color: lightsteelblue;
    border-top-width: 1px;
    border-left-color: lightsteelblue;
    border-left-width: 1px;
    border-right-color: lightsteelblue;
    border-right-width: 1px;
    border-bottom-color: lightsteelblue;
    border-bottom-width: 1px;

Sorry for the sloppy code block here, but I had to show you what's important and I don't know how to insert quoted CSS code on this website. In any case, to ensure you see what I'm talking about, the important CSS is less indented here...

What I then did (as shown here) is very specifically tweak the percentages until I found the ones that worked perfectly to fit display, no matter what device screen is used.

Granted, I think the "resize: none;" is overkill, but better safe than sorry and now the consumers will not have anyway to resize the box, nor will it matter what device they are viewing it from.

It works great.


You mus use nvarchar text too. that's mean you have to simply had a "N" before your massive string and that's it! no limitation anymore

SET @SQL = N'SomeMassiveString > 4000 chars...';

Determining if an Object is of primitive type

public static boolean isValidType(Class<?> retType)
    if (retType.isPrimitive() && retType != void.class) return true;
    if (Number.class.isAssignableFrom(retType)) return true;
    if (AbstractCode.class.isAssignableFrom(retType)) return true;
    if (Boolean.class == retType) return true;
    if (Character.class == retType) return true;
    if (String.class == retType) return true;
    if (Date.class.isAssignableFrom(retType)) return true;
    if (byte[].class.isAssignableFrom(retType)) return true;
    if (Enum.class.isAssignableFrom(retType)) return true;
    return false;

React - How to get parameter value from query string?

most simple solution!

in routing :

   <Route path="/app/someUrl/:id" exact component={binder} />

in react code :

componentDidMount() {
    var id = window.location.href.split('/')[window.location.href.split('/').length - 1];
    var queryString = "http://url/api/controller/" + id
      .then(res => {
        this.setState({ data: res });

How to get a path to a resource in a Java JAR file

The following path worked for me: classpath:/path/to/resource/in/jar

CSS hide scroll bar, but have element scrollable

You can make use of the SlimScroll plugin to make a div scrollable even if it is set to overflow: hidden;(i.e. scrollbar hidden).

You can also control touch scroll as well as the scroll speed using this plugin.

Hope this helps :)

Cordova - Error code 1 for command | Command failed for

I'm using Visual Studio 2015, and I've found that the first thing to do is look in the build output.

I found this error reported there:

Reading build config file: \build.json... SyntaxError: Unexpected token

The solution for that was to remove the bom from the build.json file

Then I hit a second problem - with this message in the build output:

FAILURE: Build failed with an exception. * What went wrong: A problem was found with the configuration of task ':packageRelease'.

File 'C:\Users\Colin\etc' specified for property 'signingConfig.storeFile' is not a file.

Easily solved by putting the correct filename into the keystore property

How to upsert (update or insert) in SQL Server 2005

Try to check for existence:


    INSERT INTO dbo.Employee(Col1, ..., ColN)
    VALUES(Val1, .., ValN)


    UPDATE dbo.Employee
    SET Col1 = Val1, Col2 = Val2, ...., ColN = ValN
    WHERE ID = @SomeID

You could easily wrap this into a stored procedure and just call that stored procedure from the outside (e.g. from a programming language like C# or whatever you're using).

Update: either you can just write this entire statement in one long string (doable - but not really very useful) - or you can wrap it into a stored procedure:

CREATE PROCEDURE dbo.InsertOrUpdateEmployee
       @ID INT,
       @Name VARCHAR(50),
       @ItemName VARCHAR(50),  
       @ItemCatName VARCHAR(50),
       @ItemQty DECIMAL(15,2)
       INSERT INTO dbo.Table1(ID, Name, ItemName, ItemCatName, ItemQty)
       VALUES(@ID, @Name, @ItemName, @ItemCatName, @ItemQty)
       UPDATE dbo.Table1
       SET Name = @Name,
           ItemName = @ItemName,
           ItemCatName = @ItemCatName,
           ItemQty = @ItemQty
       WHERE ID = @ID

and then just call that stored procedure from your ADO.NET code

CSS center content inside div

There are many ways to center any element. I listed some

  1. Set it's width to some value and add margin: 0 auto.

.partners {_x000D_
    width: 80%;_x000D_
    margin: 0 auto;_x000D_

  1. Split into 3 column layout

.partners {_x000D_
    width: 80%;_x000D_
    margin-left: 10%;_x000D_

  1. Use bootstrap layout

<div class="row">_x000D_
    <div class="col-sm-4"></div>_x000D_
    <div class="col-sm-4">Your Content / Image here</div>_x000D_

jQuery checkbox onChange

There is a typo error :

$('#activelist :checkbox')...

Should be :


How to make a vertical line in HTML

Rotate a <hr> 90 degrees:

<hr style="width:100px; transform:rotate(90deg);">

JavaScript: How to find out if the user browser is Chrome?

If you're feeling brave, you can experiment with browser sniffing and get a version:

var ua = navigator.userAgent;
if(/chrome/i.test(ua)) {
    var uaArray = ua.split(' ')
    ,   version = uaArray[uaArray.length - 2].substr(7);

This detected version might be a Chrome version, or a Edge version, or something else. Browser plugins can easily change userAgent and platform and other things though, so this is not recommended.

Apologies to The Big Lebowski for using his answer within mine.

Stop setInterval

USE this i hope help you

var interval;

function updateDiv(){
        url: 'getContent.php',
        success: function(data){
        error: function(){
            /* clearInterval(interval); */
            stopinterval(); // stop the interval
            $('.square').html('<span style="color:red">Connection problems</span>');

function playinterval(){
  interval = setInterval(function(){updateDiv();},3000); 
  return false;

function stopinterval(){
  return false;


Where can I download an offline installer of Cygwin?

Not a direct answer to your question, but you can get the most commonly used utilities from without having to jump through the hoops with that horrible Cygwin installer.

Here is a slightly more informative link

Java Project: Failed to load ApplicationContext

I faced this issue, and that is when a Bean (@Bean) was not instantiated properly as it was not given the correct parameters in my test class.

Detailed 500 error message, ASP + IIS 7.5

Fot people who have tried EVERYTHING and just CANNOT get the error details to show, like me, it's a good idea to check the different levels of configuration. I have a config file on Website level and on Application level (inside the website) check both. Also, as it turned out, I had Detailed Errors disabled on the highest node in IIS (just underneath Start Page, it has the name that is the same as the webservers computername). Check the Error Pages there.

Deserializing JSON data to C# using JSON.NET

Building off of bbant's answer, this is my complete solution for deserializing JSON from a remote URL.

using Newtonsoft.Json;
using System.Net.Http;

namespace Base
    public class ApiConsumer<T>
        public T data;
        private string url;

        public CalendarApiConsumer(string url)
            this.url = url;
   = getItems();

        private T getItems()
            T result = default(T);
            HttpClient client = new HttpClient();

            // This allows for debugging possible JSON issues
            var settings = new JsonSerializerSettings
                Error = (sender, args) =>
                    if (System.Diagnostics.Debugger.IsAttached)

            using (HttpResponseMessage response = client.GetAsync(this.url).Result)
                if (response.IsSuccessStatusCode)
                    result = JsonConvert.DeserializeObject<T>(response.Content.ReadAsStringAsync().Result, settings);
            return result;

Usage would be like:

ApiConsumer<FeedResult> feed = new ApiConsumer<FeedResult>("");

Where FeedResult is the class generated using the Xamasoft JSON Class Generator

Here is a screenshot of the settings I used, allowing for weird property names which the web version could not account for.

Xamasoft JSON Class Generator

Mapping object to dictionary and vice versa

I think you should use reflection. Something like this:

private T ConvertDictionaryTo<T>(IDictionary<string, object> dictionary) where T : new()
    Type type = typeof (T);
    T ret = new T();

    foreach (var keyValue in dictionary)
        type.GetProperty(keyValue.Key).SetValue(ret, keyValue.Value, null);

    return ret;

It takes your dictionary and loops through it and sets the values. You should make it better but it's a start. You should call it like this:

SomeClass someClass = ConvertDictionaryTo<SomeClass>(a);

Is it possible to use "return" in stored procedure?

It is possible.

When you use Return inside a procedure, the control is transferred to the calling program which calls the procedure. It is like an exit in loops.

It won't return any value.

Removing html5 required attribute with jQuery

If you want to set required to true


if you want to set required to false


Difference between HashSet and HashMap?

A HashMap is to add, get, remove, ... objects indexed by a custom key of any type.
A HashSet is to add elements, remove elements and check if elements are present by comparing their hashes.

So a HashMap contains the elements and a HashSet remembers their hashes.

PostgreSQL function for last inserted ID

You can use RETURNING id after insert query.

INSERT INTO distributors (id, name) VALUES (DEFAULT, 'ALI') RETURNING id;

and result:


In the above example id is auto-increment filed.

Django, creating a custom 500/404 error page

If all you need is to show custom pages which have some fancy error messages for your site when DEBUG = False, then add two templates named 404.html and 500.html in your templates directory and it will automatically pick up this custom pages when a 404 or 500 is raised.

Why should I use a pointer rather than the object itself?

With pointers ,

  • can directly talk to the memory.

  • can prevent lot of memory leaks of a program by manipulating pointers.

How do I prevent people from doing XSS in Spring MVC?

When you are trying to prevent XSS, it's important to think of the context. As an example how and what to escape is very different if you are ouputting data inside a variable in a javascript snippet as opposed to outputting data in an HTML tag or an HTML attribute.

I have an example of this here:

Also checkout the OWASP XSS Prevention Cheat Sheet:

So the short answer is, make sure you escape output like suggested by Tendayi Mawushe, but take special care when you are outputting data in HTML attributes or javascript.

How to get a random value from dictionary?

Try this:

import random
a = dict(....) # a is some dictionary
random_key = random.sample(a, 1)[0]

This definitely works.

How to set username and password for SmtpClient object in .NET?

The SmtpClient can be used by code:

SmtpClient mailer = new SmtpClient();
mailer.Host = "";
mailer.Credentials = new System.Net.NetworkCredential("yourusername", "yourpassword");

Generate Controller and Model

php artisan make:controller --resource Backend/API/DemoController --model=Demo

Markdown: continue numbered list

Notice how in Macmade's solution, you can see an extra line of code above the "Code block".

Here are two better solutions:

  1. Indent the code block by an extra 4 spaces (so usually 8, in this nested list example, 12). This will put the code in a <pre> element. On SO, you can even specify syntax highlight with a
    <!-- language: lang-js --> indented by 4 spaces (+1 here due to the nested list).

    1. item 1
    2. item 2

      Code.block('JavaScript', maybe)?
    3. item 3

  2. Or, just put the Code block within backticks and indent by 4 spaces (here, 1 extra because of the nested list). You'll get a regular indented text paragraph, with a <code> element inside it. This one you can't syntax-highlight:

    1. item 1
    2. item 2

      Code block

    3. item 3

Note: you can click "edit" on this answer to see the underlying Markdown code. No need to save ;)

Select all occurrences of selected word in VSCode

In my MacOS case for some reason Cmd+Shift+L is not working while pressing the short cut on the keyboard (although it work just fine while clicking on this option in menu: Selection -> Select All Occurences). So for me pressing Cmd+FN+F2 did the trick (FN is for enabling "F2" obviously).

Btw, if you forget this shortcut just do right-click on the selection and see "Change All Occurrences" option

Config Error: This configuration section cannot be used at this path

Before reinstalling iis and possibly all of your sites, go to: C:\inetpub\history

There should be number of folders (example: CFGHISTORY_0000000029). Each time a root config file is modified, and entry is made in there. (by default backups of the last 10 modifications are saved)

Look for a backup folder that has the right date and time for it, Click on it and see if there is a file called; applicationhost.config

Compare this to your current applicationhost.config file, or replace your current version with it (make a backup first!!!).

I recently had my localhost iis file modified by a windows 2004 update package, which locked a few features at the root (such as handlers), which prevented localhost sites from working - hence my search.

If you open the file in Visual Code, you can see each area that is locked with a overrideModeDefault="Deny"

This might get you a step closer, and also a way to recover if this file ever gets corrupted.

HTML5 canvas ctx.fillText won't do line breaks?

Here is my function to draw multiple lines of text center in canvas (only break the line, don't break-word)

var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");

let text = "Hello World \n Hello World 2222 \n AAAAA \n thisisaveryveryveryveryveryverylongword. "
ctx.font = "20px Arial";

fillTextCenter(ctx, text, 0, 0, c.width, c.height)

function fillTextCenter(ctx, text, x, y, width, height) {
    ctx.textBaseline = 'middle';
    ctx.textAlign = "center";

    const lines = text.match(/[^\r\n]+/g);
    for(let i = 0; i < lines.length; i++) {
        let xL = (width - x) / 2
        let yL =  y + (height / (lines.length + 1)) * (i+1)

        ctx.fillText(lines[i], xL, yL)
<canvas id="myCanvas" width="300" height="150" style="border:1px solid #000;"></canvas>

If you want to fit text size to canvas, you can also check here

How to hide only the Close (x) button?

If you really want to hide it, as in "not visible", then you will probably have to create a borderless form and draw the caption components yourself. VisualStyles library has the Windows Elements available. You would also have to add back in the functionality of re-sizing the form or moving the form by grabbing the caption bar. Not to mention the system menu in the corner.

In most cases, it's hard to justify having the "close" button not available, especially when you want a modal form with minimizing capabilities. Minimizing a modal form really makes no sense.

Remove a character at a certain position in a string - javascript

you can use substring() method. ex,

var x = "Hello world"
var x = x.substring(0, i) + 'h' + x.substring(i+1);

How to export dataGridView data Instantly to Excel on button click?

I'm adding this answer because none of the other methods use OpenXMLWriter, despite the fact that it is faster than OpenXML DOM and both faster and more reliable than COM/Interop, and because some of the other methods use the clipboard, which I would caution against, as it's output is unreliable.

The details can be found in my answer in the link below, however that example is for a DataTable, but you can adapt it to using a DataGridView by just changing the row/column loops to reference a dgv instead of a dt.

How to export DataTable to Excel

Count how many rows have the same value

Use this query this will give your output:

  ,( select 
       count (*) as num_value 
     from Table 
      where num =t.num) cnt 
from Table t;

Flask Download a File

You need to make sure that the value you pass to the directory argument is an absolute path, corrected for the current location of your application.

The best way to do this is to configure UPLOAD_FOLDER as a relative path (no leading slash), then make it absolute by prepending current_app.root_path:

@app.route('/uploads/<path:filename>', methods=['GET', 'POST'])
def download(filename):
    uploads = os.path.join(current_app.root_path, app.config['UPLOAD_FOLDER'])
    return send_from_directory(directory=uploads, filename=filename)

It is important to reiterate that UPLOAD_FOLDER must be relative for this to work, e.g. not start with a /.

A relative path could work but relies too much on the current working directory being set to the place where your Flask code lives. This may not always be the case.

How to check if a column exists in a SQL Server table?

//Only checks
and TABLE_SCHEMA = 'Schema_Name'
and TABLE_NAME = 'Table_Name'
and COLUMN_NAME = 'Column_Name'
and DATA_TYPE = 'Column_Type') -- Where statement lines can be deleted.



Can you target <br /> with css?

old question but this is a pretty neat and clean fix, might come in use for people who are still wondering if it's possible :):

    content: '.';_x000D_
    display: inline-block;_x000D_
    width: 100%;_x000D_
    border-bottom: 1px dashed black;_x000D_

with this fix you can also remove BRs on websites ( just set the width to 0px )

Is it possible to pass parameters programmatically in a Microsoft Access update query?

Many thanks for the information about using the QueryDefs collection! I have been wondering about this for a while.

I did it a different way, without using VBA, by using a table containing the query parameters.


SELECT a_table.a_field 
FROM QueryParameters, a_table 
WHERE a_table.a_field BETWEEN QueryParameters.a_field_min 
AND QueryParameters.a_field_max

Where QueryParameters is a table with two fields, a_field_min and a_field_max

It can even be used with GROUP BY, if you include the query parameter fields in the GROUP BY clause, and the FIRST operator on the parameter fields in the HAVING clause.

Creating stored procedure and SQLite?

SQLite has had to sacrifice other characteristics that some people find useful, such as high concurrency, fine-grained access control, a rich set of built-in functions, stored procedures, esoteric SQL language features, XML and/or Java extensions, tera- or peta-byte scalability, and so forth

Source : Appropriate Uses For SQLite

Thymeleaf: Concatenation - Could not parse as expression

You can concat many kind of expression by sorrounding your simple/complex expression between || characters:

<p th:text="|${bean.field} ! ${bean.field}|">Static content</p>

Execute PHP scripts within Node.js web server

If php is in FPM mode node-phpfpm could be an option, check the documenation

How can I call the 'base implementation' of an overridden virtual method?

You can't do it by C#, but you can edit MSIL.

IL code of your Main method:

.method private hidebysig static void Main() cil managed
    .maxstack 1
    .locals init (
        [0] class MsilEditing.A a)
    L_0000: nop 
    L_0001: newobj instance void MsilEditing.B::.ctor()
    L_0006: stloc.0 
    L_0007: ldloc.0 
    L_0008: callvirt instance void MsilEditing.A::X()
    L_000d: nop 
    L_000e: ret 

You should change opcode in L_0008 from callvirt to call

L_0008: call instance void MsilEditing.A::X()

How do I do base64 encoding on iOS?

For an update to use the NSData (NSDataBase64Encoding) category methods in iOS7 see my answer here:

Where is the itoa function in Linux?

EDIT: Sorry, I should have remembered that this machine is decidedly non-standard, having plugged in various non-standard libc implementations for academic purposes ;-)

As itoa() is indeed non-standard, as mentioned by several helpful commenters, it is best to use sprintf(target_string,"%d",source_int) or (better yet, because it's safe from buffer overflows) snprintf(target_string, size_of_target_string_in_bytes, "%d", source_int). I know it's not quite as concise or cool as itoa(), but at least you can Write Once, Run Everywhere (tm) ;-)

Here's the old (edited) answer

You are correct in stating that the default gcc libc does not include itoa(), like several other platforms, due to it not technically being a part of the standard. See here for a little more info. Note that you have to

#include <stdlib.h>

Of course you already know this, because you wanted to use itoa() on Linux after presumably using it on another platform, but... the code (stolen from the link above) would look like:


/* itoa example */
#include <stdio.h>
#include <stdlib.h>

int main ()
  int i;
  char buffer [33];
  printf ("Enter a number: ");
  scanf ("%d",&i);
  itoa (i,buffer,10);
  printf ("decimal: %s\n",buffer);
  itoa (i,buffer,16);
  printf ("hexadecimal: %s\n",buffer);
  itoa (i,buffer,2);
  printf ("binary: %s\n",buffer);
  return 0;


Enter a number: 1750
decimal: 1750
hexadecimal: 6d6
binary: 11011010110

Hope this helps!

onChange and onSelect in DropDownList

I bet the onchange is getting fired after the onselect, essentially re-enabling the select.

I'd recommend you implement only the onchange, inspect which option has been selected, and enable or disabled based on that.

To get the value of the selected option use:


Which will yield .. nothing since you haven't specified a value for each option .. :(

<select id="mySelect" onChange="enable();">
<option onSelect="disable();" value="no">No</option>
<option onSelect="enable();" value="yes">Yes</option>

Now it will yield "yes" or "no"

Returning Arrays in Java

You have a couple of basic misconceptions about Java:

I want it to return the array without having to explicitly tell the console to print.

1) Java does not work that way. Nothing ever gets printed implicitly. (Java does not support an interactive interpreter with a "repl" loop ... like Python, Ruby, etc.)

2) The "main" doesn't "return" anything. The method signature is:

  public static void main(String[] args)

and the void means "no value is returned". (And, sorry, no you can't replace the void with something else. If you do then the java command won't recognize the "main" method.)

3) If (hypothetically) you did want your "main" method to return something, and you altered the declaration to allow that, then you still would need to use a return statement to tell it what value to return. Unlike some language, Java does not treat the value of the last statement of a method as the return value for the method. You have to use a return statement ...

Why doesn't git recognize that my file has been changed, therefore git add not working

i have the same problem here VS2015 didn't recognize my js files changes, removing remotes from repository settings and then re-adding the remote URL path solved my problem.

python: how to get information about a function?



if you're generally poking around.

How to access parent scope from within a custom directive *with own scope* in AngularJS?

Accessing controller method means accessing a method on parent scope from directive controller/link/scope.

If the directive is sharing/inheriting the parent scope then it is quite straight forward to just invoke a parent scope method.

Little more work is required when you want to access parent scope method from Isolated directive scope.

There are few options (may be more than listed below) to invoke a parent scope method from isolated directives scope or watch parent scope variables (option#6 specially).

Note that I used link function in these examples but you can use a directive controller as well based on requirement.

Option#1. Through Object literal and from directive html template


<!DOCTYPE html>
<html ng-app="plunker">

    <meta charset="utf-8" />
    <title>AngularJS Plunker</title>
    <script>document.write('<base href="' + document.location + '" />');</script>
    <link rel="stylesheet" href="style.css" />
    <script data-require="[email protected]" src="" data-semver="1.3.9"></script>
    <script src="app.js"></script>

  <body ng-controller="MainCtrl">
    <p>Hello {{name}}!</p>

    <p> Directive Content</p>
    <sd-items-filter selected-items="selectedItems" selected-items-changed="selectedItemsChanged(selectedItems)" items="items"> </sd-items-filter>

    <P style="color:red">Selected Items (in parent controller) set to: {{selectedItemsReturnedFromDirective}} </p>




<select ng-model="selectedItems" multiple="multiple" style="height: 200px; width: 250px;" ng-change="selectedItemsChanged({selectedItems:selectedItems})" ng-options=" as group by item.model for item in items | orderBy:'name'">


var app = angular.module('plunker', []);

app.directive('sdItemsFilter', function() {
  return {
    restrict: 'E',
    scope: {
      items: '=',
      selectedItems: '=',
      selectedItemsChanged: '&'
    templateUrl: "itemfilterTemplate.html"

app.controller('MainCtrl', function($scope) {
  $ = 'TARS';

  $scope.selectedItems = ["allItems"];

  $scope.selectedItemsChanged = function(selectedItems1) {
    $scope.selectedItemsReturnedFromDirective = selectedItems1;

  $scope.items = [{
    "id": "allItems",
    "name": "All Items",
    "order": 0
  }, {
    "id": "CaseItem",
    "name": "Case Item",
    "model": "PredefinedModel"
  }, {
    "id": "Application",
    "name": "Application",
    "model": "Bank"


working plnkr:

Option#2. Through Object literal and from directive link/scope


<!DOCTYPE html>
<html ng-app="plunker">

    <meta charset="utf-8" />
    <title>AngularJS Plunker</title>
    <script>document.write('<base href="' + document.location + '" />');</script>
    <link rel="stylesheet" href="style.css" />
    <script data-require="[email protected]" src="" data-semver="1.3.9"></script>
    <script src="app.js"></script>

  <body ng-controller="MainCtrl">
    <p>Hello {{name}}!</p>

    <p> Directive Content</p>
    <sd-items-filter selected-items="selectedItems" selected-items-changed="selectedItemsChanged(selectedItems)" items="items"> </sd-items-filter>

    <P style="color:red">Selected Items (in parent controller) set to: {{selectedItemsReturnedFromDirective}} </p>




<select ng-model="selectedItems" multiple="multiple" style="height: 200px; width: 250px;" 
 ng-change="selectedItemsChangedDir()" ng-options=" as group by item.model for item in items | orderBy:'name'">


var app = angular.module('plunker', []);

app.directive('sdItemsFilter', function() {
  return {
    restrict: 'E',
    scope: {
      items: '=',
      selectedItems: '=',
      selectedItemsChanged: '&'
    templateUrl: "itemfilterTemplate.html",
    link: function (scope, element, attrs){
      scope.selectedItemsChangedDir = function(){

app.controller('MainCtrl', function($scope) {
  $ = 'TARS';

  $scope.selectedItems = ["allItems"];

  $scope.selectedItemsChanged = function(selectedItems1) {
    $scope.selectedItemsReturnedFromDirective = selectedItems1;

  $scope.items = [{
    "id": "allItems",
    "name": "All Items",
    "order": 0
  }, {
    "id": "CaseItem",
    "name": "Case Item",
    "model": "PredefinedModel"
  }, {
    "id": "Application",
    "name": "Application",
    "model": "Bank"

working plnkr:

Option#3. Through Function reference and from directive html template


<!DOCTYPE html>
<html ng-app="plunker">

    <meta charset="utf-8" />
    <title>AngularJS Plunker</title>
    <script>document.write('<base href="' + document.location + '" />');</script>
    <link rel="stylesheet" href="style.css" />
    <script data-require="[email protected]" src="" data-semver="1.3.9"></script>
    <script src="app.js"></script>

  <body ng-controller="MainCtrl">
    <p>Hello {{name}}!</p>

    <p> Directive Content</p>
    <sd-items-filter selected-items="selectedItems" selected-items-changed="selectedItemsChanged" items="items"> </sd-items-filter>

    <P style="color:red">Selected Items (in parent controller) set to: {{selectedItemsReturnFromDirective}} </p>




<select ng-model="selectedItems" multiple="multiple" style="height: 200px; width: 250px;" 
 ng-change="selectedItemsChanged()(selectedItems)" ng-options=" as group by item.model for item in items | orderBy:'name'">


var app = angular.module('plunker', []);

app.directive('sdItemsFilter', function() {
  return {
    restrict: 'E',
    scope: {
      items: '=',
      selectedItemsChanged: '&'
    templateUrl: "itemfilterTemplate.html"

app.controller('MainCtrl', function($scope) {
  $ = 'TARS';

  $scope.selectedItems = ["allItems"];

  $scope.selectedItemsChanged = function(selectedItems1) {
    $scope.selectedItemsReturnFromDirective = selectedItems1;

  $scope.items = [{
    "id": "allItems",
    "name": "All Items",
    "order": 0
  }, {
    "id": "CaseItem",
    "name": "Case Item",
    "model": "PredefinedModel"
  }, {
    "id": "Application",
    "name": "Application",
    "model": "Bank"

working plnkr:

Option#4. Through Function reference and from directive link/scope


<!DOCTYPE html>
<html ng-app="plunker">

    <meta charset="utf-8" />
    <title>AngularJS Plunker</title>
    <script>document.write('<base href="' + document.location + '" />');</script>
    <link rel="stylesheet" href="style.css" />
    <script data-require="[email protected]" src="" data-semver="1.3.9"></script>
    <script src="app.js"></script>

  <body ng-controller="MainCtrl">
    <p>Hello {{name}}!</p>

    <p> Directive Content</p>
    <sd-items-filter selected-items="selectedItems" selected-items-changed="selectedItemsChanged" items="items"> </sd-items-filter>

    <P style="color:red">Selected Items (in parent controller) set to: {{selectedItemsReturnedFromDirective}} </p>




<select ng-model="selectedItems" multiple="multiple" style="height: 200px; width: 250px;" ng-change="selectedItemsChangedDir()" ng-options=" as group by item.model for item in items | orderBy:'name'">


var app = angular.module('plunker', []);

app.directive('sdItemsFilter', function() {
  return {
    restrict: 'E',
    scope: {
      items: '=',
      selectedItems: '=',
      selectedItemsChanged: '&'
    templateUrl: "itemfilterTemplate.html",
    link: function (scope, element, attrs){
      scope.selectedItemsChangedDir = function(){

app.controller('MainCtrl', function($scope) {
  $ = 'TARS';

  $scope.selectedItems = ["allItems"];

  $scope.selectedItemsChanged = function(selectedItems1) {
    $scope.selectedItemsReturnedFromDirective = selectedItems1;

  $scope.items = [{
    "id": "allItems",
    "name": "All Items",
    "order": 0
  }, {
    "id": "CaseItem",
    "name": "Case Item",
    "model": "PredefinedModel"
  }, {
    "id": "Application",
    "name": "Application",
    "model": "Bank"


working plnkr:

Option#5: Through ng-model and two way binding, you can update parent scope variables.. So, you may not require to invoke parent scope functions in some cases.


<!DOCTYPE html>
<html ng-app="plunker">

    <meta charset="utf-8" />
    <title>AngularJS Plunker</title>
    <script>document.write('<base href="' + document.location + '" />');</script>
    <link rel="stylesheet" href="style.css" />
    <script data-require="[email protected]" src="" data-semver="1.3.9"></script>
    <script src="app.js"></script>

  <body ng-controller="MainCtrl">
    <p>Hello {{name}}!</p>

    <p> Directive Content</p>
    <sd-items-filter ng-model="selectedItems" selected-items-changed="selectedItemsChanged" items="items"> </sd-items-filter>

    <P style="color:red">Selected Items (in parent controller) set to: {{selectedItems}} </p>




<select ng-model="selectedItems" multiple="multiple" style="height: 200px; width: 250px;" 
 ng-options=" as group by item.model for item in items | orderBy:'name'">


var app = angular.module('plunker', []);

app.directive('sdItemsFilter', function() {
  return {
    restrict: 'E',
    scope: {
      items: '=',
      selectedItems: '=ngModel'
    templateUrl: "itemfilterTemplate.html"

app.controller('MainCtrl', function($scope) {
  $ = 'TARS';

  $scope.selectedItems = ["allItems"];

  $scope.items = [{
    "id": "allItems",
    "name": "All Items",
    "order": 0
  }, {
    "id": "CaseItem",
    "name": "Case Item",
    "model": "PredefinedModel"
  }, {
    "id": "Application",
    "name": "Application",
    "model": "Bank"

working plnkr:

Option#6: Through $watch and $watchCollection It is two way binding for items in all above examples, if items are modified in parent scope, items in directive would also reflect the changes.

If you want to watch other attributes or objects from parent scope, you can do that using $watch and $watchCollection as given below


<!DOCTYPE html>
<html ng-app="plunker">

  <meta charset="utf-8" />
  <title>AngularJS Plunker</title>
    document.write('<base href="' + document.location + '" />');
  <link rel="stylesheet" href="style.css" />
  <script data-require="[email protected]" src="" data-semver="1.3.9"></script>
  <script src="app.js"></script>

<body ng-controller="MainCtrl">
  <p>Hello {{user}}!</p>
  <p>directive is watching name and current item</p>
        <input type="text" ng-model="id" />
        <input type="text" ng-model="name" />
        <input type="text" ng-model="model" />

  <button style="margin-left:50px" type="buttun" ng-click="addItem()">Add Item</button>

  <p>Directive Contents</p>
  <sd-items-filter ng-model="selectedItems" current-item="currentItem" name="{{name}}" selected-items-changed="selectedItemsChanged" items="items"></sd-items-filter>

  <P style="color:red">Selected Items (in parent controller) set to: {{selectedItems}}</p>


script app.js

var app = angular.module('plunker', []);

app.directive('sdItemsFilter', function() {
  return {
    restrict: 'E',
    scope: {
      name: '@',
      currentItem: '=',
      items: '=',
      selectedItems: '=ngModel'
    template: '<select ng-model="selectedItems" multiple="multiple" style="height: 140px; width: 250px;"' +
      'ng-options=" as group by item.model for item in items | orderBy:\'name\'">' +
      '<option>--</option> </select>',
    link: function(scope, element, attrs) {
      scope.$watchCollection('currentItem', function() {
      scope.$watch('name', function() {

 app.controller('MainCtrl', function($scope) {
  $scope.user = 'World';

  $scope.addItem = function() {
      id: $,
      name: $,
      model: $scope.model
    $scope.currentItem = {};
    $ = $;
    $ = $;
    $scope.currentItem.model = $scope.model;

  $scope.selectedItems = ["allItems"];

  $scope.items = [{
    "id": "allItems",
    "name": "All Items",
    "order": 0
  }, {
    "id": "CaseItem",
    "name": "Case Item",
    "model": "PredefinedModel"
  }, {
    "id": "Application",
    "name": "Application",
    "model": "Bank"

You can always refer AngularJs documentation for detailed explanations about directives.

Is there an auto increment in sqlite?

Beside rowid, you can define your own auto increment field but it is not recommended. It is always be better solution when we use rowid that is automatically increased.

The AUTOINCREMENT keyword imposes extra CPU, memory, disk space, and disk I/O overhead and should be avoided if not strictly needed. It is usually not needed.

Read here for detailed information.

Chrome blocks different origin requests

This is a security update. If an attacker can modify some file in the web server (the JS one, for example), he can make every loaded pages to download another script (for example to keylog your password or steal your SessionID and send it to his own server).

To avoid it, the browser check the Same-origin policy

Your problem is that the browser is trying to load something with your script (with an Ajax request) that is on another domain (or subdomain). To avoid it (if it is on your own website) you can:

What is the "Upgrade-Insecure-Requests" HTTP header?

This explains the whole thing:

The HTTP Content-Security-Policy (CSP) upgrade-insecure-requests directive instructs user agents to treat all of a site's insecure URLs (those served over HTTP) as though they have been replaced with secure URLs (those served over HTTPS). This directive is intended for web sites with large numbers of insecure legacy URLs that need to be rewritten.

The upgrade-insecure-requests directive is evaluated before block-all-mixed-content and if it is set, the latter is effectively a no-op. It is recommended to set one directive or the other, but not both.

The upgrade-insecure-requests directive will not ensure that users visiting your site via links on third-party sites will be upgraded to HTTPS for the top-level navigation and thus does not replace the Strict-Transport-Security (HSTS) header, which should still be set with an appropriate max-age to ensure that users are not subject to SSL stripping attacks.


Is it possible to specify proxy credentials in your web.config?

Directory Services/LDAP lookups can be used to serve this purpose. It involves some changes at infrastructure level, but most production environments have such provision

React JS onClick event handler

Use ECMA2015. Arrow functions make "this" a lot more intuitive.

import React from 'react';

class TestApp extends React.Component {
   getComponent(e, index) {
           'background-color': '#ccc'
   render() {
       return (
               <li onClick={(e) => this.getComponent(e, 1)}>Component 1</li>
               <li onClick={(e) => this.getComponent(e, 2)}>Component 2</li>
               <li onClick={(e) => this.getComponent(e, 3)}>Component 3</li>
React.renderComponent(<TestApp /> , document.getElementById('soln1'));`

Where are the Properties.Settings.Default stored?

In order to work with newer versions of Windows' policy of only allowing read access by default to the Program Files folder (unless you prompt for elevation with UAC, but that's another topic...), your application will have a settings folder under %userprofile%\appdata\local or %userprofile%\Local Settings\Application Data depending on which version of Windows you're running, for settings that are user specific. If you store settings for all users, then they'll be in the corresponding folder under C:\users or C:\Documents and Settings for all user profiles (ex: C:\users\public\appdata\local).

comparing 2 strings alphabetically for sorting purposes

You do say that the comparison is for sorting purposes. Then I suggest instead:


It returns -1 since "a" < "b", 1 or 0 otherwise, like you need for Array.prototype.sort()

Keep in mind that sorting is locale dependent. E.g. in German, ä is a variant of a, so "ä".localeCompare("b", "de-DE") returns -1. In Swedish, ä is one of the last letters in the alphabet, so "ä".localeCompare("b", "se-SE") returns 1.

Without the second parameter to localeCompare, the browser's locale is used. Which in my experience is never what I want, because then it'll sort differently than the server, which has a fixed locale for all users.

Run CRON job everyday at specific time

you can write multiple lines in case of different minutes, for example you want to run at 10:01 AM and 2:30 PM

1 10 * * * php -f /var/www/package/index.php controller function

30 14 * * * php -f /var/www/package/index.php controller function

but the following is the best solution for running cron multiple times in a day as minutes are same, you can mention hours like 10,30 .

30 10,14 * * * php -f /var/www/package/index.php controller function

How do I open multiple instances of Visual Studio Code?

If you want to open multiple instances of the same folder, then it is not currently supported. Watch and upvote this GitHub issue if you want to see it implemented: Support to open a project folder in multiple Visual Studio Code windows

How do I convert a numpy array to (and display) an image?

How to show images stored in numpy array with example (works in Jupyter notebook)

I know there are simpler answers but this one will give you understanding of how images are actually drawn from a numpy array.

Load example

from sklearn.datasets import load_digits
digits = load_digits()
digits.images.shape   #this will give you (1797, 8, 8). 1797 images, each 8 x 8 in size

Display array of one image

array([[ 0.,  0.,  5., 13.,  9.,  1.,  0.,  0.],
       [ 0.,  0., 13., 15., 10., 15.,  5.,  0.],
       [ 0.,  3., 15.,  2.,  0., 11.,  8.,  0.],
       [ 0.,  4., 12.,  0.,  0.,  8.,  8.,  0.],
       [ 0.,  5.,  8.,  0.,  0.,  9.,  8.,  0.],
       [ 0.,  4., 11.,  0.,  1., 12.,  7.,  0.],
       [ 0.,  2., 14.,  5., 10., 12.,  0.,  0.],
       [ 0.,  0.,  6., 13., 10.,  0.,  0.,  0.]])

Create empty 10 x 10 subplots for visualizing 100 images

import matplotlib.pyplot as plt
fig, axes = plt.subplots(10,10, figsize=(8,8))

Plotting 100 images

for i,ax in enumerate(axes.flat):


enter image description here

What does axes.flat do? It creates a numpy enumerator so you can iterate over axis in order to draw objects on them. Example:

import numpy as np
x = np.arange(6).reshape(2,3)
for item in (x.flat):
    print (item, end=' ')

Can't access RabbitMQ web management interface after fresh install

If you are in Mac OS, you need to open the /usr/local/etc/rabbitmq/rabbitmq-env.conf and set NODE_IP_ADDRESS=, it used to be Then add another user as the accepted answer suggested. After that, restart rabbitMQ, brew services restart rabbitmq

Python: For each list element apply a function across the list

Some readable python:

def JoeCalimar(l):
    masterList = []
    for i in l:
        for j in l:
    pos = masterList.index(min(masterList))
    a = pos/len(masterList)
    b = pos%len(masterList)
    return (l[a],l[b])

Let me know if something is not clear.

What are these attributes: `aria-labelledby` and `aria-hidden`

The primary consumers of these properties are user agents such as screen readers for blind people. So in the case with a Bootstrap modal, the modal's div has role="dialog". When the screen reader notices that a div becomes visible which has this role, it'll speak the label for that div.

There are lots of ways to label things (and a few new ones with ARIA), but in some cases it is appropriate to use an existing element as a label (semantic) without using the <label> HTML tag. With HTML modals the label is usually a <h> header. So in the Bootstrap modal case, you add aria-labelledby=[IDofModalHeader], and the screen reader will speak that header when the modal appears.

Generally speaking a screen reader is going to notice whenever DOM elements become visible or invisible, so the aria-hidden property is frequently redundant and can probably be skipped in most cases.

set serveroutput on in oracle procedure

"SET serveroutput ON" is a SQL*Plus command and is not valid PL/SQL.

How do I execute multiple SQL Statements in Access' Query Editor?

You can easily write a bit code that will read in a file. You can either assume one sql statement per line, or assume the ;

So, assuming you have a text file such as:

insert into tblTest (t1) values ('2000');

update tbltest set t1 = '2222'
       where id = 5;

insert into tblTest (t1,t2,t3) 
       values ('2001','2002','2003');

Note the in the above text file we free to have sql statements on more then one line.

the code you can use to read + run the above script is:

Sub SqlScripts()

   Dim vSql       As Variant
   Dim vSqls      As Variant
   Dim strSql     As String
   Dim intF       As Integer

   intF = FreeFile()
   Open "c:\sql.txt" For Input As #intF
   strSql = input(LOF(intF), #intF)
   Close intF
   vSql = Split(strSql, ";")

   On Error Resume Next
   For Each vSqls In vSql
      CurrentDb.Execute vSqls

End Sub

You could expand on placing some error msg if the one statement don't work, such as

if err.number <> 0 then
   debug.print "sql err" & err.Descripiton & "-->" vSqls
end dif

Regardless, the above split() and string read does alow your sql to be on more then one line...

SELECT with LIMIT in Codeigniter

I don't know what version of CI you were using back in 2013, but I am using CI3 and I just tested with two null parameters passed to limit() and there was no LIMIT or OFFSET in the rendered query (I checked by using get_compiled_select()).

This means that -- assuming your have correctly posted your coding attempt -- you don't need to change anything (or at least the old issue is no longer a CI issue).

If this was my project, this is how I would write the method to return an indexed array of objects or an empty array if there are no qualifying rows in the result set.

function nationList($limit = null, $start = null) {
    // assuming the language value is sanitized/validated/whitelisted
    return $this->db
        ->select(', nation.name_' . $this->session->userdata('language') . ' AS name')
        ->limit($limit, $start)

These refinements remove unnecessary syntax, conditions, and the redundant loop.

For reference, here is the CI core code:

 * @param   int $value  LIMIT value
 * @param   int $offset OFFSET value
 * @return  CI_DB_query_builder
public function limit($value, $offset = 0)
    is_null($value) OR $this->qb_limit = (int) $value;
    empty($offset) OR $this->qb_offset = (int) $offset;

    return $this;

So the $this->qb_limit and $this->qb_offset class objects are not updated because null evaluates as true when fed to is_null() or empty().

how to view the contents of a .pem certificate

Use the -printcert command like this:

keytool -printcert -file certificate.pem

Define variable to use with IN operator (T-SQL)

If you want to do this without using a second table, you can do a LIKE comparison with a CAST:

DECLARE @myList varchar(15)
SET @myList = ',1,2,3,4,'

FROM myTable
WHERE @myList LIKE '%,' + CAST(myColumn AS varchar(15)) + ',%'

If the field you're comparing is already a string then you won't need to CAST.

Surrounding both the column match and each unique value in commas will ensure an exact match. Otherwise, a value of 1 would be found in a list containing ',4,2,15,'

Eclipse C++ : "Program "g++" not found in PATH"

The reason is that eclipse cannot find your gcc or g++ environment variable path.

You might have tried to run c or c++ or fortran but eclipse cannot find out the compiler.

So, add the path in your environment variable.

  1. Windows -> Search -environment variables -> click on environmental variables at bottom.

  2. Click on path ->edit -> new -> your variable path

Path should be entire, for example:


Make sure that the variable is permanently stored. It is not erased after you close the environment variables GUI.

Sometimes you might find it difficult to add a path variable. Make sure windows is updated.

Even if Windows is updated and you have problems, directly go to the registry and navigate to the below.

HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Environment

Add your path here. Remove any unnecessary repetitions of path variables.

Note: You need to add your path variables in system environment variables -path

How do I measure request and response times at once using cURL?

Another option that is perhaps the simplest one in terms of the command line is adding the built-in --trace-time option:

curl -X POST -d @file server:port --trace-time

Even though it technically does not output the timings of the various steps as requested by the OP, it does display the timestamps for all steps of the request as shown below. Using this, you can (fairly easily) calculate how long each step has taken.

$ curl --trace-time -v -o /dev/null
13:29:11.148734 * Rebuilt URL to:
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     013:29:11.149958 *   Trying
13:29:11.149993 * TCP_NODELAY set
13:29:11.163177 * Connected to ( port 443 (#0)
13:29:11.164768 * ALPN, offering h2
13:29:11.164804 * ALPN, offering http/1.1
13:29:11.164833 * successfully set certificate verify locations:
13:29:11.164863 *   CAfile: none
  CApath: /etc/ssl/certs
13:29:11.165046 } [5 bytes data]
13:29:11.165099 * (304) (OUT), TLS handshake, Client hello (1):
13:29:11.165128 } [512 bytes data]
13:29:11.189518 * (304) (IN), TLS handshake, Server hello (2):
13:29:11.189537 { [100 bytes data]
13:29:11.189628 * TLSv1.2 (IN), TLS handshake, Certificate (11):
13:29:11.189658 { [2104 bytes data]
13:29:11.190243 * TLSv1.2 (IN), TLS handshake, Server key exchange (12):
13:29:11.190277 { [115 bytes data]
13:29:11.190507 * TLSv1.2 (IN), TLS handshake, Server finished (14):
13:29:11.190539 { [4 bytes data]
13:29:11.190770 * TLSv1.2 (OUT), TLS handshake, Client key exchange (16):
13:29:11.190797 } [37 bytes data]
13:29:11.190890 * TLSv1.2 (OUT), TLS change cipher, Client hello (1):
13:29:11.190915 } [1 bytes data]
13:29:11.191023 * TLSv1.2 (OUT), TLS handshake, Finished (20):
13:29:11.191053 } [16 bytes data]
13:29:11.204324 * TLSv1.2 (IN), TLS handshake, Finished (20):
13:29:11.204358 { [16 bytes data]
13:29:11.204417 * SSL connection using TLSv1.2 / ECDHE-ECDSA-CHACHA20-POLY1305
13:29:11.204451 * ALPN, server accepted to use h2
13:29:11.204483 * Server certificate:
13:29:11.204520 *  subject: C=US; ST=California; L=Mountain View; O=Google LLC;
13:29:11.204555 *  start date: Oct  2 07:29:00 2018 GMT
13:29:11.204585 *  expire date: Dec 25 07:29:00 2018 GMT
13:29:11.204623 *  subjectAltName: host "" matched cert's ""
13:29:11.204663 *  issuer: C=US; O=Google Trust Services; CN=Google Internet Authority G3
13:29:11.204701 *  SSL certificate verify ok.
13:29:11.204754 * Using HTTP2, server supports multi-use
13:29:11.204795 * Connection state changed (HTTP/2 confirmed)
13:29:11.204840 * Copying HTTP/2 data in stream buffer to connection buffer after upgrade: len=0
13:29:11.204881 } [5 bytes data]
13:29:11.204983 * Using Stream ID: 1 (easy handle 0x55846ef24520)
13:29:11.205034 } [5 bytes data]
13:29:11.205104 > GET / HTTP/2
13:29:11.205104 > Host:
13:29:11.205104 > User-Agent: curl/7.61.0
13:29:11.205104 > Accept: */*
13:29:11.205104 > 
13:29:11.218116 { [5 bytes data]
13:29:11.218173 * Connection state changed (MAX_CONCURRENT_STREAMS == 100)!
13:29:11.218211 } [5 bytes data]
13:29:11.251936 < HTTP/2 200 
13:29:11.251962 < date: Fri, 19 Oct 2018 10:29:11 GMT
13:29:11.251998 < expires: -1
13:29:11.252046 < cache-control: private, max-age=0
13:29:11.252085 < content-type: text/html; charset=ISO-8859-1
13:29:11.252119 < p3p: CP="This is not a P3P policy! See for more info."
13:29:11.252160 < server: gws
13:29:11.252198 < x-xss-protection: 1; mode=block
13:29:11.252228 < x-frame-options: SAMEORIGIN
13:29:11.252262 < set-cookie: 1P_JAR=2018-10-19-10; expires=Sun, 18-Nov-2018 10:29:11 GMT; path=/;
13:29:11.252297 < set-cookie: NID=141=pzXxp1jrJmLwFVl9bLMPFdGCtG8ySQKxB2rlDWgerrKJeXxfdmB1HhJ1UXzX-OaFQcnR1A9LKYxi__PWMigjMBQHmI3xkU53LI_TsYRbkMNJNdxs-caQQ7fEcDGE694S; expires=Sat, 20-Apr-2019 10:29:11 GMT; path=/;; HttpOnly
13:29:11.252336 < alt-svc: quic=":443"; ma=2592000; v="44,43,39,35"
13:29:11.252368 < accept-ranges: none
13:29:11.252408 < vary: Accept-Encoding
13:29:11.252438 < 
13:29:11.252473 { [5 bytes data]
100 12215    0 12215    0     0   112k      0 --:--:-- --:--:-- --:--:--  112k
13:29:11.255674 * Connection #0 to host left intact

How to auto-remove trailing whitespace in Eclipse?

For php there is also an option:enter image description here

How can I change all input values to uppercase using Jquery?

You can use each()

$('#id-submit').click(function () {
          this.value = this.value.toUpperCase();          

C++: what regex library should I use?

Boost has regex in it.

That should fill the bill

What is the difference between printf() and puts() in C?

When comparing puts() and printf(), even though their memory consumption is almost the same, puts() takes more time compared to printf().

Java - Get a list of all Classes loaded in the JVM

From Oracle doc you can use -Xlog option that has a possibility to write into file.

java -Xlog:class+load=info:classloaded.txt

Efficient Algorithm for Bit Reversal (from MSB->LSB to LSB->MSB) in C

Bit reversal in pseudo code

source -> byte to be reversed b00101100 destination -> reversed, also needs to be of unsigned type so sign bit is not propogated down

copy into temp so original is unaffected, also needs to be of unsigned type so that sign bit is not shifted in automaticaly

bytecopy = b0010110

LOOP8: //do this 8 times test if bytecopy is < 0 (negative)

    set bit8 (msb) of reversed = reversed | b10000000 

else do not set bit8

shift bytecopy left 1 place
bytecopy = bytecopy << 1 = b0101100 result

shift result right 1 place
reversed = reversed >> 1 = b00000000
8 times no then up^ LOOP8
8 times yes then done.

How should I log while using multiprocessing in Python?

Since we can represent multiprocess logging as many publishers and one subscriber (listener), using ZeroMQ to implement PUB-SUB messaging is indeed an option.

Moreover, PyZMQ module, the Python bindings for ZMQ, implements PUBHandler, which is object for publishing logging messages over a zmq.PUB socket.

There's a solution on the web, for centralized logging from distributed application using PyZMQ and PUBHandler, which can be easily adopted for working locally with multiple publishing processes.

formatters = {
    logging.DEBUG: logging.Formatter("[%(name)s] %(message)s"),
    logging.INFO: logging.Formatter("[%(name)s] %(message)s"),
    logging.WARN: logging.Formatter("[%(name)s] %(message)s"),
    logging.ERROR: logging.Formatter("[%(name)s] %(message)s"),
    logging.CRITICAL: logging.Formatter("[%(name)s] %(message)s")

# This one will be used by publishing processes
class PUBLogger:
    def __init__(self, host, port=config.PUBSUB_LOGGER_PORT):
        self._logger = logging.getLogger(__name__)
        self.ctx = zmq.Context() = self.ctx.socket(zmq.PUB)'tcp://{0}:{1}'.format(socket.gethostbyname(host), port))
        self._handler = PUBHandler(
        self._handler.formatters = formatters

    def logger(self):
        return self._logger

# This one will be used by listener process
class SUBLogger:
    def __init__(self, ip, output_dir="", port=config.PUBSUB_LOGGER_PORT):
        self.output_dir = output_dir
        self._logger = logging.getLogger()

        self.ctx = zmq.Context()
        self._sub = self.ctx.socket(zmq.SUB)
        self._sub.bind('tcp://*:{1}'.format(ip, port))
        self._sub.setsockopt(zmq.SUBSCRIBE, "")

        handler = handlers.RotatingFileHandler(os.path.join(output_dir, "client_debug.log"), "w", 100 * 1024 * 1024, 10)
        formatter = logging.Formatter("%(asctime)s;%(levelname)s - %(message)s")

  def sub(self):
      return self._sub

  def logger(self):
      return self._logger

#  And that's the way we actually run things:

# Listener process will forever listen on SUB socket for incoming messages
def run_sub_logger(ip, event):
    sub_logger = SUBLogger(ip)
    while not event.is_set():
            topic, message = sub_logger.sub.recv_multipart(flags=zmq.NOBLOCK)
            log_msg = getattr(logging, topic.lower())
        except zmq.ZMQError as zmq_error:
            if zmq_error.errno == zmq.EAGAIN:

# Publisher processes loggers should be initialized as follows:

class Publisher:
    def __init__(self, stop_event, proc_id):
        self.stop_event = stop_event
        self.proc_id = proc_id
        self._logger = pub_logger.PUBLogger('').logger

     def run(self):"{0} - Sending message".format(proc_id))

def run_worker(event, proc_id):
    worker = Publisher(event, proc_id)

# Starting subscriber process so we won't loose publisher's messages
sub_logger_process = Process(target=run_sub_logger,
                                 args=(''), stop_event,))

#Starting publisher processes
for i in range(MAX_WORKERS_PER_CLIENT):
                                 args=(stop_event, i,)))
for p in processes:

Empty an array in Java / processing

You can simply assign null to the reference. (This will work for any type of array, not just ints)

int[] arr = new int[]{1, 2, 3, 4};
arr = null;

This will 'clear out' the array. You can also assign a new array to that reference if you like:

int[] arr = new int[]{1, 2, 3, 4};
arr = new int[]{6, 7, 8, 9};

If you are worried about memory leaks, don't be. The garbage collector will clean up any references left by the array.

Another example:

float[] arr = ;// some array that you want to clear
arr = new float[arr.length];

This will create a new float[] initialized to the default value for float.

phpmailer: Reply using only "Reply To" address

I have found the answer to this, and it is annoyingly/frustratingly simple! Basically the reply to addresses needed to be added before the from address as such:

$mail->addReplyTo('[email protected]', 'Reply to name');
$mail->SetFrom('[email protected]', 'Mailbox name');

Looking at the phpmailer code in more detail this is the offending line:

public function SetFrom($address, $name = '',$auto=1) {
   $address = trim($address);
   $name = trim(preg_replace('/[\r\n]+/', '', $name)); //Strip breaks and trim
   if (!self::ValidateAddress($address)) {
     $this->SetError($this->Lang('invalid_address').': '. $address);
     if ($this->exceptions) {
       throw new phpmailerException($this->Lang('invalid_address').': '.$address);
     echo $this->Lang('invalid_address').': '.$address;
     return false;
   $this->From = $address;
   $this->FromName = $name;
   if ($auto) {
      if (empty($this->ReplyTo)) {
         $this->AddAnAddress('ReplyTo', $address, $name);
      if (empty($this->Sender)) {
         $this->Sender = $address;
   return true;

Specifically this line:

if (empty($this->ReplyTo)) {
   $this->AddAnAddress('ReplyTo', $address, $name);

Thanks for your help everyone!

How do I execute cmd commands through a batch file?

@echo off
title Command Executer
color 1b

echo Command Executer by: YourNameHere
echo #################################
: execute
echo Please Type A Command Here:
set /p cmd=Command:
goto execute

how to hide keyboard after typing in EditText in android?

This should work.

InputMethodManager inputManager = (InputMethodManager) context.getSystemService(Context.INPUT_METHOD_SERVICE); 

Just make sure that this.getCurrentFocus() does not return null, which it would if nothing has focus.

test attribute in JSTL <c:if> tag

You can also use something like

<c:if test="${ testObject.testPropert == "testValue" }">...</c:if>

Generating CSV file for Excel, how to have a newline inside a value

This will not work if you try to import the file into EXCEL.

Associate the file extension csv with EXCEL.EXE so you will be able to invoke EXCEL by double-clicking the csv file.

Here I place some text followed by the NewLine Char followed by some more text AND enclosing the whole string with double quotes.

Do not use a CR since EXCEL will place part of the string in the next cell.

""text" + NL + "text""

When you invoke EXCEL, you will see this. You may have to auto size the height to see it all. Where the line breaks will depend on the width of the cell.



Here's the code in Basic

CHR$(34,"2", 10,"DATE", 34)

from unix timestamp to datetime

Without moment.js:

var time_to_show = 1509968436; // unix timestamp in seconds_x000D_
var t = new Date(time_to_show * 1000);_x000D_
var formatted = ('0' + t.getHours()).slice(-2) + ':' + ('0' + t.getMinutes()).slice(-2);_x000D_

Youtube API Limitations

Apart from other answer There are calculator provided by Youtube to check your usage. It is good to identify your usage.

enter image description here

Sending Email in Android using JavaMail API without using the default/built-in app

I found a shorter alternative for others who need help. The code is:

package com.example.mail;

import java.util.Properties;

import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public class SendMailTLS {

    public static void main(String[] args) {

        final String username = "[email protected]";
        final String password = "password";

        Properties props = new Properties();
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.starttls.enable", "true");
        props.put("", "");
        props.put("mail.smtp.port", "587");

        Session session = Session.getInstance(props,
          new javax.mail.Authenticator() {
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication("username", "password");

        try {

            Message message = new MimeMessage(session);
            message.setFrom(new InternetAddress("[email protected]"));
                InternetAddress.parse("[email protected]"));
            message.setSubject("Testing Subject");
            message.setText("Dear Mail Crawler,"
                + "\n\n No spam to my email, please!");



        } catch (MessagingException e) {
            throw new RuntimeException(e);

Source: Sending Email via JavaMail API

Hope this Helps! Good Luck!

Is there an easy way to add a border to the top and bottom of an Android View?

My answers is based on @Emile version but I use transparent color instead of solid.
This example will draw a 2dp bottom border.

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="" >
        <shape android:shape="rectangle" >
            <stroke  android:width="2dp"
                     android:color="#50C0E9" />
            <solid android:color="@android:color/transparent" />
    <item  android:bottom="2dp" >
        <shape android:shape="rectangle" >
            <stroke  android:width="2dp"
                     android:color="@color/bgcolor" />
            <solid android:color="@android:color/transparent" />

@color/bgcolor is the color of the background on wich you draw your view with border.

If you want to change the position of the border change the offset with one of:


or combine them to have 2 or more borders:

android:bottom="2dp" android:top="2dp"

Printing an int list in a single line python3

You want to say

for i in array:
    print(i, end=" ")

The syntax i in array iterates over each member of the list. So, array[i] was trying to access array[1], array[2], and array[3], but the last of these is out of bounds (array has indices 0, 1, and 2).

You can get the same effect with print(" ".join(map(str,array))).

Using prepared statements with JDBCTemplate

Try the following:

PreparedStatementCreator creator = new PreparedStatementCreator() {
    public PreparedStatement createPreparedStatement(Connection con) throws SQLException {
        PreparedStatement updateSales = con.prepareStatement(
        updateSales.setInt(1, 75); 
        updateSales.setString(2, "Colombian"); 
        return updateSales;

Git removing upstream from local repository

Using git version there is no "remove" command for remote. Use "rm" instead.

$ git remote rm upstream
$ git remote add upstream

or, as noted in the previous answer, set-url works.

I don't know when the command changed, but Ubuntu 12.04 shipped with

Retrieve all values from HashMap keys in an ArrayList Java

List constructor accepts any data structure that implements Collection interface to be used to build a list.

To get all the keys from a hash map to a list:

Map<String, Integer> map = new HashMap<String, Integer>();
List<String> keys = new ArrayList<>(map.keySet());

To get all the values from a hash map to a list:

Map<String, Integer> map = new HashMap<String, Integer>();
List<Integer> values = new ArrayList<>(map.values());

Recursively list all files in a directory including files in symlink directories

find -L /var/www/ -type l

# man find
-L     Follow  symbolic links.  When find examines or prints information about files, the information used shall be taken from the

properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched.

how to kill the tty in unix

The simplest way is with the pkill command. In your case:

pkill -9 -t pts/6
pkill -9 -t pts/9
pkill -9 -t pts/10

Regarding tty sessions, the commands below are always useful:

w - shows active terminal sessions

tty - shows your current terminal session (so you won't close it by accident)

last | grep logged - shows currently logged users

Sometimes we want to close all sessions of an idle user (ie. when connections are lost abruptly).

pkill -u username - kills all sessions of 'username' user.

And sometimes when we want to kill all our own sessions except the current one, so I made a script for it. There are some cosmetics and some interactivity (to avoid accidental running on the script).

MYSESSION=`tty | cut -d"/" -f3-`
OTHERSESSIONS=`w $MYUSER | grep "^$MYUSER" | grep -v "$MYSESSION" | cut -d" " -f2`
printf "\e[33mCurrent session\e[0m: $MYUSER[$MYSESSION]\n"

if [[ ! -z $OTHERSESSIONS ]]; then
  printf "\e[33mOther sessions:\e[0m\n"
  w $MYUSER | egrep "LOGIN@|^$MYUSER" | grep -v "$MYSESSION" | column -t
  echo ----------
  read -p "Do you want to force close all your other sessions? [Y]Yes/[N]No: " answer
  answer=`echo $answer | tr A-Z a-z`
  confirm=("y" "yes")

  if [[ "${confirm[@]}" =~ "$answer" ]]; then
         pkill -9 -t $SESSION
         echo Session $SESSION closed.
        echo "There are no other sessions for the user '$MYUSER'".

gcc-arm-linux-gnueabi command not found

If you are on a 64bit build of ubuntu or debian (see e.g. 'cat /proc/version') you should simply use the 64bit cross compilers, if you cloned

git clone

then the 64bit tools are in


use that directory for the gcc-toolchain. A useful tutorial for compiling that I followed is available here Building and compiling Raspberry PI Kernel (use the -x64 path from above as ${CCPREFIX})

Database development mistakes made by application developers

Blaming the db engine when the query that ran sooo fast on your development machine blows up and choke once you throw some traffic at the application.

Android: Creating a Circular TextView?

Create an texview_design.xml file and populate it with the following code. Put it in res/drawable.

<shape xmlns:android="" >

        <solid android:color="#98AFC7" />

            android:color="#98AFC7" />

            android:topRightRadius="20dp" />


Then in your main XML file just add the following line for each TextView:


Second way (not recommended): circle Download this circle and place it in your drawable folder and then make it your TextView's background. and then set the gravity to center.

Then it will look like this:

enter image description here

What's the difference between a Python module and a Python package?

Any Python file is a module, its name being the file's base name without the .py extension. A package is a collection of Python modules: while a module is a single Python file, a package is a directory of Python modules containing an additional file, to distinguish a package from a directory that just happens to contain a bunch of Python scripts. Packages can be nested to any depth, provided that the corresponding directories contain their own file.

The distinction between module and package seems to hold just at the file system level. When you import a module or a package, the corresponding object created by Python is always of type module. Note, however, when you import a package, only variables/functions/classes in the file of that package are directly visible, not sub-packages or modules. As an example, consider the xml package in the Python standard library: its xml directory contains an file and four sub-directories; the sub-directory etree contains an file and, among others, an file. See what happens when you try to interactively import package/modules:

>>> import xml
>>> type(xml)
<type 'module'>
>>> xml.etree.ElementTree
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'etree'
>>> import xml.etree
>>> type(xml.etree)
<type 'module'>
>>> xml.etree.ElementTree
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'ElementTree'
>>> import xml.etree.ElementTree
>>> type(xml.etree.ElementTree)
<type 'module'>
>>> xml.etree.ElementTree.parse
<function parse at 0x00B135B0>

In Python there also are built-in modules, such as sys, that are written in C, but I don't think you meant to consider those in your question.


The new ASP.NET Web API is a continuation of the previous WCF Web API project (although some of the concepts have changed).

WCF was originally created to enable SOAP-based services. For simpler RESTful or RPCish services (think clients like jQuery) ASP.NET Web API should be good choice.

For us, WCF is used for SOAP and Web API for REST. I wish Web API supported SOAP too. We are not using advanced features of WCF. Here is comparison from MSDN:

enter image description here Web API is all about HTTP and REST based GET,POST,PUT,DELETE with well know MVC style of programming and JSON returnable; web API is for all the light weight process and pure HTTP based components. For one to go ahead with WCF even for simple or simplest single web service it will bring all the extra baggage. For light weight simple service for ajax or dynamic calls always WebApi just solves the need. This neatly complements or helps in parallel to the MVC.

Check out the podcast : Hanselminutes Podcast 264 - This is not your father's WCF - All about the WebAPI with Glenn Block by Scott Hanselman for more information.

In the scenarios listed below you should go for WCF:

  1. If you need to send data on protocols like TCP, MSMQ or MIME
  2. If the consuming client just knows how to consume SOAP messages

WEB API is a framework for developing RESTful/HTTP services.

There are so many clients that do not understand SOAP like Browsers, HTML5, in those cases WEB APIs are a good choice.

HTTP services header specifies how to secure service, how to cache the information, type of the message body and HTTP body can specify any type of content like HTML not just XML as SOAP services.

Expected response code 220 but got code "", with message "" in Laravel

I was facing the same issue. After researching too much on Google and StackOverflow. I found a solution very simple

First, you need to set environment like this

[email protected]
[email protected]

you have to change your Gmail address and password

Now you have to on less secure apps by following this link

How can I convert an image into Base64 string using JavaScript?

There are multiple approaches you can choose from:

1. Approach: FileReader

Load the image as blob via XMLHttpRequest and use the FileReader API (readAsDataURL()) to convert it to a dataURL:

function toDataURL(url, callback) {
  var xhr = new XMLHttpRequest();
  xhr.onload = function() {
    var reader = new FileReader();
    reader.onloadend = function() {
  };'GET', url);
  xhr.responseType = 'blob';

toDataURL('', function(dataUrl) {
  console.log('RESULT:', dataUrl)

This code example could also be implemented using the WHATWG fetch API:

const toDataURL = url => fetch(url)
  .then(response => response.blob())
  .then(blob => new Promise((resolve, reject) => {
    const reader = new FileReader()
    reader.onloadend = () => resolve(reader.result)
    reader.onerror = reject

  .then(dataUrl => {
    console.log('RESULT:', dataUrl)

These approaches:

  • lack in browser support
  • have better compression
  • work for other file types as well

Browser Support:

2. Approach: Canvas

Load the image into an Image-Object, paint it to a nontainted canvas and convert the canvas back to a dataURL.

function toDataURL(src, callback, outputFormat) {
  var img = new Image();
  img.crossOrigin = 'Anonymous';
  img.onload = function() {
    var canvas = document.createElement('CANVAS');
    var ctx = canvas.getContext('2d');
    var dataURL;
    canvas.height = this.naturalHeight;
    canvas.width = this.naturalWidth;
    ctx.drawImage(this, 0, 0);
    dataURL = canvas.toDataURL(outputFormat);
  img.src = src;
  if (img.complete || img.complete === undefined) {
    img.src = "data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///ywAAAAAAQABAAACAUwAOw==";
    img.src = src;

  function(dataUrl) {
    console.log('RESULT:', dataUrl)

In detail

Supported input formats:

image/png, image/jpeg, image/jpg, image/gif, image/bmp, image/tiff, image/x-icon, image/svg+xml, image/webp, image/xxx

Supported output formats:

image/png, image/jpeg, image/webp(chrome)

Browser Support:

3. Approach: Images from the local file system

If you want to convert images from the users file system you need to take a different approach. Use the FileReader API:

function encodeImageFileAsURL(element) {
  var file = element.files[0];
  var reader = new FileReader();
  reader.onloadend = function() {
    console.log('RESULT', reader.result)
<input type="file" onchange="encodeImageFileAsURL(this)" />

App not setup: This app is still in development mode

This is an answer I haven't seen much around (this it was in a comment somewhere) although yes taking the app off development mode will work this can be bad for security or really annoying if the app isn't ready yet but you need to submit the app for review on account of needing access to special permissions (e.g. user_birthday).

What I did instead to fix the error was go to{appId}/roles/ or from the app dashboard click roles on the left side

Then add the user account(s) to either developer or tester. Developers will need to be verified by mobile and will get access to the app to make changes but a tester will only need to be verified by email (not sure if even this is necessary but it probably is) and will only be able to use the API instead of make changes to settings.

If the app is ready for the public, obviously just take the app off development mode.

CSS property to pad text inside of div

The CSS property you are looking for is padding. The problem with padding is that it adds to the width of the original element, so if you have a div with a width of 300px, and add 10px of padding to it, the width will now be 320px (10px on the left and 10px on the right).

To prevent this you can add box-sizing: border-box; to the div, this makes it maintain the designated width, even if you add padding. So your CSS would look like this:

div {
    box-sizing: border-box;
    padding: 10px;

you can read more about box-sizing and it's overall browser support here:

Web scraping with Python

If we think of getting name of items from any specific category then we can do that by specifying the class name of that category using css selector:

import requests ; from bs4 import BeautifulSoup

soup = BeautifulSoup(requests.get('').text, "lxml")
for link in'div._2kSfQ4'):

This is the partial search results:

Puma, USPA, Adidas & moreUp to 70% OffMen's Shoes
Shirts, T-Shirts...Under ?599For Men
Nike, UCB, Adidas & moreUnder ?999Men's Sandals, Slippers
Philips & moreStarting ?99LED Bulbs & Emergency Lights

how to install apk application from my pc to my mobile android

To install an APK on your mobile, you can either:

  1. Use ADB from the Android SDK, and do the following command: adb install filename.apk. Note, you'll need to enable USB debugging for this to work.
  2. Transfer the file to your device, then open it with a file manager, such as Linda File Manager.

Note, that you'll have to enable installing packages from Unknown Sources in your Applications settings.

As for getting USB to work, I suggest consulting the Android StackExchange for advice.

Open multiple Eclipse workspaces on the Mac

Instead of copying around, create an automator that runs the shell script above.

Run automator, create Application.

choose Utilities->Run shell script, and add in the above script (need full path to eclipse)

Then you can drag this to your Dock as a normal app.

Repeat for other workspaces.

You can even simply change the icon -򪮘

How do I convert a String to an int in Java?

public static int parseInt(String s)throws NumberFormatException

You can use Integer.parseInt() to convert a String to an int.

Convert a String, "20", to a primitive int:

String n = "20";
int r = Integer.parseInt(n); // Returns a primitive int


If the string does not contain a parsable integer, it will throw NumberFormatException:

String n = "20I"; // Throws NumberFormatException
int r = Integer.parseInt(n);

public static Integer valueOf(String s)throws NumberFormatException

You can use Integer.valueOf(). In this it will return an Integer object.

String n = "20";
Integer r = Integer.valueOf(n); // Returns a new Integer() object.



Using jQuery to programmatically click an <a> link

Add onclick="window.location = this.href" to your <a> element. After this modification it could be .click()ed with expected behaviour. To do so with every link on your page, you can add this:

<script type="text/javascript">
    $(function () {
        $("a").attr("onclick", "window.location = this.href");

Alarm Manager Example

After ten years, you can read this training explanation on the official documentation.

error CS0234: The type or namespace name 'Script' does not exist in the namespace 'System.Web'

I found this MSDN forum post which suggests two solutions to your problem.

First solution (not recommended):

Find the .Net Framework 3.5 and 2.0 folder

Copy System.Web.Extensions.dll from 3.5 and System.Web.dll from 2.0 to the application folder

Add the reference to these two assemblies

Change the referenced assemblies property, setting "Copy Local" to true And build to test your application to ensure all code can work

Second solution (Use a different class / library):

The user who had posted the question claimed that Uri.EscapeUriString and How to: Serialize and Deserialize JSON Data helped him replicate the behavior of JavaScriptSerializer.

You could also try to use Json.Net. It's a third party library and pretty powerful.

Sort a list of Class Instances Python

In addition to the solution you accepted, you could also implement the special __lt__() ("less than") method on the class. The sort() method (and the sorted() function) will then be able to compare the objects, and thereby sort them. This works best when you will only ever sort them on this attribute, however.

class Foo(object):

     def __init__(self, score):
         self.score = score

     def __lt__(self, other):
         return self.score < other.score

l = [Foo(3), Foo(1), Foo(2)]

How to know if a Fragment is Visible?

One thing to be aware of, is that isVisible() returns the visible state of the current fragment. There is a problem in the support library, where if you have nested fragments, and you hide the parent fragment (and therefore all the children), the child still says it is visible.

isVisible() is final, so can't override unfortunately. My workaround was to create a BaseFragment class that all my fragments extend, and then create a method like so:

public boolean getIsVisible()
    if (getParentFragment() != null && getParentFragment() instanceof BaseFragment)
        return isVisible() && ((BaseFragment) getParentFragment()).getIsVisible();
        return isVisible();

I do isVisible() && ((BaseFragment) getParentFragment()).getIsVisible(); because we want to return false if any of the parent fragments are hidden.

This seems to do the trick for me.

jQuery .ajax() POST Request throws 405 (Method Not Allowed) on RESTful WCF

You can create the required headers in a filter too.

public class AllowAccessFilter implements Filter {
    public void doFilter(ServletRequest sRequest, ServletResponse sResponse, FilterChain chain) throws IOException, ServletException {
        System.out.println("in AllowAccessFilter.doFilter");
        HttpServletRequest request = (HttpServletRequest)sRequest;
        HttpServletResponse response = (HttpServletResponse)sResponse;
        response.setHeader("Access-Control-Allow-Origin", "*");
        response.setHeader("Access-Control-Allow-Methods", "GET, POST, PUT");
        response.setHeader("Access-Control-Allow-Headers", "Content-Type"); 
        chain.doFilter(request, response);

Twitter bootstrap scrollable modal

The problem with @grenoult's CSS solution (which does work, mostly), is that it is fully responsive and on mobile when the keyboard pops up (i.e. when they click in an input in the modal dialog) the screen size changes and the modal dialog's size changes and it can hide the input they just clicked on so they can't see what they are typing.

The better solution for me was to use jquery as follows:

$(".modal-body").css({ "max-height" : $(window).height() - 212, "overflow-y" : "auto" });

It isn't responsive to changing the window size, but that doesn't happen that often anyway.

Best database field type for a URL

varchar(max) for SQLServer2005

varchar(65535) for MySQL 5.0.3 and later

This will allocate storage as need and shouldn't affect performance.

ERROR: Error 1005: Can't create table (errno: 121)

Something I noticed was that I had "other_database" and "Other_Database" in my databases. That caused this problem as I actually had same reference in other database which caused this mysterious error!

How do I hide the status bar in a Swift iOS app?

In my case, I was looking for the status bar to hide/show on demand; instead of just when the view loads or disappears.

swift 3.x

//show status bar initially
var showStatusBar = true

//set the parameters
override var prefersStatusBarHidden: Bool {

    if showStatusBar == true {

        //does not prefer status bar hidden
        print("does not prefer status bar hidden")
        return false

    } else {

        //does prefer status bar hidden
        print("does prefer status bar hidden")
    return true


//ex: hide status bar and call parameter function again whenever you want
        showStatusBar = false

PowerShell: Create Local User Account

Another alternative is the old school NET USER commands:

NET USER username "password" /ADD

OK - you can't set all the options but it's a lot less convoluted for simple user creation & easy to script up in Powershell.

NET LOCALGROUP "group" "user" /add to set group membership.

execute function after complete page load

This way you can handle the both cases - if the page is already loaded or not:

document.onreadystatechange = function(){
    if (document.readyState === "complete") {
    else {
       window.onload = function () {

set environment variable in python script

There are many good answers here but you should avoid at all cost to pass untrusted variables to subprocess using shell=True as this is a security risk. The variables can escape to the shell and run arbitrary commands! If you just can't avoid it at least use python3's shlex.quote() to escape the string (if you have multiple space-separated arguments, quote each split instead of the full string).

shell=False is always the default where you pass an argument array.

Now the safe solutions...

Method #1

Change your own process's environment - the new environment will apply to python itself and all subprocesses.

os.environ['LD_LIBRARY_PATH'] = 'my_path'
command = ['sqsub', '-np', var1, '/homedir/anotherdir/executable']

Method #2

Make a copy of the environment and pass is to the childen. You have total control over the children environment and won't affect python's own environment.

myenv = os.environ.copy()
myenv['LD_LIBRARY_PATH'] = 'my_path'
command = ['sqsub', '-np', var1, '/homedir/anotherdir/executable']
subprocess.check_call(command, env=myenv)

Method #3

Unix only: Execute env to set the environment variable. More cumbersome if you have many variables to modify and not portabe, but like #2 you retain full control over python and children environments.

command = ['env', 'LD_LIBRARY_PATH=my_path', 'sqsub', '-np', var1, '/homedir/anotherdir/executable']

Of course if var1 contain multiple space-separated argument they will now be passed as a single argument with spaces. To retain original behavior with shell=True you must compose a command array that contain the splitted string:

command = ['sqsub', '-np'] + var1.split() + ['/homedir/anotherdir/executable']

Convert Time DataType into AM PM Format:

This returns like 11:30 AM

select CONVERT(VARCHAR(5), FromTime, 108) + ' ' + RIGHT(CONVERT(VARCHAR(30), FromTime, 9),2)
from tablename

How to loop through each and every row, column and cells in a GridView and get its value

As it's said by "Tim Schmelter" this is the best way : just change in it's code the seconde loop ( GridView2.Columns[i].Count by row.Cells.Count ) so it looks seem's that:

foreach(GridViewRow row in GridView2.Rows)
    for(int i = 0; i < GridView2.Columns.Count; i++)
        String header = GridView2.Columns[i].HeaderText;
        String cellText = row.Cells[i].Text;

thank you.

mysql: get record count between two date-time

select * from yourtable where created < now() and created > '2011-04-25 04:00:00'

How to bind a List<string> to a DataGridView control?

you can also use linq and anonymous types to achieve the same result with much less code as described here.

UPDATE: blog is down, here's the content:

(..) The values shown in the table represent the length of strings instead of string values (!) It may seem strange, but that’s how binding mechanism works by default – given an object it will try to bind to the first property of that object (the first property it can find). When passed an instance the String class the property it binds to is String.Length since there’s no other property that would provide the actual string itself.

That means that to get our binding right we need a wrapper object that will expose the actual value of a string as a property:

public class StringWrapper
     string stringValue;
     public string StringValue { get { return stringValue; } set { stringValue = value; } }

     public StringWrapper(string s)
     StringValue = s;

   List<StringWrapper> testData = new List<StringWrapper>();

   // add data to the list / convert list of strings to list of string wrappers


While this solution works as expected it requires quite a few lines of code (mostly to convert list of strings to the list of string wrappers).

We can improve this solution by using LINQ and anonymous types- we’ll use LINQ query to create a new list of string wrappers (string wrapper will be an anonymous type in our case).

 var values = from data in testData select new { Value = data };


The last change we’re going to make is to move the LINQ code to an extension method:

public static class StringExtensions
     public static IEnumerable CreateStringWrapperForBinding(this IEnumerable<string> strings)
     var values = from data in strings
     select new { Value = data };

     return values.ToList();

This way we can reuse the code by calling single method on any collection of strings:


react router v^4.0.0 Uncaught TypeError: Cannot read property 'location' of undefined

I've tried everything suggested here but didn't work for me. So in case I can help anyone with a similar issue, every single tutorial I've checked is not updated to work with version 4.

Here is what I've done to make it work

import React from 'react';
import App from './App';

import ReactDOM from 'react-dom';
import {
} from 'react-router-dom';

                <Route path="/" render={()=><App items={temasArray}/>}/>
        </HashRouter >
    ), document.getElementById('root'));

That's the only way I have managed to make it work without any errors or warnings.

In case you want to pass props to your component for me the easiest way is this one:

 <Route path="/" render={()=><App items={temasArray}/>}/>

How to switch activity without animation in Android?

The line in the theme style works fine, yet that replaces the animation with a white screen. Especially on a slower phone - it is really annoying. So, if you want an instant transition - you could use this in the theme style:

<item name="android:windowAnimationStyle">@null</item>
<item name="android:windowDisablePreview">true</item>

Center the content inside a column in Bootstrap 4

2020 : Similar Issue

If your content is a set of buttons that you want to center on a page, then wrap them in a row and use justify-content-center.

Sample code below:

<div class="row justify-content-center">

    <button>Action A</button>
    <button>Action B</button>
    <button>Action C</button> 


Aren't promises just callbacks?

No promises are just wrapper on callbacks

example You can use javascript native promises with node js

my cloud 9 code link :

* Created by dixit-lab on 20/6/16.

var express = require('express');
var request = require('request');   //Simplified HTTP request client.

var app = express();

function promisify(url) {
    return new Promise(function (resolve, reject) {
    request.get(url, function (error, response, body) {
    if (!error && response.statusCode == 200) {
    else {

//get all the albums of a user who have posted post 100
app.get('/listAlbums', function (req, res) {
//get the post with post id 100
promisify('').then(function (result) {
var obj = JSON.parse(result);
return promisify('' + obj.userId + '/albums')
.catch(function (e) {
.then(function (result) {


var server = app.listen(8081, function () {

var host = server.address().address
var port = server.address().port

console.log("Example app listening at http://%s:%s", host, port)


//run webservice on browser : http://localhost:8081/listAlbums

Real mouse position in canvas

The Simple 1:1 Scenario

For situations where the canvas element is 1:1 compared to the bitmap size, you can get the mouse positions by using this snippet:

function getMousePos(canvas, evt) {
    var rect = canvas.getBoundingClientRect();
    return {
      x: evt.clientX - rect.left,
      y: evt.clientY -

Just call it from your event with the event and canvas as arguments. It returns an object with x and y for the mouse positions.

As the mouse position you are getting is relative to the client window you'll have to subtract the position of the canvas element to convert it relative to the element itself.

Example of integration in your code:

//put this outside the event loop..
var canvas = document.getElementById("imgCanvas");
var context = canvas.getContext("2d");

function draw(evt) {
    var pos = getMousePos(canvas, evt);

    context.fillStyle = "#000000";
    context.fillRect (pos.x, pos.y, 4, 4);

Note: borders and padding will affect position if applied directly to the canvas element so these needs to be considered via getComputedStyle() - or apply those styles to a parent div instead.

When Element and Bitmap are of different sizes

When there is the situation of having the element at a different size than the bitmap itself, for example, the element is scaled using CSS or there is pixel-aspect ratio etc. you will have to address this.


function  getMousePos(canvas, evt) {
  var rect = canvas.getBoundingClientRect(), // abs. size of element
      scaleX = canvas.width / rect.width,    // relationship bitmap vs. element for X
      scaleY = canvas.height / rect.height;  // relationship bitmap vs. element for Y

  return {
    x: (evt.clientX - rect.left) * scaleX,   // scale mouse coordinates after they have
    y: (evt.clientY - * scaleY     // been adjusted to be relative to element

With transformations applied to context (scale, rotation etc.)

Then there is the more complicated case where you have applied transformation to the context such as rotation, skew/shear, scale, translate etc. To deal with this you can calculate the inverse matrix of the current matrix.

Newer browsers let you read the current matrix via the currentTransform property and Firefox (current alpha) even provide a inverted matrix through the mozCurrentTransformInverted. Firefox however, via mozCurrentTransform, will return an Array and not DOMMatrix as it should. Neither Chrome, when enabled via experimental flags, will return a DOMMatrix but a SVGMatrix.

In most cases however you will have to implement a custom matrix solution of your own (such as my own solution here - free/MIT project) until this get full support.

When you eventually have obtained the matrix regardless of path you take to obtain one, you'll need to invert it and apply it to your mouse coordinates. The coordinates are then passed to the canvas which will use its matrix to convert it to back wherever it is at the moment.

This way the point will be in the correct position relative to the mouse. Also here you need to adjust the coordinates (before applying the inverse matrix to them) to be relative to the element.

An example just showing the matrix steps

function draw(evt) {
    var pos = getMousePos(canvas, evt);        // get adjusted coordinates as above
    var imatrix = matrix.inverse();            // get inverted matrix somehow
    pos = imatrix.applyToPoint(pos.x, pos.y);  // apply to adjusted coordinate

    context.fillStyle = "#000000";
    context.fillRect(pos.x-1, pos.y-1, 2, 2);

An example of using currentTransform when implemented would be:

    var pos = getMousePos(canvas, e);          // get adjusted coordinates as above
    var matrix = ctx.currentTransform;         // W3C (future)
    var imatrix = matrix.invertSelf();         // invert

    // apply to point:
    var x = pos.x * imatrix.a + pos.y * imatrix.c + imatrix.e;
    var y = pos.x * imatrix.b + pos.y * imatrix.d + imatrix.f;

Update I made a free solution (MIT) to embed all these steps into a single easy-to-use object that can be found here and also takes care of a few other nitty-gritty things most ignore.

How to print a certain line of a file with PowerShell?

This will show the 10th line of myfile.txt:

get-content myfile.txt | select -first 1 -skip 9

both -first and -skip are optional parameters, and -context, or -last may be useful in similar situations.

CSS/Javascript to force html table row on a single line


td, th {
  white-space: nowrap;
  overflow: hidden;

How to get the first line of a file in a bash script?

The question didn't ask which is fastest, but to add to the sed answer, -n '1p' is badly performing as the pattern space is still scanned on large files. Out of curiosity I found that 'head' wins over sed narrowly:

# best:
head -n1 $bigfile >/dev/null

# a bit slower than head (I saw about 10% difference):
sed '1q' $bigfile >/dev/null

# VERY slow:
sed -n '1p' $bigfile >/dev/null

Convert JSON string to dict using Python

use simplejson or cjson for speedups

import simplejson as json




Are there other whitespace codes like &nbsp for half-spaces, em-spaces, en-spaces etc useful in HTML?

Yes, many.

Including, but not limited to:

  • non breaking space : &#160; or &nbsp;
  • narrow no-break space : &#8239; (no character reference available)
  • en space : &#8194; or &ensp;
  • em space : &#8195; or &emsp;
  • 3-per-em space : &#8196; or &emsp13;
  • 4-per-em space : &#8197; or &emsp14;
  • 6-per-em space : &#8198; (no character reference available)
  • figure space : &#8199; or &numsp; 
  • punctuation space : &#8200; or &puncsp;
  • thin space : &#8201; or &thinsp;
  • hair space : &#8202; or &hairsp;

span{background-color: red;}
<tr><td>non breaking space:</td><td> <span>&#160;</span> or <span>&nbsp;</span></td></tr>_x000D_
<tr><td>narrow no-break space:</td><td> <span>&#8239;</span></td></tr>_x000D_
<tr><td>en space:</td><td> <span>&#8194;</span> or <span>&ensp;</span></td></tr>_x000D_
<tr><td>em space:</td><td> <span>&#8195;</span> or <span>&emsp;</span></td></tr>_x000D_
<tr><td>3-per-em space:</td><td> <span>&#8196;</span> or <span>&emsp13;</span></td></tr>_x000D_
<tr><td>4-per-em space:</td><td> <span>&#8197;</span> or <span>&emsp14;</span></td></tr>_x000D_
<tr><td>6-per-em space:</td><td> <span>&#8198;</span></td></tr>_x000D_
<tr><td>figure space:</td><td> <span>&#8199;</span> or <span>&numsp;</span></td></tr>_x000D_
<tr><td>punctuation space:</td><td> <span>&#8200;</span> or <span>&puncsp;</td></tr>_x000D_
<tr><td>thin space:</td><td> <span>&#8201;</span> or <span>&thinsp;</span></td></tr>_x000D_
<tr><td>hair space:</td><td> <span>&#8202;</span> or <span>&hairsp;</span></td></tr>_x000D_

How to change the value of ${user} variable used in Eclipse templates

This is the file we're all looking for (inside your Eclipse workspace):


You will find an @author tag with the name you want to change. Restart Eclipse and it will work.

For accents you have to use the Unicode format (e.g. '\u00E1' for á).

You can also modify the 'ini' file as prior answers suggest or set the user name var for a global solution. Or override the @author tag in the Preferences menu for a local solution. Those are both valid solutions to this problem.

But if you're looking for 'that' author name that is bothering most of us, is in that file.

How to find longest string in the table column data


Simple logical operators in Bash

if ([ $NUM1 == 1 ] || [ $NUM2 == 1 ]) && [ -z "$STR" ]
    echo STR is empty but should have a value.

method in class cannot be applied to given types

The generateNumbers(int[] numbers) function definition has arguments (int[] numbers)that expects an array of integers. However, in the main, generateNumbers(); doesn't have any arguments.

To resolve it, simply add an array of numbers to the arguments while calling thegenerateNumbers() function in the main.

Sending email with gmail smtp with codeigniter email library

Change it to the following:

$ci = get_instance();
$config['protocol'] = "smtp";
$config['smtp_host'] = "ssl://";
$config['smtp_port'] = "465";
$config['smtp_user'] = "[email protected]"; 
$config['smtp_pass'] = "yourpassword";
$config['charset'] = "utf-8";
$config['mailtype'] = "html";
$config['newline'] = "\r\n";


$ci->email->from('[email protected]', 'Blabla');
$list = array('[email protected]');
$this->email->reply_to('[email protected]', 'Explendid Videos');
$ci->email->subject('This is an email test');
$ci->email->message('It is working. Great!');

How do you create a REST client for Java?

I am currently using I like their simplicity and the way examples are shown, but mostly I was sold when I read:

What are the dependencies?

None. The goal of this library is to be a single class class with some inner static classes. The test project does require Jetty in order to test requests against an actual HTTP server implementation.

which sorted out some problems on a java 1.6 project. As for decoding json into objects gson is just invincible :)

Tab separated values in awk


awk -v FS='\t' -v OFS='\t' ...

Example from one of my scripts.

I use the FS and OFS variables to manipulate BIND zone files, which are tab delimited:

awk -v FS='\t' -v OFS='\t' \
    -v record_type=$record_type \
    -v hostname=$hostname \
    -v ip_address=$ip_address '
$1==hostname && $3==record_type {$4=ip_address}
' $zone_file > $temp

This is a clean and easy to read way to do this.

How to distinguish between left and right mouse click with jQuery

There are a lot of very good answers, but I just want to touch on one major difference between IE9 and IE < 9 when using event.button.

According to the old Microsoft specification for event.button the codes differ from the ones used by W3C. W3C considers only 3 cases:

  1. Left mouse button is clicked - event.button === 1
  2. Right mouse button is clicked - event.button === 3
  3. Middle mouse button is clicked - event.button === 2

In older Internet Explorers however Microsoft are flipping a bit for the pressed button and there are 8 cases:

  1. No button is clicked - event.button === 0 or 000
  2. Left button is clicked - event.button === 1 or 001
  3. Right button is clicked - event.button === 2 or 010
  4. Left and right buttons are clicked - event.button === 3 or 011
  5. Middle button is clicked - event.button === 4 or 100
  6. Middle and left buttons are clicked - event.button === 5 or 101
  7. Middle and right buttons are clicked - event.button === 6 or 110
  8. All 3 buttons are clicked - event.button === 7 or 111

Despite the fact that this is theoretically how it should work, no Internet Explorer has ever supported the cases of two or three buttons simultaneously pressed. I am mentioning it because the W3C standard cannot even theoretically support this.

How can I solve a connection pool problem between ASP.NET and SQL Server?

This is mainly due to the connection not been closed in the application. Use "MinPoolSize" and "MaxPoolSize" in the connection string.

How do I write a Windows batch script to copy the newest file from a directory?

This will open a second cmd.exe window. If you want it to go away, replace the /K with /C.

Obviously, replace new_file_loc with whatever your new file location will be.

@echo off
for /F %%i in ('dir /B /O:-D *.txt') do (
    call :open "%%i"
    exit /B 0
    start "window title" "cmd /K copy %~1 new_file_loc"
exit /B 0

The right way of setting <a href=""> when it's a local file

The href value inside the base tag will become your reference point for all your relative paths and thus override your current directory path value otherwise - the '~' is the root of your site

        <base href="~/" />

How can I send an email through the UNIX mailx command?

echo "Sending emails ..."
NOW=$(date +"%F %H:%M")
echo $NOW  " Running service" >> open_files.log
header=`echo "Service Restarting: " $NOW`

mail -s "$header" [email protected],   \
              [email protected], \ < open_files.log