Programs & Examples On #Svn checkout

Questions regarding SVN checkout operations.

Difference between checkout and export in SVN

As you stated, a checkout includes the .svn directories. Thus it is a working copy and will have the proper information to make commits back (if you have permission). If you do an export you are just taking a copy of the current state of the repository and will not have any way to commit back any changes.

How to git-svn clone the last n revisions from a Subversion repository?

You've already discovered the simplest way to specify a shallow clone in Git-SVN, by specifying the SVN revision number that you want to start your clone at ( -r$REV:HEAD).

For example: git svn clone -s -r1450:HEAD some/svn/repo

Git's data structure is based on pointers in a directed acyclic graph (DAG), which makes it trivial to walk back n commits. But in SVN ( and therefore in Git-SVN) you will have to find the revision number yourself.

SVN checkout the contents of a folder, not the folder itself

svn co svn://path destination

To specify current directory, use a "." for your destination directory:

svn checkout file:///home/landonwinters/svn/waterproject/trunk .

How can I get the full/absolute URL (with domain) in Django?

If you can't get access to request then you can't use get_current_site(request) as recommended in some solutions here. You can use a combination of the native Sites framework and get_absolute_url instead. Set up at least one Site in the admin, make sure your model has a get_absolute_url() method, then:

>>> from django.contrib.sites.models import Site
>>> domain = Site.objects.get_current().domain
>>> obj = MyModel.objects.get(id=3)
>>> path = obj.get_absolute_url()

>>> url = 'http://{domain}{path}'.format(domain=domain, path=path)
>>> print(url)

How can I easily switch between PHP versions on Mac OSX?

If you install PHP with homebrew, you can switch between versions very easily. Say you want php56 to point to Version 5.6.17, you just do:

brew switch php56 5.6.17

Jquery/Ajax call with timer

If you want to set something on a timer, you can use JavaScript's setTimeout or setInterval methods:

setTimeout ( expression, timeout );
setInterval ( expression, interval );

Where expression is a function and timeout and interval are integers in milliseconds. setTimeout runs the timer once and runs the expression once whereas setInterval will run the expression every time the interval passes.

So in your case it would work something like this:

setInterval(function() {
    //call $.ajax here
}, 5000); //5 seconds

As far as the Ajax goes, see jQuery's ajax() method. If you run an interval, there is nothing stopping you from calling the same ajax() from other places in your code.

If what you want is for an interval to run every 30 seconds until a user initiates a form submission...and then create a new interval after that, that is also possible:

setInterval() returns an integer which is the ID of the interval.

var id = setInterval(function() {
    //call $.ajax here
}, 30000); // 30 seconds

If you store that ID in a variable, you can then call clearInterval(id) which will stop the progression.

Then you can reinstantiate the setInterval() call after you've completed your ajax form submission.

How do you fix a MySQL "Incorrect key file" error when you can't repair the table?

You must change the location of MySQL's temporary folder which is '/tmp' in most cases to a location with a bigger disk space. Change it in MySQL's config file.

Basically your server is running out of disk space where /tmp is located.

Breaking a list into multiple columns in Latex

Using the multicol package and embedding your list in a multicols environment does what you want:


    \item a
    \item b
    \item c
    \item d
    \item e
    \item f

How to remove outliers from a dataset


z <- df[df$x > quantile(df$x, .25) - 1.5*IQR(df$x) & 
        df$x < quantile(df$x, .75) + 1.5*IQR(df$x), ] #rows

accomplish this task quite easily?

How can I convert an image into Base64 string using JavaScript?

You could use FileAPI, but it's pretty much unsupported.

How to do vlookup and fill down (like in Excel) in R?

Solution #2 of @Ben's answer is not reproducible in other more generic examples. It happens to give the correct lookup in the example because the unique HouseType in houses appear in increasing order. Try this:

hous <- read.table(header = TRUE,   stringsAsFactors = FALSE,   text="HouseType HouseTypeNo
  Semi            1
  ECIIsHome       17
  Single          2
  Row             3
  Single          2
  Apartment       4
  Apartment       4
  Row             3")

largetable <- data.frame(HouseType = as.character(sample(unique(hous$HouseType), 1000, replace = TRUE)), stringsAsFactors = FALSE)
lookup <- unique(hous)

Bens solution#2 gives

housenames <- as.numeric(1:length(unique(hous$HouseType)))
names(housenames) <- unique(hous$HouseType)
base2 <- data.frame(HouseType = largetable$HouseType,
                    HouseTypeNo = (housenames[largetable$HouseType]))

which when

unique(base2$HouseTypeNo[ base2$HouseType=="ECIIsHome" ])
[1] 2

when the correct answer is 17 from the lookup table

The correct way to do it is

 hous <- read.table(header = TRUE,   stringsAsFactors = FALSE,   text="HouseType HouseTypeNo
      Semi            1
      ECIIsHome       17
      Single          2
      Row             3
      Single          2
      Apartment       4
      Apartment       4
      Row             3")

largetable <- data.frame(HouseType = as.character(sample(unique(hous$HouseType), 1000, replace = TRUE)), stringsAsFactors = FALSE)

housenames <- tapply(hous$HouseTypeNo, hous$HouseType, unique)
base2 <- data.frame(HouseType = largetable$HouseType,
  HouseTypeNo = (housenames[largetable$HouseType]))

Now the lookups are performed correctly

unique(base2$HouseTypeNo[ base2$HouseType=="ECIIsHome" ])

I tried to edit Bens answer but it gets rejected for reasons I cannot understand.

What do \t and \b do?

\t is the tab character, and is doing exactly what you're anticipating based on the action of \b - it goes to the next tab stop, then gets decremented, and then goes to the next tab stop (which is in this case the same tab stop, because of the \b.

HttpServletRequest to complete URL

You can write a simple one liner with a ternary and if you make use of the builder pattern of the StringBuffer from .getRequestURL():

private String getUrlWithQueryParms(final HttpServletRequest request) { 
    return request.getQueryString() == null ? request.getRequestURL().toString() :

But that is just syntactic sugar.

Get all table names of a particular database by SQL query?

Yes oracle is :

select * from user_tables

That is if you only want objects owned by the logged in user/schema otherwise you can use all_tables or dba_tables which includes system tables.

Simplest way to detect keypresses in javascript

Use event.key and modern JS!

No number codes anymore. You can use "Enter", "ArrowLeft", "r", or any key name directly, making your code far more readable.

NOTE: The old alternatives (.keyCode and .which) are Deprecated.

document.addEventListener("keypress", function onEvent(event) {
    if (event.key === "ArrowLeft") {
        // Move Left
    else if (event.key === "Enter") {
        // Open Menu...

Mozilla Docs

Supported Browsers

ScalaTest in sbt: is there a way to run a single test without tags?

Here's the Scalatest page on using the runner and the extended discussion on the -t and -z options.

This post shows what commands work for a test file that uses FunSpec.

Here's the test file:

package com.github.mrpowers.scalatest.example

import org.scalatest.FunSpec

class CardiBSpec extends FunSpec {

  describe("realName") {

    it("returns her birth name") {
      assert(CardiB.realName() === "Belcalis Almanzar")


  describe("iLike") {

    it("works with a single argument") {
      assert(CardiB.iLike("dollars") === "I like dollars")

    it("works with multiple arguments") {
      assert(CardiB.iLike("dollars", "diamonds") === "I like dollars, diamonds")

    it("throws an error if an integer argument is supplied") {

    it("does not compile with integer arguments") {
      assertDoesNotCompile("""CardiB.iLike(1, 2, 3)""")



This command runs the four tests in the iLike describe block (from the SBT command line):

testOnly *CardiBSpec -- -z iLike

You can also use quotation marks, so this will also work:

testOnly *CardiBSpec -- -z "iLike"

This will run a single test:

testOnly *CardiBSpec -- -z "works with multiple arguments"

This will run the two tests that start with "works with":

testOnly *CardiBSpec -- -z "works with"

I can't get the -t option to run any tests in the CardiBSpec file. This command doesn't run any tests:

testOnly *CardiBSpec -- -t "works with multiple arguments"

Looks like the -t option works when tests aren't nested in describe blocks. Let's take a look at another test file:

class CalculatorSpec extends FunSpec {
  it("adds two numbers") {
    assert(Calculator.addNumbers(3, 4) === 7)

-t can be used to run the single test:

testOnly *CalculatorSpec -- -t "adds two numbers"

-z can also be used to run the single test:

testOnly *CalculatorSpec -- -z "adds two numbers"

See this repo if you'd like to run these examples. You can find more info on running tests here.

Python: 'ModuleNotFoundError' when trying to import module from imported package

For me when I created a file and saved it as python file, I was getting this error during importing. I had to create a filename with the type ".py" , like and then save it as a python file. post trying to import the file worked for me.

High-precision clock in Python

If Python 3 is an option, you have two choices:

  • time.perf_counter which always use the most accurate clock on your platform. It does include time spent outside of the process.
  • time.process_time which returns the CPU time. It does NOT include time spent outside of the process.

The difference between the two can be shown with:

from time import (



Which outputs:


VBA Date as integer

Public SUB test()
    Dim mdate As Date
    mdate = now()
    MsgBox (Round(CDbl(mdate), 0))

Horizontal swipe slider with jQuery and touch devices support?

In my opinion iosSlider is amazing. It works in almost any device and it is well documented. It's free for personal usage, but for commercial sites license costs $20.

Also a great option is touchCarousel or RoyalSlider from same author. These two have everything you'll need, but also not free and have a price of $10-12

Skipping Incompatible Libraries at compile

That message isn't actually an error - it's just a warning that the file in question isn't of the right architecture (e.g. 32-bit vs 64-bit, wrong CPU architecture). The linker will keep looking for a library of the right type.

Of course, if you're also getting an error along the lines of can't find lPI-Http then you have a problem :-)

It's hard to suggest what the exact remedy will be without knowing the details of your build system and makefiles, but here are a couple of shots in the dark:

  1. Just to check: usually you would add flags to CFLAGS rather than CTAGS - are you sure this is correct? (What you have may be correct - this will depend on your build system!)
  2. Often the flag needs to be passed to the linker too - so you may also need to modify LDFLAGS

If that doesn't help - can you post the full error output, plus the actual command (e.g. gcc foo.c -m32 -Dxxx etc) that was being executed?

Select first 4 rows of a data.frame in R

If you have less than 4 rows, you can use the head function ( head(data, 4) or head(data, n=4)) and it works like a charm. But, assume we have the following dataset with 15 rows

>data <- data <- read.csv("./data.csv", sep = ";", header=TRUE)

 LungCap Age Height Smoke Gender Caesarean
1    6.475   6   62.1    no   male        no
2   10.125  18   74.7   yes female        no
3    9.550  16   69.7    no female       yes
4   11.125  14   71.0    no   male        no
5    4.800   5   56.9    no   male        no
6    6.225  11   58.7    no female        no
7    4.950   8   63.3    no   male       yes
8    7.325  11   70.4    no  male         no
9    8.875  15   70.5    no   male        no
10   6.800  11   59.2    no   male        no
11   6.900  12   59.3    no   male        no
12   6.100  13   59.4    no   male        no
13   6.110  14   59.5    no   male        no
14   6.120  15   59.6    no   male        no
15   6.130  16   59.7    no   male        no

Let's say, you want to select the first 10 rows. The easiest way to do it would be data[1:10, ].

> data[1:10,]
   LungCap Age Height Smoke Gender Caesarean
1    6.475   6   62.1    no   male        no
2   10.125  18   74.7   yes female        no
3    9.550  16   69.7    no female       yes
4   11.125  14   71.0    no   male        no
5    4.800   5   56.9    no   male        no
6    6.225  11   58.7    no female        no
7    4.950   8   63.3    no   male       yes
8    7.325  11   70.4    no  male         no
9    8.875  15   70.5    no   male        no
10   6.800  11   59.2    no   male        no

However, let's say you try to retrieve the first 19 rows and see the what happens - you will have missing values

> data[1:19,]
     LungCap Age Height Smoke Gender Caesarean
1      6.475   6   62.1    no   male        no
2     10.125  18   74.7   yes female        no
3      9.550  16   69.7    no female       yes
4     11.125  14   71.0    no   male        no
5      4.800   5   56.9    no   male        no
6      6.225  11   58.7    no female        no
7      4.950   8   63.3    no   male       yes
8      7.325  11   70.4    no  male         no
9      8.875  15   70.5    no   male        no
10     6.800  11   59.2    no   male        no
11     6.900  12   59.3    no   male        no
12     6.100  13   59.4    no   male        no
13     6.110  14   59.5    no   male        no
14     6.120  15   59.6    no   male        no
15     6.130  16   59.7    no   male        no
NA        NA  NA     NA  <NA>   <NA>      <NA>
NA.1      NA  NA     NA  <NA>   <NA>      <NA>
NA.2      NA  NA     NA  <NA>   <NA>      <NA>
NA.3      NA  NA     NA  <NA>   <NA>      <NA>

and with the head() function,

> head(data, 19) # or head(data, n=19)
   LungCap Age Height Smoke Gender Caesarean
1    6.475   6   62.1    no   male        no
2   10.125  18   74.7   yes female        no
3    9.550  16   69.7    no female       yes
4   11.125  14   71.0    no   male        no
5    4.800   5   56.9    no   male        no
6    6.225  11   58.7    no female        no
7    4.950   8   63.3    no   male       yes
8    7.325  11   70.4    no  male         no
9    8.875  15   70.5    no   male        no
10   6.800  11   59.2    no   male        no
11   6.900  12   59.3    no   male        no
12   6.100  13   59.4    no   male        no
13   6.110  14   59.5    no   male        no
14   6.120  15   59.6    no   male        no
15   6.130  16   59.7    no   male        no

Hope this help!

Postgresql 9.2 pg_dump version mismatch

For Macs with Homebrew. I had this problem when fetching the db from Heroku. I've fixed it just running:

brew upgrade postgresql

How to search JSON data in MySQL?

For Mysql8->


SELECT properties, properties->"$.price" FROM book where isbn='978-9730228236' and  JSON_EXTRACT(properties, "$.price") > 400;


mysql> select * from book\G;
*************************** 1. row ***************************
id: 1
isbn: 978-9730228236
properties: {"price": 44.99, "title": "High-Performance Java Persistence", "author": "Vlad Mihalcea", "publisher": "Amazon"}
1 row in set (0.00 sec)

Wheel file installation

You normally use a tool like pip to install wheels. Leave it to the tool to discover and download the file if this is for a project hosted on PyPI.

For this to work, you do need to install the wheel package:

pip install wheel

You can then tell pip to install the project (and it'll download the wheel if available), or the wheel file directly:

pip install project_name  # discover, download and install
pip install wheel_file.whl  # directly install the wheel

The wheel module, once installed, also is runnable from the command line, you can use this to install already-downloaded wheels:

python -m wheel install wheel_file.whl

Also see the wheel project documentation.

How to resize array in C++?

  1. Use std::vector or
  2. Write your own method. Allocate chunk of memory using new. with that memory you can expand till the limit of memory chunk.

MySQL Orderby a number, Nulls last

To achieve following result :

1, 2, 3, 4, NULL, NULL, NULL.

USE syntax, place -(minus sign) before field name and use inverse order_type(Like: If you want order by ASC order then use DESC or if you want DESC order then use ASC)

SELECT * FROM tablename WHERE visible=1 ORDER BY -position DESC

System.MissingMethodException: Method not found?

I resolved this issue by installing the correct .NET Framework version on the server. The website was running under version 4.0 and the assembly it was calling to was compiled for 4.5. After installation of .NET Framework 4.5 and upgrading the website to 4.5, all works fine.

Output to the same line overwriting previous output?

to overwiting the previous line in python all wath you need is to add end='\r' to the print function, test this example:

import time
for j in range(1,5):
   print('waiting : '+j, end='\r')

Auto-indent spaces with C in vim?

Simply run:

user@host:~ $ echo set autoindent >> .vimrc

Split string in Lua?

If you are splitting a string in Lua, you should try the string.gmatch() or string.sub() methods. Use the string.sub() method if you know the index you wish to split the string at, or use the string.gmatch() if you will parse the string to find the location to split the string at.

Example using string.gmatch() from Lua 5.1 Reference Manual:

 t = {}
 s = "from=world, to=Lua"
 for k, v in string.gmatch(s, "(%w+)=(%w+)") do
   t[k] = v

Getting index value on razor foreach

All of the above answers require logic in the view. Views should be dumb and contain as little logic as possible. Why not create properties in your view model that correspond to position in the list eg:

public int Position {get; set}

In your view model builder you set the position 1 through 4.

BUT .. there is even a cleaner way. Why not make the CSS class a property of your view model? So instead of the switch statement in your partial, you would just do this:

<div class="@Model.GridCSS">

Move the switch statement to your view model builder and populate the CSS class there.

Unable to show a Git tree in terminal

A solution is to create an Alias in your .gitconfig and call it easily:

    tree = log --graph --decorate --pretty=oneline --abbrev-commit

And when you call it next time, you'll use:

git tree

To put it in your ~/.gitconfig without having to edit it, you can do:

git config --global alias.tree "log --graph --decorate --pretty=oneline --abbrev-commit"  

(If you don't use the --global it will put it in the .git/config of your current repo.)

XPath OR operator for different nodes

All title nodes with zipcode or book node as parent:

Version 1:


Version 2:


Version 3: (results are sorted based on source data rather than the order of book then zipcode)

//title[../../../*[book or magazine] or ../../../../*[city/zipcode]]

or - used within true/false - a Boolean operator in xpath

| - a Union operator in xpath that appends the query to the right of the operator to the result set from the left query.

How to add click event to a iframe with JQuery

You can solve it very easily, just wrap that iframe in wrapper, and track clicks on it.

Like this:

<div id="iframe_id_wrapper"> <iframe id="iframe_id" src=""></iframe> </div>

And disable pointer events on iframe itself.

#iframe_id { pointer-events: none; }

After this changes your code will work like expected.

$('#iframe_id_wrapper').click(function() { //run function that records clicks });

WRONGTYPE Operation against a key holding the wrong kind of value php

I faced this issue when trying to set something to redis. The problem was that I previously used "set" method to set data with a certain key, like

$redis->set('persons', $persons)

Later I decided to change to "hSet" method, and I tried it this way

foreach($persons as $person){
    $redis->hSet('persons', $person->id, $person);

Then I got the aforementioned error. So, what I had to do is to go to redis-cli and manually delete "persons" entry with

del persons

It simply couldn't write different data structure under existing key, so I had to delete the entry and hSet then.

Execute Insert command and return inserted Id in Sql

SQL Server stored procedure:

    @na varchar(50),
    @occ varchar(50),

    INSERT INTO Mem_Basic
    VALUES (@na, @occ)


C# code:

public int CreateNewMember(string Mem_NA, string Mem_Occ )
    // values 0 --> -99 are SQL reserved.
    int new_MEM_BASIC_ID = -1971;   
    SqlConnection SQLconn = new SqlConnection(Config.ConnectionString);
    SqlCommand cmd = new SqlCommand("INS_MEM_BASIC", SQLconn);

    cmd.CommandType = CommandType.StoredProcedure;

    SqlParameter outPutVal = new SqlParameter("@New_MEM_BASIC_ID", SqlDbType.Int);

    outPutVal.Direction = ParameterDirection.Output;
    cmd.Parameters.Add("@na", SqlDbType.Int).Value = Mem_NA;
    cmd.Parameters.Add("@occ", SqlDbType.Int).Value = Mem_Occ;


    if (outPutVal.Value != DBNull.Value) new_MEM_BASIC_ID = Convert.ToInt32(outPutVal.Value);
        return new_MEM_BASIC_ID;

I hope these will help to you ....

You can also use this if you want ...

public int CreateNewMember(string Mem_NA, string Mem_Occ )
    using (SqlConnection con=new SqlConnection(Config.ConnectionString))
        int newID;
        var cmd = "INSERT INTO Mem_Basic(Mem_Na,Mem_Occ) VALUES(@na,@occ);SELECT CAST(scope_identity() AS int)";

        using(SqlCommand cmd=new SqlCommand(cmd, con))
            cmd.Parameters.AddWithValue("@na", Mem_NA);
            cmd.Parameters.AddWithValue("@occ", Mem_Occ);

            newID = (int)insertCommand.ExecuteScalar();

            if (con.State == System.Data.ConnectionState.Open) con.Close();
                return newID;

Why do symbols like apostrophes and hyphens get replaced with black diamonds on my website?

You need to change your text to 'Plain text' before pasting into the HTML document. This looks like an error I've had before by pasting straight from MS word.

MS word and other rich text editors often place hidden or invalid chars into your code. Try using &mdash; for your dashes, or &rsquo; for apostrophes (etc), to eliminate the need for relying on your char encoding.

How to ensure that there is a delay before a service is started in systemd?

You can create a .timer systemd unit file to control the execution of your .service unit file.

So for example, to wait for 1 minute after boot-up before starting your foo.service, create a foo.timer file in the same directory with the contents:


It is important that the service is disabled (so it doesn't start at boot), and the timer enabled, for all this to work (thanks to user tride for this):

systemctl disable foo.service
systemctl enable foo.timer

You can find quite a few more options and all information needed here:

Vue.js get selected option on @change

The changed value will be in

const app = new Vue({_x000D_
  el: "#app",_x000D_
  data: function() {_x000D_
    return {_x000D_
      message: "Vue"_x000D_
  methods: {_x000D_
    onChange(event) {_x000D_
<script src="[email protected]/dist/vue.js"></script>_x000D_
<div id="app">_x000D_
  <select name="LeaveType" @change="onChange" class="form-control">_x000D_
   <option value="1">Annual Leave/ Off-Day</option>_x000D_
   <option value="2">On Demand Leave</option>_x000D_

Convert PDF to image with high resolution

Please take note before down voting, this solution is for Gimp using a graphical interface, and not for ImageMagick using a command line, but it worked perfectly fine for me as an alternative, and that is why I found it needful to share here.

Follow these simple steps to extract images in any format from PDF documents

  1. Download GIMP Image Manipulation Program
  2. Open the Program after installation
  3. Open the PDF document that you want to extract Images
  4. Select only the pages of the PDF document that you would want to extract images from. N/B: If you need only the cover images, select only the first page.
  5. Click open after selecting the pages that you want to extract images from
  6. Click on File menu when GIMP when the pages open
  7. Select Export as in the File menu
  8. Select your preferred file type by extension (say png) below the dialog box that pops up.
  9. Click on Export to export your image to your desired location.
  10. You can then check your file explorer for the exported image.

That's all.

I hope this helps

How do I upload a file with the JS fetch API?

To submit a single file, you can simply use the File object from the input's .files array directly as the value of body: in your fetch() initializer:

const myInput = document.getElementById('my-input');

// Later, perhaps in a form 'submit' handler or the input's 'change' handler:
fetch('', {
  method: 'POST',
  body: myInput.files[0],

This works because File inherits from Blob, and Blob is one of the permissible BodyInit types defined in the Fetch Standard.

How to make an authenticated web request in Powershell?

For those that need Powershell to return additional information like the Http StatusCode, here's an example. Included are the two most likely ways to pass in credentials.

Its a slightly modified version of this SO answer:
How to obtain numeric HTTP status codes in PowerShell

$req = [system.Net.WebRequest]::Create($url)
# method 1 $req.UseDefaultCredentials = $true
# method 2 $req.Credentials = New-Object System.Net.NetworkCredential($username, $pwd, $domain); 
    $res = $req.GetResponse()
catch [System.Net.WebException]
    $res = $_.Exception.Response

$int = [int]$res.StatusCode
$status = $res.StatusCode
return "$int $status"

ECMAScript 6 class destructor

Is there such a thing as destructors for ECMAScript 6?

No. EcmaScript 6 does not specify any garbage collection semantics at all[1], so there is nothing like a "destruction" either.

If I register some of my object's methods as event listeners in the constructor, I want to remove them when my object is deleted

A destructor wouldn't even help you here. It's the event listeners themselves that still reference your object, so it would not be able to get garbage-collected before they are unregistered.
What you are actually looking for is a method of registering listeners without marking them as live root objects. (Ask your local eventsource manufacturer for such a feature).

1): Well, there is a beginning with the specification of WeakMap and WeakSet objects. However, true weak references are still in the pipeline [1][2].

When adding a Javascript library, Chrome complains about a missing source map, why?

When it s annoying with warnings like: DevTools failed to load SourceMap: Could not load content for http://********/bootstrap/4.5.0/css/ HTTP error: status code 404, net::ERR_HTTP_RESPONSE_CODE_FAILURE

Follow this path and remove that tricky /*# */ in bootstrap.min.css

Python [Errno 98] Address already in use

First of all find the python process ID using this command

ps -fA | grep python

You will get a pid number by naming of your python process on second column

Then kill the process using this command

kill -9 pid

Material Design not styling alert dialogs

You can consider this project:

It can provide you material theme alert dialogs almost the same as lollipop's. Compatible with Android 2.1.

is there a function in lodash to replace matched item

var arr= [{id: 1, name: "Person 1"}, {id:2, name:"Person 2"}];
var index = _.findIndex(arr, {id: 1});
arr[index] = {id: 100, name: 'xyz'}

Storing a Key Value Array into a compact JSON string

If the logic parsing this knows that {"key": "slide0001.html", "value": "Looking Ahead"} is a key/value pair, then you could transform it in an array and hold a few constants specifying which index maps to which key.

For example:

var data = ["slide0001.html", "Looking Ahead"];

var C_KEY = 0;
var C_VALUE = 1;

var value = data[C_VALUE];

So, now, your data can be:

    ["slide0001.html", "Looking Ahead"],
    ["slide0008.html", "Forecast"],
    ["slide0021.html", "Summary"]

If your parsing logic doesn't know ahead of time about the structure of the data, you can add some metadata to describe it. For example:

{ meta: { keys: [ "key", "value" ] },
  data: [
    ["slide0001.html", "Looking Ahead"],
    ["slide0008.html", "Forecast"],
    ["slide0021.html", "Summary"]

... which would then be handled by the parser.

Magento: Set LIMIT on collection

The way to do was looking at the code in code/core/Mage/Catalog/Model/Resource/Category/Flat/Collection.php at line 380 in Magento 1.7.2 on the function setPage($pageNum, $pageSize)

 $collection = Mage::getModel('model')
     ->setCurPage(2) // 2nd page
     ->setPageSize(10); // 10 elements per pages

I hope this will help someone.

Setting default permissions for newly created files and sub-directories under a directory in Linux?

It's ugly, but you can use the setfacl command to achieve exactly what you want.

On a Solaris machine, I have a file that contains the acls for users and groups. Unfortunately, you have to list all of the users (at least I couldn't find a way to make this work otherwise):


Name the file acl.lst and fill in your real user names instead of user_X.

You can now set those acls on your directory by issuing the following command:

setfacl -f acl.lst /your/dir/here

How can I get an int from stdio in C?

The typical way is with scanf:

int input_value;

scanf("%d", &input_value);

In most cases, however, you want to check whether your attempt at reading input succeeded. scanf returns the number of items it successfully converted, so you typically want to compare the return value against the number of items you expected to read. In this case you're expecting to read one item, so:

if (scanf("%d", &input_value) == 1)
    // it succeeded
    // it failed

Of course, the same is true of all the scanf family (sscanf, fscanf and so on).

Docker error response from daemon: "Conflict ... already in use by container"

It looks like a container with the name qgis-desktop-2-4 already exists in the system. You can check the output of the below command to confirm if it indeed exists:

$ docker ps -a

The last column in the above command's output is for names.

If the container exists, remove it using:

$ docker rm qgis-desktop-2-4

Or forcefully using,

$ docker rm -f qgis-desktop-2-4

And then try creating a new container.

php refresh current page?

$_SERVER['REQUEST_URI'] should work.

AndroidStudio SDK directory does not exists

Create or edit file under android directory

For window path should be like this

sdk.dir = C\:\\Users\\user name\\AppData\\Local\\Android\\sdk

For linux system path should be like this

sdk.dir = /home/user name/Android/Sdk/

Simple linked list in C++

Both functions are wrong. First of all function initNode has a confusing name. It should be named as for example initList and should not do the task of addNode. That is, it should not add a value to the list.

In fact, there is not any sense in function initNode, because the initialization of the list can be done when the head is defined:

Node *head = nullptr;


Node *head = NULL;

So you can exclude function initNode from your design of the list.

Also in your code there is no need to specify the elaborated type name for the structure Node that is to specify keyword struct before name Node.

Function addNode shall change the original value of head. In your function realization you change only the copy of head passed as argument to the function.

The function could look as:

void addNode(Node **head, int n)
    Node *NewNode = new Node {n, *head};
    *head = NewNode;

Or if your compiler does not support the new syntax of initialization then you could write

void addNode(Node **head, int n)
    Node *NewNode = new Node;
    NewNode->x = n;
    NewNode->next = *head;
    *head = NewNode;

Or instead of using a pointer to pointer you could use a reference to pointer to Node. For example,

void addNode(Node * &head, int n)
    Node *NewNode = new Node {n, head};
    head = NewNode;

Or you could return an updated head from the function:

Node * addNode(Node *head, int n)
    Node *NewNode = new Node {n, head};
    head = NewNode;
    return head;

And in main write:

head = addNode(head, 5);

ReDim Preserve to a Multi-Dimensional Array in Visual Basic 6

I know this is a bit old but I think there might be a much simpler solution that requires no additional coding:

Instead of transposing, redimming and transposing again, and if we talk about a two dimensional array, why not just store the values transposed to begin with. In that case redim preserve actually increases the right (second) dimension from the start. Or in other words, to visualise it, why not store in two rows instead of two columns if only the nr of columns can be increased with redim preserve.

the indexes would than be 00-01, 01-11, 02-12, 03-13, 04-14, 05-15 ... 0 25-1 25 etcetera instead of 00-01, 10-11, 20-21, 30-31, 40-41 etcetera.

As long as there is only one dimension that needs to be redimmed-preserved the approach would still work: just put that dimension last.

As only the second (or last) dimension can be preserved while redimming, one could maybe argue that this is how arrays are supposed to be used to begin with. I have not seen this solution anywhere so maybe I'm overlooking something?

(Posted earlier on similar question regarding two dimensions, extended answer here for more dimensions)

Get driving directions using Google Maps API v2

You can also try the following project that aims to help use that api. It's here:

How it works, definitly simply:

public class MainActivity extends ActionBarActivity implements DCACallBack{
 * Get the Google Direction between mDevice location and the touched location using the     Walk
 * @param point
private void getDirections(LatLng point) {
     GDirectionsApiUtils.getDirection(this, mDeviceLatlong, point,     GDirectionsApiUtils.MODE_WALKING);

 * The callback
 * When the direction is built from the google server and parsed, this method is called and give you the expected direction
public void onDirectionLoaded(List<GDirection> directions) {        
    // Display the direction or use the DirectionsApiUtils
    for(GDirection direction:directions) {
        Log.e("MainActivity", "onDirectionLoaded : Draw GDirections Called with path " + directions);
        GDirectionsApiUtils.drawGDirection(direction, mMap);

Java/ JUnit - AssertTrue vs AssertFalse

assertTrue will fail if the second parameter evaluates to false (in other words, it ensures that the value is true). assertFalse does the opposite.

assertTrue("This will succeed.", true);
assertTrue("This will fail!", false);

assertFalse("This will succeed.", false);
assertFalse("This will fail!", true);

As with many other things, the best way to become familiar with these methods is to just experiment :-).

Set Encoding of File to UTF8 With BOM in Sublime Text 3

Into Preferences > Settings - Users
File : Preferences.sublime-settings

Write this :

"show_encoding" : true,

It's explain on the release note date 17 December 2013. Build 3059. Official site Sublime Text 3

How to downgrade to older version of Gradle

got it resolved:

uninstall the entire android studio

uninstalling android with the following commands

rm -Rf /Applications/Android\  
rm -Rf ~/Library/Preferences/AndroidStudio*  
rm -Rf ~/Library/Preferences/*  
rm -Rf ~/Library/Preferences/*  
rm -Rf ~/Library/Application\ Support/AndroidStudio*  
rm -Rf ~/Library/Logs/AndroidStudio*  
rm -Rf ~/Library/Caches/AndroidStudio*  
rm -Rf ~/.AndroidStudio*  
rm -Rf ~/.gradle  
rm -Rf ~/.android  
rm -Rf ~/Library/Android*  
rm -Rf /usr/local/var/lib/android-sdk/  
rm -Rf /Users/<username>/.tooling/gradle

Remove your project and clone it again and then goto Gradle Scripts and open and change the below url which ever version you need


How to align two divs side by side using the float, clear, and overflow elements with a fixed position div/

This answer may have to be modified depending on what you were trying to achieve with position: fixed;. If all you want is two columns side by side then do the following:

I floated both columns to the left.

Note: I added min-height to each column for illustrative purposes and I simplified your CSS.

body {_x000D_
  background-color: #444;_x000D_
  margin: 0;_x000D_
#wrapper {_x000D_
  width: 1005px;_x000D_
  margin: 0 auto;_x000D_
#rightcolumn {_x000D_
  border: 1px solid white;_x000D_
  float: left;_x000D_
  min-height: 450px;_x000D_
  color: white;_x000D_
#leftcolumn {_x000D_
  width: 250px;_x000D_
  background-color: #111;_x000D_
#rightcolumn {_x000D_
  width: 750px;_x000D_
  background-color: #777;_x000D_
<div id="wrapper">_x000D_
  <div id="leftcolumn">_x000D_
  <div id="rightcolumn">_x000D_

If you would like the left column to stay in place as you scroll do the following:

Here we float the right column to the right while adding position: relative; to #wrapper and position: fixed; to #leftcolumn.

Note: I again used min-height for illustrative purposes and can be removed for your needs.

body {_x000D_
  background-color: #444;_x000D_
  margin: 0;_x000D_
#wrapper {_x000D_
  width: 1005px;_x000D_
  margin: 0 auto;_x000D_
  position: relative;_x000D_
#rightcolumn {_x000D_
  border: 1px solid white;_x000D_
  min-height: 750px;_x000D_
  color: white;_x000D_
#leftcolumn {_x000D_
  width: 250px;_x000D_
  background-color: #111;_x000D_
  min-height: 100px;_x000D_
  position: fixed;_x000D_
#rightcolumn {_x000D_
  width: 750px;_x000D_
  background-color: #777;_x000D_
  float: right;_x000D_
<div id="wrapper">_x000D_
  <div id="leftcolumn">_x000D_
  <div id="rightcolumn">_x000D_

How to find if directory exists in Python

So close! os.path.isdir returns True if you pass in the name of a directory that currently exists. If it doesn't exist or it's not a directory, then it returns False.

Java resource as file

Here is a bit of code from one of my applications... Let me know if it suits your needs. You can use this if you know the file you want to use.

URL defaultImage = ClassA.class.getResource("/packageA/subPackage/image-name.png");
File imageFile = new File(defaultImage.toURI());

Hope that helps.

Is there a Google Sheets formula to put the name of the sheet into a cell?

You have 2 options, and I am not sure if I am a fan of either of them, but that is my opinion. You may feel differently:

Option 1: Force the function to run.

A function in a cell does not run unless it references a cell that has changed. Changing a sheet name does not trigger any functions in the spreadsheet. But we can force the function to run by passing a range to it and whenever an item in that range changes, the function will trigger.

You can use the below script to create a custom function which will retrieve the name:

function mySheetName() {
  var key = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet().getName();
  return key;

and in the cell place the following:


Now if any value in a cell in that passed range changes the script will run. This takes a second to run the script and sets a message in the cell each time any value is changed so this could become annoying very quickly. As already mentioned, it also requires a change in the range to cause it to trigger, so not really helpful on a fairly static file.

Option 2: Use the OnChange Event

While the run time feels better than the above option, and this does not depend on a value changing in the spreadsheet's cells, I do not like this because it forces where the name goes. You could use a Utilities sheet to define this location in various sheets if you wish. Below is the basic idea and may get you started if you like this option.

The OnChange event is triggered when the sheet name is changed. You can make the code below more sophisticated to check for errors, check the sheet ID to only work on a given sheet, etc. The basic code, however, is:

function setSheetName(e) {
  var key = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet().getName();

Once you have saved the code, in the script editor set the Current Project's On Change Trigger to this function. It will write the sheet name to cell K1 on any change event. To set the trigger, select Current project's triggers under the Edit menu.

Cannot perform runtime binding on a null reference, But it is NOT a null reference

My solution to this error was that a copy and paste from another project that had a reference to @Model.Id. This particular page didn't have a model but the error line was so far off from the actual error I about never found it!

What is the maximum number of characters that nvarchar(MAX) will hold?

From char and varchar (Transact-SQL)

varchar [ ( n | max ) ]

Variable-length, non-Unicode character data. n can be a value from 1 through 8,000. max indicates that the maximum storage size is 2^31-1 bytes. The storage size is the actual length of data entered + 2 bytes. The data entered can be 0 characters in length. The ISO synonyms for varchar are char varying or character varying.

Recover SVN password from local cache

Your SVN passwords in Ubuntu (12.04) are in:


However in newer versions they are encrypted, as earlier someone mentioned. To find gnome-keyring passwords, I suggest You to use 'gkeyring' program.

To install it on Ubuntu – add repository :

sudo add-apt-repository ppa:kampka/ppa
sudo apt-get update

Install it:

sudo apt-get install gkeyring

And run as following:

gkeyring --id 15 --output=name,secret

Try different key ids to find pair matching what you are looking for. Thanks to kampka for the soft.

Get IP address of an interface on Linux

In addition to the ioctl() method Filip demonstrated you can use getifaddrs(). There is an example program at the bottom of the man page.

Table variable error: Must declare the scalar variable "@temp"

If you bracket the @ you can use it directly

declare @TEMP table (ID int, Name varchar(max))
insert into @temp values (1,'one'), (2,'two')

WHERE [@TEMP].[ID] = 1

How can I use a custom font in Java?

If you want to use the font to draw with graphics2d or similar, this works:

InputStream stream = ClassLoader.getSystemClassLoader().getResourceAsStream("roboto-bold.ttf")
Font font = Font.createFont(Font.TRUETYPE_FONT, stream).deriveFont(48f)

Use querystring variables in MVC controller

public ActionResult SomeAction(string start, string end)

The framework will map the query string parameters to the method parameters.

php timeout - set_time_limit(0); - don't work

Checkout this, This is from PHP MANUAL, This may help you.

If you're using PHP_CLI SAPI and getting error "Maximum execution time of N seconds exceeded" where N is an integer value, try to call set_time_limit(0) every M seconds or every iteration. For example:



$stmt = $db->query($sql);

while ($row = $stmt->fetchRow()) {
    // your code here


Install psycopg2 on Ubuntu

I prefer using pip in case you are using virtualenv:

  1. apt install libpython2.7 libpython2.7-dev
  2. pip install psycopg2

How can I rebuild indexes and update stats in MySQL innoDB?

To date (mysql 8.0.18) there is no suitable function inside mysql to re-create indexes.
Since mysql 8.0 myisam is slowly phasing into deprecated status, innodb is the current main storage engine.
In most practical cases innodb is the best choice and it's supposed to keep indexes working well.
In most practical cases innodb also does a good job, you do not need to recreate indexes. Almost always.

When it comes to large tables with hundreds of GB data amd rows and a lot of writing the situation changes, indexes can degrade in performance.
In my personal case I've seen performance drop from ~15 minutes for a count(*) using a secondary index to 4300 minutes after 2 months of writing to the table with linear time increase.
After recreating the index the performance goes back to 15 minutes.

To date we have two options to do that:
Innodb doesn't support optimization so in both cases the entire table will be read and re-created.
This means you need the storage for the temporary file and depending on the table a lot of time (I've cases where an optimize takes a week to complete). This will compact the data and rebuild all indexes.
Despite not being officially recommended, I highly recommend the OPTIMIZE process on write-heavy tables up to 100GB in size.

You manually drop the key by name, you manually create it again. In a production environment you'll want to create it first, then drop the old version.
The upside: this can be a lot faster than optimize. The downside: you need to manually create the syntax.
"SHOW CREATE TABLE" can be used to quickly see which indexes are available and how they are called.

1) To just update statistics you can use the already mentioned "ANALYZE TABLE".
2) If you experience performance degradation on write-heavy servers you might need to restart mysql. There are a couple of bugs in current mysql (8.0) that can cause significant slowdown without showing up in error log. Eventually those slowdowns lead to a server crash but it can take weeks or even months to build up to the crash, in this process the server gets slower and slower in responses.
3) If you wish to re-create a large table that takes weeks to complete or fails after hours due to internal data integrity problems you should do a CREATE TABLE LIKE, INSERT INTO SELECT *. then 'atomic RENAME' the tables.
4) If INSERT INTO SELECT * takes hours to days to complete on huge tables you can speed up the process by about 20-30 times using a multi-threaded approach. You "partition" the table into chunks and INSERT INTO SELECT * in parallel.

Best way to store a key=>value array in JavaScript?

Objects inside an array:

var cars = [
        { "id": 1, brand: "Ferrari" }
        , { "id": 2, brand: "Lotus" }
        , { "id": 3, brand: "Lamborghini" }

SELECT with LIMIT in Codeigniter

Try this...

function nationList($limit=null, $start=null) {
    if ($this->session->userdata('language') == "it") {
        $this->db->select(', nation.name_it as name');

    if ($this->session->userdata('language') == "en") {
        $this->db->select(', nation.name_en as name');

    $this->db->order_by("name", "asc");

    if ($limit != '' && $start != '') {
       $this->db->limit($limit, $start);
    $query  = $this->db->get();

    $nation = array();
    foreach ($query->result() as $row) {
        array_push($nation, $row);

    return $nation;     

How large is a DWORD with 32- and 64-bit code?

It is defined as:

typedef unsigned long       DWORD;

However, according to the MSDN:

On 32-bit platforms, long is synonymous with int.

Therefore, DWORD is 32bit on a 32bit operating system. There is a separate define for a 64bit DWORD:

typdef unsigned _int64 DWORD64;

Hope that helps.

determine DB2 text string length

This will grab records with strings (in the fieldName column) that are 10 characters long:

 select * from table where length(fieldName)=10

Convert String to Double - VB

Try looking at Double.TryParse() if you are using .NET 1.1/2.0/3.0/3.5/4.0/4.5

Javascript validation: Block special characters

I think checking keypress events is not completely adequate, as I believe users can copy/paste into input boxes without triggering a keypress.

So onblur is probably somewhat more reliable (but is less immediate).

To truly make sure characters you don't want are not entered into input boxes (or textareas, etc.), I think you will need to

  1. check keypress (if you want to give immediate feedback) and
  2. also check onblur,
  3. as well as validating inputs on the server (which is the only real way to make sure nothing unwanted gets into your data).

The code samples in the other answers will work fine for doing the client-side checks (just don't rely only on checking keypress events), but as was pointed out in the accepted answer, a server-side check is really required.

How can I list all collections in the MongoDB shell?

The following commands on mongoshell are common.

show databases
show collections


show dbs
use mydb

Sometimes it's useful to see all collections as well as the indexes on the collections which are part of the overall namespace:

Here's how you would do that:

db.getCollectionNames().forEach(function(collection) {
    indexes = db[collection].getIndexes();
    print("Indexes for " + collection + ":");

Between the three commands and this snippet, you should be well covered!

Looking for a 'cmake clean' command to clear up CMake output

A solution that I found recently is to combine the out-of-source build concept with a Makefile wrapper.

In my top-level CMakeLists.txt file, I include the following to prevent in-source builds:

    message( FATAL_ERROR "In-source builds not allowed. Please make a new directory (called a build directory) and run CMake from there. You may need to remove CMakeCache.txt." )

Then, I create a top-level Makefile, and include the following:

# -----------------------------------------------------------------------------
# CMake project wrapper Makefile ----------------------------------------------
# -----------------------------------------------------------------------------

SHELL := /bin/bash
RM    := rm -rf
MKDIR := mkdir -p

all: ./build/Makefile
    @ $(MAKE) -C build

    @  ($(MKDIR) build > /dev/null)
    @  (cd build > /dev/null 2>&1 && cmake ..)

    @  ($(MKDIR) build > /dev/null)
    @  (cd build > /dev/null 2>&1 && cmake .. > /dev/null 2>&1)
    @- $(MAKE) --silent -C build clean || true
    @- $(RM) ./build/Makefile
    @- $(RM) ./build/src
    @- $(RM) ./build/test
    @- $(RM) ./build/CMake*
    @- $(RM) ./build/cmake.*
    @- $(RM) ./build/*.cmake
    @- $(RM) ./build/*.txt

ifeq ($(findstring distclean,$(MAKECMDGOALS)),)
    $(MAKECMDGOALS): ./build/Makefile
    @ $(MAKE) -C build $(MAKECMDGOALS)

The default target all is called by typing make, and invokes the target ./build/Makefile.

The first thing the target ./build/Makefile does is to create the build directory using $(MKDIR), which is a variable for mkdir -p. The directory build is where we will perform our out-of-source build. We provide the argument -p to ensure that mkdir does not scream at us for trying to create a directory that may already exist.

The second thing the target ./build/Makefile does is to change directories to the build directory and invoke cmake.

Back to the all target, we invoke $(MAKE) -C build, where $(MAKE) is a Makefile variable automatically generated for make. make -C changes the directory before doing anything. Therefore, using $(MAKE) -C build is equivalent to doing cd build; make.

To summarize, calling this Makefile wrapper with make all or make is equivalent to doing:

mkdir build
cd build
cmake ..

The target distclean invokes cmake .., then make -C build clean, and finally, removes all contents from the build directory. I believe this is exactly what you requested in your question.

The last piece of the Makefile evaluates if the user-provided target is or is not distclean. If not, it will change directories to build before invoking it. This is very powerful because the user can type, for example, make clean, and the Makefile will transform that into an equivalent of cd build; make clean.

In conclusion, this Makefile wrapper, in combination with a mandatory out-of-source build CMake configuration, make it so that the user never has to interact with the command cmake. This solution also provides an elegant method to remove all CMake output files from the build directory.

P.S. In the Makefile, we use the prefix @ to suppress the output from a shell command, and the prefix @- to ignore errors from a shell command. When using rm as part of the distclean target, the command will return an error if the files do not exist (they may have been deleted already using the command line with rm -rf build, or they were never generated in the first place). This return error will force our Makefile to exit. We use the prefix @- to prevent that. It is acceptable if a file was removed already; we want our Makefile to keep going and remove the rest.

Another thing to note: This Makefile may not work if you use a variable number of CMake variables to build your project, for example, cmake .. -DSOMEBUILDSUSETHIS:STRING="foo" -DSOMEOTHERBUILDSUSETHISTOO:STRING="bar". This Makefile assumes you invoke CMake in a consistent way, either by typing cmake .. or by providing cmake a consistent number of arguments (that you can include in your Makefile).

Finally, credit where credit is due. This Makefile wrapper was adapted from the Makefile provided by the C++ Application Project Template.

Getting the URL of the current page using Selenium WebDriver

Put sleep. It will work. I have tried. The reason is that the page wasn't loaded yet. Check this question to know how to wait for load - Wait for page load in Selenium

How do I specify C:\Program Files without a space in it for programs that can't handle spaces in file paths?

You can use the following methods to specify C:\Program Files without a space in it for programs that can't handle spaces in file paths:

'Path to Continuum Reports Subdirectory - Note use DOS equivalent (no spaces)
RepPath = "c:\progra~1\continuum_reports\" or
RepPath = C:\Program Files\Continuum_Reports  'si es para 64 bits.

' Path to Continuum Reports Subdirectory - Note use DOS equivalent (no spaces)
RepPath = "c:\progra~2\continuum_reports\" 'or
RepPath = C:\Program Files (x86)\Continuum_Reports  'si es para 32 bits.

What are the Ruby modes and options?

opt is new for ruby 1.9. The various options are documented in :

"Input string was not in a correct format."

In my case I forgot to put double curly brace to escape. {{myobject}}

IOException: Too many open files

Aside from looking into root cause issues like file leaks, etc. in order to do a legitimate increase the "open files" limit and have that persist across reboots, consider editing


by adding something like this

jetty soft nofile 2048
jetty hard nofile 4096

where "jetty" is the username in this case. For more details on limits.conf, see

log off and then log in again and run

ulimit -n

to verify that the change has taken place. New processes by this user should now comply with this change. This link seems to describe how to apply the limit on already running processes but I have not tried it.

The default limit 1024 can be too low for large Java applications.

Java Swing - how to show a panel on top of another panel?

JOptionPane.showInternalInputDialog probably does what you want. If not, it would be helpful to understand what it is missing.

Reading an integer from user input

Try this it will not throw exception and user can try again:

        Console.WriteLine("1. Add account.");
        Console.WriteLine("Enter choice: ");
        int choice = 0;
        while (!Int32.TryParse(Console.ReadLine(), out choice))
            Console.WriteLine("Wrong input! Enter choice number again:");

Check date with todays date

public static boolean itIsToday(long date){
    boolean result = false;
        Calendar calendarData = Calendar.getInstance();
        calendarData.set(Calendar.HOUR_OF_DAY, 0);
        calendarData.set(Calendar.MINUTE, 0);
        calendarData.set(Calendar.SECOND, 0);
        calendarData.set(Calendar.MILLISECOND, 0);

        Calendar calendarToday = Calendar.getInstance();
        calendarToday.set(Calendar.HOUR_OF_DAY, 0);
        calendarToday.set(Calendar.MINUTE, 0);
        calendarToday.set(Calendar.SECOND, 0);
        calendarToday.set(Calendar.MILLISECOND, 0);

        if(calendarToday.getTimeInMillis() == calendarData.getTimeInMillis()) {
            result = true;
    }catch (Exception exception){
        Log.e(TAG, exception);
    return result;

How to check that Request.QueryString has a specific value or not in ASP.NET?

To resolve your problem, write the following line on your page's Page_Load method.

if (String.IsNullOrEmpty(Request.QueryString["aspxerrorpath"])) return;

.Net 4.0 provides more closer look to null, empty or whitespace strings, use it as shown in the following line:

if(string.IsNullOrWhiteSpace(Request.QueryString["aspxerrorpath"])) return;

This will not run your next statements (your business logics) if query string does not have aspxerrorpath.

Message: Trying to access array offset on value of type null

This happens because $cOTLdata is not null but the index 'char_data' does not exist. Previous versions of PHP may have been less strict on such mistakes and silently swallowed the error / notice while 7.4 does not do this anymore.

To check whether the index exists or not you can use isset():


Which means the line should look something like this:

$len = isset($cOTLdata['char_data']) ? count($cOTLdata['char_data']) : 0;

Note I switched the then and else cases of the ternary operator since === null is essentially what isset already does (but in the positive case).

ssh : Permission denied (publickey,gssapi-with-mic)

And I think this will clearify the cause of posted problem, actualy this is bug of pssh itself (contains inside ""). It is pssh's lib file. And there is documented issue for -A case: There are two possible resolutions to use version of pssh containing this bug in case you forced to use passphrase for private key access:

  1. Correct your "" as described in link listed before in my post.
  2. Using your favorite pass keeper.

Thnks for attention, hope it helps!

Parse v. TryParse

If the string can not be converted to an integer, then

  • int.Parse() will throw an exception
  • int.TryParse() will return false (but not throw an exception)

Get JSON data from external URL and display it in a div as plain text

You can do this with JSONP like this:

function insertReply(content) {
    document.getElementById('output').innerHTML = content;

// create script element
var script = document.createElement('script');
// assing src with callback name
script.src = '';
// insert script to document and load content

But source must be aware that you want it to call function passed as callback parameter to it.

With google API it would look like this:

function insertReply(content) {
    document.getElementById('output').innerHTML = content;

// create script element
var script = document.createElement('script');
// assing src with callback name
script.src = '';
// insert script to document and load content

Check how data looks like when you pass callback to google api:

Here is quite good explanation of JSONP:

Pick images of root folder from sub-folder

The relative reference would be

<img src="../images/logo.png">

If you know the location relative to the root of the server, that may be simplest approach for an app with a complex nested directory hierarchy - it would be the same from all folders.

For example, if your directory tree depicted in your question is relative to the root of the server, then index.html and sub_folder/sub.html would both use:

<img src="/images/logo.png">

If the images folder is instead in the root of an application like foo below the server root (e.g., then index.html ( e.g and sub_folder/sub.html ( both use:

<img src="/foo/images/logo.png">

Batch script to delete files

Consider that the files you need to delete have an extension txt and is located in the location D:\My Folder, then you could use the below code inside the bat file.

cd "D:\My Folder"
DEL *.txt 

What is a lambda expression in C++11?

Lambda expressions are typically used to encapsulate algorithms so that they can be passed to another function. However, it is possible to execute a lambda immediately upon definition:

[&](){ ...your code... }(); // immediately executed lambda expression

is functionally equivalent to

{ ...your code... } // simple code block

This makes lambda expressions a powerful tool for refactoring complex functions. You start by wrapping a code section in a lambda function as shown above. The process of explicit parameterization can then be performed gradually with intermediate testing after each step. Once you have the code-block fully parameterized (as demonstrated by the removal of the &), you can move the code to an external location and make it a normal function.

Similarly, you can use lambda expressions to initialize variables based on the result of an algorithm...

int a = []( int b ){ int r=1; while (b>0) r*=b--; return r; }(5); // 5!

As a way of partitioning your program logic, you might even find it useful to pass a lambda expression as an argument to another lambda expression...

[&]( std::function<void()> algorithm ) // wrapper section
   ...your wrapper code...
   ...your wrapper code...
([&]() // algorithm section
   ...your algorithm code...

Lambda expressions also let you create named nested functions, which can be a convenient way of avoiding duplicate logic. Using named lambdas also tends to be a little easier on the eyes (compared to anonymous inline lambdas) when passing a non-trivial function as a parameter to another function. Note: don't forget the semicolon after the closing curly brace.

auto algorithm = [&]( double x, double m, double b ) -> double
   return m*x+b;

int a=algorithm(1,2,3), b=algorithm(4,5,6);

If subsequent profiling reveals significant initialization overhead for the function object, you might choose to rewrite this as a normal function.

Eclipse Optimize Imports to Include Static Imports

Select the constant, type

Ctrl + 1  (quick fix)

Select "Convert to static import." from the drop down.

"Quick fix" has options even though it is not an error.

How to use BeanUtils.copyProperties?

There are two BeanUtils.copyProperties(parameter1, parameter2) in Java.

One is

org.apache.commons.beanutils.BeanUtils.copyProperties(Object dest, Object orig)

Another is

org.springframework.beans.BeanUtils.copyProperties(Object source, Object target)

Pay attention to the opposite position of parameters.

How to handle ETIMEDOUT error?

This is caused when your request response is not received in given time(by timeout request module option).

Basically to catch that error first, you need to register a handler on error, so the unhandled error won't be thrown anymore: out.on('error', function (err) { /* handle errors here */ }). Some more explanation here.

In the handler you can check if the error is ETIMEDOUT and apply your own logic: if (err.message.code === 'ETIMEDOUT') { /* apply logic */ }.

If you want to request for the file again, I suggest using node-retry or node-backoff modules. It makes things much simpler.

If you want to wait longer, you can set timeout option of request yourself. You can set it to 0 for no timeout.

Copy multiple files in Python

You can use os.listdir() to get the files in the source directory, os.path.isfile() to see if they are regular files (including symbolic links on *nix systems), and shutil.copy to do the copying.

The following code copies only the regular files from the source directory into the destination directory (I'm assuming you don't want any sub-directories copied).

import os
import shutil
src_files = os.listdir(src)
for file_name in src_files:
    full_file_name = os.path.join(src, file_name)
    if os.path.isfile(full_file_name):
        shutil.copy(full_file_name, dest)

What is the (function() { } )() construct in JavaScript?

It is a function expression, it stands for Immediately Invoked Function Expression (IIFE). IIFE is simply a function that is executed right after it is created. So insted of the function having to wait until it is called to be executed, IIFE is executed immediately. Let's construct the IIFE by example. Suppose we have an add function which takes two integers as args and returns the sum lets make the add function into an IIFE,

Step 1: Define the function

function add (a, b){
    return a+b;

Step2: Call the function by wrap the entire functtion declaration into parentheses

(function add (a, b){
    return a+b;

Step 3: To invock the function immediatly just remove the 'add' text from the call.

(function add (a, b){
    return a+b;

The main reason to use an IFFE is to preserve a private scope within your function. Inside your javascript code you want to make sure that, you are not overriding any global variable. Sometimes you may accidentaly define a variable that overrides a global variable. Let's try by example. suppose we have an html file called iffe.html and codes inside body tag are-

    <div id = 'demo'></div>
        document.getElementById("demo").innerHTML = "Hello JavaScript!";

Well, above code will execute with out any question, now assume you decleard a variable named document accidentaly or intentional.

    <div id = 'demo'></div>
        document.getElementById("demo").innerHTML = "Hello JavaScript!";
        const document = "hi there";

you will endup in a SyntaxError: redeclaration of non-configurable global property document.

But if your desire is to declear a variable name documet you can do it by using IFFE.

    <div id = 'demo'></div>
            const document = "hi there";
            this.document.getElementById("demo").innerHTML = "Hello JavaScript!";
        document.getElementById("demo").innerHTML = "Hello JavaScript!";


enter image description here

Let's try by an another example, suppose we have an calculator object like bellow-

        var calculator = {
                return a+b;
                return a*b;

Well it's working like a charm, what if we accidently re-assigne the value of calculator object.

        var calculator = {
                return a+b;
                return a*b;
        calculator = "scientific calculator";

yes you will endup with a TypeError: calculator.mul is not a function iffe.html

But with the help of IFFE we can create a private scope where we can create another variable name calculator and use it;

        var calculator = {
                return a+b;
                return a*b;
        var cal = (function(){
            var calculator = {
                    return a-b;
                    return a/b;
            return calculator;

Output: enter image description here

What is the difference between char array and char pointer in C?

You're not allowed to change the contents of a string constant, which is what the first p points to. The second p is an array initialized with a string constant, and you can change its contents.

Pandas - Get first row value of a given column

To get e.g the value from column 'test' and row 1 it works like


as only df[['test']].values[0] gives back a array

DataGridView - Focus a specific cell

I had a similar problem. I've hidden some columns and afterwards I tried to select the first row. This didn't really work:

datagridview1.Rows[0].Selected = true;

So I tried selecting cell[0,0], but it also didn't work, because this cell was not displayed. Now my final solution is working very well:

datagridview1.SelectionMode = DataGridViewSelectionMode.FullRowSelect;    
datagridview1.CurrentCell = datagridview1.FirstDisplayedCell;

So this selects the complete first row.

could not extract ResultSet in hibernate

I Used the following properties in my file and the issue got resolved




earlier was getting an error

There was an unexpected error (type=Internal Server Error, status=500).
could not extract ResultSet; SQL [n/a]; nested exception is 
org.hibernate.exception.SQLGrammarException: could not extract ResultSet
org.springframework.dao.InvalidDataAccessResourceUsageException: could not extract ResultSet; SQL [n/a]; nested exception is org.hibernate.exception.SQLGrammarException: could not extract ResultSet
at org.springframework.orm.jpa.vendor.HibernateJpaDialect.convertHibernateAccessException(
at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(
at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(

How can I get Eclipse to show .* files?

In the package explorer, in the upper right corner of the view, there is a little down arrow. Tool tip will say view menu. From that menu, select filters

filters menu

From there, uncheck .* resources.

So Package Explorer -> View Menu -> Filters -> uncheck .* resources.

With Eclipse Kepler and OS X this is a bit different:

Package Explorer -> Customize View -> Filters -> uncheck .* resources

Set up an HTTP proxy to insert a header

You can also install Fiddler ( which is very easy to install (easier than Apache for example).

After launching it, it will register itself as system proxy. Then open the "Rules" menu, and choose "Customize Rules..." to open a JScript file which allow you to customize requests.

To add a custom header, just add a line in the OnBeforeRequest function:

oSession.oRequest.headers.Add("MyHeader", "MyValue");

trying to align html button at the center of the my page

There are multiple ways to fix the same. PFB two of them -

1st Way using position: fixed - position: fixed; positions relative to the viewport, which means it always stays in the same place even if the page is scrolled. Adding the left and top value to 50% will place it into the middle of the screen.

 button {
   position: fixed;
   left: 50%;

2nd Way using margin: auto -margin: 0 auto; for horizontal centering, but margin: auto; has refused to work for vertical centering… until now! But actually absolute centering only requires a declared height and these styles:

button {
  margin: auto;
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  height: 40px;

database vs. flat files

Don't build it if you can buy it.

I heard this quote recently, and it really seems fitting as a guide line. Ask yourself this... How much time was spent working on the file handling portion of your app? I suspect a fair amount of time was spent optimizing this code for performance. If you had been using a relational database all along, you would have spent considerably less time handling this portion of your application. You would have had more time for the true "business" aspect of your app.

Swift - encode URL

Swift 4 & 5

To encode a parameter in URL I find using .alphanumerics character set the easiest option:

let encoded = parameter.addingPercentEncoding(withAllowedCharacters: .alphanumerics)
let url = "\(encoded!)"

Using any of the standard Character Sets for URL Encoding (like URLQueryAllowedCharacterSet or URLHostAllowedCharacterSet) won't work, because they do not exclude = or & characters.

Note that by using .alphanumerics it will encode some characters that do not need to be encoded (like -, ., _ or ~ -– see 2.3. Unreserved characters in RFC 3986). I find using .alphanumerics simpler than constructing a custom character set and do not mind some additional characters to be encoded. If that bothers you, construct a custom character set as is described in How to percent encode a URL String, like for example:

var allowed = CharacterSet.alphanumerics
allowed.insert(charactersIn: "-._~") // as per RFC 3986
let encoded = parameter.addingPercentEncoding(withAllowedCharacters: allowed)
let url = "\(encoded!)"

Warning: The encoded parameter is force unwrapped. For invalid unicode string it might crash. See Why is the return value of String.addingPercentEncoding() optional?. Instead of force unwrapping encoded! you can use encoded ?? "" or use if let encoded = ....

How do I get the latest version of my code?

To answer your questions there are simply two steps:-

  1. Pull the latest changes from your git repo using git pull
  2. Clean your local working directory having unstaged changes using git checkout -- . .This will show the latest changes in your local repo from your remote git repo. cleaning all the local unstaged changes.

Please note git checkout -- . will discard all your changes in the local working directory. In case you want to discard any change for selective file use git checkout -- <filename>. And in case you don't want to lose your unstaged changes use git stash as it will clean your local working directory of all the unstaged changes while saving it if you need it in the future.

How to fill in proxy information in cntlm config file?

Without any configuration, you can simply issue the following command (modifying myusername and mydomain with your own information):

cntlm -u myusername -d mydomain -H


cntlm -u myusername@mydomain -H

It will ask you the password of myusername and will give you the following output:

PassLM          1AD35398BE6565DDB5C4EF70C0593492
PassNT          77B9081511704EE852F94227CF48A793
PassNTLMv2      A8FC9092D566461E6BEA971931EF1AEC    # Only for user 'myusername', domain 'mydomain'

Then create the file cntlm.ini (or cntlm.conf on Linux using default path) with the following content (replacing your myusername, mydomain and A8FC9092D566461E6BEA971931EF1AEC with your information and the result of the previous command):

Username    myusername
Domain      mydomain

NoProxy     127.0.0.*, 192.168.*

Gateway     yes

SOCKS5Proxy 5866

Auth        NTLMv2
PassNTLMv2  A8FC9092D566461E6BEA971931EF1AEC

Then you will have a local open proxy on local port 5865 and another one understanding SOCKS5 protocol at local port 5866.

Selecting a Record With MAX Value

What do you mean costs too much? Too much what?

SELECT MAX(Balance) AS MaxBalance, CustomerID FROM CUSTOMERS GROUP BY CustomerID

If your table is properly indexed (Balance) and there has got to be an index on the PK than I am not sure what you mean about costs too much or seems unreliable? There is nothing unreliable about an aggregate that you are using and telling it to do. In this case, MAX() does exactly what you tell it to do - there's nothing magical about it.

Take a look at MAX() and if you want to filter it use the HAVING clause.

What is the difference between Session.Abandon() and Session.Clear()


will destroy/kill the entire session.


removes/clears the session data (i.e. the keys and values from the current session) but the session will be alive.

Compare to Session.Abandon() method, Session.Clear() doesn't create the new session, it just make all variables in the session to NULL.

Session ID will remain same in both the cases, as long as the browser is not closed.


It removes all keys and values from the session-state collection.


It deletes an item from the session-state collection.


It deletes an item at a specified index from the session-state collection.


This property specifies the time-out period assigned to the Session object for the application. (the time will be specified in minutes).

If the user does not refresh or request a page within the time-out period, then the session ends.

jQuery SVG, why can't I addClass?

Here is my rather inelegant but working code that deals with the following issues (without any dependencies):

  • classList not existing on <svg> elements in IE
  • className not representing the class attribute on <svg> elements in IE
  • Old IE's broken getAttribute() and setAttribute() implementations

It uses classList where possible.


var classNameContainsClass = function(fullClassName, className) {
    return !!fullClassName &&
           new RegExp("(?:^|\\s)" + className + "(?:\\s|$)").test(fullClassName);

var hasClass = function(el, className) {
    if (el.nodeType !== 1) {
        return false;
    if (typeof el.classList == "object") {
        return (el.nodeType == 1) && el.classList.contains(className);
    } else {
        var classNameSupported = (typeof el.className == "string");
        var elClass = classNameSupported ? el.className : el.getAttribute("class");
        return classNameContainsClass(elClass, className);

var addClass = function(el, className) {
    if (el.nodeType !== 1) {
    if (typeof el.classList == "object") {
    } else {
        var classNameSupported = (typeof el.className == "string");
        var elClass = classNameSupported ?
            el.className : el.getAttribute("class");
        if (elClass) {
            if (!classNameContainsClass(elClass, className)) {
                elClass += " " + className;
        } else {
            elClass = className;
        if (classNameSupported) {
            el.className = elClass;
        } else {
            el.setAttribute("class", elClass);

var removeClass = (function() {
    function replacer(matched, whiteSpaceBefore, whiteSpaceAfter) {
        return (whiteSpaceBefore && whiteSpaceAfter) ? " " : "";

    return function(el, className) {
        if (el.nodeType !== 1) {
        if (typeof el.classList == "object") {
        } else {
            var classNameSupported = (typeof el.className == "string");
            var elClass = classNameSupported ?
                el.className : el.getAttribute("class");
            elClass = elClass.replace(new RegExp("(^|\\s)" + className + "(\\s|$)"), replacer);
            if (classNameSupported) {
                el.className = elClass;
            } else {
                el.setAttribute("class", elClass);
    }; //added semicolon here

Example usage:

var el = document.getElementById("someId");
if (hasClass(el, "someClass")) {
    removeClass(el, "someClass");
addClass(el, "someOtherClass");

What is a CSRF token? What is its importance and how does it work?

The root of it all is to make sure that the requests are coming from the actual users of the site. A csrf token is generated for the forms and Must be tied to the user's sessions. It is used to send requests to the server, in which the token validates them. This is one way of protecting against csrf, another would be checking the referrer header.

How do I access the HTTP request header fields via JavaScript?

If you want to access referrer and user-agent, those are available to client-side Javascript, but not by accessing the headers directly.

To retrieve the referrer, use document.referrer.
To access the user-agent, use navigator.userAgent.

As others have indicated, the HTTP headers are not available, but you specifically asked about the referer and user-agent, which are available via Javascript.

React Router Pass Param to Component

Here's typescript version. works on "react-router-dom": "^4.3.1"

export const AppRouter: React.StatelessComponent = () => {
    return (
                <Route exact path="/problem/:problemId" render={props => <ProblemPage {...props.match.params} />} />
                <Route path="/" exact component={App} />

and component

export class ProblemPage extends React.Component<ProblemRouteTokens> {

    public render(): JSX.Element {
        return <div>{this.props.problemId}</div>;

where ProblemRouteTokens

export interface ProblemRouteTokens { problemId: string; }

How can moment.js be imported with typescript?

Not sure when this changed, but with the latest version of typescript, you just need to use import moment from 'moment'; and everything else should work as normal.


Looks like moment recent fixed their import. As of at least 2.24.0 you'll want to use import * as moment from 'moment';

Best way to check for IE less than 9 in JavaScript without library

I've decided to go with object detection instead.

After reading this: and this:

I'd use something like

if(!!document.createElement('canvas').getContext) alert('what is needed, supported');

Pointer arithmetic for void pointer in C

You can't do pointer arithmetic on void * types, for exactly this reason!

Visual Studio: Relative Assembly References Paths

Probably, the easiest way to achieve this is to simply add the reference to the assembly and then (manually) patch the textual representation of the reference in the corresponding Visual Studio project file (extension .csproj) such that it becomes relative.

I've done this plenty of times in VS 2005 without any problems.

Calculating Time Difference

You cannot calculate the differences separately ... what difference would that yield for 7:59 and 8:00 o'clock? Try

import time

which gives you the seconds since the start of the epoch.

You can then get the intermediate time with something like

timestamp1 = time.time()
# Your code here
timestamp2 = time.time()
print "This took %.2f seconds" % (timestamp2 - timestamp1)

Back to previous page with header( "Location: " ); in PHP

Storing previous url in a session variable is bad, because the user might right click on multiple pages and then come back and save.

unless you save the previous url in the session variable to a hidden field in the form and after save header( "Location: save URL of calling page" );

How to write to a file without overwriting current contents?

Instead of "w" use "a" (append) mode with open function:

with open("games.txt", "a") as text_file:

Internet Explorer cache location

If it's been moved you can also (in IE 11, and I'm pretty sure this translates back to at least 10):

  • Tools - Internet Options
  • Under Browsing history click Settings
  • Under Current location it shows the directory name

Note: The View files button will open a Windows Explorer window there.

For example, mine shows C:\BrowserCache\IE\Temporary Internet Files

How do I expire a PHP session after 30 minutes?

Well i understand the aboves answers are correct but they are on application level, why don't we simply use .htaccess file to set the expire time ?

<IfModule mod_php5.c>
    #Session timeout
    php_value session.cookie_lifetime 1800
    php_value session.gc_maxlifetime 1800

Push local Git repo to new remote including all branches and tags

Every time I Google how to do this I end up reading this same thread, but it doesn't get me where I need to be, so hopefully this will help my future self and others too.

I started a new local project that I want to push to my repo (BitBucket). Here is what I did:

  1. navigate to my local project root
  2. initiate with: git init
  3. add all files with: git add .
  4. commit with: git commit -m "Initial commit"
  5. go to my repo (BitBucket)
  6. create new repository: new_project
  7. go back to my local project
  8. add the remote with: git remote add origin [email protected]:AndrewFox/new_project.git
  9. push the commit with: git push origin master -f

The -f flag is to force the push, otherwise it will identify that the two repo's are different and fail.

How to escape the % (percent) sign in C's printf?

You can escape it by posting a double '%' like this: %%

Using your example:


Escaping '%' sign is only for printf. If you do:

char a[5];
strcpy(a, "%%");
printf("This is a's value: %s\n", a);

It will print: This is a's value: %%

Hbase quickly count number of rows

To count the Hbase table record count on a proper YARN cluster you have to set the map reduce job queue name as well:

hbase org.apache.hadoop.hbase.mapreduce.RowCounter -Dmapreduce.job.queuename= < Your Q Name which you have SUBMIT access>

Date format in dd/MM/yyyy hh:mm:ss


Difference between getAttribute() and getParameter()


A "parameter" is a name/value pair sent from the client to the server - typically, from an HTML form. Parameters can only have String values. Sometimes (e.g. using a GET request) you will see these encoded directly into the URL (after the ?, each in the form name=value, and each pair separated by an &). Other times, they are included in the body of the request, when using methods such as POST.

An "attribute" is a server-local storage mechanism - nothing stored in scoped attribues is ever transmitted outside the server unless you explicitly make that happen. Attributes have String names, but store Object values. Note that attributes are specific to Java (they store Java Objects), while parameters are platform-independent (they are only formatted strings composed of generic bytes).

There are four scopes of attributes in total: "page" (for JSPs and tag files only), "request" (limited to the current client's request, destroyed after request is completed), "session" (stored in the client's session, invalidated after the session is terminated), "application" (exist for all components to access during the entire deployed lifetime of your application).

The bottom line is: use parameters when obtaining data from the client, use scoped attributes when storing objects on the server for use internally by your application only.

Oracle Error ORA-06512

ORA-06512 is part of the error stack. It gives us the line number where the exception occurred, but not the cause of the exception. That is usually indicated in the rest of the stack (which you have still not posted).

In a comment you said

"still, the error comes when pNum is not between 12 and 14; when pNum is between 12 and 14 it does not fail"

Well, your code does this:

IF ((pNum < 12) OR (pNum > 14)) THEN     

That is, it raises an exception when pNum is not between 12 and 14. So does the rest of the error stack include this line?

ORA-06510: PL/SQL: unhandled user-defined exception

If so, all you need to do is add an exception block to handle the error. Perhaps:


    IF ((pNum < 12) OR (pNum > 14)) THEN     
        RAISE vSOME_EX;
        EXECUTE IMMEDIATE  'INSERT INTO M'||pNum||'GR (CV, SUP, IDM'||pNum||') VALUES('||pCv||', '||pSup||', '||pIdM||')';
    END IF;
    when vsome_ex then
                                 , 'This is not a valid table:  M'||pNum||'GR');


The documentation covers handling PL/SQL exceptions in depth.

How to run a specific Android app using Terminal?

I keep this build-and-run script handy, whenever I am working from command line:

#!/usr/bin/env bash

echo "Package: $PACKAGE"

echo "Building the project with tasks: $TASKS"
./gradlew $TASKS

echo "Uninstalling $PACKAGE"
adb uninstall $PACKAGE

echo "Installing $APK_LOCATION"
adb install $APK_LOCATION

echo "Starting $ACTIVITY"
adb shell am start -n $PACKAGE/$ACTIVITY

calling parent class method from child class object in java

NOTE calling parent method via super will only work on parent class, If your parent is interface, and wants to call the default methods then need to add interfaceName before super like IfscName.super.method();

interface Vehicle {
    //Non abstract method
    public default void printVehicleTypeName() { //default keyword can be used only in interface.

class FordFigo extends FordImpl implements Vehicle, Ford {
    public void printVehicleTypeName() { 

Interface name is needed because same default methods can be available in multiple interface name that this class extends. So explicit call to a method is required.

Strange problem with Subversion - "File already exists" when trying to recreate a directory that USED to be in my repository

Had similar problem. To resolve it, updated from svn trunk with option of priority of local files.

svn update path/ --accept=mine-full

After You could commit as usual. Of course, be careful using it.

How to change time in DateTime?

You can't change a DateTime value - it's immutable. However, you can change the variable to have a new value. The easiest way of doing that to change just the time is to create a TimeSpan with the relevant time, and use the DateTime.Date property:

DateTime s = ...;
TimeSpan ts = new TimeSpan(10, 30, 0);
s = s.Date + ts;

s will now be the same date, but at 10.30am.

Note that DateTime disregards daylight saving time transitions, representing "naive" Gregorian time in both directions (see Remarks section in the DateTime docs). The only exceptions are .Now and .Today: they retrieve current system time which reflects these events as they occur.

This is the kind of thing which motivated me to start the Noda Time project, which is now production-ready. Its ZonedDateTime type is made "aware" by linking it to a tz database entry.

How to time Java program execution speed

Here are a few ways to find the execution time in Java:

1) System.nanoTime()

long startTime = System.nanoTime();
.....your code....
long endTime   = System.nanoTime();
long totalTime = endTime - startTime;
System.out.println("Execution time in nanoseconds  : " + totalTime);
System.out.println("Execution time in milliseconds : " + totalTime / 1000000);

2) System.currentTimeMillis()

long startTime = System.currentTimeMillis();
.....your code....
long endTime = System.currentTimeMillis();
long totalTime = endTime - startTime;
System.out.println("Execution time in milliseconds  : " + totalTime);


long startTime =;
.....your code....
long endTime =;
long totalTime = endTime - startTime;
System.out.println("Execution time in milliseconds: " + totalTime);


Instant start =;
.....your code....
Instant end =;
Duration interval = Duration.between(start, end);
System.out.println("Execution time in seconds: " +interval.getSeconds());

4) Date.getTime()

long startTime = new Date().getTime();
.....your code....
long endTime = new Date().getTime();
long totalTime = endTime - startTime;
System.out.println("Execution time in milliseconds: " + totalTime);

How to find the length of an array in shell?

$ a=(1 2 3 4)
$ echo ${#a[@]}

How do you make Git work with IntelliJ?

On unix systems, you can use the following command to determine where git is installed:

whereis git

If you are using MacOS and did a recent update, it is possible you have to agree to the licence terms again. Try typing 'git' in a terminal, and see if you get the following message:

Agreeing to the Xcode/iOS license requires admin privileges, please re-run as root via sudo.

Determining image file size + dimensions via Javascript?

Check the uploaded image size using Javascript

<script type="text/javascript">
    function check(){
      var imgpath=document.getElementById('imgfile');
      if (!imgpath.value==""){
        var img=imgpath.files[0].size;
        var imgsize=img/1024; 

Html code

<form method="post" enctype="multipart/form-data" onsubmit="return check();">
<input type="file" name="imgfile" id="imgfile"><br><input type="submit">

Counting the number of non-NaN elements in a numpy ndarray in Python


~ inverts the boolean matrix returned from np.isnan.

np.count_nonzero counts values that is not 0\false. .sum should give the same result. But maybe more clearly to use count_nonzero

Testing speed:

In [23]: data = np.random.random((10000,10000))

In [24]: data[[np.random.random_integers(0,10000, 100)],:][:, [np.random.random_integers(0,99, 100)]] = np.nan

In [25]: %timeit data.size - np.count_nonzero(np.isnan(data))
1 loops, best of 3: 309 ms per loop

In [26]: %timeit np.count_nonzero(~np.isnan(data))
1 loops, best of 3: 345 ms per loop

In [27]: %timeit data.size - np.isnan(data).sum()
1 loops, best of 3: 339 ms per loop

data.size - np.count_nonzero(np.isnan(data)) seems to barely be the fastest here. other data might give different relative speed results.

MVC Razor Radio Button

I done this in a way like:

  @Html.RadioButtonFor(model => model.Gender, "M", false)@Html.Label("Male")
  @Html.RadioButtonFor(model => model.Gender, "F", false)@Html.Label("Female")

Convert JSONArray to String Array

Here is the code :

// XXX satisfies only with this particular string format
        String s = "[{\"name\":\"IMG_20130403_140457.jpg\"},{\"name\":\"IMG_20130403_145006.jpg\"},{\"name\":\"IMG_20130403_145112.jpg\"},{\"name\":\"IMG_20130404_085559.jpg\"},{\"name\":\"IMG_20130404_113700.jpg\"},{\"name\":\"IMG_20130404_113713.jpg\"},{\"name\":\"IMG_20130404_135706.jpg\"},{\"name\":\"IMG_20130404_161501.jpg\"},{\"name\":\"IMG_20130405_082413.jpg\"},{\"name\":\"IMG_20130405_104212.jpg\"},{\"name\":\"IMG_20130405_160524.jpg\"},{\"name\":\"IMG_20130408_082456.jpg\"},{\"name\":\"test.jpg\"}]";
        s = s.replace("[", "").replace("]", "");
        s = s.substring(1, s.length() - 1);
        String[] split = s.split("[}][,][{]");
        for (String string : split) {

Array formula on Excel for Mac

Select the range, press CONTROL+U and then press ?+RETURN.

Is it possible to change the package name of an Android app on Google Play?

No, you cannot change package name unless you're okay with publishing it as a new app in Play Store:

Once you publish your application under its manifest package name, this is the unique identity of the application forever more. Switching to a different name results in an entirely new application, one that can’t be installed as an update to the existing application. Android manual confirms it as well here:

Caution: Once you publish your application, you cannot change the package name. The package name defines your application's identity, so if you change it, then it is considered to be a different application and users of the previous version cannot update to the new version. If you're okay with publishing new version of your app as a completely new entity, you can do it of course - just remove old app from Play Store (if you want) and publish new one, with different package name.

How can I calculate the number of lines changed between two commits in Git?

You want the --stat option of git diff, or if you're looking to parse this in a script, the --numstat option.

git diff --stat <commit-ish> <commit-ish>

--stat produces the human-readable output you're used to seeing after merges; --numstat produces a nice table layout that scripts can easily interpret.

I somehow missed that you were looking to do this on multiple commits at the same time - that's a task for git log. Ron DeVera touches on this, but you can actually do a lot more than what he mentions. Since git log internally calls the diff machinery in order to print requested information, you can give it any of the diff stat options - not just --shortstat. What you likely want to use is:

git log --author="Your name" --stat <commit1>..<commit2>

but you can use --numstat or --shortstat as well. git log can also select commits in a variety other ways - have a look at the documentation. You might be interested in things like --since (rather than specifying commit ranges, just select commits since last week) and --no-merges (merge commits don't actually introduce changes), as well as the pretty output options (--pretty=oneline, short, medium, full...).

Here's a one-liner to get total changes instead of per-commit changes from git log (change the commit selection options as desired - this is commits by you, from commit1 to commit2):

git log --numstat --pretty="%H" --author="Your Name" commit1..commit2 | awk 'NF==3 {plus+=$1; minus+=$2} END {printf("+%d, -%d\n", plus, minus)}'

(you have to let git log print some identifying information about the commit; I arbitrarily chose the hash, then used awk to only pick out the lines with three fields, which are the ones with the stat information)

Make TextBox uneditable

Using the TextBox.ReadOnly property

TextBox.ReadOnly = true;

For a Non-Grey background you can change the TextBox.BackColor property to SystemColors.Window Color

textBox.BackColor = System.Drawing.SystemColors.Window;

When this property is set to true, the contents of the control cannot be changed by the user at runtime. With this property set to true, you can still set the value of the Text property in code. You can use this feature instead of disabling the control with the Enabled property to allow the contents to be copied and ToolTips to be shown.

How do I declare an array of undefined or no initial size?

malloc() (and its friends free() and realloc()) is the way to do this in C.

What is the easiest way to ignore a JPA field during persistence?

There are multiple solutions depending on the entity attribute type.

Basic attributes

Consider you have the following account table:

The account table

The account table is mapped to the Account entity like this:

@Entity(name = "Account")
public class Account {

    private Long id;

    private User owner;

    private String iban;

    private long cents;

    private double interestRate;

    private Timestamp createdOn;

    private double dollars;

    private long interestCents;

    private double interestDollars;

    private void postLoad() {
        this.dollars = cents / 100D;

        long months = createdOn.toLocalDateTime()
            .until(, ChronoUnit.MONTHS);
        double interestUnrounded = ( ( interestRate / 100D ) * cents * months ) / 12;
        this.interestCents = BigDecimal.valueOf(interestUnrounded)
            .setScale(0, BigDecimal.ROUND_HALF_EVEN).longValue();

        this.interestDollars = interestCents / 100D;

    //Getters and setters omitted for brevity

The basic entity attributes are mapped to table columns, so properties like id, iban, cents are basic attributes.

But the dollars, interestCents, and interestDollars are computed properties, so you annotate them with @Transient to exclude them from SELECT, INSERT, UPDATE, and DELETE SQL statements.

So, for basic attributes, you need to use @Transient in order to exclude a given property from being persisted.


Assuming you have the following post and post_comment tables:

The post and post_comment tables

You want to map the latestComment association in the Post entity to the latest PostComment entity that was added.

To do that, you can use the @JoinFormula annotation:

@Entity(name = "Post")
@Table(name = "post")
public class Post {
    private Long id;
    private String title;
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinFormula("(" +
        "SELECT " +
        "FROM post_comment pc " +
        "WHERE pc.post_id = id " +
        "ORDER BY pc.created_on DESC " +
        "LIMIT 1" +
    private PostComment latestComment;
    //Getters and setters omitted for brevity

When fetching the Post entity, you can see that the latestComment is fetched, but if you want to modify it, the change is going to be ignored.

So, for associations, you can use @JoinFormula to ignore the write operations while still allowing reading the association.


Another way to ignore associations that are already mapped by the entity identifier is to use @MapsId.

For instance, consider the following one-to-one table relationship:

The post and post_details tables

The PostDetails entity is mapped like this:

@Entity(name = "PostDetails")
@Table(name = "post_details")
public class PostDetails {
    private Long id;
    @Column(name = "created_on")
    private Date createdOn;
    @Column(name = "created_by")
    private String createdBy;
    @OneToOne(fetch = FetchType.LAZY)
    private Post post;
    public PostDetails() {}
    public PostDetails(String createdBy) {
        createdOn = new Date();
        this.createdBy = createdBy;
    //Getters and setters omitted for brevity

Notice that both the id attribute and the post association map the same database column, which is the post_details Primary Key column.

To exclude the id attribute, the @MapsId annotation will tell Hibernate that the post association takes care of the table Primary Key column value.

So, when the entity identifier and an association share the same column, you can use @MapsId to ignore the entity identifier attribute and use the association instead.

Using insertable = false, updatable = false

Another option is to use insertable = false, updatable = false for the association which you want to be ignored by Hibernate.

For instance, we can map the previous one-to-one association like this:

@Entity(name = "PostDetails")
@Table(name = "post_details")
public class PostDetails {

    @Column(name = "post_id")
    private Long id;

    @Column(name = "created_on")
    private Date createdOn;

    @Column(name = "created_by")
    private String createdBy;

    @JoinColumn(name = "post_id", insertable = false, updatable = false)
    private Post post;

    //Getters and setters omitted for brevity

    public void setPost(Post post) { = post;
        if (post != null) {
   = post.getId();

The insertable and updatable attributes of the @JoinColumn annotation will instruct Hibernate to ignore the post association since the entity identifier takes care of the post_id Primary Key column.

Correct Semantic tag for copyright info - html5

In a link, if you put rel=license it: Indicates that the main content of the current document is covered by the copyright license described by the referenced document. Source:

So, for example, <a rel="license" href="">Copyrighted but you can use what's here as long as you credit me</a> gives a human something to read and lets computers know that the rest of the page is licensed under the CC BY 4.0 license.

Error handling in AngularJS http get then construct

Try this

function sendRequest(method, url, payload, done){

        var datatype = (method === "JSONP")? "jsonp" : "json";
                method: method,
                url: url,
                dataType: datatype,
                data: payload || {},
                cache: true,
                timeout: 1000 * 60 * 10
                done(null,; // server response
                responseHandler(res, done);

    function responseHandler(res, done){
            default: done(res.status + ": " + res.statusText);

PermGen elimination in JDK 8

PermGen space is replaced by MetaSpace in Java 8. The PermSize and MaxPermSize JVM arguments are ignored and a warning is issued if present at start-up.

Most allocations for the class metadata are now allocated out of native memory. * The classes that were used to describe class metadata have been removed.

Main difference between old PermGen and new MetaSpace is, you don't have to mandatory define upper limit of memory usage. You can keep MetaSpace space limit unbounded. Thus when memory usage increases you will not get OutOfMemoryError error. Instead the reserved native memory is increased to full-fill the increase memory usage.

You can define the max limit of space for MetaSpace, and then it will throw OutOfMemoryError : Metadata space. Thus it is important to define this limit cautiously, so that we can avoid memory waste.

Forbidden You don't have permission to access /wp-login.php on this server

This should work :

The instructions says that you add a separate .htaccess containing the lines above to the wp-admin folder - and leave the main .htaccess, in the root, alone.

if that don't help , you can try this:

copy the .htaccess file as is from the wp-admin and placed it in the root folder and bingo! It should work ! if you face new error after this let us know.

for reference you can look here as well:

Check using this:

<IfModule mod_security.c>
SecFilterEngine Off
SecFilterScanPOST Off

Singleton design pattern vs Singleton beans in Spring container

Spring singleton bean is described as 'per container per bean'. Singleton scope in Spring means that same object at same memory location will be returned to same bean id. If one creates multiple beans of different ids of the same class then container will return different objects to different ids. This is like a key value mapping where key is bean id and value is the bean object in one spring container. Where as Singleton pattern ensures that one and only one instance of a particular class will ever be created per classloader.

Open a webpage in the default browser

This should work:

Dim webAddress As String = ""

How to enumerate an enum with String type?

Xcode 10 with Swift 4.2

enum Filter: String, CaseIterable {

    case salary = "Salary"
    case experience = "Experience"
    case technology = "Technology"
    case unutilized = "Unutilized"
    case unutilizedHV = "Unutilized High Value"

    static let allValues = { $0.rawValue }

Call it



["Salary", "Experience", "Technology", "Unutilized", "Unutilized High Value"]

Older versions

For enum representing Int

enum Filter: Int {
    case salary
    case experience
    case technology
    case unutilized
    case unutilizedHV
    static let allRawValues = salary.rawValue...unutilizedHV.rawValue  // First to last case
    static let allValues = { Filter(rawValue: $0)!.rawValue }

Call it like this:



[0, 1, 2, 3, 4]

For enum representing String

enum Filter: Int {
    case salary
    case experience
    case technology
    case unutilized
    case unutilizedHV
    static let allRawValues = salary.rawValue...unutilizedHV.rawValue  // First to last case
    static let allValues = { Filter(rawValue: $0)!.description }

extension Filter: CustomStringConvertible {
    var description: String {
        switch self {
        case .salary: return "Salary"
        case .experience: return "Experience"
        case .technology: return "Technology"
        case .unutilized: return "Unutilized"
        case .unutilizedHV: return "Unutilized High Value"

Call it



["Salary", "Experience", "Technology", "Unutilized", "Unutilized High Value"]

Converting a column within pandas dataframe from int to string

In [16]: df = DataFrame(np.arange(10).reshape(5,2),columns=list('AB'))

In [17]: df
   A  B
0  0  1
1  2  3
2  4  5
3  6  7
4  8  9

In [18]: df.dtypes
A    int64
B    int64
dtype: object

Convert a series

In [19]: df['A'].apply(str)
0    0
1    2
2    4
3    6
4    8
Name: A, dtype: object

In [20]: df['A'].apply(str)[0]
Out[20]: '0'

Don't forget to assign the result back:

df['A'] = df['A'].apply(str)

Convert the whole frame

In [21]: df.applymap(str)
   A  B
0  0  1
1  2  3
2  4  5
3  6  7
4  8  9

In [22]: df.applymap(str).iloc[0,0]
Out[22]: '0'

df = df.applymap(str)

How to push to History in React Router v4?

/*Step 1*/
myFunction(){  this.props.history.push("/home"); }
 <button onClick={()=>this.myFunction()} className={'btn btn-primary'}>Go 

Missing MVC template in Visual Studio 2015

I had the same issue with the MVC template not appearing in VS2015.

I checked Web Developer Tools when originally installing. It was still checked when trying to Modify the install. I tried unchecking and updating the install but next time I went back to Modify, it was still checked. And still no MVC template.

I got it working by uninstalling: Microsoft ASP.NET Web Frameworks and Tools 2015 via the Programs and Features windows and re-installing. Here's the link for those who don't have it.

How to check if a process is running via a batch script

I usually execute following command in cmd prompt to check if my program.exe is running or not:

tasklist | grep program

System.Windows.Markup.XamlParseException' occurred in PresentationFramework.dll?

UPDATE: this is not the solution but it's a workaround for a problem that can cause the exception presented in the question.

I've solved changing from Release Configuration to Debug Configuration.

How to implement a Boolean search with multiple columns in pandas

the query() method can do that very intuitively. Express your condition in a string to be evaluated like the following example :

df = df.query("columnNameA <= @x or columnNameB == @y")

with x and y are declared variables which you can refer to with @

What's the fastest way in Python to calculate cosine similarity given sparse matrix data?

I have tried some methods above. However, the experiment by @zbinsd has its limitation. The sparsity of matrix used in the experiment is extremely low while the real sparsity is usually over 90%. In my condition, the sparse is with the shape of (7000, 25000) and the sparsity of 97%. The method 4 is extremely slow and I can't tolerant getting the results. I use the method 6 which is finished in 10 s. Amazingly, I try the method below and it's finished in only 0.247 s.

import sklearn.preprocessing as pp

def cosine_similarities(mat):
    col_normed_mat = pp.normalize(mat.tocsc(), axis=0)
    return col_normed_mat.T * col_normed_mat

This efficient method is linked by enter link description here

How to use goto statement correctly

goto is an unused reserved word in the language. So there is no goto. But, if you want absurdist theater you could coax one out of a language feature of labeling. But, rather than label a for loop which is sometimes useful you label a code block. You can, within that code block, call break on the label, spitting you to the end of the code block which is basically a goto, that only jumps forward in code.

        if (true) break my_goto;
    } //goto end location.

This will print 1, 2, 3, 4, 5, 7, 8. As the breaking the code block jumped to just after the code block. You can move the my_goto: { and if (true) break my_goto; and } //goto end location. statements. The important thing is just the break must be within the labeled code block.

This is even uglier than a real goto. Never actually do this.

But, it is sometimes useful to use labels and break and it is actually useful to know that if you label the code block and not the loop when you break you jump forward. So if you break the code block from within the loop, you not only abort the loop but you jump over the code between the end of the loop and the codeblock.

Detect enter press in JTextField

Do you want to do something like this ?

JTextField mTextField = new JTextField();
    mTextField.addKeyListener(new KeyAdapter() {
        public void keyPressed(KeyEvent e) {
            if(e.getKeyCode() == KeyEvent.VK_ENTER){
                // something like...
               // or...


Timer Interval 1000 != 1 second?

Instead of Tick event, use Elapsed event.

timer.Elapsed += new EventHandler(TimerEventProcessor);

and change the signiture of TimerEventProcessor method;

private void TimerEventProcessor(object sender, ElapsedEventArgs e)
  label1.Text = _counter.ToString();
  _counter += 1;

Extracting first n columns of a numpy matrix

I know this is quite an old question -

A = [[1, 2, 3],
     [4, 5, 6],
     [7, 8, 9]]

Let's say, you want to extract the first 2 rows and first 3 columns

A_NEW = A[0:2, 0:3]
A_NEW = [[1, 2, 3],
         [4, 5, 6]]

Understanding the syntax

A_NEW = A[start_index_row : stop_index_row, 
          start_index_column : stop_index_column)]

If one wants row 2 and column 2 and 3

A_NEW = A[1:2, 1:3]

Reference the numpy indexing and slicing article - Indexing & Slicing

sudo: docker-compose: command not found

I will leave this here as a possible fix, worked for me at least and might help others. Pretty sure this would be a linux only fix.

I decided to not go with the pip install and go with the github version (option one on the installation guide).

Instead of placing the copied docker-compose directory into /usr/local/bin/docker-compose from the curl/github command, I went with /usr/bin/docker-compose which is the location of Docker itself and will force the program to run in root. So it works in root and sudo but now won't work without sudo so the opposite effect which is what you want to run it as a user anyways.

Declaring variable workbook / Worksheet vba

Lots of answers above! here is my take:

Sub kl()

    Dim wb As Workbook
    Dim ws As Worksheet

    Set ws = Sheets("name")
    Set wb = ThisWorkbook

With ws
End With

End Sub

your first (perhaps accidental) mistake as we have all mentioned is "Sheet"... should be "Sheets"

The with block is useful because if you set wb to anything other than the current workbook, it will ececute properly

Get the current first responder without using a private API

Code below work.

- (id)ht_findFirstResponder
    //ignore hit test fail view
    if (self.userInteractionEnabled == NO || self.alpha <= 0.01 || self.hidden == YES) {
        return nil;
    if ([self isKindOfClass:[UIControl class]] && [(UIControl *)self isEnabled] == NO) {
        return nil;

    //ignore bound out screen
    if (CGRectIntersectsRect(self.frame, [UIApplication sharedApplication].keyWindow.bounds) == NO) {
        return nil;

    if ([self isFirstResponder]) {
        return self;

    for (UIView *subView in self.subviews) {
        id result = [subView ht_findFirstResponder];
        if (result) {
            return result;
    return nil;

Flatten list of lists

Flatten the list to "remove the brackets" using a nested list comprehension. This will un-nest each list stored in your list of lists!

list_of_lists = [[180.0], [173.8], [164.2], [156.5], [147.2], [138.2]]
flattened = [val for sublist in list_of_lists for val in sublist]

Nested list comprehensions evaluate in the same manner that they unwrap (i.e. add newline and tab for each new loop. So in this case:

flattened = [val for sublist in list_of_lists for val in sublist]

is equivalent to:

flattened = []
for sublist in list_of_lists:
    for val in sublist:

The big difference is that the list comp evaluates MUCH faster than the unraveled loop and eliminates the append calls!

If you have multiple items in a sublist the list comp will even flatten that. ie

>>> list_of_lists = [[180.0, 1, 2, 3], [173.8], [164.2], [156.5], [147.2], [138.2]]
>>> flattened  = [val for sublist in list_of_lists for val in sublist]
>>> flattened 
[180.0, 1, 2, 3, 173.8, 164.2, 156.5, 147.2,138.2]

How to create a JavaScript callback for knowing when an image is loaded?

Not suitable for 2008 when the question was asked, but these days this works well for me:

async function newImageSrc(src) {
  // Get a reference to the image in whatever way suits.
  let image = document.getElementById('image-id');

  // Update the source.
  img.src = src;

  // Wait for it to load.
  await new Promise((resolve) => { image.onload = resolve; });

  // Done!
  console.log('image loaded! do something...');

Simulate limited bandwidth from within Chrome?

Original article:

Simulate Slow Connection using Chrome Go ahead and install Chrome if you don’t already have it installed on your system. Once you do, open a new tab and then press CTRL + SHIFT + I to open the developer tools window or click on the hamburger icon, then More tools and then Developer tools.

enter image description here

This will bring up the Developer Tools window, which will probably be docked on the right side of the screen. I prefer it docked at the bottom of the screen since you can see more data. To do this, click on the three vertical dots and then click on the middle dock position.

enter image description here

Now go ahead and click on the Network tab. On the right, you should see a label called No Throttling.

enter image description here

If you click on that, you’ll get a dropdown list of a pre-configured speed that you can use to simulate a slow connection.

enter image description here

The choices range from Offline to WiFi and the numbers are shown as Latency, Download, Upload. The slowest is GPRS followed by Regular 2G, then Good 2G, then Regular 3G, Good 3G, Regular 4G, DSL and then WiFi. Pick one of the options and then reload the page you are on or type in another URL in the address bar. Just make sure you are in the same tab where the developer tools are being displayed. The throttling only works for the tab you have it enabled for.

If you want to use your own specific values, you can click the Add button under Custom. Click on the Add Custom Profile button to add a new profile.

enter image description here

When using GPRS, it took a whopping 16 seconds to load! Overall, this is a great tool that is built right into Chrome that you can use for testing your website load time on slower connections. If you have any questions, feel free to comment. Enjoy!

Regex: Check if string contains at least one digit

In perl:

if($testString =~ /\d/) 
    print "This string contains at least one digit"

where \d matches to a digit.

Create text file and fill it using bash

if [ -e $policy ]; then
  echo "File $1.json already exists!"
  cat > $file_location <<EOF
      "contact": {
          "name": "xyz",
          "phonenumber":   "xxx-xxx-xxxx"

This code checks if the given JSON file of the user is present in test home directory or not. If it's not present it will create it with the content. You can modify the file location and content according to your needs.

How to run Conda?

If you have installed anaconda, but if you are not able to execute conda command from terminal, it means the path is not probably set, try :

export PATH=~/anaconda/bin:$PATH

See this link.

what does "dead beef" mean?

The value of 0xDEADBEEF has three practical benefits, mostly for older systems. Old assembler/C hacks, like me, would use it to fill unallocated memory to coax out memory issues. Also, it's a pun of the slang term "dead meat". The programmer is dead meat if DEADBEEF winds up in his pointers. I congratulate the guy who first thought of using the value DEADBEEF. It's clever in many ways.

As for practical reasons, firstly, it's more noticeable in a hex memory dump because it actually spells words as opposed to random hex values.

Secondly, if the value winds up in a pointer, it's more likely to induce a memory out-of-range fault. An address of DEADBEEF was out of the address range of systems (we're talking last century systems now) regardless of the system's endian.

Thirdly, it is more likely to induce a fault on systems that require even boundary pointer values for accessing 16/32/64-bit data. The value is more likely to fault because both of the 16 bit values (DEAD, BEEF) are odd.

How to list all Git tags?

And here is how you find the remote tags:

git ls-remote --tags origin

Exponentiation in Python - should I prefer ** operator instead of math.pow and math.sqrt?

math.sqrt is the C implementation of square root and is therefore different from using the ** operator which implements Python's built-in pow function. Thus, using math.sqrt actually gives a different answer than using the ** operator and there is indeed a computational reason to prefer numpy or math module implementation over the built-in. Specifically the sqrt functions are probably implemented in the most efficient way possible whereas ** operates over a large number of bases and exponents and is probably unoptimized for the specific case of square root. On the other hand, the built-in pow function handles a few extra cases like "complex numbers, unbounded integer powers, and modular exponentiation".

See this Stack Overflow question for more information on the difference between ** and math.sqrt.

In terms of which is more "Pythonic", I think we need to discuss the very definition of that word. From the official Python glossary, it states that a piece of code or idea is Pythonic if it "closely follows the most common idioms of the Python language, rather than implementing code using concepts common to other languages." In every single other language I can think of, there is some math module with basic square root functions. However there are languages that lack a power operator like ** e.g. C++. So ** is probably more Pythonic, but whether or not it's objectively better depends on the use case.

How to install and run phpize

This might help someone on ubuntu. No promises.

sudo apt-get install libcurl3 php5-dev libcurl4-gnutls-dev libmagic-dev
sudo apt-get install php-http make
sudo pecl install pecl_http

And adding "" to php.ini (Normally located at /etc/php5/apache2/php.ini)

Then restart Apache (sudo service apache2 restart).

If in doubt, check your apache logs:

sudo su --
cd /var/log/apache2
tail -25 error.log

Is starting or failing?

Date formatting in WPF datagrid

Binding="{Binding YourColumn ,StringFormat='yyyy-MM-dd'}"

What is the difference between Scala's case class and class?

A case class is a class that may be used with the match/case statement.

def isIdentityFun(term: Term): Boolean = term match {
  case Fun(x, Var(y)) if x == y => true
  case _ => false

You see that case is followed by an instance of class Fun whose 2nd parameter is a Var. This is a very nice and powerful syntax, but it cannot work with instances of any class, therefore there are some restrictions for case classes. And if these restrictions are obeyed, it is possible to automatically define hashcode and equals.

The vague phrase "a recursive decomposition mechanism via pattern matching" means just "it works with case". (Indeed, the instance followed by match is compared to (matched against) the instance that follows case, Scala has to decompose them both, and has to recursively decompose what they are made of.)

What case classes are useful for? The Wikipedia article about Algebraic Data Types gives two good classical examples, lists and trees. Support for algebraic data types (including knowing how to compare them) is a must for any modern functional language.

What case classes are not useful for? Some objects have state, the code like connection.setConnectTimeout(connectTimeout) is not for case classes.

And now you can read A Tour of Scala: Case Classes

java.util.Date format SSSSSS: if not microseconds what are the last 3 digits?

SSSSSS is microseconds. Let us say the time is 10:30:22 (Seconds 22) and 10:30:22.1 would be 22 seconds and 1/10 of a second . Extending the same logic , 10:32.22.000132 would be 22 seconds and 132/1,000,000 of a second, which is nothing but microseconds.

installing urllib in Python3.6

urllib is a standard python library (built-in) so you don't have to install it. just import it if you need to use request by:

import urllib.request

if it's not work maybe you compiled python in wrong way, so be kind and give us more details.

Remove a prefix from a string

I think you can use methods of the str type to do this. There's no need for regular expressions:

def remove_prefix(text, prefix):
    if text.startswith(prefix): # only modify the text if it starts with the prefix
         text = text.replace(prefix, "", 1) # remove one instance of prefix
    return text

Is it possible to find out the users who have checked out my project on GitHub?

Use the GitHub Network Graph to Track Forks

You have no way to see who has checked out your repository using standard git commands such as git clone, but you can see who has forked your repository on GitHub using the Network Graph Visualizer. At the time of this answer, you can access this feature in at least two ways:

  1. From the "Network" tab just to the right of the "Code" tab on the navigation bar at the top of your repository.
  2. By clicking on the numbers (if non-zero) in the call-out just to the right of the "Fork" widget on the right-hand side.

For example, here is a partial screenshot of the rbenv network graph:

rbenv network graph

The "Members" tab at the top of the Network Graph will also show you a different view, listing the names of the people who currently have forks on GitHub. It obviously will not show people who cloned outside of GitHub, or folks who have subsequently deleted their forks.

How do I calculate the normal vector of a line segment?

If we define dx = x2 - x1 and dy = y2 - y1, then the normals are (-dy, dx) and (dy, -dx).

Note that no division is required, and so you're not risking dividing by zero.

Undefined variable: $_SESSION

Another possibility for this warning (and, most likely, problems with app behavior) is that the original author of the app relied on session.auto_start being on (defaults to off)

If you don't want to mess with the code and just need it to work, you can always change php configuration and restart php-fpm (if this is a web app):

/etc/php.d/my-new-file.ini :

session.auto_start = 1

(This is correct for CentOS 8, adjust for your OS/packaging)

Multi column forms with fieldsets

There are a couple of things that need to be adjusted in your layout:

  1. You are nesting col elements within form-group elements. This should be the other way around (the form-group should be within the col-sm-xx element).

  2. You should always use a row div for each new "row" in your design. In your case, you would need at least 5 rows (Username, Password and co, Title/First/Last name, email, Language). Otherwise, your problematic .col-sm-12 is still on the same row with the above 3 .col-sm-4 resulting in a total of columns greater than 12, and causing the overlap problem.

Here is a fixed demo.

And an excerpt of what the problematic section HTML should become:

    <legend>Personal Information</legend>
    <div class='row'>
        <div class='col-sm-4'>    
            <div class='form-group'>
                <label for="user_title">Title</label>
                <input class="form-control" id="user_title" name="user[title]" size="30" type="text" />
        <div class='col-sm-4'>
            <div class='form-group'>
                <label for="user_firstname">First name</label>
                <input class="form-control" id="user_firstname" name="user[firstname]" required="true" size="30" type="text" />
        <div class='col-sm-4'>
            <div class='form-group'>
                <label for="user_lastname">Last name</label>
                <input class="form-control" id="user_lastname" name="user[lastname]" required="true" size="30" type="text" />
    <div class='row'>
        <div class='col-sm-12'>
            <div class='form-group'>

                <label for="user_email">Email</label>
                <input class="form-control required email" id="user_email" name="user[email]" required="true" size="30" type="text" />

What is the difference between bool and Boolean types in C#

bool is an alias for the Boolean class. I use the alias when declaring a variable and the class name when calling a method on the class.

psql: FATAL: role "postgres" does not exist

If you're using docker, make sure you're NOT using POSTGRES_USER=something_else, as this variable is used by the standard image to know the name of the PostgreSQL admin user (default as postgres).

In my case, I was using this variable with the intent to set another user to my specific database, but it ended up of course changing the main PostgreSQL user.

Converting a PDF to PNG

Try to extract a single page.

$page = 4

gs -sDEVICE=pngalpha -dFirstPage="$page" -dLastPage="$page" -o thumb.png -r144 input.pdf

How to use protractor to check if an element is visible?

If there are multiple elements in DOM with same class name. But only one of element is visible.

        return ele.isDisplayed();

In this example filter takes a collection of elements and returns a single visible element using isDisplayed().

Injecting Mockito mocks into a Spring bean

The best way is:

<bean id="dao" class="org.mockito.Mockito" factory-method="mock"> 
    <constructor-arg value="com.package.Dao" /> 

In the context file this mock must be listed before any autowired field depending on it is declared.

How to plot a very simple bar chart (Python, Matplotlib) using input *.txt file?

You're talking about histograms, but this doesn't quite make sense. Histograms and bar charts are different things. An histogram would be a bar chart representing the sum of values per year, for example. Here, you just seem to be after bars.

Here is a complete example from your data that shows a bar of for each required value at each date:

import pylab as pl
import datetime

data = """0 14-11-2003
1 15-03-1999
12 04-12-2012
33 09-05-2007
44 16-08-1998
55 25-07-2001
76 31-12-2011
87 25-06-1993
118 16-02-1995
119 10-02-1981
145 03-05-2014"""

values = []
dates = []

for line in data.split("\n"):
    x, y = line.split()
    dates.append(datetime.datetime.strptime(y, "%d-%m-%Y").date())

fig = pl.figure()
ax = pl.subplot(111), values, width=100)

You need to parse the date with strptime and set the x-axis to use dates (as described in this answer).

If you're not interested in having the x-axis show a linear time scale, but just want bars with labels, you can do this instead:

fig = pl.figure()
ax = pl.subplot(111), values)

EDIT: Following comments, for all the ticks, and for them to be centred, pass the range to set_ticks (and move them by half the bar width):

fig = pl.figure()
ax = pl.subplot(111)
width=0.8, values, width=width)
ax.set_xticks(np.arange(len(dates)) + width/2)
ax.set_xticklabels(dates, rotation=90)

JOIN queries vs multiple queries

Construct both separate queries and joins, then time each of them -- nothing helps more than real-world numbers.

Then even better -- add "EXPLAIN" to the beginning of each query. This will tell you how many subqueries MySQL is using to answer your request for data, and how many rows scanned for each query.

The most sophisticated way for creating comma-separated Strings from a Collection/Array/List?

In case someone stumbled over this in more recent times, I have added a simple variation using Java 8 reduce(). It also includes some of the already mentioned solutions by others:

import java.util.Arrays;
import java.util.List;

import org.apache.commons.lang.StringUtils;    


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

    List<String> strings = Arrays.asList("abc", "de", "fg");
    String commaSeparated = strings
        .reduce((s1, s2) -> {return s1 + "," + s2; })



    System.out.println(StringUtils.join(strings, ","));


How do I get the path of the current executed file in Python?

I was running into a similar problem, and I think this might solve the problem:

def module_path(local_function):
   ''' returns the module path without the use of __file__.  Requires a function defined
   locally in the module.
   return os.path.abspath(inspect.getsourcefile(local_function))

It works for regular scripts and in idle. All I can say is try it out for others!

My typical usage:

from toolbox import module_path
def main():
   pass # Do stuff

global __modpath__
__modpath__ = module_path(main)

Now I use __modpath__ instead of __file__.