Programs & Examples On #Helpermethods

Can Rails Routing Helpers (i.e. mymodel_path(model)) be Used in Models?

Any logic having to do with what is displayed in the view should be delegated to a helper method, as methods in the model are strictly for handling data.

Here is what you could do:

# In the helper...

def link_to_thing(text, thing)
  (thing.url?) ? link_to(text, thing_path(thing)) : link_to(text, thing.url)

# In the view...

<%= link_to_thing("text", @thing) %>

Binary Data Posting with curl

You don't need --header "Content-Length: $LENGTH".

curl --request POST --data-binary "@template_entry.xml" $URL

Note that GET request does not support content body widely.

Also remember that POST request have 2 different coding schema. This is first form:

  $ nc -l -p 6666 &
  $ curl  --request POST --data-binary "@README" http://localhost:6666

User-Agent: curl/7.21.0 (x86_64-pc-linux-gnu) libcurl/7.21.0 OpenSSL/0.9.8o zlib/ libidn/1.15 libssh2/1.2.6
Host: localhost:6666
Accept: */*
Content-Length: 9309
Content-Type: application/x-www-form-urlencoded
Expect: 100-continue

.. -*- mode: rst; coding: cp1251; fill-column: 80 -*-
.. contents::

You probably request this:

-F/--form name=content
           (HTTP) This lets curl emulate a filled-in form in
              which a user has pressed the submit button. This
              causes curl to POST data using the Content- Type
              multipart/form-data according to RFC2388. This
              enables uploading of binary files etc. To force the
              'content' part to be a file, prefix the file name
              with an @ sign. To just get the content part from a
              file, prefix the file name with the symbol <. The
              difference between @ and < is then that @ makes a
              file get attached in the post as a file upload,
              while the < makes a text field and just get the
              contents for that text field from a file.

Violation of PRIMARY KEY constraint. Cannot insert duplicate key in object

To prevent inserting a record that exist already. I'd check if the ID value exists in the database. For the example of a Table created with an IDENTITY PRIMARY KEY:

CREATE TABLE [dbo].[Persons] (    
    LastName VARCHAR(40) NOT NULL,
    FirstName VARCHAR(40)

When JANE DOE and JOE BROWN already exist in the database.

INSERT INTO [dbo].[Persons] (FirstName,LastName)
INSERT INTO Persons (FirstName,LastName) 

DATABASE OUTPUT of TABLE [dbo].[Persons] will be:

ID    LastName   FirstName
1     DOE        Jane
2     BROWN      JOE

I'd check if i should update an existing record or insert a new one. As the following JAVA example:

int NewID = 1;
boolean IdAlreadyExist = false;
// Using SQL database connection
// STEP 1: Set property
System.setProperty("", "true");
// STEP 2: Register JDBC driver
// STEP 3: Open a connection
try (Connection conn1 = DriverManager.getConnection(DB_URL, USER,pwd) {
    String Select = "select * from Persons where  ID = " + ID;
    Statement st1 = conn1.createStatement();
    ResultSet rs1 = st1.executeQuery(Select);
    // iterate through the java resultset
    while ( {
        int ID = rs1.getInt("ID");
        if (NewID==ID) {
            IdAlreadyExist = true;

} catch (SQLException e1) {
if (IdAlreadyExist==false) {
    //Insert new record code here
} else {
    //Update existing record code here

XPath with multiple conditions

Here, we can do this way as well:

//category [@name='category name']/author[contains(text(),'authorname')]


//category [@name='category name']//author[contains(text(),'authorname')]

To Learn XPATH in detail please visit- selenium xpath in detail

Initialize a string in C to empty string

You want to set the first character of the string to zero, like this:

char myString[10];
myString[0] = '\0';

(Or myString[0] = 0;)

Or, actually, on initialisation, you can do:

char myString[10] = "";

But that's not a general way to set a string to zero length once it's been defined.

Scale iFrame css width 100% like an image

You could use viewport units here instead of %. Like this:

iframe {
    max-width: 100vw;
    max-height: 56.25vw; /* height/width ratio = 315/560 = .5625 */

DEMO (Resize to see the effect)

body {_x000D_
  margin: 0;_x000D_
.a {_x000D_
  max-width: 560px;_x000D_
  background: grey;_x000D_
img {_x000D_
  width: 100%;_x000D_
  height: auto_x000D_
iframe {_x000D_
  max-width: 100vw;_x000D_
  max-height: 56.25vw;_x000D_
  /* 315/560 = .5625 */_x000D_
<div class="a">_x000D_
  <img src="" width="560" height="315" />_x000D_
<div class="a">_x000D_
  <iframe width="560" height="315" src="" frameborder="0" allowfullscreen></iframe>_x000D_

.NET - Get protocol, host, and port

Even though @Rick has the accepted answer for this question, there's actually a shorter way to do this, using the poorly named Uri.GetLeftPart() method.

Uri url = new Uri("");
string output = url.GetLeftPart(UriPartial.Authority);

There is one catch to GetLeftPart(), however. If the port is the default port for the scheme, it will strip it out. Since port 80 is the default port for http, the output of GetLeftPart() in my example above will be

If the port number had been something other than 80, it would be included in the result.

Where is Ubuntu storing installed programs?

Just for an addition reference to the above answers. I can not use dpkg -L to find the correct path for cuda. See the results I got from dpkg -L

$ dpkg -L cuda

the correct path is /usr/local/cuda

$ ll /usr/local | grep cuda

lrwxrwxrwx  1 root root    8 Oct 20 18:45 cuda -> cuda-9.0/

drwxr-xr-x 15 root root 4096 Oct 20 18:44 cuda-9.0/

Btw, I did install cuda by the command of

dpkg -i xx_cuda_xxx.deb

How to convert characters to HTML entities using plain JavaScript

I adapted one of the answers from the referenced question, but added the ability to define an explicit mapping for character names.

var char_names = {

function HTMLEncode(str){
     var aStr = str.split(''),
         i = aStr.length,
         aRet = [];

     while (--i >= 0) {
      var iC = aStr[i].charCodeAt();
       if (iC < 32 || (iC > 32 && iC < 65) || iC > 127 || (iC>90 && iC<97)) {
        if(char_names[iC]!=undefined) {
        else {
       } else {
    return aRet.reverse().join('');

var text = "Übergroße Äpfel mit Würmer";


What is the printf format specifier for bool?

You can't, but you can print 0 or 1

_Bool b = 1;
printf("%d\n", b);


"Find next" in Vim

You may be looking for the n key.

How can I display a messagebox in ASP.NET?

Alert message with redirect

Response.Write("<script language='javascript'>window.alert('Popup message ');window.location='webform.aspx';</script>");

Only alert message

Response.Write("<script language='javascript'>window.alert('Popup message ')</script>");

Moment JS - check if a date is today or in the future

Since no one seems to have mentioned it yet, the simplest way to check if a Moment date object is in the past:


Or in the future:


Just leave the args blank -- that'll default to now.

There's also isSameOrAfter and isSameOrBefore.

N.B. this factors in time. If you only care about the day, see Dipendu's answer.

Renaming branches remotely in Git

I don't know why but @Sylvain Defresne's answer does not work for me.

git branch new-branch-name origin/old-branch-name
git push origin --set-upstream new-branch-name
git push origin :old-branch-name

I have to unset the upstream and then I can set the stream again. The following is how I did it.

git checkout -b new-branch-name
git branch --unset-upstream
git push origin new-branch-name -u
git branch origin :old-branch-name

Access denied for root user in MySQL command-line

By default there is no password is set for root user in XAMPP.

You can set password for root user of MySQL.

Navigate to


and set password for root user.

Note:Please change the port number in above url if your Apache in on different port.

Open XAMPP control panel Click "Shell" button

Command prompt window will open now in that window type

mysql -u root -p;

It will ask for password type the password which you have set for root user.

There you go ur logged in as root user :D Now do what u want to do :P

How to write text on a image in windows using python opencv2

I had a similar problem. I would suggest using the PIL library in python as it draws the text in any given font, compared to limited fonts in OpenCV. With PIL you can choose any font installed on your system.

from PIL import ImageFont, ImageDraw, Image
import numpy as np
import cv2

image = cv2.imread("lena.png")

# Convert to PIL Image
cv2_im_rgb = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
pil_im = Image.fromarray(cv2_im_rgb)

draw = ImageDraw.Draw(pil_im)

# Choose a font
font = ImageFont.truetype("Roboto-Regular.ttf", 50)

# Draw the text
draw.text((0, 0), "Your Text Here", font=font)

# Save the image
cv2_im_processed = cv2.cvtColor(np.array(pil_im), cv2.COLOR_RGB2BGR)
cv2.imwrite("result.png", cv2_im_processed)


How can I make a "color map" plot in matlab?

I also suggest using contourf(Z). For my problem, I wanted to visualize a 3D histogram in 2D, but the contours were too smooth to represent a top view of histogram bars.

So in my case, I prefer to use jucestain's answer. The default shading faceted of pcolor() is more suitable. However, pcolor() does not use the last row and column of the plotted matrix. For this, I used the padarray() function:

pcolor(padarray(Z,[1 1],0,'post'))

Sorry if that is not really related to the original post

JavaScript function to add X months to a date

Just to add on to the accepted answer and the comments.

var x = 12; //or whatever offset
var CurrentDate = new Date();

//For the very rare cases like the end of a month
//eg. May 30th - 3 months will give you March instead of February
var date = CurrentDate.getDate();

How do I connect to a specific Wi-Fi network in Android programmatically?

Before connecting WIFI network you need to check security type of the WIFI network ScanResult class has a capabilities. This field gives you type of network


There are three types of WIFI networks.

First, instantiate a WifiConfiguration object and fill in the network’s SSID (note that it has to be enclosed in double quotes), set the initial state to disabled, and specify the network’s priority (numbers around 40 seem to work well).

WifiConfiguration wfc = new WifiConfiguration();

wfc.SSID = "\"".concat(ssid).concat("\"");
wfc.status = WifiConfiguration.Status.DISABLED;
wfc.priority = 40;

Now for the more complicated part: we need to fill several members of WifiConfiguration to specify the network’s security mode. For open networks.


For networks using WEP; note that the WEP key is also enclosed in double quotes.


if (isHexString(password)) wfc.wepKeys[0] = password;
else wfc.wepKeys[0] = "\"".concat(password).concat("\"");
wfc.wepTxKeyIndex = 0;

For networks using WPA and WPA2, we can set the same values for either.


wfc.preSharedKey = "\"".concat(password).concat("\"");

Finally, we can add the network to the WifiManager’s known list

WifiManager wfMgr = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
int networkId = wfMgr.addNetwork(wfc);
if (networkId != -1) {
 // success, can call wfMgr.enableNetwork(networkId, true) to connect

How to remove all the occurrences of a char in c++ string

The algorithm std::replace works per element on a given sequence (so it replaces elements with different elements, and can not replace it with nothing). But there is no empty character. If you want to remove elements from a sequence, the following elements have to be moved, and std::replace doesn't work like this.

You can try to use std::remove (together with std::erase) to achieve this.

str.erase(std::remove(str.begin(), str.end(), 'a'), str.end());

R numbers from 1 to 100

Your mistake is looking for range, which gives you the range of a vector, for example:

range(c(10, -5, 100))


 -5 100

Instead, look at the : operator to give sequences (with a step size of one):


or you can use the seq function to have a bit more control. For example,

##Step size of 2
seq(1, 100, by=2)


##length.out: desired length of the sequence
seq(1, 100, length.out=5)

Auto-Submit Form using JavaScript

Try using document.getElementById("myForm") instead of document.myForm.

var auto_refresh = setInterval(function() { submitform(); }, 10000);

function submitform()

Find if current time falls in a time range

The TimeOfDay property returns a TimeSpan value.

Try the following code:

TimeSpan time = DateTime.Now.TimeOfDay;

if (time > new TimeSpan(11, 59, 00)        //Hours, Minutes, Seconds
 && time < new TimeSpan(13, 01, 00)) {
    //match found

Also, new DateTime() is the same as DateTime.MinValue and will always be equal to 1/1/0001 12:00:00 AM. (Value types cannot have non-empty default values) You want to use DateTime.Now.

How to set-up a favicon?

Below given some information about fav Icon

What Is FavIcon? ? FavIcon is nothing but small image which appears top left along with the application address bar title.Standard size specification for favicon.ico is 16 by 16 pixel. Please see below attached figure.

enter image description here

How It Works ? ? Usually we add our FavIcon.ico image in the route solution folder and automatically application picks it while running. But most of the time we might have to use below both link reference.

               <link rel="icon" href="favicon.ico" type="image/ico"/>
               <link rel="shortcut icon" href="favicon.ico" type="image/x-icon"/>

Some browser expect one (rel="icon") Some other browser expect other rel="shortcut icon"

? Type=”image/x-icon” OR Type=”image/ico”: once expect exact ico image and one expect any image even formatted from .jpg or .pn ..etc.

? We have to use above two tags to the common pages like – Master page , Main frame which is getting used in all the pages

How to compile for Windows on Linux with gcc/g++?

I've used mingw on Linux to make Windows executables in C, I suspect C++ would work as well.

I have a project, ELLCC, that packages clang and other things as a cross compiler tool chain. I use it to compile clang (C++), binutils, and GDB for Windows. Follow the download link at for pre-compiled binaries for several Linux hosts.

How to call Stored Procedure in a View?

I was able to call stored procedure in a view (SQL Server 2005).

CREATE FUNCTION [dbo].[dimMeasure] 

     SELECT * FROM OPENROWSET('SQLNCLI', 'Server=localhost; Trusted_Connection=yes;', 'exec ceaw.dbo.sp_dimMeasure2')

Inside stored procedure we need to set:

set nocount on
CREATE VIEW [dbo].[dimMeasure]

SELECT * FROM OPENROWSET('SQLNCLI', 'Server=localhost;Trusted_Connection=yes;', 'exec ceaw.dbo.sp_dimMeasure2')


How do I check if a number is positive or negative in C#?

if (num < 0) {
if (num > 0) {
if (num == 0) {
  //neither positive or negative,

or use "else ifs"

The maximum value for an int type in Go

The germane part:

Since integer types use two's complement arithmetic, you can infer the min/max constant values for int and uint. For example,

const MaxUint = ^uint(0) 
const MinUint = 0 
const MaxInt = int(MaxUint >> 1) 
const MinInt = -MaxInt - 1

As per @CarelZA's comment:

uint8  : 0 to 255 
uint16 : 0 to 65535 
uint32 : 0 to 4294967295 
uint64 : 0 to 18446744073709551615 
int8   : -128 to 127 
int16  : -32768 to 32767 
int32  : -2147483648 to 2147483647 
int64  : -9223372036854775808 to 9223372036854775807

How to get a pixel's x,y coordinate color from an image?

Building on Jeff's answer, your first step would be to create a canvas representation of your PNG. The following creates an off-screen canvas that is the same width and height as your image and has the image drawn on it.

var img = document.getElementById('my-image');
var canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
canvas.getContext('2d').drawImage(img, 0, 0, img.width, img.height);

After that, when a user clicks, use event.offsetX and event.offsetY to get the position. This can then be used to acquire the pixel:

var pixelData = canvas.getContext('2d').getImageData(event.offsetX, event.offsetY, 1, 1).data;

Because you are only grabbing one pixel, pixelData is a four entry array containing the pixel's R, G, B, and A values. For alpha, anything less than 255 represents some level of transparency with 0 being fully transparent.

Here is a jsFiddle example: I used jQuery for convenience in all of this, but it is by no means required.

Note: getImageData falls under the browser's same-origin policy to prevent data leaks, meaning this technique will fail if you dirty the canvas with an image from another domain or (I believe, but some browsers may have solved this) SVG from any domain. This protects against cases where a site serves up a custom image asset for a logged in user and an attacker wants to read the image to get information. You can solve the problem by either serving the image from the same server or implementing Cross-origin resource sharing.

How can I divide two integers stored in variables in Python?

x / y

quotient of x and y

x // y 

(floored) quotient of x and y

How to put a List<class> into a JSONObject and then read that object?

Let us assume that the class is Data with two objects name and dob which are both strings.

Initially, check if the list is empty. Then, add the objects from the list to a JSONArray

JSONArray allDataArray = new JSONArray();
List<Data> sList = new ArrayList<String>();

    //if List not empty
    if (!(sList.size() ==0)) {

        //Loop index size()
        for(int index = 0; index < sList.size(); index++) {
            JSONObject eachData = new JSONObject();
            try {
                eachData.put("name", sList.get(index).getName());
                eachData.put("dob", sList.get(index).getDob());
            } catch (JSONException e) {
    } else {
        //Do something when sList is empty

Finally, add the JSONArray to a JSONObject.

JSONObject root = new JSONObject();
    try {
        root.put("data", allDataArray);
    } catch (JSONException e) {

You can further get this data as a String too.

String jsonString = root.toString();

Can I force a UITableView to hide the separator between empty cells?

I use the following:

UIView *view = [[UIView alloc] init];
myTableView.tableFooterView = view;
[view release];

Doing it in viewDidLoad. But you can set it anywhere.

Tomcat is web server or application server?

Apache Tomcat is an open source software implementation of the Java Servlet and JavaServer Pages technologies.

Since Tomcat does not implement the full Java EE specification for an application server, it can be considered as a web server.


How can I download a specific Maven artifact in one command line?

One could use dependency:copy ( which takes a list of artifacts defined in the plugin configuration section and copies them to a specified location, renaming them or stripping the version if desired. This goal can resolve the artifacts from remote repositories if they don't exist in either the local repository or the reactor.

Not all the properties of the plugin could be used in maven CLI. The properties which have "User Property:" property defined could be specified. In the below example I am downloading junit to my temp folder and stripping the vesion from the jar file.

mvn org.apache.maven.plugins:maven-dependency-plugin:2.8:copy -Dartifact=junit:junit:4.11 -DoutputDirectory=/tmp -Dmdep.stripVersion=true

where artifact=junit:junit:4.11 is the maven coordinates. And you specify artifcat as groupId:artifactId:version[:packaging[:classifier]]

(Thanks to Pascal Thivent for providing his in the first place. I am adding another answer)

How to force browser to download file?

You are setting the response headers after writing the contents of the file to the output stream. This is quite late in the response lifecycle to be setting headers. The correct sequence of operations should be to set the headers first, and then write the contents of the file to the servlet's outputstream.

Therefore, your method should be written as follows (this won't compile as it is a mere representation):

response.setHeader("Content-Transfer-Encoding", "binary");
response.setHeader("Content-Disposition","attachment; filename=\"" + "xxx\"");//fileName);
File f= new File(fileName);

InputStream in = new FileInputStream(f);
BufferedInputStream bin = new BufferedInputStream(in);
DataInputStream din = new DataInputStream(bin);

while(din.available() > 0){

The reason for the failure is that it is possible for the actual headers sent by the servlet would be different from what you are intending to send. After all, if the servlet container does not know what headers (which appear before the body in the HTTP response), then it may set appropriate headers to ensure that the response is valid; setting the headers after the file has been written is therefore futile and redundant as the container might have already set the headers. You could confirm this by looking at the network traffic using Wireshark or a HTTP debugging proxy like Fiddler or WebScarab.

You may also refer to the Java EE API documentation for ServletResponse.setContentType to understand this behavior:

Sets the content type of the response being sent to the client, if the response has not been committed yet. The given content type may include a character encoding specification, for example, text/html;charset=UTF-8. The response's character encoding is only set from the given content type if this method is called before getWriter is called.

This method may be called repeatedly to change content type and character encoding. This method has no effect if called after the response has been committed.


How do I parse a HTML page with Node.js

jsdom is too strict to do any real screen scraping sort of things, but beautifulsoup doesn't choke on bad markup.

node-soupselect is a port of python's beautifulsoup into nodejs, and it works beautifully

Laravel Controller Subfolder routing

If you're using Laravel 5.3 or above, there's no need to get into so much of complexity like other answers have said. Just use default artisan command to generate a new controller. For eg, if I want to create a User controller in User folder. I would type

php artisan make:controller User/User

In routes,

Route::get('/dashboard', 'User\User@dashboard');

doing just this would be fine and now on localhost/dashboard is where the page resides.

Hope this helps.

Gets last digit of a number

public static void main(String[] args) {


public static int lastDigit(int number)
    //your code goes here. 
    int last = number % 10;

    return last;



REST URI convention - Singular or plural name of resource while creating it

I know most people are between deciding whether to use plural or singular. The issue that has not been addressed here is that the client will need to know which one you are using, and they are always likely to make a mistake. This is where my suggestion comes from.

How about both? And by that, I mean use singular for your whole API and then create routes to forward requests made in the plural form to the singular form. For example:

GET  /resources     =     GET  /resource
GET  /resources/1   =     GET  /resource/1
POST /resources/1   =     POST /resource/1

You get the picture. No one is wrong, minimal effort, and the client will always get it right.

How to fix org.hibernate.LazyInitializationException - could not initialize proxy - no Session

If you using Spring mark the class as @Transactional, then Spring will handle session management.

public class MyClass {

By using @Transactional, many important aspects such as transaction propagation are handled automatically. In this case if another transactional method is called the method will have the option of joining the ongoing transaction avoiding the "no session" exception.

WARNING If you do use @Transactional, please be aware of the resulting behavior. See this article for common pitfalls. For example, updates to entities are persisted even if you don't explicitly call save

Phone Number Validation MVC


[Required(ErrorMessage = "You must provide a phone number")]
[Display(Name = "Home Phone")]
[RegularExpression(@"^\(?([0-9]{3})\)?[-. ]?([0-9]{3})[-. ]?([0-9]{4})$", ErrorMessage = "Not a valid phone number")]
public string PhoneNumber { get; set; }


@Html.LabelFor(model => model.PhoneNumber)
@Html.EditorFor(model => model.PhoneNumber)
@Html.ValidationMessageFor(model => model.PhoneNumber)

Looping through list items with jquery

To solve this without jQuery .each() you'd have to fix your code like this:

var listItems = $("#productList").find("li");
var ind, len, product;

for ( ind = 0, len = listItems.length; ind < len; ind++ ) {
    product = $(listItems[ind]);

    // ...

Bugs in your original code:

  1. for ... in will also loop through all inherited properties; i.e. you will also get a list of all functions that are defined by jQuery.

  2. The loop variable li is not the list item, but the index to the list item. In that case the index is a normal array index (i.e. an integer)

Basically you are save to use .each() as it is more comfortable, but espacially when you are looping bigger arrays the code in this answer will be much faster.

For other alternatives to .each() you can check out this performance comparison:

Static link of shared library function in gcc

Yeah, I know this is an 8 year-old question, but I was told that it was possible to statically link against a shared-object library and this was literally the top hit when I searched for more information about it.

To actually demonstrate that statically linking a shared-object library is not possible with ld (gcc's linker) -- as opposed to just a bunch of people insisting that it's not possible -- use the following gcc command:

gcc -o executablename objectname.o -Wl,-Bstatic

(Of course you'll have to compile objectname.o from sourcename.c, and you should probably make up your own shared-object library as well. If you do, use -Wl,--library-path,. so that ld can find your library in the local directory.)

The actual error you receive is:

/usr/bin/ld: attempted static link of dynamic object `'
collect2: error: ld returned 1 exit status

Hope that helps.

How to my "exe" from PyCharm project

You cannot directly save a Python file as an exe and expect it to work -- the computer cannot automatically understand whatever code you happened to type in a text file. Instead, you need to use another program to transform your Python code into an exe.

I recommend using a program like Pyinstaller. It essentially takes the Python interpreter and bundles it with your script to turn it into a standalone exe that can be run on arbitrary computers that don't have Python installed (typically Windows computers, since Linux tends to come pre-installed with Python).

To install it, you can either download it from the linked website or use the command:

pip install pyinstaller

...from the command line. Then, for the most part, you simply navigate to the folder containing your source code via the command line and run:


You can find more information about how to use Pyinstaller and customize the build process via the documentation.

You don't necessarily have to use Pyinstaller, though. Here's a comparison of different programs that can be used to turn your Python code into an executable.

svn : how to create a branch from certain revision of trunk

Try below one:

svn copy 
  -m "Creating a private branch of /calc/trunk."  --parents

No slash "\" between the svn URLs.

Rounding BigDecimal to *always* have two decimal places

value = value.setScale(2, RoundingMode.CEILING)

json_decode to array

This is a late contribution, but there is a valid case for casting json_decode with (array).
Consider the following:

$jsondata = '';
$arr = json_decode($jsondata, true);
foreach ($arr as $k=>$v){
    echo $v; // etc.

If $jsondata is ever returned as an empty string (as in my experience it often is), json_decode will return NULL, resulting in the error Warning: Invalid argument supplied for foreach() on line 3. You could add a line of if/then code or a ternary operator, but IMO it's cleaner to simply change line 2 to ...

$arr = (array) json_decode($jsondata,true);

... unless you are json_decodeing millions of large arrays at once, in which case as @TCB13 points out, performance could be negatively effected.

How do I pipe a subprocess call to a text file?

If you want to write the output to a file you can use the stdout-argument of

It takes None, subprocess.PIPE, a file object or a file descriptor. The first is the default, stdout is inherited from the parent (your script). The second allows you to pipe from one command/process to another. The third and fourth are what you want, to have the output written to a file.

You need to open a file with something like open and pass the object or file descriptor integer to call:

f = open("blah.txt", "w")["/home/myuser/", "/tmp/ad_xml",  "/tmp/video_xml"], stdout=f)

I'm guessing any valid file-like object would work, like a socket (gasp :)), but I've never tried.

As marcog mentions in the comments you might want to redirect stderr as well, you can redirect this to the same location as stdout with stderr=subprocess.STDOUT. Any of the above mentioned values works as well, you can redirect to different places.

difference between variables inside and outside of __init__()

Without Self

Create some objects:

class foo(object):
    x = 'original class'

c1, c2 = foo(), foo()

I can change the c1 instance, and it will not affect the c2 instance:

c1.x = 'changed instance'
>>> 'original class'

But if I change the foo class, all instances of that class will be changed as well:

foo.x = 'changed class'
>>> 'changed class'

Please note how Python scoping works here:

>>> 'changed instance'

With Self

Changing the class does not affect the instances:

class foo(object):
    def __init__(self):
        self.x = 'original self'

c1 = foo()
foo.x = 'changed class'
>>> 'original self'

Modal width (increase)

Simply Use !important after giving width of that class that is override your class.

For Example

.modal .modal-dialog {
  width: 850px !important;

Hopefully this will works for you.

jQuery - Disable Form Fields

try this



vice versa for the select also.

String MinLength and MaxLength validation don't work ( mvc)

They do now, with latest version of MVC (and jquery validate packages). mvc51-release-notes#Unobtrusive

Thanks to this answer for pointing it out!

Remove Duplicate objects from JSON Array

var standardsList = [
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Geometry"},
    {"Grade": "Math 1", "Domain": "Counting & Cardinality"},
    {"Grade": "Math 1", "Domain": "Counting & Cardinality"},
    {"Grade": "Math 1", "Domain": "Orders of Operation"},
    {"Grade": "Math 2", "Domain": "Geometry"},
    {"Grade": "Math 2", "Domain": "Geometry"}

 function uniqurArray(array){
                         var a = array.concat();
                        for(var i=0; i<a.length; i++) {
                            for(var j=i+1; j<a.length; j++) {
                                if(a[i].Grade === a[j].Grade){
                                    a.splice(j--, 1);

                        return a;

    uniqurArray(standardsList) // put this js in console and you get uniq object in array

When should you use a class vs a struct in C++?

They are pretty much the same thing. Thanks to the magic of C++, a struct can hold functions, use inheritance, created using "new" and so on just like a class

The only functional difference is that a class begins with private access rights, while a struct begins with public. This is the maintain backwards compatibility with C.

In practice, I've always used structs as data holders and classes as objects.

Entity Framework: One Database, Multiple DbContexts. Is this a bad idea?

My gut told me the same thing when I came across this design.

I am working on a code base where there are three dbContexts to one database. 2 out of the 3 dbcontexts are dependent on information from 1 dbcontext because it serves up the administrative data. This design has placed constraints on how you can query your data. I ran into this problem where you cannot join across dbcontexts. Instead what you are required to do is query the two separate dbcontexts then do a join in memory or iterate through both to get the combination of the two as a result set. The problem with that is instead of querying for a specific result set you are now loading all your records into memory and then doing a join against the two result sets in memory. It can really slow things down.

I would ask the question "just because you can, should you?"

See this article for the problem I came across related to this design. The specified LINQ expression contains references to queries that are associated with different contexts

Get screenshot on Windows with Python?

Worth noting that ImageGrab only works on MSWindows.

For cross platform compatibility, a person may be best off with using the wxPython library.

import wx
wx.App()  # Need to create an App instance before doing anything
screen = wx.ScreenDC()
size = screen.GetSize()
bmp = wx.EmptyBitmap(size[0], size[1])
mem = wx.MemoryDC(bmp)
mem.Blit(0, 0, size[0], size[1], screen, 0, 0)
del mem  # Release bitmap
bmp.SaveFile('screenshot.png', wx.BITMAP_TYPE_PNG)

Is the server running on host "localhost" (::1) and accepting TCP/IP connections on port 5432?

Wild stab in the dark: You're on a machine with an IPv6 resolver where localhost defaults to the IPv6 address ::1, but listen_addresses in postgresql.conf is set to or not * or you're using an older PostgreSQL built with a C library that doesn't have transparent IPv6 support.

Change listen_addresses to localhost and make sure localhost resolves to both the IPv4 and IPv6 addresses, or set it to ::1, to explicitly specify both IPv4 and IPv6. Or just set it to * to listen on all interfaces. Alternately, if you don't care about IPv6, connect to instead of localhost.

See this Google search or this Stack Overflow search for more information.

(Posting despite my close-vote because I voted the question for migration).

Sleep function in ORACLE

Create a procedure which just does your lock and install it into a different user, who is "trusted" with dbms_lock ( USERA ), grant USERA access to dbms_lock.

Then just grant USERB access to this function. They then wont need to be able to access DBMS_LOCK

( make sure you don't have usera and userb in your system before running this )

Connect as a user with grant privs for dbms_lock, and can create users

drop user usera cascade;
drop user userb cascade;
create user usera default tablespace users identified by abc123;
grant create session to usera;
grant resource to usera;
grant execute on dbms_lock to usera;

create user userb default tablespace users identified by abc123;
grant create session to userb;
grant resource to useb

connect usera/abc123;

create or replace function usera.f_sleep( in_time number ) return number is
 return 1;

grant execute on usera.f_sleep to userb;

connect userb/abc123;

/* About to sleep as userb */
select usera.f_sleep(5) from dual;
/* Finished sleeping as userb */

/* Attempt to access dbms_lock as userb.. Should fail */


/* Finished */

Create nice column output in python

Scolp is a new library that lets you pretty print streaming columnar data easily while auto-adjusting column width.

(Disclaimer: I am the author)

Overwriting txt file in java


My biggest "D'oh" moment! I've been compiling it on Eclipse rather than cmd which was where I was executing it. So my newly compiled classes went to the bin folder and the compiled class file via command prompt remained the same in my src folder. I recompiled with my new code and it works like a charm.

File fold = new File("../playlist/" + existingPlaylist.getText() + ".txt");

File fnew = new File("../playlist/" + existingPlaylist.getText() + ".txt");

String source = textArea.getText();

try {
    FileWriter f2 = new FileWriter(fnew, false);

} catch (IOException e) {

How to get duplicate items from a list using LINQ?

Here's another option:

var list = new List<string> { "6", "1", "2", "4", "6", "5", "1" };

var set = new HashSet<string>();
var duplicates = list.Where(x => !set.Add(x));

HTML set image on browser tab

It's called a Favicon, have a read.

<link rel="shortcut icon" href=""/>

You can use this neat tool to generate cross-browser compatible Favicons.

how to execute php code within javascript

You could use it ports a bunch of PHP functionality to javascript, but if it's just echos, and the script is in a php file, you could do something like this:

alert("<?php echo "asdasda";?>");

don't worry about the shifty-looking use of double-quotes, PHP will render that before the browser sees it.

as for using ajax, the easiest way is to use a library, like jQuery. With that you can do:

  url: 'test.php',
  success: function(data) {

and test.php would be:

  echo 'asdasda';

it would write the contents of test.php to whatever element has the result class.

onSaveInstanceState () and onRestoreInstanceState ()

I think this thread was quite old. I just mention another case, that onSaveInstanceState() will also be called, is when you call Activity.moveTaskToBack(boolean nonRootActivity).

Unable to set default python version to python3 in ubuntu

At first, Make sure Python3 is installed on your computer

Go to your terminal and type:

cd ~/ to go to your home directory

If you didn't set up your .bash_profile yet, type touch .bash_profile to create your .bash_profile.

Or, type open -e .bash_profile to edit the file.

Copy and save alias python=python3 in the .bash_profile.

Close and reopen your Terminal. Then type the following command to check if Python3 is your default version now:

python --version

You should see python 3.x.y is your default version.


How can I expose more than 1 port with Docker?

To expose just one port, this is what you need to do:

docker run -p <host_port>:<container_port>

To expose multiple ports, simply provide multiple -p arguments:

docker run -p <host_port1>:<container_port1> -p <host_port2>:<container_port2>

VBA array sort function?

Take a look here:
Edit: The referenced source ( has since closed, but here are the relevant author comments:

There are many algorithms available on the web for sorting. The most versatile and usually the quickest is the Quicksort algorithm. Below is a function for it.

Call it simply by passing an array of values (string or numeric; it doesn't matter) with the Lower Array Boundary (usually 0) and the Upper Array Boundary (i.e. UBound(myArray).)

Example: Call QuickSort(myArray, 0, UBound(myArray))

When it's done, myArray will be sorted and you can do what you want with it.

Public Sub QuickSort(vArray As Variant, inLow As Long, inHi As Long)
  Dim pivot   As Variant
  Dim tmpSwap As Variant
  Dim tmpLow  As Long
  Dim tmpHi   As Long

  tmpLow = inLow
  tmpHi = inHi

  pivot = vArray((inLow + inHi) \ 2)

  While (tmpLow <= tmpHi)
     While (vArray(tmpLow) < pivot And tmpLow < inHi)
        tmpLow = tmpLow + 1

     While (pivot < vArray(tmpHi) And tmpHi > inLow)
        tmpHi = tmpHi - 1

     If (tmpLow <= tmpHi) Then
        tmpSwap = vArray(tmpLow)
        vArray(tmpLow) = vArray(tmpHi)
        vArray(tmpHi) = tmpSwap
        tmpLow = tmpLow + 1
        tmpHi = tmpHi - 1
     End If

  If (inLow < tmpHi) Then QuickSort vArray, inLow, tmpHi
  If (tmpLow < inHi) Then QuickSort vArray, tmpLow, inHi
End Sub

Note that this only works with single-dimensional (aka "normal"?) arrays. (There's a working multi-dimensional array QuickSort here.)

"elseif" syntax in JavaScript

Actually, technically when indented properly, it would be:

if (condition) {
} else {
    if (condition) {
    } else {

There is no else if, strictly speaking.

(Update: Of course, as pointed out, the above is not considered good style.)

Why use @Scripts.Render("~/bundles/jquery")

You can also use:

@Scripts.RenderFormat("<script type=\"text/javascript\" src=\"{0}\"></script>", "~/bundles/mybundle")

To specify the format of your output in a scenario where you need to use Charset, Type, etc.

how to get the host url using javascript from the current page

I like this one depending of purpose

window.location.href.split("/")[2] == "localhost:17000" //always domain + port

You can apply it on any url-string

var url = "http://localhost:17000/sub1/sub2/mypage.html?q=12";
url.split("/")[2] == "localhost:17000"
url.split("/")[url.split("/").length-1] == "mypage.html?q=12"

Removing protocol, domain & path from url-string (relative path)

var arr = url.split("/");
if (arr.length>3)
   "/" + arr.splice(3, arr.length).join("/") == "/sub1/sub2/mypage.html?q=12"

Notification Icon with the new Firebase Cloud Messaging system

Thought I would add an answer to this one, since my problem was simple but hard to notice. In particular I had copy/pasted an existing meta-data element when creating my, which used an android:value tag to specify its value. This will not work for the notification icon, and once I changed it to android:resource everything worked as expected.

What is the use of the square brackets [] in sql statements?

Column names can contain characters and reserved words that will confuse the query execution engine, so placing brackets around them at all times prevents this from happening. Easier than checking for an issue and then dealing with it, I guess.

Why can't decimal numbers be represented exactly in binary?

The high scoring answer above nailed it.

First you were mixing base 2 and base 10 in your question, then when you put a number on the right side that is not divisible into the base you get problems. Like 1/3 in decimal because 3 doesnt go into a power of 10 or 1/5 in binary which doesnt go into a power of 2.

Another comment though NEVER use equal with floating point numbers, period. Even if it is an exact representation there are some numbers in some floating point systems that can be accurately represented in more than one way (IEEE is bad about this, it is a horrible floating point spec to start with, so expect headaches). No different here 1/3 is not EQUAL to the number on your calculator 0.3333333, no matter how many 3's there are to the right of the decimal point. It is or can be close enough but is not equal. so you would expect something like 2*1/3 to not equal 2/3 depending on the rounding. Never use equal with floating point.

Freeing up a TCP/IP port?

You can use tcpkill (part of the dsniff package) to kill the connection that's on the port you need:

sudo tcpkill -9 port PORT_NUMBER

Omitting the first line from any Linux command output

ls -lart | tail -n +2 #argument means starting with line 2

Best way to strip punctuation from a string

For the convenience of usage, I sum up the note of striping punctuation from a string in both Python 2 and Python 3. Please refer to other answers for the detailed description.

Python 2

import string

s = "string. With. Punctuation?"
table = string.maketrans("","")
new_s = s.translate(table, string.punctuation)      # Output: string without punctuation

Python 3

import string

s = "string. With. Punctuation?"
table = str.maketrans(dict.fromkeys(string.punctuation))  # OR {key: None for key in string.punctuation}
new_s = s.translate(table)                          # Output: string without punctuation

Open new Terminal Tab from command line (Mac OS X)

Here's how it's done by bash_it:

function tab() {
  osascript 2>/dev/null <<EOF
    tell application "System Events"
      tell process "Terminal" to keystroke "t" using command down
    tell application "Terminal"
      do script with command "cd \"$PWD\"; $*" in window 1
    end tell

After adding this to your .bash_profile, you'd use the tab command to open the current working directory in a new tab.


Resetting a multi-stage form with jQuery


Importing a GitHub project into Eclipse

Using the command line is an option, and would remove the need for an Eclipse Plugin. First, create a directory to hold the project.

mkdir myGitRepo
cd myGitRepo

Clone the desired repository in the directory you just created.

git clone

Then open Eclipse and select the directory you created (myGitRepo) as the Eclipse Workspace.

Don't worry that the Project Explorer is empty, Eclipse can't recognize the source files yet.

Lastly, create a new Java project with the exact same name as the project you pulled. In this case, it was 'gitTutorial'.

File -> New -> Java Project

At this point, the project's sub directories should contain the files pulled from Github. Take a look at the following post in my blog for a more detailed explanation.

How do I print part of a rendered HTML page in JavaScript?

I would go about it somewhat like this:

        <title>Print Test Page</title>
            printDivCSS = new String ('<link href="myprintstyle.css" rel="stylesheet" type="text/css">')
            function printDiv(divId) {
                window.frames["print_frame"].document.body.innerHTML=printDivCSS + document.getElementById(divId).innerHTML;

        <h1><b><center>This is a test page for printing</center></b><hr color=#00cc00 width=95%></h1>
        <b>Div 1:</b> <a href="javascript:printDiv('div1')">Print</a><br>
        <div id="div1">This is the div1's print output</div>
        <b>Div 2:</b> <a href="javascript:printDiv('div2')">Print</a><br>
        <div id="div2">This is the div2's print output</div>
        <b>Div 3:</b> <a href="javascript:printDiv('div3')">Print</a><br>
        <div id="div3">This is the div3's print output</div>
        <iframe name="print_frame" width="0" height="0" frameborder="0" src="about:blank"></iframe>

How to get AM/PM from a datetime in PHP

You need to convert it to a UNIX timestamp (using strtotime) and then back into the format you require using the date function.

For example:

$currentDateTime = '08/04/2010 22:15:00';
$newDateTime = date('h:i A', strtotime($currentDateTime));

PHP - Extracting a property from an array of objects

Warning create_function() has been DEPRECATED as of PHP 7.2.0. Relying on this function is highly discouraged.

You can use the array_map() function.
This should do it:

$catIds = array_map(create_function('$o', 'return $o->id;'), $objects);

As @Relequestual writes below, the function is now integrated directly in the array_map. The new version of the solution looks like this:

$catIds = array_map(function($o) { return $o->id;}, $objects);

jQuery .each() with input elements


This will alert the value of input type number fields

Demo is present at

Why is Node.js single threaded?

Node.js was created explicitly as an experiment in async processing. The theory was that doing async processing on a single thread could provide more performance and scalability under typical web loads than the typical thread-based implementation.

And you know what? In my opinion that theory's been borne out. A node.js app that isn't doing CPU intensive stuff can run thousands more concurrent connections than Apache or IIS or other thread-based servers.

The single threaded, async nature does make things complicated. But do you honestly think it's more complicated than threading? One race condition can ruin your entire month! Or empty out your thread pool due to some setting somewhere and watch your response time slow to a crawl! Not to mention deadlocks, priority inversions, and all the other gyrations that go with multithreading.

In the end, I don't think it's universally better or worse; it's different, and sometimes it's better and sometimes it's not. Use the right tool for the job.

Why does this "Slow network detected..." log appear in Chrome?

I also had the same errors with fontawesome's fonts. Then I downloaded the lastest fontawesome's fonts and replace to the old fonts. And the errors are gone.

how to get session id of client in Client

* Please Note: as of v0.9 the set and get API has been deprecated *

The following code should only be used for version < 0.9

It can be done through the handshake/authorization mechanism.

var cookie = require('cookie');
io.set('authorization', function (data, accept) {
    // check if there's a cookie header
    if (data.headers.cookie) {
        // if there is, parse the cookie
        data.cookie = cookie.parse(data.headers.cookie);
        // note that you will need to use the same key to grad the
        // session id, as you specified in the Express setup.
        data.sessionID = data.cookie['express.sid'];
    } else {
       // if there isn't, turn down the connection with a message
       // and leave the function.
       return accept('No cookie transmitted.', false);
    // accept the incoming connection
    accept(null, true);

All the attributes, that are assigned to the data object are now accessible through the handshake attribute of the connection object.

io.sockets.on('connection', function (socket) {
    console.log('sessionID ' + socket.handshake.sessionID);

How to reset / remove chrome's input highlighting / focus border?

This will definitely work. Orange outline won't show up anymore.. Common for all tags:

*:focus {
    outline: none;

Specific to some tag, ex: input tag


What are Long-Polling, Websockets, Server-Sent Events (SSE) and Comet?

Tieme put a lot of effort into his excellent answer, but I think the core of the OP's question is how these technologies relate to PHP rather than how each technology works.

PHP is the most used language in web development besides the obvious client side HTML, CSS, and Javascript. Yet PHP has 2 major issues when it comes to real-time applications:

  1. PHP started as a very basic CGI. PHP has progressed very far since its early stage, but it happened in small steps. PHP already had many millions of users by the time it became the embed-able and flexible C library that it is today, most of whom were dependent on its earlier model of execution, so it hasn't yet made a solid attempt to escape the CGI model internally. Even the command line interface invokes the PHP library ( on Linux, php5ts.dll on Windows, etc) as if it still a CGI processing a GET/POST request. It still executes code as if it just has to build a "page" and then end its life cycle. As a result, it has very little support for multi-thread or event-driven programming (within PHP userspace), making it currently unpractical for real-time, multi-user applications.

Note that PHP does have extensions to provide event loops (such as libevent) and threads (such as pthreads) in PHP userspace, but very, very, few of the applications use these.

  1. PHP still has significant issues with garbage collection. Although these issues have been consistently improving (likely its greatest step to end the life cycle as described above), even the best attempts at creating long-running PHP applications require being restarted on a regular basis. This also makes it unpractical for real-time applications.

PHP 7 will be a great step to fix these issues as well, and seems very promising as a platform for real-time applications.

What is the maximum length of data I can put in a BLOB column in MySQL?

A BLOB can be 65535 bytes maximum. If you need more consider using a MEDIUMBLOB for 16777215 bytes or a LONGBLOB for 4294967295 bytes.

Hope, it will help you.

How to get terminal's Character Encoding

locale command with no arguments will print the values of all of the relevant environment variables except for LANGUAGE.

For current encoding:

locale charmap

For available locales:

locale -a

For available encodings:

locale -m

Swift - encode URL

Had need of this myself, so I wrote a String extension that both allows for URLEncoding strings, as well as the more common end goal, converting a parameter dictionary into "GET" style URL Parameters:

extension String {
    func URLEncodedString() -> String? {
        var escapedString = self.addingPercentEncoding(withAllowedCharacters: .urlHostAllowed)
        return escapedString
    static func queryStringFromParameters(parameters: Dictionary<String,String>) -> String? {
        if (parameters.count == 0)
            return nil
        var queryString : String? = nil
        for (key, value) in parameters {
            if let encodedKey = key.URLEncodedString() {
                if let encodedValue = value.URLEncodedString() {
                    if queryString == nil
                        queryString = "?"
                        queryString! += "&"
                    queryString! += encodedKey + "=" + encodedValue
        return queryString


Get the cartesian product of a series of lists?

import itertools
>>> for i in itertools.product([1,2,3],['a','b'],[4,5]):
...         print i
(1, 'a', 4)
(1, 'a', 5)
(1, 'b', 4)
(1, 'b', 5)
(2, 'a', 4)
(2, 'a', 5)
(2, 'b', 4)
(2, 'b', 5)
(3, 'a', 4)
(3, 'a', 5)
(3, 'b', 4)
(3, 'b', 5)

How to return string value from the stored procedure

change your

return @str1+'present in the string' ;


set @r = @str1+'present in the string' 

PHP read and write JSON from file

If you want to display the JSON data in well defined formate you can modify the code as:

file_put_contents($file, json_encode($json,TRUE));

$headers = array('http'=>array('method'=>'GET','header'=>'Content: type=application/json \r\n'.'$agent \r\n'.'$hash'));


$str = file_get_contents("list.txt",FILE_USE_INCLUDE_PATH,$context);



foreach($str1 as $key=>$value)

    echo "key is: $key.\n";

    echo "values are: \t";
        foreach ($value as $k) {

        echo " $k. \t";
        # code...
        echo "<br></br>";
        echo "\n";


Best way to run scheduled tasks

A New Task Scheduler Class Library for .NET

Note: Since this library was created, Microsoft has introduced a new task scheduler (Task Scheduler 2.0) for Windows Vista. This library is a wrapper for the Task Scheduler 1.0 interface, which is still available in Vista and is compatible with Windows XP, Windows Server 2003 and Windows 2000.

Generating an array of letters in the alphabet

C# 3.0 :

char[] az = Enumerable.Range('a', 'z' - 'a' + 1).Select(i => (Char)i).ToArray();
foreach (var c in az)

yes it does work even if the only overload of Enumerable.Range accepts int parameters ;-)

Codeigniter LIKE with wildcard(%)

For Full like you can user :


For %$query you can use

$this->db->like('title', $query, 'before');

and for $query% you can use

$this->db->like('title', $query, 'after');

100% width in React Native Flexbox


In order to flex only the center text, a different approach can be taken - Unflex the other views.

  • Let flexDirection remain at 'column'
  • remove the alignItems : 'center' from container
  • add alignSelf:'center' to the textviews that you don't want to flex

You can wrap the Text component in a View component and give the View a flex of 1.

The flex will give :

100% width if the flexDirection:'row' in styles.container

100% height if the flexDirection:'column' in styles.container

Convert Json Array to normal Java list

Maybe it's only a workaround (not very efficient) but you could do something like this:

String[] resultingArray = yourJSONarray.join(",").split(",");

Obviously you can change the ',' separator with anything you like (I had a JSONArray of email addresses)

node.js - how to write an array to file

We can simply write the array data to the filesystem but this will raise one error in which ',' will be appended to the end of the file. To handle this below code can be used:

var fs = require('fs');

var file = fs.createWriteStream('hello.txt');
file.on('error', function(err) { Console.log(err) });
data.forEach(value => file.write(`${value}\r\n`));


is used for the new Line.


won't help. Please refer this

Re-ordering factor levels in data frame

Assuming your dataframe is mydf:

mydf$task <- factor(mydf$task, levels = c("up", "down", "left", "right", "front", "back"))

MySQL ERROR 1045 (28000): Access denied for user 'bill'@'localhost' (using password: YES)


~$ mysql -u root -p
Enter Password:

mysql> grant all privileges on *.* to bill@localhost identified by 'pass' with grant option;

await is only valid in async function

Yes, await / async was a great concept, but the implementation is completely broken.

For whatever reason, the await keyword has been implemented such that it can only be used within an async method. This is in fact a bug, though you will not see it referred to as such anywhere but right here. The fix for this bug would be to implement the await keyword such that it can only be used TO CALL an async function, regardless of whether the calling function is itself synchronous or asynchronous.

Due to this bug, if you use await to call a real asynchronous function somewhere in your code, then ALL of your functions must be marked as async and ALL of your function calls must use await.

This essentially means that you must add the overhead of promises to all of the functions in your entire application, most of which are not and never will be asynchronous.

If you actually think about it, using await in a function should require the function containing the await keyword TO NOT BE ASYNC - this is because the await keyword is going to pause processing in the function where the await keyword is found. If processing in that function is paused, then it is definitely NOT asynchronous.

So, to the developers of javascript and ECMAScript - please fix the await/async implementation as follows...

  • await can only be used to CALL async functions.
  • await can appear in any kind of function, synchronous or asynchronous.
  • Change the error message from "await is only valid in async function" to "await can only be used to call async functions".

Checking if a worksheet-based checkbox is checked

Building on the previous answers, you can leverage the fact that True is -1 and False is 0 and shorten your code like this:

Sub Button167_Click()
  Range("Y12").Value = _
    Abs(Worksheets(1).Shapes("Check Box 1").OLEFormat.Object.Value > 0)
End Sub

If the checkbox is checked, .Value = 1.

Worksheets(1).Shapes("Check Box 1").OLEFormat.Object.Value > 0 returns True.

Applying the Abs function converts True to 1.

If the checkbox is unchecked, .Value = -4146.

Worksheets(1).Shapes("Check Box 1").OLEFormat.Object.Value > 0 returns False.

Applying the Abs function converts False to 0.

How to see the CREATE VIEW code for a view in PostgreSQL?

select definition from pg_views where viewname = 'my_view'

Spring Boot: Unable to start EmbeddedWebApplicationContext due to missing EmbeddedServletContainerFactory bean

A SpringApplication will attempt to create the right type of ApplicationContext on your behalf. By default, an AnnotationConfigApplicationContext or AnnotationConfigEmbeddedWebApplicationContext will be used, depending on whether you are developing a web application or not.

The algorithm used to determine a ‘web environment’ is fairly simplistic (based on the presence of a few classes). You can use setWebEnvironment(boolean webEnvironment) if you need to override the default.

It is also possible to take complete control of the ApplicationContext type that will be used by calling setApplicationContextClass(…?).

[Tip] It is often desirable to call setWebEnvironment(false) when using SpringApplication within a JUnit test.

Installing Apple's Network Link Conditioner Tool

You can also install any of the Hardware IO Tools without installing XCode itself. Simply visit Apple's Download Center and search for "Hardware IO".

Axios get access to response header fields

In case of CORS requests, browsers can only access the following response headers by default:

  • Cache-Control
  • Content-Language
  • Content-Type
  • Expires
  • Last-Modified
  • Pragma

If you would like your client app to be able to access other headers, you need to set the Access-Control-Expose-Headers header on the server:

Access-Control-Expose-Headers: Access-Token, Uid

Difference between a class and a module

¦               ¦ class                     ¦ module                          ¦
¦ instantiation ¦ can be instantiated       ¦ can *not* be instantiated       ¦
¦ usage         ¦ object creation           ¦ mixin facility. provide         ¦
¦               ¦                           ¦   a namespace.                  ¦
¦ superclass    ¦ module                    ¦ object                          ¦
¦ methods       ¦ class methods and         ¦ module methods and              ¦
¦               ¦   instance methods        ¦   instance methods              ¦
¦ inheritance   ¦ inherits behaviour and can¦ No inheritance                  ¦
¦               ¦   be base for inheritance ¦                                 ¦
¦ inclusion     ¦ cannot be included        ¦ can be included in classes and  ¦
¦               ¦                           ¦   modules by using the include  ¦
¦               ¦                           ¦   command (includes all         ¦
¦               ¦                           ¦   instance methods as instance  ¦
¦               ¦                           ¦   methods in a class/module)    ¦
¦ extension     ¦ can not extend with       ¦ module can extend instance by   ¦
¦               ¦   extend command          ¦   using extend command (extends ¦
¦               ¦   (only with inheritance) ¦   given instance with singleton ¦
¦               ¦                           ¦   methods from module)          ¦

vba listbox multicolumn add

Simplified example (with counter):

With Me.lstbox
    .ColumnCount = 2
    .ColumnWidths = "60;60"
    .List(i, 0) = Company_ID
    .List(i, 1) = Company_name 
    i = i + 1

end with

Make sure to start the counter with 0, not 1 to fill up a listbox.

How do I do a case-insensitive string comparison?

This is another regex which I have learned to love/hate over the last week so usually import as (in this case yes) something that reflects how im feeling! make a normal function.... ask for input, then use ....something = re.compile(r'foo*|spam*', yes.I)...... re.I (yes.I below) is the same as IGNORECASE but you cant make as many mistakes writing it!

You then search your message using regex's but honestly that should be a few pages in its own , but the point is that foo or spam are piped together and case is ignored. Then if either are found then lost_n_found would display one of them. if neither then lost_n_found is equal to None. If its not equal to none return the user_input in lower case using "return lost_n_found.lower()"

This allows you to much more easily match up anything thats going to be case sensitive. Lastly (NCS) stands for "no one cares seriously...!" or not case sensitive....whichever

if anyone has any questions get me on this..

    import re as yes

    def bar_or_spam():

        message = raw_input("\nEnter FoO for BaR or SpaM for EgGs (NCS): ") 

        message_in_coconut = yes.compile(r'foo*|spam*',  yes.I)

        lost_n_found =

        if lost_n_found != None:
            return lost_n_found.lower()
            print ("Make tea not love")

    whatz_for_breakfast = bar_or_spam()

    if whatz_for_breakfast == foo:
        print ("BaR")

    elif whatz_for_breakfast == spam:
        print ("EgGs")

Merge DLL into EXE?

Download ilmerge and ilmergre gui . makes joining the files so easy ive used these and works great

How can I escape square brackets in a LIKE clause?

Here is what I actually used:

like 'WC![R]S123456' ESCAPE '!'

Count number of rows within each group

dplyr package does this with count/tally commands, or the n() function:

First, some data:

df <- data.frame(x = rep(1:6, rep(c(1, 2, 3), 2)), year = 1993:2004, month = c(1, 1:11))

Now the count:

count(df, year, month)
df %>% count(year, month)

We can also use a slightly longer version with piping and the n() function:

df %>% 
  group_by(year, month) %>%
  summarise(number = n())

or the tally function:

df %>% 
  group_by(year, month) %>%

what is .subscribe in angular?

A Subscription is an object that represents a disposable resource, usually the execution of an Observable. A Subscription has one important method, unsubscribe, that takes no argument and just disposes of the resource held by the subscription.

import { interval } from 'rxjs';

const observable = interval(1000);
const subscription = observable.subscribe(a=> console.log(a));

/** This cancels the ongoing Observable execution which
was started by calling subscribe with an Observer.*/


A Subscription essentially just has an unsubscribe() function to release resources or cancel Observable executions.

import { interval } from 'rxjs';

const observable1 = interval(400);
const observable2 = interval(300);

const subscription = observable1.subscribe(x => console.log('first: ' + x));
const childSubscription = observable2.subscribe(x => console.log('second: ' + x));


setTimeout(() => {
// It unsubscribes BOTH subscription and childSubscription
}, 1000);

According to the official documentation, Angular should unsubscribe for you, but apparently, there is a bug.

How to debug a stored procedure in Toad?

Basic Steps to Debug a Procedure in Toad

  1. Load your Procedure in Toad Editor.
  2. Put debug point on the line where you want to debug.See the first screenshot.
  3. Right click on the editor Execute->Execute PLSQL(Debugger).See the second screeshot.
  4. A window opens up,you need to select the procedure from the left side and pass parameters for that procedure and then click Execute.See the third screenshot.
  5. Now start your debugging check Debug-->Step Over...Add Watch etc.

Reference:Toad Debugger


Execute In Debug


Set position / size of UI element as percentage of screen size

Use the PercentRelativeLayout or PercentFrameLayout from the Percent Supoort Library


val() doesn't trigger change() in jQuery


The change event is sent to an element when its value changes. This event is limited to <input> elements, <textarea> boxes and <select> elements. For select boxes, checkboxes, and radio buttons, the event is fired immediately when the user makes a selection with the mouse, but for the other element types the event is deferred until the element loses focus.

Getting execute permission to xp_cmdshell

To expand on what has been provided for automatically exporting data as csv to a network share via SQL Server Agent.

(1) Enable the xp_cmdshell procedure:

-- To allow advanced options to be changed.
EXEC sp_configure 'show advanced options', 1

-- Enable the xp_cmdshell procedure
EXEC sp_configure 'xp_cmdshell', 1

(2) Create a login 'Domain\TestUser' (windows user) for the non-sysadmin user that has public access to the master database. Done through user mapping

(3) Give log on as batch job: Navigate to Local Security Policy -> Local Policies -> User Rights Assignment. Add user to "Log on as a batch job"

(4) Give read/write permissions to network folder for domain\user

(5) Grant EXEC permission on the xp_cmdshell stored procedure:

GRANT EXECUTE ON xp_cmdshell TO [Domain\TestUser]

(6) Create a proxy account that xp_cmdshell will be run under using sp_xp_cmdshell_proxy_account

EXEC sp_xp_cmdshell_proxy_account 'Domain\TestUser', 'password_for_domain_user'

(7) If the sp_xp_cmdshell_proxy_account command doesn't work, manually create it

create credential ##xp_cmdshell_proxy_account## with identity = 'Domain\DomainUser', secret = 'password'

(8) Enable SQL Server Agent. Open SQL Server Configuration Manager, navigate to SQL Server Services, enable SQL Server Agent.

(9) Create automated job. Open SSMS, select SQL Server Agent, then right-click jobs and click "New Job".

(10) Select "Owner" as your created user. Select "Steps", make "type" = T-SQL. Fill out command field similar to below. Set delimiter as ','

EXEC master..xp_cmdshell 'SQLCMD -q "select * from master" -o file.csv -s "," 

(11) Fill out schedules accordingly.

Why is using a wild card with a Java import statement bad?

please see my article Import on Demand is Evil

In short, the biggest problem is that your code can break when a class is added to a package you import. For example:

import java.awt.*;
import java.util.*;

// ...

List list;

In Java 1.1, this was fine; List was found in java.awt and there was no conflict.

Now suppose you check in your perfectly working code, and a year later someone else brings it out to edit it, and is using Java 1.2.

Java 1.2 added an interface named List to java.util. BOOM! Conflict. The perfectly working code no longer works.

This is an EVIL language feature. There is NO reason that code should stop compiling just because a type is added to a package...

In addition, it makes it difficult for a reader to determine which "Foo" you're using.

"No Content-Security-Policy meta tag found." error in my phonegap application

There are errors in your meta tag.


<meta http-equiv="Content-Security-Policy" content="default-src *; style-src 'self' 'unsafe-inline'; script-src: 'self' 'unsafe-inline' 'unsafe-eval'>


<meta http-equiv="Content-Security-Policy" content="default-src *; style-src 'self' 'unsafe-inline'; script-src 'self' 'unsafe-inline' 'unsafe-eval'"/>

Note the colon after "script-src", and the end double-quote of the meta tag.

Get bytes from std::string in C++

I dont think you want to use the c# code you have there. They provide System.Text.Encoding.ASCII(also UTF-*)

string str = "some text;
byte[] bytes = System.Text.Encoding.ASCII.GetBytes(str);

your problems stem from ignoring the encoding in c# not your c++ code

Maven:Failed to execute goal org.apache.maven.plugins:maven-resources-plugin:2.7:resources

This could be a issue in mvn home path in IntellijIdea IDE. For me it worked out when I set the mvn home directory correctly.enter image description here

No 'Access-Control-Allow-Origin' - Node / Apache Port Issue

The top answer worked fine for me, except that I needed to whitelist more than one domain.

Also, top answer suffers from the fact that OPTIONS request isn't handled by middleware and you don't get it automatically.

I store whitelisted domains as allowed_origins in Express configuration and put the correct domain according to origin header since Access-Control-Allow-Origin doesn't allow specifying more than one domain.

Here's what I ended up with:

var _ = require('underscore');

function allowCrossDomain(req, res, next) {
  res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS');

  var origin = req.headers.origin;
  if (_.contains(app.get('allowed_origins'), origin)) {
    res.setHeader('Access-Control-Allow-Origin', origin);

  if (req.method === 'OPTIONS') {
  } else {

app.configure(function () {

Delete empty lines using sed

You are most likely seeing the unexpected behavior because your text file was created on Windows, so the end of line sequence is \r\n. You can use dos2unix to convert it to a UNIX style text file before running sed or use

sed -r "/^\r?$/d"

to remove blank lines whether or not the carriage return is there.

sed: print only matching group

And for yet another option, I'd go with awk!

echo "foo bar <foo> bla 1 2 3.4" | awk '{ print $(NF-1), $NF; }'

This will split the input (I'm using STDIN here, but your input could easily be a file) on spaces, and then print out the last-but-one field, and then the last field. The $NF variables hold the number of fields found after exploding on spaces.

The benefit of this is that it doesn't matter if what precedes the last two fields changes, as long as you only ever want the last two it'll continue to work.

"for line in..." results in UnicodeDecodeError: 'utf-8' codec can't decode byte

This is an example for converting a CSV file in Python 3:

    inputReader = csv.reader(open(argv[1], encoding='ISO-8859-1'), delimiter=',',quotechar='"')
except IOError:

Inserting a string into a list without getting split into characters

You have to add another list:


Truncate (not round off) decimal numbers in javascript

var a = 5.467;
var truncated = Math.floor(a * 100) / 100; // = 5.46

jQuery delete confirmation box

    if (!confirm("Do you want to delete")){
      return false;

How to merge 2 JSON objects from 2 files using jq?

First, {"value": .value} can be abbreviated to just {value}.

Second, the --argfile option (available in jq 1.4 and jq 1.5) may be of interest as it avoids having to use the --slurp option.

Putting these together, the two objects in the two files can be combined in the specified way as follows:

$ jq -n --argfile o1 file1 --argfile o2 file2 '$o1 * $o2 | {value}'

The '-n' flag tells jq not to read from stdin, since inputs are coming from the --argfile options here.

Note on --argfile

The jq manual deprecates --argfile because its semantics are non-trivial: if the specified input file contains exactly one JSON entity, then that entity is read as is; otherwise, the items in the stream are wrapped in an array.

If you are uncomfortable using --argfile, there are several alternatives you may wish to consider. In doing so, be assured that using --slurpfile does not incur the inefficiencies of the -s command-line option when the latter is used with multiple files.

What is the purpose of Order By 1 in SQL select statement?

it simply means sorting the view or table by 1st column of query's result.

Initialising an array of fixed size in python

Do this:

>>> d = [ [ None for y in range( 2 ) ] for x in range( 2 ) ]
>>> d
[[None, None], [None, None]]
>>> d[0][0] = 1
>>> d
[[1, None], [None, None]]

The other solutions will lead to this kind of problem:

>>> d = [ [ None ] * 2 ] * 2
>>> d
[[None, None], [None, None]]
>>> d[0][0] = 1
>>> d
[[1, None], [1, None]]

master branch and 'origin/master' have diverged, how to 'undiverge' branches'?

I had same message when I was trying to edit last commit message, of already pushed commit, using: git commit --amend -m "New message" When I pushed the changes using git push --force-with-lease repo_name branch_name there were no issues.

How to create a temporary directory?

Use mktemp -d. It creates a temporary directory with a random name and makes sure that file doesn't already exist. You need to remember to delete the directory after using it though.

How to convert PDF files to images

Regarding PDFiumSharp: After elaboration I was able to create PNG files from a PDF solution.

This is my code:

using PDFiumSharp;
using System.Collections.Generic;
using System.Drawing;
using System.IO;

public class Program
    static public void Main(String[] args)
        var renderfoo = new Renderfoo()
        renderfoo.RenderPDFAsImages(@"C:\Temp\example.pdf", @"C:\temp");

public class Renderfoo

    public void RenderPDFAsImages(string Inputfile, string OutputFolder)
        string fileName = Path.GetFileNameWithoutExtension(Inputfile);

        using (PDFiumSharp.PdfDocument doc = new PDFiumSharp.PdfDocument(Inputfile))
            for (int i = 0; i < doc.Pages.Count; i++)
                var page = doc.Pages[i];
                using (var bitmap = new System.Drawing.Bitmap((int)page.Width, (int)page.Height))
                    var grahpics = Graphics.FromImage(bitmap);
                    var targetFile = Path.Combine(OutputFolder, fileName + "_" + i + ".png");


For starters, you need to take the following steps to get the PDFium wrapper up and running:

  • Run the Custom Code tool for both tt files via right click in Visual Studio
  • Compile the GDIPlus Project
  • Copy the compiled assemblies (from the GDIPlus project) to your project
  • Reference both PDFiumSharp and PDFiumsharp.GdiPlus assemblies in your project

  • Make sure that pdfium_x64.dll and/or pdfium_x86.dll are both found in your project output directory.

What is the difference between a URI, a URL and a URN?

Easy to explain:

Lets assume the following

URI is your Name

URL is your address with your name in-order to communicate with you.

  • my name is Loyola

    Loyola is URI

  • my address is TN, Chennai 600001.

TN, Chennai 600 001, Loyola is URL

Hope you understand,

Now lets see a precise example

in the above you can communicate with a page called firstpage.html (URI) using following

Hence URI is subset of URL but not vice-versa.

How do I set default values for functions parameters in Matlab?

This is my simple way to set default values to a function, using "try":

function z = myfun (a,varargin)

%% Default values
b = 1;
c = 1;
d = 1;
e = 1;

    b = varargin{1};
    c = varargin{2};
    d = varargin{3};
    e = varargin{4};

%% Calculation
z = a * b * c * d * e ;


How to set value to form control in Reactive Forms in Angular

Try this.

editqueForm ={
   user: [this.question.user],
   questioning: [this.question.questioning, Validators.required],
   questionType: [this.question.questionType, Validators.required],
   options: new FormArray([])

setValue() and patchValue()

if you want to set the value of one control, this will not work, therefor you have to set the value of both controls:

formgroup.setValue({name: ‘abc’, age: ‘25’});

It is necessary to mention all the controls inside the method. If this is not done, it will throw an error.

On the other hand patchvalue() is a lot easier on that part, let’s say you only want to assign the name as a new value:


Convert string in base64 to image and save on filesystem in Python

You can use Pillow.

pip install Pillow

image = base64.b64decode(str(base64String))       
fileName = 'test.jpeg'

imagePath = FILE_UPLOAD_DIR + fileName

img =, 'jpeg')
return fileName

reference for complete source code:

MySQL query to get column names?

when you want to check your all table structure with some filed then use this code. In this query i select column_name,column_type and table_name for more details . I use order by column_type so i can see it easily.

WHERE `TABLE_SCHEMA`='yourdatabasename' order by DATA_TYPE;

If you want to check only double type filed then you can do it easily

WHERE `TABLE_SCHEMA`='yourdatabasename' AND DATA_TYPE like '%bigint%'  order by DATA_TYPE;

enter image description here

if you want to check which field allow null type etc then you can use this

WHERE `TABLE_SCHEMA`='yourdatabasename' and DATA_TYPE like '%bigint%' and IS_NULLABLE ='NO' order by COLUMN_TYPE;

enter image description here

you want to check more then thik link also help you.

define a List like List<int,string>?

With the new ValueTuple from C# 7 (VS 2017 and above), there is a new solution:

List<(int,string)> mylist= new List<(int,string)>();

Which creates a list of ValueTuple type. If you're targeting .Net Framework 4.7+ or .Net Core, it's native, otherwise you have to get the ValueTuple package from nuget.

It's a struct opposing to Tuple, which is a class. It also has the advantage over the Tuple class that you could create a named tuple, like this:

var mylist = new List<(int myInt, string myString)>();

That way you can access like mylist[0].myInt and mylist[0].myString

How do I wrap text in a span?

Wrapping can be done in various ways. I'll mention 2 of them:

1.) text wrapping - using white-space property

2.) word wrapping - using word-wrap property

By the way, in order to work using these 2 approaches, I believe you need to set the "display" property to block of the corresponding span element.

However, as Kirill already mentioned, it's a good idea to think about it for a moment. You're talking about forcing the text into a paragraph. PARAGRAPH. That should ring some bells in your head, shouldn't it? ;)

How can I read user input from the console?

a = double.Parse(Console.ReadLine());

Beware that if the user enters something that cannot be parsed to a double, an exception will be thrown.


To expand on my answer, the reason it's not working for you is that you are getting an input from the user in string format, and trying to put it directly into a double. You can't do that. You have to extract the double value from the string first.

If you'd like to perform some sort of error checking, simply do this:

if ( double.TryParse(Console.ReadLine(), out a) ) {
  Console.Writeline("Sonuç "+ a * Math.PI;); 
else {
  Console.WriteLine("Invalid number entered. Please enter number in format: #.#");

Thanks to Öyvind and abatischev for helping me refine my answer.

Folder is locked and I can't unlock it

I research a lot on this issue but no solution fix my problem until I try this:

My repo folder is shared with a Windows xp virtual machine, so I execute the clean up from the VM and then execute SVN UPDATE from the host.

It worked for me.

Greetings from Costa Rica.

Android/Java - Date Difference in days

I found a very easy way to do this and it's what I'm using in my app.

Let's say you have the dates in Time objects (or whatever, we just need the milliseconds):

Time date1 = initializeDate1(); //get the date from somewhere
Time date2 = initializeDate2(); //get the date from somewhere

long millis1 = date1.toMillis(true);
long millis2 = date2.toMillis(true);

long difference = millis2 - millis1 ;

//now get the days from the difference and that's it
long days = TimeUnit.MILLISECONDS.toDays(difference);

//now you can do something like
if(days == 7)
    //do whatever when there's a week of difference

if(days >= 30)
    //do whatever when it's been a month or more

How can I monitor the thread count of a process on linux?

To get the number of threads for a given pid:

$ ps -o nlwp <pid>

Where nlwp stands for Number of Light Weight Processes (threads). Thus ps aliases nlwp to thcount, which means that

$ ps -o thcount <pid>

does also work.

If you want to monitor the thread count, simply use watch:

$ watch ps -o thcount <pid>

To get the sum of all threads running in the system:

$ ps -eo nlwp | tail -n +2 | awk '{ num_threads += $1 } END { print num_threads }'

How to stop/cancel 'git log' command in terminal?

You can hit the key q (for quit) and it should take you to the prompt.

Please see this link.

How to switch Python versions in Terminal?

As Inian suggested, you should alias python to point to python 3. It is very easy to do, and very easy to switchback, personally i have an alias setup for p2=python2 and p3=python3 as well to save on keystrokes. Read here for more information: How do I create a Bash alias?

Here is an example of doing so for python:

alias python=python3

Like so:

$ python --version
Python 2.7.6
$ python3 --version
Python 3.4.3
$ alias python=python3
$ python --version
Python 3.4.3

See here for the original:

LNK2019: unresolved external symbol _main referenced in function ___tmainCRTStartup

I had this problem minutes ago. It went away when I added 'extern "C"' to the main() definition.

Oddly, another simple program I wrote yesterday is almost identical, does not have the extern "C", yet compiled without this linker error.

This makes me think the problem is some subtle setting to be found deep in some configuration dialog, and that 'extern "C"' doesn't really solve the underlying problem, but superficially makes things work.

Git: "Corrupt loose object"

Working on a VM, in my notebook, battery died, got this error;

error: object file .git/objects/ce/theRef is empty error: object file .git/objects/ce/theRef is empty fatal: loose object theRef (stored in .git/objects/ce/theRef) is corrupt

I managed to get the repo working again with only 2 commands and without losing my work (modified files/uncommitted changes)

find .git/objects/ -size 0 -exec rm -f {} \;
git fetch origin

After that I ran a git status, the repo was fine and there were my changes (waiting to be committed, do it now..).

git version 1.9.1

Remember to backup all changes you remember, just in case this solution doesn't works and a more radical approach is needed.

getApplication() vs. getApplicationContext()

Compare getApplication() and getApplicationContext().

getApplication returns an Application object which will allow you to manage your global application state and respond to some device situations such as onLowMemory() and onConfigurationChanged().

getApplicationContext returns the global application context - the difference from other contexts is that for example, an activity context may be destroyed (or otherwise made unavailable) by Android when your activity ends. The Application context remains available all the while your Application object exists (which is not tied to a specific Activity) so you can use this for things like Notifications that require a context that will be available for longer periods and independent of transient UI objects.

I guess it depends on what your code is doing whether these may or may not be the same - though in normal use, I'd expect them to be different.

How can I scan barcodes on iOS?

Check out ZBar reads QR Code and ECN/ISBN codes and is available as under the LGPL v2 license.

JavaScript for handling Tab Key press

try this

   <div class="linkCollection">
             <a tabindex=1 href="">link</a>    
             <a tabindex=2 href="">link</a>    
             <a tabindex=3 href="">link</a>    
             <a tabindex=4 href="">link</a>    
             <a tabindex=5 href="">link</a>    
             <a tabindex=6 href="">link</a>    
             <a tabindex=7 href="">link</a>    
             <a tabindex=8 href="">link</a>    
             <a tabindex=9 href="">link</a>    
             <a tabindex=10 href="">link</a>   


  $(".linkCollection a").focus(function(){
    var href=$(this).attr('href');
    // href variable holds the active selected link.

don't forgot to add jQuery library

<script src=""></script>

Rendering an in React

Add up to Dmitry's answer, if you don't want to handle unique key IDs manually, you can use React.Children.toArray as proposed in the React documentation


Returns the children opaque data structure as a flat array with keys assigned to each child. Useful if you want to manipulate collections of children in your render methods, especially if you want to reorder or slice this.props.children before passing it down.


React.Children.toArray() changes keys to preserve the semantics of nested arrays when flattening lists of children. That is, toArray prefixes each key in the returned array so that each element’s key is scoped to the input array containing it.

, i) => <li>Test</li>)

How to specify table's height such that a vertical scroll bar appears?

to set the height of table, you need to first set css property "display: block" then you can add "width/height" properties. I find this Mozilla Article a very good resource to learn how to style tables : Link

How to loop through a plain JavaScript object with the objects as members?

ECMAScript-2017, just finalized a month ago, introduces Object.values(). So now you can do this:

let v;
for (v of Object.values(validation_messages))
   console.log(v.your_name);   // jimmy billy

How to manually set an authenticated user in Spring Security / SpringMVC

Ultimately figured out the root of the problem.

When I create the security context manually no session object is created. Only when the request finishes processing does the Spring Security mechanism realize that the session object is null (when it tries to store the security context to the session after the request has been processed).

At the end of the request Spring Security creates a new session object and session ID. However this new session ID never makes it to the browser because it occurs at the end of the request, after the response to the browser has been made. This causes the new session ID (and hence the Security context containing my manually logged on user) to be lost when the next request contains the previous session ID.

How to open port in Linux

The following configs works on Cent OS 6 or earlier

As stated above first have to disable selinux.

Step 1 nano /etc/sysconfig/selinux

Make sure the file has this configurations



Then restart the system

Step 2

iptables -A INPUT -m state --state NEW -p tcp --dport 8080 -j ACCEPT

Step 3

sudo service iptables save

For Cent OS 7

step 1

firewall-cmd --zone=public --permanent --add-port=8080/tcp

Step 2

firewall-cmd --reload

Select and trigger click event of a radio button in jquery

In my case i had to load images on radio button click, I just uses the regular onclick event and it worked for me.

 <input type="radio" name="colors" value="{{}}" id="{{}}-option" class="color_radion"  onclick="return get_images(this, {{}})">

  function get_images(obj, color){


Sticky and NON-Sticky sessions

When your website is served by only one web server, for each client-server pair, a session object is created and remains in the memory of the web server. All the requests from the client go to this web server and update this session object. If some data needs to be stored in the session object over the period of interaction, it is stored in this session object and stays there as long as the session exists.

However, if your website is served by multiple web servers which sit behind a load balancer, the load balancer decides which actual (physical) web-server should each request go to. For example, if there are 3 web servers A, B and C behind the load balancer, it is possible that is served from server A, is served from server B and are served from server C.

Now, if the requests are being served from (physically) 3 different servers, each server has created a session object for you and because these session objects sit on three independent boxes, there's no direct way of one knowing what is there in the session object of the other. In order to synchronize between these server sessions, you may have to write/read the session data into a layer which is common to all - like a DB. Now writing and reading data to/from a db for this use-case may not be a good idea. Now, here comes the role of sticky-session.

If the load balancer is instructed to use sticky sessions, all of your interactions will happen with the same physical server, even though other servers are present. Thus, your session object will be the same throughout your entire interaction with this website.

To summarize, In case of Sticky Sessions, all your requests will be directed to the same physical web server while in case of a non-sticky loadbalancer may choose any webserver to serve your requests.

As an example, you may read about Amazon's Elastic Load Balancer and sticky sessions here :

Change Placeholder Text using jQuery

Moving your first line to the bottom does it for me:

$(function () {
    $('#serMemdd').change(function () {
        var k = $(this).val();
        if (k == 1) {
            $("#serMemtb").attr("placeholder", "Type a name (Lastname, Firstname)").placeholder();
        else if (k == 2) {
            $("#serMemtb").attr("placeholder", "Type an ID").placeholder();
        else if (k == 3) {
            $("#serMemtb").attr("placeholder", "Type a Location").placeholder();
    $('input[placeholder], textarea[placeholder]').placeholder();

from unix timestamp to datetime

If using react:

import Moment from 'react-moment';
Moment.globalFormat = 'D MMM YYYY';


<td><Moment unix>{1370001284}</Moment></td>

Explaining Python's '__enter__' and '__exit__'

try adding my answers (my thought of learning) :

__enter__ and [__exit__] both are methods that are invoked on entry to and exit from the body of "the with statement" (PEP 343) and implementation of both is called context manager.

the with statement is intend to hiding flow control of try finally clause and make the code inscrutable.

the syntax of the with statement is :

with EXPR as VAR:

which translate to (as mention in PEP 343) :

mgr = (EXPR)
exit = type(mgr).__exit__  # Not calling it yet
value = type(mgr).__enter__(mgr)
exc = True
        VAR = value  # Only if "as VAR" is present
        # The exceptional case is handled here
        exc = False
        if not exit(mgr, *sys.exc_info()):
        # The exception is swallowed if exit() returns true
    # The normal and non-local-goto cases are handled here
    if exc:
        exit(mgr, None, None, None)

try some code:

>>> import logging
>>> import socket
>>> import sys

#server socket on another terminal / python interpreter
>>> s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
>>> s.listen(5)
>>> s.bind((socket.gethostname(), 999))
>>> while True:
>>>    (clientsocket, addr) = s.accept()
>>>    print('get connection from %r' % addr[0])
>>>    msg = clientsocket.recv(1024)
>>>    print('received %r' % msg)
>>>    clientsocket.send(b'connected')
>>>    continue

#the client side
>>> class MyConnectionManager:
>>>     def __init__(self, sock, addrs):
>>>         logging.basicConfig(level=logging.DEBUG, format='%(asctime)s \
>>>         : %(levelname)s --> %(message)s')
>>>'Initiating My connection')
>>>         self.sock = sock
>>>         self.addrs = addrs
>>>     def __enter__(self):
>>>         try:
>>>             self.sock.connect(addrs)
>>>   'connection success')
>>>             return self.sock
>>>         except:
>>>             logging.warning('Connection refused')
>>>             raise
>>>     def __exit__(self, type, value, tb):
>>>   'CM suppress exception')
>>>             return False
>>> addrs = (socket.gethostname())
>>> s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
>>> with MyConnectionManager(s, addrs) as CM:
>>>     try:
>>>         CM.send(b'establishing connection')
>>>         msg = CM.recv(1024)
>>>         print(msg)
>>>     except:
>>>         raise
#will result (client side) :
2018-12-18 14:44:05,863         : INFO --> Initiating My connection
2018-12-18 14:44:05,863         : INFO --> connection success
2018-12-18 14:44:05,864         : INFO --> CM suppress exception

#result of server side
get connection from ''
received b'establishing connection'

and now try manually (following translate syntax):

>>> s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) #make new socket object
>>> mgr = MyConnection(s, addrs)
2018-12-18 14:53:19,331         : INFO --> Initiating My connection
>>> ext = mgr.__exit__
>>> value = mgr.__enter__()
2018-12-18 14:55:55,491         : INFO --> connection success
>>> exc = True
>>> try:
>>>     try:
>>>         VAR = value
>>>         VAR.send(b'establishing connection')
>>>         msg = VAR.recv(1024)
>>>         print(msg)
>>>     except:
>>>         exc = False
>>>         if not ext(*sys.exc_info()):
>>>             raise
>>> finally:
>>>     if exc:
>>>         ext(None, None, None)
#the result:
2018-12-18 15:01:54,208         : INFO --> CM suppress exception

the result of the server side same as before

sorry for my bad english and my unclear explanations, thank you....

A network-related or instance-specific error occurred while establishing a connection to SQL Server

Sql Server fire this error when your application don't have enough rights to access the database. there are several reason about this error . To fix this error you should follow the following instruction.

  1. Try to connect sql server from your server using management studio . if you use windows authentication to connect sql server then set your application pool identity to server administrator .

  2. if you use sql server authentication then check you connection string in web.config of your web application and set user id and password of sql server which allows you to log in .

  3. if your database in other server(access remote database) then first of enable remote access of sql server form sql server property from sql server management studio and enable TCP/IP form sql server configuration manager .

  4. after doing all these stuff and you still can't access the database then check firewall of server form where you are trying to access the database and add one rule in firewall to enable port of sql server(by default sql server use 1433 , to check port of sql server you need to check sql server configuration manager network protocol TCP/IP port).

  5. if your sql server is running on named instance then you need to write port number with sql serer name for example 117.312.21.21/nameofsqlserver,1433.

  6. If you are using cloud hosting like amazon aws or microsoft azure then server or instance will running behind cloud firewall so you need to enable 1433 port in cloud firewall if you have default instance or specific port for sql server for named instance.

  7. If you are using amazon RDS or SQL azure then you need to enable port from security group of that instance.

  8. If you are accessing sql server through sql server authentication mode them make sure you enabled "SQL Server and Windows Authentication Mode" sql server instance property. enter image description here

    1. Restart your sql server instance after making any changes in property as some changes will require restart.

if you further face any difficulty then you need to provide more information about your web site and sql server .

Partial Dependency (Databases)

Partial dependency implies is a situation where a non-prime attribute(An attribute that does not form part of the determinant(Primary key/Candidate key)) is functionally dependent to a portion/part of a primary key/Candidate key.

Why am I getting the message, "fatal: This operation must be run in a work tree?"

If none of the above usual ways help you, look at the call trace underneath this error message ("fatal: This operation . . .") and locate the script and line which is raising the actual error. Once you locate that error() call, disable it and see if the operation you are trying completes even with some warnings/messages - ignore them for now. If so, finally after completing it might mention the part of the operation that was not completed successfully. Now, address this part separately as applicable.

Relating above logic to my case, I was getting this error message "fatal: This operation . . ." when I was trying to get the Android-x86 code with repo sync . . .. and the call trace showed raise GitError("cannot initialize work tree") as the error() call causing the above error message ("fatal: . . ."). So, after commenting that GitError() in .repo/repo/, repo sync . . . continued and finally indicated error for three projects that were not properly synced. I just deleted their *.git folders from their relevant paths in the Android-x86 source tree locally and ran repo sync . . . again and tasted success!

Setting max-height for table cell contents

Possibly not cross browser but I managed get this:

basically it requires a fixed height header and footer. and it absolute positions the table.

    table {
        width: 50%;
        height: 50%;
        border-spacing: 0;
    td {
        border: 1px solid black;
    #content {
        overflow: hidden;

React.js create loop through Array

In CurrentGame component you need to change initial state because you are trying use loop for participants but this property is undefined that's why you get error.,

getInitialState: function(){
    return {
       data: {
          participants: [] 

also, as player in .map is Object you should get properties from it {
   return <li key={player.championId}>{player.summonerName}</li>
   // -------------------^^^^^^^^^^^---------^^^^^^^^^^^^^^


How to auto adjust table td width from the content

you could also use display: table insted of tables. Divs are way more flexible than tables.


.table {_x000D_
   display: table;_x000D_
   border-collapse: collapse;_x000D_
.table .table-row {_x000D_
   display: table-row;_x000D_
.table .table-cell {_x000D_
   display: table-cell;_x000D_
   text-align: left;_x000D_
   vertical-align: top;_x000D_
   border: 1px solid black;_x000D_
<div class="table">_x000D_
 <div class="table-row">_x000D_
  <div class="table-cell">test</div>_x000D_
  <div class="table-cell">test1123</div>_x000D_
 <div class="table-row">_x000D_
  <div class="table-cell">test</div>_x000D_
  <div class="table-cell">test123</div>_x000D_

How to "pull" from a local branch into another one?

Quite old post, but it might help somebody new into git.

I will go with

git rebase master
  • much cleaner log history and no merge commits (if done properly)
  • need to deal with conflicts, but it's not that difficult.

What does mysql error 1025 (HY000): Error on rename of './foo' (errorno: 150) mean?

If you are using a client like MySQL Workbench, right click the desired table from where a foreign key is to be deleted, then select the foreign key tab and delete the indexes.

Then you can run the query like this:

alter table table_name drop foreign_key_col_name;

Retrieve filename from file descriptor in C

As Tyler points out, there's no way to do what you require "directly and reliably", since a given FD may correspond to 0 filenames (in various cases) or > 1 (multiple "hard links" is how the latter situation is generally described). If you do still need the functionality with all the limitations (on speed AND on the possibility of getting 0, 2, ... results rather than 1), here's how you can do it: first, fstat the FD -- this tells you, in the resulting struct stat, what device the file lives on, how many hard links it has, whether it's a special file, etc. This may already answer your question -- e.g. if 0 hard links you will KNOW there is in fact no corresponding filename on disk.

If the stats give you hope, then you have to "walk the tree" of directories on the relevant device until you find all the hard links (or just the first one, if you don't need more than one and any one will do). For that purpose, you use readdir (and opendir &c of course) recursively opening subdirectories until you find in a struct dirent thus received the same inode number you had in the original struct stat (at which time if you want the whole path, rather than just the name, you'll need to walk the chain of directories backwards to reconstruct it).

If this general approach is acceptable, but you need more detailed C code, let us know, it won't be hard to write (though I'd rather not write it if it's useless, i.e. you cannot withstand the inevitably slow performance or the possibility of getting != 1 result for the purposes of your application;-).

HTML email with Javascript

you can use html radio/checkbox input with labels and css to achieve the expanding effects you want.

Make Error 127 when running trying to compile code

Error 127 means one of two things:

  1. file not found: the path you're using is incorrect. double check that the program is actually in your $PATH, or in this case, the relative path is correct -- remember that the current working directory for a random terminal might not be the same for the IDE you're using. it might be better to just use an absolute path instead.
  2. ldso is not found: you're using a pre-compiled binary and it wants an interpreter that isn't on your system. maybe you're using an x86_64 (64-bit) distro, but the prebuilt is for x86 (32-bit). you can determine whether this is the answer by opening a terminal and attempting to execute it directly. or by running file -L on /bin/sh (to get your default/native format) and on the compiler itself (to see what format it is).

if the problem is (2), then you can solve it in a few diff ways:

  1. get a better binary. talk to the vendor that gave you the toolchain and ask them for one that doesn't suck.
  2. see if your distro can install the multilib set of files. most x86_64 64-bit distros allow you to install x86 32-bit libraries in parallel.
  3. build your own cross-compiler using something like crosstool-ng.
  4. you could switch between an x86_64 & x86 install, but that seems a bit drastic ;).

How to stretch a fixed number of horizontal navigation items evenly and fully across a specified container

This is the sort of thing that the CSS flexbox model will fix, because it will let you specify that each li will receive an equal proportion of the remaining width.

Is it possible to add dynamically named properties to JavaScript object?

It can be useful if mixed new property add in runtime:

data = {, newPropery: value}

However, spread operator use shallow copy but here we assign data to itself so should lose nothing

How to combine GROUP BY, ORDER BY and HAVING

Steps for Using Group by,Having By and Order by...

Select Attitude ,count(*) from Person
group by person
HAving PersonAttitude='cool and friendly'
Order by PersonName.

Resolve promises one after another (i.e. in sequence)?

Nicest solution that I was able to figure out was with bluebird promises. You can just do Promise.resolve(files).each(fs.readFileAsync); which guarantees that promises are resolved sequentially in order.

What does "var" mean in C#?

It means that the type of the local being declared will be inferred by the compiler based upon its first assignment:

// This statement:
var foo = "bar";
// Is equivalent to this statement:
string foo = "bar";

Notably, var does not define a variable to be of a dynamic type. So this is NOT legal:

var foo = "bar";
foo = 1; // Compiler error, the foo variable holds strings, not ints

var has only two uses:

  1. It requires less typing to declare variables, especially when declaring a variable as a nested generic type.
  2. It must be used when storing a reference to an object of an anonymous type, because the type name cannot be known in advance: var foo = new { Bar = "bar" };

You cannot use var as the type of anything but locals. So you cannot use the keyword var to declare field/property/parameter/return types.

Best way to convert text files between character sets?

DOS/Windows: use Code page

chcp 65001>NUL
type ascii.txt > unicode.txt

Command chcp can be used to change the code page. Code page 65001 is Microsoft name for UTF-8. After setting code page, the output generated by following commands will be of code page set.

RSpec: how to test if a method was called?

it "should call 'bar' with appropriate arguments" do
  expect(subject).to receive(:bar).with("an argument I want")

How to insert a large block of HTML in JavaScript?

If I understand correctly, you're looking for a multi-line representation, for readability? You want something like a here-string in other languages. Javascript can come close with this:

var x =
    "<div> \
    <span> \
    <p> \
    some text \
    </p> \

What does the restrict keyword mean in C++?

As others said, if means nothing as of C++14, so let's consider the __restrict__ GCC extension which does the same as the C99 restrict.


restrict says that two pointers cannot point to overlapping memory regions. The most common usage is for function arguments.

This restricts how the function can be called, but allows for more compile optimizations.

If the caller does not follow the restrict contract, undefined behavior.

The C99 N1256 draft 6.7.3/7 "Type qualifiers" says:

The intended use of the restrict qualifier (like the register storage class) is to promote optimization, and deleting all instances of the qualifier from all preprocessing translation units composing a conforming program does not change its meaning (i.e., observable behavior).

and "Formal definition of restrict" gives the gory details.

A possible optimization

The Wikipedia example is very illuminating.

It clearly shows how as it allows to save one assembly instruction.

Without restrict:

void f(int *a, int *b, int *x) {
  *a += *x;
  *b += *x;

Pseudo assembly:

load R1 ? *x    ; Load the value of x pointer
load R2 ? *a    ; Load the value of a pointer
add R2 += R1    ; Perform Addition
set R2 ? *a     ; Update the value of a pointer
; Similarly for b, note that x is loaded twice,
; because x may point to a (a aliased by x) thus 
; the value of x will change when the value of a
; changes.
load R1 ? *x
load R2 ? *b
add R2 += R1
set R2 ? *b

With restrict:

void fr(int *restrict a, int *restrict b, int *restrict x);

Pseudo assembly:

load R1 ? *x
load R2 ? *a
add R2 += R1
set R2 ? *a
; Note that x is not reloaded,
; because the compiler knows it is unchanged
; "load R1 ? *x" is no longer needed.
load R2 ? *b
add R2 += R1
set R2 ? *b

Does GCC really do it?

g++ 4.8 Linux x86-64:

g++ -g -std=gnu++98 -O0 -c main.cpp
objdump -S main.o

With -O0, they are the same.

With -O3:

void f(int *a, int *b, int *x) {
    *a += *x;
   0:   8b 02                   mov    (%rdx),%eax
   2:   01 07                   add    %eax,(%rdi)
    *b += *x;
   4:   8b 02                   mov    (%rdx),%eax
   6:   01 06                   add    %eax,(%rsi)  

void fr(int *__restrict__ a, int *__restrict__ b, int *__restrict__ x) {
    *a += *x;
  10:   8b 02                   mov    (%rdx),%eax
  12:   01 07                   add    %eax,(%rdi)
    *b += *x;
  14:   01 06                   add    %eax,(%rsi) 

For the uninitiated, the calling convention is:

  • rdi = first parameter
  • rsi = second parameter
  • rdx = third parameter

GCC output was even clearer than the wiki article: 4 instructions vs 3 instructions.


So far we have single instruction savings, but if pointer represent arrays to be looped over, a common use case, then a bunch of instructions could be saved, as mentioned by supercat and michael.

Consider for example:

void f(char *restrict p1, char *restrict p2, size_t size) {
     for (size_t i = 0; i < size; i++) {
         p1[i] = 4;
         p2[i] = 9;

Because of restrict, a smart compiler (or human), could optimize that to:

memset(p1, 4, size);
memset(p2, 9, size);

Which is potentially much more efficient as it may be assembly optimized on a decent libc implementation (like glibc) Is it better to use std::memcpy() or std::copy() in terms to performance?, possibly with SIMD instructions.

Without, restrict, this optimization could not be done, e.g. consider:

char p1[4];
char *p2 = &p1[1];
f(p1, p2, 3);

Then for version makes:

p1 == {4, 4, 4, 9}

while the memset version makes:

p1 == {4, 9, 9, 9}

Does GCC really do it?

GCC 5.2.1.Linux x86-64 Ubuntu 15.10:

gcc -g -std=c99 -O0 -c main.c
objdump -dr main.o

With -O0, both are the same.

With -O3:

  • with restrict:

    3f0:   48 85 d2                test   %rdx,%rdx
    3f3:   74 33                   je     428 <fr+0x38>
    3f5:   55                      push   %rbp
    3f6:   53                      push   %rbx
    3f7:   48 89 f5                mov    %rsi,%rbp
    3fa:   be 04 00 00 00          mov    $0x4,%esi
    3ff:   48 89 d3                mov    %rdx,%rbx
    402:   48 83 ec 08             sub    $0x8,%rsp
    406:   e8 00 00 00 00          callq  40b <fr+0x1b>
                            407: R_X86_64_PC32      memset-0x4
    40b:   48 83 c4 08             add    $0x8,%rsp
    40f:   48 89 da                mov    %rbx,%rdx
    412:   48 89 ef                mov    %rbp,%rdi
    415:   5b                      pop    %rbx
    416:   5d                      pop    %rbp
    417:   be 09 00 00 00          mov    $0x9,%esi
    41c:   e9 00 00 00 00          jmpq   421 <fr+0x31>
                            41d: R_X86_64_PC32      memset-0x4
    421:   0f 1f 80 00 00 00 00    nopl   0x0(%rax)
    428:   f3 c3                   repz retq

    Two memset calls as expected.

  • without restrict: no stdlib calls, just a 16 iteration wide loop unrolling which I do not intend to reproduce here :-)

I haven't had the patience to benchmark them, but I believe that the restrict version will be faster.

Strict aliasing rule

The restrict keyword only affects pointers of compatible types (e.g. two int*) because the strict aliasing rules says that aliasing incompatible types is undefined behavior by default, and so compilers can assume it does not happen and optimize away.

See: What is the strict aliasing rule?

Does it work for references?

According to the GCC docs it does: with syntax:

int &__restrict__ rref

There is even a version for this of member functions:

void T::fn () __restrict__

iloc giving 'IndexError: single positional indexer is out-of-bounds'

This happens when you index a row/column with a number that is larger than the dimensions of your dataframe. For instance, getting the eleventh column when you have only three.

import pandas as pd

df = pd.DataFrame({'Name': ['Mark', 'Laura', 'Adam', 'Roger', 'Anna'],
                   'City': ['Lisbon', 'Montreal', 'Lisbon', 'Berlin', 'Glasgow'],
                   'Car': ['Tesla', 'Audi', 'Porsche', 'Ford', 'Honda']})

You have 5 rows and three columns:

    Name      City      Car
0   Mark    Lisbon    Tesla
1  Laura  Montreal     Audi
2   Adam    Lisbon  Porsche
3  Roger    Berlin     Ford
4   Anna   Glasgow    Honda

Let's try to index the eleventh column (it doesn't exist):

df.iloc[:, 10] # there is obviously no 11th column

IndexError: single positional indexer is out-of-bounds

If you are a beginner with Python, remember that df.iloc[:, 10] would refer to the eleventh column.

Is there a TRY CATCH command in Bash

I've developed an almost flawless try & catch implementation in bash, that allows you to write code like:

    echo 'Hello'
    echo 'This will not be displayed'

    echo "Error in $__EXCEPTION_SOURCE__ at line: $__EXCEPTION_LINE__!"

You can even nest the try-catch blocks inside themselves!

try {
    echo 'Hello'

    try {
        echo 'Nested Hello'
        echo 'This will not execute'
    } catch {
        echo "Nested Caught (@ $__EXCEPTION_LINE__)"

    echo 'This will not execute too'

} catch {
    echo "Error in $__EXCEPTION_SOURCE__ at line: $__EXCEPTION_LINE__!"

The code is a part of my bash boilerplate/framework. It further extends the idea of try & catch with things like error handling with backtrace and exceptions (plus some other nice features).

Here's the code that's responsible just for try & catch:

set -o pipefail
shopt -s expand_aliases
declare -ig __oo__insideTryCatch=0

# if try-catch is nested, then set +e before so the parent handler doesn't catch us
alias try="[[ \$__oo__insideTryCatch -gt 0 ]] && set +e;
           __oo__insideTryCatch+=1; ( set -e;
           trap \"Exception.Capture \${LINENO}; \" ERR;"
alias catch=" ); Exception.Extract \$? || "

Exception.Capture() {
    local script="${BASH_SOURCE[1]#./}"

    if [[ ! -f /tmp/stored_exception_source ]]; then
        echo "$script" > /tmp/stored_exception_source
    if [[ ! -f /tmp/stored_exception_line ]]; then
        echo "$1" > /tmp/stored_exception_line
    return 0

Exception.Extract() {
    if [[ $__oo__insideTryCatch -gt 1 ]]
        set -e


    __EXCEPTION_CATCH__=( $(Exception.GetLastException) )

    local retVal=$1
    if [[ $retVal -gt 0 ]]
        # export __EXCEPTION_SOURCE__="${__EXCEPTION_CATCH__[(${#__EXCEPTION_CATCH__[@]}-1)]}"
        # export __EXCEPTION_LINE__="${__EXCEPTION_CATCH__[(${#__EXCEPTION_CATCH__[@]}-2)]}"
        export __EXCEPTION_SOURCE__="${__EXCEPTION_CATCH__[-1]}"
        export __EXCEPTION_LINE__="${__EXCEPTION_CATCH__[-2]}"
        export __EXCEPTION__="${__EXCEPTION_CATCH__[@]:0:(${#__EXCEPTION_CATCH__[@]} - 2)}"
        return 1 # so that we may continue with a "catch"

Exception.GetLastException() {
    if [[ -f /tmp/stored_exception ]] && [[ -f /tmp/stored_exception_line ]] && [[ -f /tmp/stored_exception_source ]]
        cat /tmp/stored_exception
        cat /tmp/stored_exception_line
        cat /tmp/stored_exception_source
        echo -e " \n${BASH_LINENO[1]}\n${BASH_SOURCE[2]#./}"

    rm -f /tmp/stored_exception /tmp/stored_exception_line /tmp/stored_exception_source
    return 0

Feel free to use, fork and contribute - it's on GitHub.

java - iterating a linked list

As the definition of Linkedlist says, it is a sequence and you are guaranteed to get the elements in order.


import java.util.LinkedList;

public class ForEachDemonstrater {
  public static void main(String args[]) {
    LinkedList<Character> pl = new LinkedList<Character>();
    for (char s : pl)

HTTP POST with Json on Body - Flutter/Dart

I implement like this:

static createUserWithEmail(String username, String email, String password) async{
    var url = ''+ "users";
    var body = {
        'user' : {
          'username': username,
          'address': email,
          'password': password

      body: json.encode(body),
      headers: {
        "Content-Type": "application/json"
      encoding: Encoding.getByName("utf-8")

How to get all possible combinations of a list’s elements?

from itertools import permutations, combinations

features = ['A', 'B', 'C']
tmp = []
for i in range(len(features)):
    oc = combinations(features, i + 1)
    for c in oc:


 ['A', 'B'],
 ['A', 'C'],
 ['B', 'C'],
 ['A', 'B', 'C']

NSDate get year/month/day

i do in this way ....

NSDate * mydate = [NSDate date];

NSCalendar * mycalendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];

NSCalendarUnit units = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;

NSDateComponents * myComponents  = [mycalendar components:units fromDate:mydate];


Installed Java 7 on Mac OS X but Terminal is still using version 6

Since i have not faced this issue , I am taking a hunch --

Can you please try this :

Where does the soft link "java_home" point to :

ls -lrt /usr/libexec/java_home

Output : (Stunted) lrwxr-xr-x java_home -> /System/Library/Frameworks/JavaVM.framework/Versions/Current/Commands/java_home

**ls -lrt /System/Library/Frameworks/JavaVM.framework/Versions My MAC Produces the following :

 lrwxr-xr-x CurrentJDK ->

 lrwxr-xr-x   Current -> A
 lrwxr-xr-x  1 root  wheel   10 Oct 18 14:39 1.6.0 -> CurrentJDK
 lrwxr-xr-x  1 root  wheel   10 Oct 18 14:39 1.6 -> CurrentJDK
 lrwxr-xr-x  1 root  wheel   10 Oct 18 14:39 1.5.0 -> CurrentJDK
 lrwxr-xr-x  1 root  wheel   10 Oct 18 14:39 1.5 -> CurrentJDK
 lrwxr-xr-x  1 root  wheel   10 Oct 18 14:39 1.4.2 -> CurrentJDK
 lrwxr-xr-x  1 root  wheel   10 Oct 18 14:39 1.4 -> CurrentJDK

Based on this , we might get a hint to proceed further ?

How to solve WAMP and Skype conflict on Windows 7?

Detail blog to fix this issue is :

You can solve this problem by following two ways:
A) Start your WAMP befor you login to skype. So that WAMP will take over the the port and there will be no conflict with the port number. And you are able to use Skype as well as WAMP.
But this is not the permanent solution for your problem. Whenever you want to start WAMP you need to signout Skype first and than only you are able to start WAMP. Which is really i don’t like.

B) Second option is to change the port of Skype itself, so that it will not conflict with WAMP. Following screen/steps will help you to solve this problem:
1) SignIn to Skype.
2) Got to the Tools -> options
3) Select the “Advanced” -> Connection
4) Unchecked “Use port 80 and 443 as alternatives for incoming connections” checkbox and click save.
5) Now Signout and SignIn again to skype. (this change will take affect only you relogin to skype)
Now every time you start WAMP will not conflict with skype.

A html space is showing as %2520 instead of %20

A bit of explaining as to what that %2520 is :

The common space character is encoded as %20 as you noted yourself. The % character is encoded as %25.

The way you get %2520 is when your url already has a %20 in it, and gets urlencoded again, which transforms the %20 to %2520.

Are you (or any framework you might be using) double encoding characters?

Edit: Expanding a bit on this, especially for LOCAL links. Assuming you want to link to the resource C:\my path\my file.html:

  • if you provide a local file path only, the browser is expected to encode and protect all characters given (in the above, you should give it with spaces as shown, since % is a valid filename character and as such it will be encoded) when converting to a proper URL (see next point).
  • if you provide a URL with the file:// protocol, you are basically stating that you have taken all precautions and encoded what needs encoding, the rest should be treated as special characters. In the above example, you should thus provide file:///c:/my%20path/my%20file.html. Aside from fixing slashes, clients should not encode characters here.


  • Slash direction - forward slashes / are used in URLs, reverse slashes \ in Windows paths, but most clients will work with both by converting them to the proper forward slash.
  • In addition, there are 3 slashes after the protocol name, since you are silently referring to the current machine instead of a remote host ( the full unabbreviated path would be file://localhost/c:/my%20path/my%file.html ), but again most clients will work without the host part (ie two slashes only) by assuming you mean the local machine and adding the third slash.

Ajax Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource

Add the below code to your .htaccess

Header set Access-Control-Allow-Origin *

It works for me.


Form inside a form, is that alright?

Another workaround would be to initiate a modal window containing its own form

What's the difference between a temp table and table variable in SQL Server?

@wcm - actually to nit pick the Table Variable isn't Ram only - it can be partially stored on disk.

A temp table can have indexes, whereas a table variable can only have a primary index. If speed is an issue Table variables can be faster, but obviously if there are a lot of records, or the need to search the temp table of a clustered index, then a Temp Table would be better.

Good background article