Programs & Examples On #Qtsql

Questions related to QtSQl Module, a collection of Qt classes that work with various relational database management systems.

how to convert a string date into datetime format in python?

The particular format for strptime:

datetime.datetime.strptime(string_date, "%Y-%m-%d %H:%M:%S.%f")
#>>> datetime.datetime(2013, 9, 28, 20, 30, 55, 782000)

How do I call a specific Java method on a click/submit event of a specific button in JSP?

Just give the individual button elements a unique name. When pressed, the button's name is available as a request parameter the usual way like as with input elements.

You only need to make sure that the button inputs have type="submit" as in <input type="submit"> and <button type="submit"> and not type="button", which only renders a "dead" button purely for onclick stuff and all.


<form action="${pageContext.request.contextPath}/myservlet" method="post">
    <input type="submit" name="button1" value="Button 1" />
    <input type="submit" name="button2" value="Button 2" />
    <input type="submit" name="button3" value="Button 3" />


public class MyServlet extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        MyClass myClass = new MyClass();

        if (request.getParameter("button1") != null) {
        } else if (request.getParameter("button2") != null) {
        } else if (request.getParameter("button3") != null) {
        } else {
            // ???

        request.getRequestDispatcher("/WEB-INF/some-result.jsp").forward(request, response);


Alternatively, use <button type="submit"> instead of <input type="submit">, then you can give them all the same name, but an unique value. The value of the <button> won't be used as label, you can just specify that yourself as child.


<form action="${pageContext.request.contextPath}/myservlet" method="post">
    <button type="submit" name="button" value="button1">Button 1</button>
    <button type="submit" name="button" value="button2">Button 2</button>
    <button type="submit" name="button" value="button3">Button 3</button>


public class MyServlet extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        MyClass myClass = new MyClass();
        String button = request.getParameter("button");

        if ("button1".equals(button)) {
        } else if ("button2".equals(button)) {
        } else if ("button3".equals(button)) {
        } else {
            // ???

        request.getRequestDispatcher("/WEB-INF/some-result.jsp").forward(request, response);


See also:

Explain the concept of a stack frame in a nutshell

If you understand stack very well then you will understand how memory works in program and if you understand how memory works in program you will understand how function store in program and if you understand how function store in program you will understand how recursive function works and if you understand how recursive function works you will understand how compiler works and if you understand how compiler works your mind will works as compiler and you will debug any program very easily

Let me explain how stack works:

First you have to know how functions are represented in stack :

Heap stores dynamically allocated values.
Stack stores automatic allocation and deletion values.

enter image description here

Let's understand with example :

def hello(x):
    if x==1:
        return "op"
    return e


Now understand parts of this program :

enter image description here

Now let's see what is stack and what are stack parts:

enter image description here

Allocation of the stack :

Remember one thing: if any function's return condition gets satisfied, no matter it has loaded the local variables or not, it will immediately return from stack with it's stack frame. It means that whenever any recursive function get base condition satisfied and we put a return after base condition, the base condition will not wait to load local variables which are located in the “else” part of program. It will immediately return the current frame from the stack following which the next frame is now in the activation record.

See this in practice:

enter image description here

Deallocation of the block:

So now whenever a function encounters return statement, it delete the current frame from the stack.

While returning from the stack, values will returned in reverse of the original order in which they were allocated in stack.

enter image description here

Using "Object.create" instead of "new"

There is really no advantage in using Object.create(...) over new object.

Those advocating this method generally state rather ambiguous advantages: "scalability", or "more natural to JavaScript" etc.

However, I have yet to see a concrete example that shows that Object.create has any advantages over using new. On the contrary there are known problems with it. Sam Elsamman describes what happens when there are nested objects and Object.create(...) is used:

var Animal = {
    traits: {},
var lion = Object.create(Animal);
lion.traits.legs = 4;
var bird = Object.create(Animal);
bird.traits.legs = 2;
alert(lion.traits.legs) // shows 2!!!

This occurs because Object.create(...) advocates a practice where data is used to create new objects; here the Animal datum becomes part of the prototype of lion and bird, and causes problems as it is shared. When using new the prototypal inheritance is explicit:

function Animal() {
    this.traits = {};

function Lion() { }
Lion.prototype = new Animal();
function Bird() { }
Bird.prototype = new Animal();

var lion = new Lion();
lion.traits.legs = 4;
var bird = new Bird();
bird.traits.legs = 2;
alert(lion.traits.legs) // now shows 4

Regarding, the optional property attributes that are passed into Object.create(...), these can be added using Object.defineProperties(...).

Replace "\\" with "\" in a string in C#

I tried the procedures of your posts but with no success.

This is what I get from debugger: enter image description here

Original string that I save into sqlite database was b\r\na .. when I read them, I get b\\r\\na (length in debugger is 6: "b" "\" "\r" "\" "\n" "a") then I try replace this string and I get string with length 6 again (you can see in picture above).

I run this short script in my test form with only one text box:

private void Form_Load(object sender, EventArgs e)
        string x = "b\\r\\na";
        string y = x.Replace(@"\\", @"\");
        this.textBox.Text = y + "\r\n\r\nLength: " + y.Length.ToString();

and I get this in text box (so, no new line characters between "b" and "a":


Length: 6

What can I do with this string to unescape backslash? (I expect new line between "b" and "a".)


OK, this is not possible to do with standard replace, because of \r and \n is one character. Is possible to replace part of string character by character but not possible to replace "half part" of one character. So, I must replace any special character separatelly, like this:

private void Form_Load(object sender, EventArgs e) {
    string z = x.Replace(@"\r\n", Environment.NewLine);

This produce correct result for me:


MVC 4 Data Annotations "Display" Attribute

Also internationalization.

I fooled around with this some a while back. Did this in my model:

[Display(Name = "XXX", ResourceType = typeof(Labels))]

I had a separate class library for all the resources, so I had Labels.resx, Labels.culture.resx, etc.

In there I had key = XXX, value = "meaningful string in that culture."

Mobile Safari: Javascript focus() method on inputfield only works with click?

This solution works well, I tested on my phone:

document.body.ontouchend = function() { document.querySelector('[name="name"]').focus(); };


Converting String to Cstring in C++

vector<char> toVector( const std::string& s ) {
  string s = "apple";  
  vector<char> v(s.size()+1);
  memcpy( &v.front(), s.c_str(), s.size() + 1 );
  return v;
vector<char> v = toVector(std::string("apple"));

// what you were looking for (mutable)
char* c =;

.c_str() works for immutable. The vector will manage the memory for you.

How to remove element from an array in JavaScript?

Array.splice() has the interesting property that one cannot use it to remove the first element. So, we need to resort to

function removeAnElement( array, index ) {

    if ( index === -1 ) {
        return array.shift();
    } else {
        return array.splice( index, 1 );

git: fatal: Could not read from remote repository

If after"git push origin master" command u see the error "could not read from remote repository" then try this out

1.ssh-keygen -t rsa -b 4096 -C "youremail"
2.eval $(ssh-agent -s)
3.ssh-add ~/.ssh/id_rsa
4.clip < ~/.ssh/ copies the ssh key that has got generated)
5.then go to your remote repository on github and goto settings-> SSH and GPG keys ->new SSH key ->enter any title and paste the copied SSH key and save it
6. now give git push origin master 

How can I install Visual Studio Code extensions offline?

A small powershell to get needed information for also visual studio extension :

function Get-VSMarketPlaceExtension {
        [Parameter(ValueFromPipeline = $true,Mandatory = $true)]
    begin {
            filters = ,@{
            criteria =,@{
                    value = $null
            flags = 1712
    process {
        foreach($Extension in $extensionName) {
            $response =  try {
                $body.filters[0].criteria[0].value = $Extension
                $Query =  $body|ConvertTo-JSON -Depth 4
                (Invoke-WebRequest -Uri "" -ErrorAction Stop -Body $Query -Method Post -ContentType "application/json")
            } catch [System.Net.WebException] { 
                Write-Verbose "An exception was caught: $($_.Exception.Message)"
            $statusCodeInt = [int]$response.StatusCode

            if ($statusCodeInt -ge 400) {
                Write-Warning "Erreur sur l'appel d'API :  $($response.StatusDescription)"
            $ObjResults = ($response.Content | ConvertFrom-Json).results
            If ($ObjResults.resultMetadata.metadataItems.count -ne 1) {
                Write-Warning "l'extension '$Extension' n'a pas été trouvée."
            $Extension = $ObjResults.extensions
            $obj2Download = ($Extension.versions[0].properties | Where-Object key -eq 'Microsoft.VisualStudio.Services.Payload.FileName').value
                displayName = $Extension.displayName
                extensionId = $Extension.extensionId
                deploymentType = ($obj2Download -split '\.')[-1]
                version = [version]$Extension.versions[0].version
                LastUpdate = [datetime]$Extension.versions[0].lastUpdated
                IsValidated = ($Extension.versions[0].flags -eq "validated")
                extensionName = $Extension.extensionName 
                publisher     = $Extension.publisher.publisherName
                SourceURL = $Extension.versions[0].assetUri +"/" + $obj2Download
                FileName = $obj2Download                     

This use marketplace API to get extension information. Exemple of usage and results :

>Get-VSMarketPlaceExtension "ProBITools.MicrosoftReportProjectsforVisualStudio"

displayName    : Microsoft Reporting Services Projects
extensionId    : 85e42f76-6afa-4a68-afb5-033d1fe08d7b
deploymentType : vsix
version        : 2.6.7
LastUpdate     : 13/05/2020 22:23:45
IsValidated    : True
extensionName  : MicrosoftReportProjectsforVisualStudio
publisher      : ProBITools
SourceURL      :
FileName       : Microsoft.DataTools.ReportingServices.vsix

All flags value are available here

Thanks to m4js7er and Adam Haynes for inspiration

How does one generate a random number in Apple's Swift language?

I use this code to generate a random number:

//  FactModel.swift
//  Collection
//  Created by Ahmadreza Shamimi on 6/11/16.
//  Copyright © 2016 Ahmadreza Shamimi. All rights reserved.

import GameKit

struct FactModel {

    let fun  = ["I love swift","My name is Ahmadreza","I love coding" ,"I love PHP","My name is ALireza","I love Coding too"]

    func getRandomNumber() -> String {

        let randomNumber  = GKRandomSource.sharedRandom().nextIntWithUpperBound(fun.count)

        return fun[randomNumber]

Python for and if on one line

You are producing a filtered list by using a list comprehension. i is still being bound to each and every element of that list, and the last element is still 'three', even if it was subsequently filtered out from the list being produced.

You should not use a list comprehension to pick out one element. Just use a for loop, and break to end it:

for elem in my_list:
    if elem == 'two':

If you must have a one-liner (which would be counter to Python's philosophy, where readability matters), use the next() function and a generator expression:

i = next((elem for elem in my_list if elem == 'two'), None)

which will set i to None if there is no such matching element.

The above is not that useful a filter; your are essentially testing if the value 'two' is in the list. You can use in for that:

elem = 'two' if 'two' in my_list else None

Creating C formatted strings (not printing them)

I haven't done this, so I'm just going to point at the right answer.

C has provisions for functions that take unspecified numbers of operands, using the <stdarg.h> header. You can define your function as void log_out(const char *fmt, ...);, and get the va_list inside the function. Then you can allocate memory and call vsprintf() with the allocated memory, format, and va_list.

Alternately, you could use this to write a function analogous to sprintf() that would allocate memory and return the formatted string, generating it more or less as above. It would be a memory leak, but if you're just logging out it may not matter.

MySQL: Error dropping database (errno 13; errno 17; errno 39)

In my case an additional file not belonging to the database was inside the database folder. Mysql found the folder not empty after dropping all tables which triggered the error. I remove the file and the drop database worked fine.

How to install an apk on the emulator in Android Studio?

Much easier is just to start your emulator, then go to sdk/platform-tools and use adb from there to install apk. Like:

adb install xxx.apk

It will install it on running emulator.

Import Certificate to Trusted Root but not to Personal [Command Line]

To print the content of Root store:

certutil -store Root

To output content to a file:

certutil -store Root > root_content.txt

To add certificate to Root store:

certutil -addstore -enterprise Root file.cer

Debug JavaScript in Eclipse

I don't believe Eclipse has a JavaScript debugger - those breakpoints are for Java code (I'm guessing you are editing a JSP file?)

Use Firebug to debug Javascript code, it's an excellent add-on that all web developers should have in their toolbox.

How to generate XML file dynamically using PHP?

To create an XMLdocument in PHP you should instance a DOMDocument class, create child nodes and append these nodes in the correct branch of the document tree.

For reference you can read

Now we will take a quick tour of the code below.

  • at line 2 we create an empty xml document (just specify xml version (1.0) and encoding (utf8))
  • now we need to populate the xml tree:
    • We have to create an xmlnode (line 5)
    • and we have to append this in the correct position. We are creating the root so we append this directly to the domdocument.
    • Note create element append the element to the node and return the node inserted, we save this reference to append the track nodes to the root node (incidentally called xml).

These are the basics, you can create and append a node in just a line (13th, for example), you can do a lot of other things with the dom api. It is up to you.

    /* create a dom document with encoding utf8 */
    $domtree = new DOMDocument('1.0', 'UTF-8');

    /* create the root element of the xml tree */
    $xmlRoot = $domtree->createElement("xml");
    /* append it to the document created */
    $xmlRoot = $domtree->appendChild($xmlRoot);

    $currentTrack = $domtree->createElement("track");
    $currentTrack = $xmlRoot->appendChild($currentTrack);

    /* you should enclose the following two lines in a cicle */
    $currentTrack->appendChild($domtree->createElement('title','title of song1.mp3'));

    $currentTrack->appendChild($domtree->createElement('title','title of song2.mp3'));

    /* get the xml printed */
    echo $domtree->saveXML();

Edit: Just one other hint: The main advantage of using an xmldocument (the dom document one or the simplexml one) instead of printing the xml,is that the xmltree is searchable with xpath query

How to remove duplicate objects in a List<MyObject> without equals/hashcode?

First override equals() method:

public boolean equals(Object obj)
    if(obj == null) return false;
    else if(obj instanceof MyObject && getTitle() == obj.getTitle() && getAuthor() == obj.getAuthor() && getURL() == obj.getURL() && getDescription() == obj.getDescription()) return true;
    else return false;

and then use:

List<MyObject> list = new ArrayList<MyObject>;
for(MyObject obj1 : list)
    for(MyObject obj2 : list)
        if(obj1.equals(obj2)) list.remove(obj1); // or list.remove(obj2);

What is a Subclass

A subclass is a class that extends another class.

public class BaseClass{
    public String getFoo(){
        return "foo";

public class SubClass extends BaseClass{


System.out.println(new SubClass().getFoo());

Will print:


This works because a subclass inherits the functionality of the class it extends.

How to send email attachments?

The simplest code I could get to is:

#for attachment email
from django.core.mail import EmailMessage

    def attachment_email(request):
            email = EmailMessage(
            'Hello', #subject
            'Body goes here', #body
            '[email protected]', #from
            ['[email protected]'], #to
            ['[email protected]'], #bcc
            reply_to=['[email protected]'],
            headers={'Message-ID': 'foo'},


It was based on the official Django documentation

Why does JSHint throw a warning if I am using const?

When you start using ECMAScript 6 this error thrown by your IDE.

There are two options available:

if you have only one file and want to use the es6 then simply add below line at the top of the file.

/*jshint esversion: 6 */

Or if you have number of js file or you are using any framework(like nodejs express)you can create a new file named .jshintrc in your root directory and add code below in the file:

    "esversion": 6

If you want to use the es6 version onward for each project you can configure your IDE.

How to import and use image in a Vue single file component?

It is heavily suggested to make use of webpack when importing pictures from assets and in general for optimisation and pathing purposes

If you wish to load them by webpack you can simply use :src='require('path/to/file')' Make sure you use : otherwise it won't execute the require statement as Javascript.

In typescript you can do almost the exact same operation: :src="require('@/assets/image.png')"

Why the following is generally considered bad practice:

  <div id="app">
    <img src="./assets/logo.png">

export default {

<style lang="scss">

When building using the Vue cli, webpack is not able to ensure that the assets file will maintain a structure that follows the relative importing. This is due to webpack trying to optimize and chunk items appearing inside of the assets folder. If you wish to use a relative import you should do so from within the static folder and use: <img src="./static/logo.png">

Should I use JSLint or JSHint JavaScript validation?

There is an another mature and actively developed "player" on the javascript linting front - ESLint:

ESLint is a tool for identifying and reporting on patterns found in ECMAScript/JavaScript code. In many ways, it is similar to JSLint and JSHint with a few exceptions:

  • ESLint uses Esprima for JavaScript parsing.
  • ESLint uses an AST to evaluate patterns in code.
  • ESLint is completely pluggable, every single rule is a plugin and you can add more at runtime.

What really matters here is that it is extendable via custom plugins/rules. There are already multiple plugins written for different purposes. Among others, there are:

And, of course, you can use your build tool of choice to run ESLint:

ORA-01830: date format picture ends before converting entire input string / Select sum where date query

I think you should not rely on the implicit conversion. It is a bad practice.

Instead you should try like this:

datenum >= to_date('11/26/2013','mm/dd/yyyy')

or like

datenum >= date '2013-09-01'

Creating and Update Laravel Eloquent

Try more parameters one which will surely find and if available update and not then it will create new

$save_data= Model::firstOrNew(['key1' => $key1value,'key'=>$key2value]);
//your values here

IOError: [Errno 13] Permission denied

IOError: [Errno 13] Permission denied: 'juliodantas2015.json'

tells you everything you need to know: though you successfully made your python program executable with your chmod, python can't open that juliodantas2015.json' file for writing. You probably don't have the rights to create new files in the folder you're currently in.

How can I insert binary file data into a binary SQL field using a simple insert statement?

If you mean using a literal, you simply have to create a binary string:

insert into Files (FileId, FileData) values (1, 0x010203040506)

And you will have a record with a six byte value for the FileData field.

You indicate in the comments that you want to just specify the file name, which you can't do with SQL Server 2000 (or any other version that I am aware of).

You would need a CLR stored procedure to do this in SQL Server 2005/2008 or an extended stored procedure (but I'd avoid that at all costs unless you have to) which takes the filename and then inserts the data (or returns the byte string, but that can possibly be quite long).

In regards to the question of only being able to get data from a SP/query, I would say the answer is yes, because if you give SQL Server the ability to read files from the file system, what do you do when you aren't connected through Windows Authentication, what user is used to determine the rights? If you are running the service as an admin (God forbid) then you can have an elevation of rights which shouldn't be allowed.

document.all vs. document.getElementById

Actually, document.all is only minimally comparable to document.getElementById. You wouldn't use one in place of the other, they don't return the same things.

If you were trying to filter through browser capabilities you could use them as in Marcel Korpel's answer like this:

if(document.getElementById){  //DOM
    element = document.getElementById(id);
} else if (document.all) {    //IE
    element = document.all[id];
} else if (document.layers){  //Netscape < 6
    element = document.layers[id];

But, functionally, document.getElementsByTagName('*') is more equivalent to document.all.

For example, if you were actually going to use document.all to examine all the elements on a page, like this:

var j = document.all.length;
for(var i = 0; i < j; i++){
   alert("Page element["+i+"] has tagName:"+document.all(i).tagName);

you would use document.getElementsByTagName('*') instead:

var k = document.getElementsByTagName("*");
var j = k.length; 
for (var i = 0; i < j; i++){
    alert("Page element["+i+"] has tagName:"+k[i].tagName); 

Structuring online documentation for a REST API

That's a very complex question for a simple answer.

You may want to take a look at existing API frameworks, like Swagger Specification (OpenAPI), and services like and

Also, here's an example of the same REST API described, organized and even styled in three different ways. It may be a good start for you to learn from existing common ways.

At the very top level I think quality REST API docs require at least the following:

  • a list of all your API endpoints (base/relative URLs)
  • corresponding HTTP GET/POST/... method type for each endpoint
  • request/response MIME-type (how to encode params and parse replies)
  • a sample request/response, including HTTP headers
  • type and format specified for all params, including those in the URL, body and headers
  • a brief text description and important notes
  • a short code snippet showing the use of the endpoint in popular web programming languages

Also there are a lot of JSON/XML-based doc frameworks which can parse your API definition or schema and generate a convenient set of docs for you. But the choice for a doc generation system depends on your project, language, development environment and many other things.

npm install vs. update - what's the difference?

The difference between npm install and npm update handling of package versions specified in package.json:

  "name":          "my-project",
  "version":       "1.0",                             // install   update
  "dependencies":  {                                  // ------------------
    "already-installed-versionless-module":  "*",     // ignores   "1.0" -> "1.1"
    "already-installed-semver-module":       "^1.4.3" // ignores   "1.4.3" -> "1.5.2"
    "already-installed-versioned-module":    "3.4.1"  // ignores   ignores
    "not-yet-installed-versionless-module":  "*",     // installs  installs
    "not-yet-installed-semver-module":       "^4.2.1" // installs  installs
    "not-yet-installed-versioned-module":    "2.7.8"  // installs  installs

Summary: The only big difference is that an already installed module with fuzzy versioning ...

  • gets ignored by npm install
  • gets updated by npm update

Additionally: install and update by default handle devDependencies differently

  • npm install will install/update devDependencies unless --production flag is added
  • npm update will ignore devDependencies unless --dev flag is added

Why use npm install at all?

Because npm install does more when you look besides handling your dependencies in package.json. As you can see in npm install you can ...

  • manually install node-modules
  • set them as global (which puts them in the shell's PATH) using npm install -g <name>
  • install certain versions described by git tags
  • install from a git url
  • force a reinstall with --force

Remove spaces from std::string in C++

string replaceinString(std::string str, std::string tofind, std::string toreplace)
        size_t position = 0;
        for ( position = str.find(tofind); position != std::string::npos; position = str.find(tofind,position) )
                str.replace(position ,1, toreplace);

use it:

string replace = replaceinString(thisstring, " ", "%20");
string replace2 = replaceinString(thisstring, " ", "-");
string replace3 = replaceinString(thisstring, " ", "+");

Check if a file is executable

Testing files, directories and symlinks

The solutions given here fail on either directories or symlinks (or both). On Linux, you can test files, directories and symlinks with:

if [[ -f "$file" && -x $(realpath "$file") ]]; then .... fi

On OS X, you should be able to install coreutils with homebrew and use grealpath.

Defining an isexec function

You can define a function for convenience:

isexec() {
    if [[ -f "$1" && -x $(realpath "$1") ]]; then

Or simply

isexec() { [[ -f "$1" && -x $(realpath "$1") ]]; }

Then you can test using:

if `isexec "$file"`; then ... fi

How to pass data in the ajax DELETE request other than headers

deleteRequest: function (url, Id, bolDeleteReq, callback, errorCallback) {
        url: urlCall,
        type: 'DELETE',
        data: {"Id": Id, "bolDeleteReq" : bolDeleteReq},
        success: callback || $.noop,
        error: errorCallback || $.noop

Note: the use of headers was introduced in JQuery 1.5.:

A map of additional header key/value pairs to send along with the request. This setting is set before the beforeSend function is called; therefore, any values in the headers setting can be overwritten from within the beforeSend function.

How do I use extern to share variables between source files?

extern tells the compiler to trust you that the memory for this variable is declared elsewhere, so it doesnt try to allocate/check memory.

Therefore, you can compile a file that has reference to an extern, but you can not link if that memory is not declared somewhere.

Useful for global variables and libraries, but dangerous because the linker does not type check.

Copying text outside of Vim with set mouse=a enabled

Another OSX-Mac option is to uncheck View->Allow Mouse Reporting (or press ?-R to toggle it.) This allows you to toggle between mouse interaction and mouse selecting, which might be useful when selecting and copy/pasting a few bits because you don't have to hold a modifier key to do it.

Note for Multiline with line numbers:

I usually have line numbers enabled so this will also copy the line numbers if you select multiple lines. If you want to copy multiple lines without the line numbers disable the numbers with :set nonu and then you can :set nu to re-enable them after you're done copying.

Saving lists to txt file

Framework 4: no need to use StreamWriter:

System.IO.File.WriteAllLines("SavedLists.txt", Lists.verbList);

How to check if an appSettings key exists?

I think the LINQ expression may be best:

   const string MyKey = "myKey"

   if (ConfigurationManager.AppSettings.AllKeys.Any(key => key == MyKey))
              // Key exists

Max size of an iOS application

50 Meg is the max for Cell data download.

But you might be able to keep it under that in the app store and then have the app download other content after the user install and runs the app, so the app can be bigger. But not sure what the apple rules are for this.

I know that all in-app purchases need to be approved, but not sure if this kind of content needs to be approved.

How to get the current directory of the cmdlet being executed

You would think that using '.\' as the path means that it's the invocation path. But not all the time. Example, if you use it inside a job ScriptBlock. In which case, it might point to %profile%\Documents.

How to split a single column values to multiple column values?

;WITH Split_Names (Name, xmlname)
    + REPLACE(Name,' ', '</name><name>') + '</name></Names>') AS xmlname
      FROM somenames

 xmlname.value('/Names[1]/name[1]','varchar(100)') AS first_name,    
 xmlname.value('/Names[1]/name[2]','varchar(100)') AS last_name
 FROM Split_Names

and also check the link below for reference

JavaScript: Parsing a string Boolean value?

You can try the following:

function parseBool(val)
    if ((typeof val === 'string' && (val.toLowerCase() === 'true' || val.toLowerCase() === 'yes')) || val === 1)
        return true;
    else if ((typeof val === 'string' && (val.toLowerCase() === 'false' || val.toLowerCase() === 'no')) || val === 0)
        return false;

    return null;

If it's a valid value, it returns the equivalent bool value otherwise it returns null.

How to find if a native DLL file is compiled as x64 or x86?

The Magic field of the IMAGE_OPTIONAL_HEADER (though there is nothing optional about the header in Windows executable images (DLL/EXE files)) will tell you the architecture of the PE.

Here's an example of grabbing the architecture from a file.

public static ushort GetImageArchitecture(string filepath) {
    using (var stream = new System.IO.FileStream(filepath, System.IO.FileMode.Open, System.IO.FileAccess.Read))
    using (var reader = new System.IO.BinaryReader(stream)) {
        //check the MZ signature to ensure it's a valid Portable Executable image
        if (reader.ReadUInt16() != 23117) 
            throw new BadImageFormatException("Not a valid Portable Executable image", filepath);

        // seek to, and read, e_lfanew then advance the stream to there (start of NT header)
        stream.Seek(0x3A, System.IO.SeekOrigin.Current); 
        stream.Seek(reader.ReadUInt32(), System.IO.SeekOrigin.Begin);

        // Ensure the NT header is valid by checking the "PE\0\0" signature
        if (reader.ReadUInt32() != 17744)
            throw new BadImageFormatException("Not a valid Portable Executable image", filepath);

        // seek past the file header, then read the magic number from the optional header
        stream.Seek(20, System.IO.SeekOrigin.Current); 
        return reader.ReadUInt16();

The only two architecture constants at the moment are:

0x10b - PE32
0x20b - PE32+


UPDATE It's been a while since I posted this answer, yet I still see that it gets a few upvotes now and again so I figured it was worth updating. I wrote a way to get the architecture of a Portable Executable image, which also checks to see if it was compiled as AnyCPU. Unfortunately the answer is in C++, but it shouldn't be too hard to port to C# if you have a few minutes to look up the structures in WinNT.h. If people are interested I'll write a port in C#, but unless people actually want it I wont spend much time stressing about it.

#include <Windows.h>

#define MKPTR(p1,p2) ((DWORD_PTR)(p1) + (DWORD_PTR)(p2))

typedef enum _pe_architecture {
    PE_ARCHITECTURE_X86     = 0x010B,
    PE_ARCHITECTURE_x64     = 0x020B

    for(unsigned long i = 0; i < pNt->FileHeader.NumberOfSections; ++i, ++pSecHd) {
        // Lookup which section contains this RVA so we can translate the VA to a file offset
        if (rva >= pSecHd->VirtualAddress && rva < (pSecHd->VirtualAddress + pSecHd->Misc.VirtualSize)) {
            DWORD delta = pSecHd->VirtualAddress - pSecHd->PointerToRawData;
            return (LPVOID)MKPTR(pDos, rva - delta);
    return NULL;

PE_ARCHITECTURE GetImageArchitecture(void *pImageBase) {
    // Parse and validate the DOS header
    if (IsBadReadPtr(pDosHd, sizeof(pDosHd->e_magic)) || pDosHd->e_magic != IMAGE_DOS_SIGNATURE)

    // Parse and validate the NT header
    IMAGE_NT_HEADERS *pNtHd = (IMAGE_NT_HEADERS*)MKPTR(pDosHd, pDosHd->e_lfanew);
    if (IsBadReadPtr(pNtHd, sizeof(pNtHd->Signature)) || pNtHd->Signature != IMAGE_NT_SIGNATURE)

    // First, naive, check based on the 'Magic' number in the Optional Header.
    PE_ARCHITECTURE architecture = (PE_ARCHITECTURE)pNtHd->OptionalHeader.Magic;

    // If the architecture is x86, there is still a possibility that the image is 'AnyCPU'
    if (architecture == PE_ARCHITECTURE_X86) {
        IMAGE_DATA_DIRECTORY comDirectory = pNtHd->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR];
        if (comDirectory.Size) {
            IMAGE_COR20_HEADER *pClrHd = (IMAGE_COR20_HEADER*)GetOffsetFromRva(pDosHd, pNtHd, comDirectory.VirtualAddress);
            // Check to see if the CLR header contains the 32BITONLY flag, if not then the image is actually AnyCpu
            if ((pClrHd->Flags & COMIMAGE_FLAGS_32BITREQUIRED) == 0)
                architecture = PE_ARCHITECTURE_ANYCPU;

    return architecture;

The function accepts a pointer to an in-memory PE image (so you can choose your poison on how to get it their; memory-mapping or reading the whole thing into memory...whatever).

How do I concatenate two lists in Python?




 >>> [1, 2, 3, 4, 5, 6]

In the above code "+" operator is used to concatenate the 2 lists into a single list.


 c=[] #Empty list in which we are going to append the values of list (a) and (b)

 for i in a:
 for j in b:



>>> [1, 2, 3, 4, 5, 6]

How to get maximum value from the Collection (for example ArrayList)?

This question is almost a year old but I have found that if you make a custom comparator for objects you can use Collections.max for an array list of objects.

import java.util.Comparator;

public class compPopulation implements Comparator<Country> {
    public int compare(Country a, Country b) {
        if (a.getPopulation() > b.getPopulation())
            return -1; // highest value first
        if (a.getPopulation() == b.Population())
            return 0;
        return 1;
ArrayList<Country> X = new ArrayList<Country>();
// create some country objects and put in the list
Country ZZ = Collections.max(X, new compPopulation());

Sorting a vector in descending order

I don't think you should use either of the methods in the question as they're both confusing, and the second one is fragile as Mehrdad suggests.

I would advocate the following, as it looks like a standard library function and makes its intention clear:

#include <iterator>

template <class RandomIt>
void reverse_sort(RandomIt first, RandomIt last)
    std::sort(first, last, 
        std::greater<typename std::iterator_traits<RandomIt>::value_type>());

Ripple effect on Android Lollipop CardView

The ripple effect was omitted in the appcompat support library which is what you're using. If you want to see the ripple use the Android L version and test it on an Android L device. Per the AppCompat v7 site:

"Why are there no ripples on pre-Lollipop? A lot of what allows RippleDrawable to run smoothly is Android 5.0’s new RenderThread. To optimize for performance on previous versions of Android, we've left RippleDrawable out for now."

Check out this link here for more info

Switch statement fall-through...should it be allowed?

As with anything: if used with care, it can be an elegant tool.

However, I think the drawbacks more than justify not to use it, and finally not to allow it anymore (C#). Among the problems are:

  • it's easy to "forget" a break
  • it's not always obvious for code maintainers that an omitted break was intentional

Good use of a switch/case fall-through:

switch (x)
case 1:
case 2:
case 3:
 Do something

Baaaaad use of a switch/case fall-through:

switch (x)
case 1:
    Some code
case 2:
    Some more code
case 3:
    Even more code

This can be rewritten using if/else constructs with no loss at all in my opinion.

My final word: stay away from fall-through case labels as in the bad example, unless you are maintaining legacy code where this style is used and well understood.

What svn command would list all the files modified on a branch?

echo You must invoke st from within branch directory
SvnUrl=`svn info | grep URL | sed 's/URL: //'`
SvnVer=`svn info | grep Revision | sed 's/Revision: //'`
svn diff -r $SvnVer --summarize $SvnUrl

How to install Android SDK Build Tools on the command line?

Most of the answers seem to ignore the fact that you may need to run the update in a headless environment with no super user rights, which means the script has to answer all the y/n license prompts automatically.

Here's the example that does the trick.


( sleep 5 && while [ 1 ]; do sleep 1; echo y; done ) \
    | android update sdk --no-ui --all \
    --filter ${FILTER}

No matter how many prompts you get, all of those will be answered. This while/sleep loop looks like simulation of the yes command, and in fact it is, well almost. The problem with yes is that it floods stdout with 'y' and there is virtually no delay between sending those characters and the version I had to deal with had no timeout option of any kind. It will "pollute" stdout and the script will fail complaining about incorrect input. The solution is to put a delay between sending 'y' to stdout, and that's exactly what while/sleep combo does.

expect is not available by default on some linux distros and I had no way to install it as part of my CI scripts, so had to use the most generic solution and nothing can be more generic than simple bash script, right?

As a matter of fact, I blogged about it (NSBogan), check it out for more details here if you are interested.

How do I create a master branch in a bare Git repository?

You don't need to use a second repository - you can do commands like git checkout and git commit on a bare repository, if only you supply a dummy work directory using the --work-tree option.

Prepare a dummy directory:

$ rm -rf /tmp/empty_directory
$ mkdir  /tmp/empty_directory

Create the master branch without a parent (works even on a completely empty repo):

$ cd your-bare-repository.git

$ git checkout --work-tree=/tmp/empty_directory --orphan master
Switched to a new branch 'master'                  <--- abort if "master" already exists

Create a commit (it can be a message-only, without adding any files, because what you need is simply having at least one commit):

$ git commit -m "Initial commit" --allow-empty --work-tree=/tmp/empty_directory 

$ git branch
* master

Clean up the directory, it is still empty.

$ rmdir  /tmp/empty_directory

Tested on git 1.9.1. (Specifically for OP, the posh-git is just a PowerShell wrapper for standard git.)

Enum String Name from Value

Just cast the int to the enumeration type:

EnumDisplayStatus status = (EnumDisplayStatus) statusFromDatabase;
string statusString = status.ToString();

gulp command not found - error after installing gulp

In my case, none of the approaches listed worked. I finally downloaded Rapid Environment Editor (ver 8).

It showed that my additions to the user environment variables weren't present. When I added them with REE, everything worked immediately.

(Running Windows 8.1)

How to check if an element of a list is a list (in Python)?

Expression you are looking for may be:

return any( isinstance(e, list) for e in my_list )


>>> my_list = [1,2]
>>> any( isinstance(e, list) for e in my_list )
>>> my_list = [1,2, [3,4,5]]
>>> any( isinstance(e, list) for e in my_list )

Set element width or height in Standards Mode

Try declaring the unit of width: = "400px"; // width in PIXELS

Clear text area

Use $('textarea').val('').

The problem with using $('textarea').text('') , or $('textarea').html('') for that matter is that it will only erase what was in the original DOM sent by the server. If a user clears it and then enters new input, the clear button will no longer work. Using .val('') handles the user input case properly.

Converting an int or String to a char array on Arduino

  1. To convert and append an integer, use operator += (or member function concat):

    String stringOne = "A long integer: ";
    stringOne += 123456789;
  2. To get the string as type char[], use toCharArray():

    char charBuf[50];
    stringOne.toCharArray(charBuf, 50)

In the example, there is only space for 49 characters (presuming it is terminated by null). You may want to make the size dynamic.


The cost of bringing in String (it is not included if not used anywhere in the sketch), is approximately 1212 bytes program memory (flash) and 48 bytes RAM.

This was measured using Arduino IDE version 1.8.10 (2019-09-13) for an Arduino Leonardo sketch.

Take n rows from a spark dataframe and pass to toPandas()

Try it:

def showDf(df, count=None, percent=None, maxColumns=0):
    if (df == None): return
    import pandas
    from IPython.display import display
    pandas.set_option('display.encoding', 'UTF-8')
    # Pandas dataframe
    dfp = None
    # maxColumns param
    if (maxColumns >= 0):
        if (maxColumns == 0): maxColumns = len(df.columns)
        pandas.set_option('display.max_columns', maxColumns)
    # count param
    if (count == None and percent == None): count = 10 # Default count
    if (count != None):
        count = int(count)
        if (count == 0): count = df.count()
        pandas.set_option('display.max_rows', count)
        dfp = pandas.DataFrame(df.head(count), columns=df.columns)
    # percent param
    elif (percent != None):
        percent = float(percent)
        if (percent >=0.0 and percent <= 1.0):
            import datetime
            now =
            seed = long(now.strftime("%H%M%S"))
            dfs = df.sample(False, percent, seed)
            count = df.count()
            pandas.set_option('display.max_rows', count)
            dfp = dfs.toPandas()    

Examples of usages are:

# Shows the ten first rows of the Spark dataframe
showDf(df, 10)
showDf(df, count=10)

# Shows a random sample which represents 15% of the Spark dataframe
showDf(df, percent=0.15) 

Find the min/max element of an array in JavaScript

For big arrays (~107 elements), Math.min and Math.max procuces a RangeError (Maximum call stack size exceeded) in node.js.

For big arrays, a quick & dirty solution is:

Array.prototype.min = function() {
    var r = this[0];
    this.forEach(function(v,i,a){if (v<r) r=v;});
    return r;

Remove insignificant trailing zeros from a number?

Here's a possible solution:

var x = 1.234000 // to become 1.234;
var y = 1.234001; // stays 1.234001

eval(x) --> 1.234
eval(y) --> 1.234001

Why does this CSS margin-top style not work?

Try using display: inline-block; on the inner div.

#outer {
    margin:50px auto 0 auto;
#inner {
    margin:50px 50px 50px 50px;

Ajax call Into MVC Controller- Url Issue

you have an type error in example of code. You forget curlybracket after success

 type: "POST",
 url: '@Url.Action("Search","Controller")',
 data: "{queryString:'" + searchVal + "'}",
 contentType: "application/json; charset=utf-8",
 dataType: "html",
 success: function (data) {
     alert("here" + data.d.toString());


LINQ: "contains" and a Lambda query

var depthead = (from s in db.M_Users
                  join m in db.M_User_Types on s.F_User_Type equals m.UserType_Id
                  where m.UserType_Name.ToUpper().Trim().Contains("DEPARTMENT HEAD")
                  select new {s.FullName,s.F_User_Type,s.userId,s.UserCode } 
               ).OrderBy(d => d.userId).ToList();

Model.AvailableDeptHead.Add(new SelectListItem { Text = "Select", Value = "0" });
for (int i = 0; i < depthead.Count; i++)
    Model.AvailableDeptHead.Add(new SelectListItem { Text = depthead[i].UserCode + " - " + depthead[i].FullName, Value = Convert.ToString(depthead[i].userId) });

How do I add a reference to the MySQL connector for .NET?

"Add a reference to MySql.Data.dll" means you need to add a library reference to the downloaded connector. The IDE will link the database connection library with your application when it compiles.

Step-by-Step Example

I downloaded the binary (no installer) zip package from the MySQL web site, extracted onto the desktop, and did the following:

  1. Create a new project in Visual Studio
  2. In the Solution Explorer, under the project name, locate References and right-click on it. Select "Add Reference".
  3. In the "Add Reference" dialog, switch to the "Browse" tab and browse to the folder containing the downloaded connector. Navigate to the "bin" folder, and select the "MySql.Data.dll" file. Click OK.
  4. At the top of your code, add using MySql.Data.MySqlClient;. If you've added the reference correctly, IntelliSense should offer to complete this for you.

EXTRACT() Hour in 24 Hour format

simple and easier solution:

select extract(hour from systimestamp) from dual;


When and why to 'return false' in JavaScript?

You use return false to prevent something from happening. So if you have a script running on submit then return false will prevent the submit from working.

Fatal error: Call to undefined function: ldap_connect()

Add path of your PHP to Windows System Path. The path should contain php.exe.

After adding the path open a new command prompt and make sure php.exe is in path by typing

C:\>php --help

Once you see proper help message from above, enable the php_ldap.dll extension in php.ini

Also copy php_ldap.dll from php/ext directory to apache/bin folder

Restart wamp and phpinfo() will now show ldap enabled.

How do I install PHP cURL on Linux Debian?

I wrote an article on topis how to [manually install curl on debian linu][1]x.

[1]: This is its shortcut:

  1. cd /usr/local/src
  2. wget
  3. tar -xvzf curl-7.36.0.tar.gz
  4. rm *.gz
  5. cd curl-7.6.0
  6. ./configure
  7. make
  8. make install

And restart Apache. If you will have an error during point 6, try to run apt-get install build-essential.

How do I set a variable to the output of a command in Bash?

Some may find this useful. Integer values in variable substitution, where the trick is using $(()) double brackets:


while (( COUNT < ${#ARR[@]} ))
  (( COUNT=$COUNT+$N ))

How do I reverse an int array in Java?

Try this code:

    int arr[] = new int[]{1,2,3,4,5,6,7};
    for(int i=0;i<arr.length/2;i++){
        int temp = arr[i];
        arr[i] = arr[(arr.length-1)-i];
        arr[(arr.length-1)-i] = temp;

ImportError: No module named 'bottle' - PyCharm

In the case where you are able to import the module when using the CLI interpreter but not in PyCharm, make sure your project interpreter in PyCharm is set to an actual interpreter (eg. /usr/bin/python2.7) and not venv (~/PycharmProject/venv/...)

How to initialize struct?

You use an implicit operator that converts the string value to a struct value:

public struct MyStruct {
  public string s;
  public int length;

  public static implicit operator MyStruct(string value) {
    return new MyStruct() { s = value, length = value.Length };



MyStruct myStruct = "Lol";



How do I upgrade to Python 3.6 with conda?

Only solution that works was create a new conda env with the name you want (you will, unfortunately, delete the old one to keep the name). Then create a new env with a new python version and re-run your script with the conda/pip installs (or the yaml file or whatever you use to keep your requirements):

conda remove --name original_name --all
conda create --name original_name python=3.8
sh  # or whatever you usually do to install dependencies

doing conda install python=3.8 doesn't work for me. Also, why do you want 3.6? Move forward with the word ;)

Note bellow doesn't work:

If you want to update the conda version of your previous env what you can also do is the following (more complicated than it should be because you cannot rename envs in conda):

  1. create a temporary new location for your current env:
conda create --name temporary_env_name --clone original_env_name
  1. delete the original env (so that the new env can have that name):
conda deactivate
conda remove --name original_env_name --all # or its alias: `conda env remove --name original_env_name`
  1. then create the new empty env with the python version you want and clone the original env:
conda create --name original_env_name python=3.8 --clone temporary_env_name

Use awk to find average of a column

awk '{ sum += $2; n++ } END { if (n > 0) print sum / n; }'

Add the numbers in $2 (second column) in sum (variables are auto-initialized to zero by awk) and increment the number of rows (which could also be handled via built-in variable NR). At the end, if there was at least one value read, print the average.

awk '{ sum += $2 } END { if (NR > 0) print sum / NR }'

If you want to use the shebang notation, you could write:


{ sum += $2 }
END { if (NR > 0) print sum / NR }

You can also control the format of the average with printf() and a suitable format ("%13.6e\n", for example).

You can also generalize the code to average the Nth column (with N=2 in this sample) using:

awk -v N=2 '{ sum += $N } END { if (NR > 0) print sum / NR }'

Selecting non-blank cells in Excel with VBA

The following VBA code should get you started. It will copy all of the data in the original workbook to a new workbook, but it will have added 1 to each value, and all blank cells will have been ignored.

Option Explicit

Public Sub exportDataToNewBook()
    Dim rowIndex As Integer
    Dim colIndex As Integer
    Dim dataRange As Range
    Dim thisBook As Workbook
    Dim newBook As Workbook
    Dim newRow As Integer
    Dim temp

    '// set your data range here
    Set dataRange = Sheet1.Range("A1:B100")

    '// create a new workbook
    Set newBook = Excel.Workbooks.Add

    '// loop through the data in book1, one column at a time
    For colIndex = 1 To dataRange.Columns.Count
        newRow = 0
        For rowIndex = 1 To dataRange.Rows.Count
            With dataRange.Cells(rowIndex, colIndex)

            '// ignore empty cells
            If .value <> "" Then
                newRow = newRow + 1
                temp = doSomethingWith(.value)
                newBook.ActiveSheet.Cells(newRow, colIndex).value = temp
                End If

            End With
        Next rowIndex
    Next colIndex
End Sub

Private Function doSomethingWith(aValue)

    '// This is where you would compute a different value
    '// for use in the new workbook
    '// In this example, I simply add one to it.
    aValue = aValue + 1

    doSomethingWith = aValue
End Function

Calculate number of hours between 2 dates in PHP

This is working in my project. I think, This will be helpful for you.

If Date is in past then invert will 1.
If Date is in future then invert will 0.

$defaultDate = date('Y-m-d');   
$datetime1   = new DateTime('2013-03-10');  
$datetime2   = new DateTime($defaultDate);  
$interval    = $datetime1->diff($datetime2);  
$days        = $interval->format('%a');
$invert      = $interval->invert;

TypeError: 'dict_keys' object does not support indexing

Clearly you're passing in d.keys() to your shuffle function. Probably this was written with python2.x (when d.keys() returned a list). With python3.x, d.keys() returns a dict_keys object which behaves a lot more like a set than a list. As such, it can't be indexed.

The solution is to pass list(d.keys()) (or simply list(d)) to shuffle.

Remove carriage return from string

I just had the same issue in my code today and tried which worked like a charm.


How to trigger a file download when clicking an HTML button or JavaScript

download attribute do it

 <a class="btn btn-success btn-sm" href="/file_path/file.type" download>
     <span>download </span>&nbsp;<i class="fa fa-download"></i>

Spring JPA and persistence.xml

If anyone wants to use purely Java configuration instead of xml configuration of hibernate, use this:

You can configure Hibernate without using persistence.xml at all in Spring like like this:

public LocalContainerEntityManagerFactoryBean entityManagerFactoryBean()
Map<String, Object> properties = new Hashtable<>();
HibernateJpaVendorAdapter adapter = new HibernateJpaVendorAdapter();
adapter.setDatabasePlatform("org.hibernate.dialect.MySQL5InnoDBDialect"); //you can change this if you have a different DB
LocalContainerEntityManagerFactoryBean factory = new LocalContainerEntityManagerFactoryBean();
factory.setPackagesToScan("package name");
return factory;

Since you are not using persistence.xml, you should create a bean that returns DataSource which you specify in the above method that sets the data source:

public DataSource springJpaDataSource()
DriverManagerDataSource dataSource = new DriverManagerDataSource();
return dataSource;

Then you use @EnableTransactionManagement annotation over this configuration file. Now when you put that annotation, you have to create one last bean:

public PlatformTransactionManager jpaTransactionManager()
return new JpaTransactionManager(

Now, don't forget to use @Transactional Annotation over those method that deal with DB.

Lastly, don't forget to inject EntityManager in your repository (This repository class should have @Repository annotation over it).

Can I apply a CSS style to an element name?

Using [name=elementName]{} without tag before will work too. It will affect all elements with this name.

For example:

[name=test] {_x000D_
  width: 100px;_x000D_
<input type=text name=test>_x000D_
<div name=test></div>

IIS 7, HttpHandler and HTTP Error 500.21

I had the same problem and just solved it. I had posted my own question on stackoverflow:

Can't PUT to my IHttpHandler, GET works fine

The solution was to set runManagedModulesForWebDavRequests to true in the modules element. My guess is that once you install WebDAV then all PUT requests are associated with it. If you need the PUT to go to your handler, you need to remove the WebDAV module and set this attribute to true.

<modules runManagedModulesForWebDavRequests="true">

So if you're running into the problem when you use the PUT verb and you have installed WebDAV then hopefully this solution will fix your problem.

Regular expression for validating names and surnames?

A very contentious subject that I seem to have stumbled along here. However sometimes it's nice to head dear little-bobby tables off at the pass and send little Robert to the headmasters office along with his semi-colons and SQL comment lines --.

This REGEX in VB.NET includes regular alphabetic characters and various circumflexed european characters. However poor old James Mc'Tristan-Smythe the 3rd will have to input his pedigree in as the Jim the Third.

<asp:RegularExpressionValidator ID="RegExValid1" Runat="server"
                    ErrorMessage="ERROR: Please enter a valid surname<br/>" SetFocusOnError="true" Display="Dynamic"
                    ControlToValidate="txtSurname" ValidationGroup="MandatoryContent"

Why is “while ( !feof (file) )” always wrong?

I'd like to provide an abstract, high-level perspective.

Concurrency and simultaneity

I/O operations interact with the environment. The environment is not part of your program, and not under your control. The environment truly exists "concurrently" with your program. As with all things concurrent, questions about the "current state" don't make sense: There is no concept of "simultaneity" across concurrent events. Many properties of state simply don't exist concurrently.

Let me make this more precise: Suppose you want to ask, "do you have more data". You could ask this of a concurrent container, or of your I/O system. But the answer is generally unactionable, and thus meaningless. So what if the container says "yes" – by the time you try reading, it may no longer have data. Similarly, if the answer is "no", by the time you try reading, data may have arrived. The conclusion is that there simply is no property like "I have data", since you cannot act meaningfully in response to any possible answer. (The situation is slightly better with buffered input, where you might conceivably get a "yes, I have data" that constitutes some kind of guarantee, but you would still have to be able to deal with the opposite case. And with output the situation is certainly just as bad as I described: you never know if that disk or that network buffer is full.)

So we conclude that it is impossible, and in fact unreasonable, to ask an I/O system whether it will be able to perform an I/O operation. The only possible way we can interact with it (just as with a concurrent container) is to attempt the operation and check whether it succeeded or failed. At that moment where you interact with the environment, then and only then can you know whether the interaction was actually possible, and at that point you must commit to performing the interaction. (This is a "synchronisation point", if you will.)


Now we get to EOF. EOF is the response you get from an attempted I/O operation. It means that you were trying to read or write something, but when doing so you failed to read or write any data, and instead the end of the input or output was encountered. This is true for essentially all the I/O APIs, whether it be the C standard library, C++ iostreams, or other libraries. As long as the I/O operations succeed, you simply cannot know whether further, future operations will succeed. You must always first try the operation and then respond to success or failure.


In each of the examples, note carefully that we first attempt the I/O operation and then consume the result if it is valid. Note further that we always must use the result of the I/O operation, though the result takes different shapes and forms in each example.

  • C stdio, read from a file:

      for (;;) {
          size_t n = fread(buf, 1, bufsize, infile);
          consume(buf, n);
          if (n == 0) { break; }

The result we must use is n, the number of elements that were read (which may be as little as zero).

  • C stdio, scanf:

      for (int a, b, c; scanf("%d %d %d", &a, &b, &c) == 3; ) {
          consume(a, b, c);

The result we must use is the return value of scanf, the number of elements converted.

  • C++, iostreams formatted extraction:

      for (int n; std::cin >> n; ) {

The result we must use is std::cin itself, which can be evaluated in a boolean context and tells us whether the stream is still in the good() state.

  • C++, iostreams getline:

      for (std::string line; std::getline(std::cin, line); ) {

The result we must use is again std::cin, just as before.

  • POSIX, write(2) to flush a buffer:

      char const * p = buf;
      ssize_t n = bufsize;
      for (ssize_t k = bufsize; (k = write(fd, p, n)) > 0; p += k, n -= k) {}
      if (n != 0) { /* error, failed to write complete buffer */ }

The result we use here is k, the number of bytes written. The point here is that we can only know how many bytes were written after the write operation.

  • POSIX getline()

      char *buffer = NULL;
      size_t bufsiz = 0;
      ssize_t nbytes;
      while ((nbytes = getline(&buffer, &bufsiz, fp)) != -1)
          /* Use nbytes of data in buffer */

    The result we must use is nbytes, the number of bytes up to and including the newline (or EOF if the file did not end with a newline).

    Note that the function explicitly returns -1 (and not EOF!) when an error occurs or it reaches EOF.

You may notice that we very rarely spell out the actual word "EOF". We usually detect the error condition in some other way that is more immediately interesting to us (e.g. failure to perform as much I/O as we had desired). In every example there is some API feature that could tell us explicitly that the EOF state has been encountered, but this is in fact not a terribly useful piece of information. It is much more of a detail than we often care about. What matters is whether the I/O succeeded, more-so than how it failed.

  • A final example that actually queries the EOF state: Suppose you have a string and want to test that it represents an integer in its entirety, with no extra bits at the end except whitespace. Using C++ iostreams, it goes like this:

      std::string input = "   123   ";   // example
      std::istringstream iss(input);
      int value;
      if (iss >> value >> std::ws && iss.get() == EOF) {
      } else {
          // error, "input" is not parsable as an integer

We use two results here. The first is iss, the stream object itself, to check that the formatted extraction to value succeeded. But then, after also consuming whitespace, we perform another I/O/ operation, iss.get(), and expect it to fail as EOF, which is the case if the entire string has already been consumed by the formatted extraction.

In the C standard library you can achieve something similar with the strto*l functions by checking that the end pointer has reached the end of the input string.

The answer

while(!feof) is wrong because it tests for something that is irrelevant and fails to test for something that you need to know. The result is that you are erroneously executing code that assumes that it is accessing data that was read successfully, when in fact this never happened.

What does <meta http-equiv="X-UA-Compatible" content="IE=edge"> do?

Use content="IE=edge,chrome=1"   Skip other X-UA-Compatible modes

<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
  • No compatibility icon
    The IE9 Address bar does not show up the Compatibility View button
    and the page does not also show up a jumble of out-of-place menus, images, and text boxes.

  • Features
    This meta tag is required to enable javascript::JSON.parse() on IE8
    (even when <!DOCTYPE html> is present)

  • Correctness
    Rendering/Execution of modern HTML/CSS/JavaScript is more valid (nicer).

  • Performance
    The Trident rendering engine should run faster in its edge mode.


In your HTML

<!DOCTYPE html> 
    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">

Or better in the configuration of your web server:
(see also the RiaD's answer)

  • Apache as proposed by pixeline

    <IfModule mod_setenvif.c>
      <IfModule mod_headers.c>
        BrowserMatch MSIE ie
        Header set X-UA-Compatible "IE=Edge,chrome=1" env=ie
    <IfModule mod_headers.c>
      Header append Vary User-Agent
  • Nginx as proposed by Stef Pause

    server {
      add_header X-UA-Compatible "IE=Edge,chrome=1";
  • Varnish proxy as proposed by Lucas Riutzel

    sub vcl_deliver {
      if( resp.http.Content-Type ~ "text/html" ) {
        set resp.http.X-UA-Compatible = "IE=edge,chrome=1";
  • IIS (since v7)

               <add name="X-UA-Compatible" value="IE=edge,chrome=1" />

Microsoft recommends Edge mode since IE11

As noticed by Lynda (see comments), the Compatibility changes in IE11 recommends Edge mode:

Starting with IE11, edge mode is the preferred document mode; it represents the highest support for modern standards available to the browser.

But the position of Microsoft was not clear. Another MSDN page did not recommend Edge mode:

Because Edge mode forces all pages to be opened in standards mode, regardless of the version of Internet Explorer, you might be tempted to use this for all pages viewed with Internet Explorer. Don't do this, as the X-UA-Compatible header is only supported starting with Windows Internet Explorer 8.

Instead, Microsoft recommended using <!DOCTYPE html>:

If you want all supported versions of Internet Explorer to open your pages in standards mode, use the HTML5 document type declaration [...]

As Ricardo explains (in the comments below) any DOCTYPE (HTML4, XHTML1...) can be used to trigger Standards Mode, not only HTML5's DOCTYPE. The important thing is to always have a DOCTYPE in the page.

Clara Onager has even noticed in an older version of Specifying legacy document modes:

Edge mode is intended for testing purposes only; do not use it in a production environment.

It is so confusing that Usman Y thought Clara Onager was speaking about:

The [...] example is provided for illustrative purposes only; don't use it in a production environment.

<meta http-equiv="X-UA-Compatible" content="IE=7,9,10" >

Well... In the rest of this answer I give more explanations why using content="IE=edge,chrome=1" is a good practice in production.


For many years (2000 to 2008), IE market share was more than 80%. And IE v6 was considered as a de facto standard (80% to 97% market share in 2003, 2004, 2005 and 2006 for IE6 only, more market share with all IE versions).

As IE6 was not respecting Web standards, developers had to test their website using IE6. That situation was great for Microsoft (MS) as web developers had to buy MS products (e.g. IE cannot be used without buying Windows), and it was more profit-making to stay non-compliant (i.e. Microsoft wanted to become the standard excluding other companies).

Therefore many many sites were IE6 compliant only, and as IE was not compliant with web standard, all these web sites was not well rendered on standards compliant browsers. Even worse, many sites required only IE.

However, at this time, Mozilla started Firefox development respecting as much as possible all the web standards (other browser were implemented to render pages as done by IE6). As more and more web developers wanted to use the new web standards features, more and more websites were more supported by Firefox than IE.

When IE market sharing was decreasing, MS realized staying standard incompatible was not a good idea. Therefore MS started to release new IE version (IE8/IE9/IE10) respecting more and more the web standards.

The web-incompatible issue

But the issue is all the websites designed for IE6: Microsoft could not release new IE versions incompatible with these old IE6-designed websites. Instead of deducing the IE version a website has been designed, MS requested developers to add extra data (X-UA-Compatible) in their pages.

IE6 is still used in 2016

Nowadays, IE6 is still used (0.7% in 2016) (4.5% in January 2014), and some internet websites are still IE6-only-compliant. Some intranet website/applications are tested using IE6. Some intranet website are 100% functional only on IE6. These companies/departments prefer to postpone the migration cost: other priorities, nobody no longer knows how the website/application has been implemented, the owner of the legacy website/application went bankrupt...

China represents 50% of IE6 usage in 2013, but it may change in the next years as Chinese Linux distribution is being broadcast.

Be confident with your web skills

If you (try to) respect web standard, you can simply always use http-equiv="X-UA-Compatible" content="IE=edge,chrome=1". To keep compatibility with old browsers, just avoid using latest web features: use the subset supported by the oldest browser you want to support. Or If you want to go further, you may adopt concepts as Graceful degradation, Progressive enhancement and Unobtrusive JavaScript. (You may also be pleased to read What should a web developer consider?.)

Do do not care about the best IE version rendering: this is not your job as browsers have to be compliant with web standards. If your site is standard compliant and use moderately latest features, therefore browsers have to be compliant with your website.

Moreover, as there are many campaigns to kill IE6 (IE6 no more, MS campaign), nowadays you may avoid wasting time with IE testing!

Personal IE6 experience

In 2009-2012, I worked for a company using IE6 as the official single browser allowed. I had to implement an intranet website for IE6 only. I decided to respect web standard but using the IE6-capable subset (HTML/CSS/JS).

It was hard, but when the company switched to IE8, the website was still well rendered because I had used Firefox and firebug to check the web-standard compatibility ;)

How do I pass a variable to the layout using Laravel' Blade templating?

I was able to solve that problem by adding this to my controller method:

    $title = 'My Title Here';
    View::share('title', $title);

$this->layout->title = 'Home page'; did not work either.

/exclude in xcopy just for a file type

For excluding multiple file types, you can use '+' to concatenate other lists. For example:

xcopy /r /d /i /s /y /exclude:excludedfileslist1.txt+excludedfileslist2.txt C:\dev\apan C:\web\apan


How to semantically add heading to a list

According to (note that this link is in the long-expired draft HTML 3.0 spec):

An unordered list typically is a bulleted list of items. HTML 3.0 gives you the ability to customise the bullets, to do without bullets and to wrap list items horizontally or vertically for multicolumn lists.

The opening list tag must be <UL>. It is followed by an optional list header (<LH>caption</LH>) and then by the first list item (<LI>). For example:

  <LH>Table Fruit</LH>

which could be rendered as:

Table Fruit

  • apples
  • oranges
  • bananas

Note: Some legacy documents may include headers or plain text before the first LI element. Implementors of HTML 3.0 user agents are advised to cater for this possibility in order to handle badly formed legacy documents.

How to process POST data in Node.js?


let body = [];
request.on('data', (chunk) => {
}).on('end', () => {
  body = Buffer.concat(body).toString();
  // at this point, `body` has the entire request body stored in it as a string

How to run Python script on terminal?

If you are working with Ubuntu, sometimes you need to run as sudo:

For Python2:

sudo python

For Python3:

sudo python3

Parse String to Date with Different Format in Java

A Date object has no format, it is a representation. The date can be presented by a String with the format you like.

E.g. "yyyy-MM-dd", "yy-MMM-dd", "dd-MMM-yy" and etc.

To acheive this you can get the use of the SimpleDateFormat

Try this,

        String inputString = "19/05/2009"; // i.e. (dd/MM/yyyy) format

        SimpleDateFormat fromUser = new SimpleDateFormat("dd/MM/yyyy"); 
        SimpleDateFormat myFormat = new SimpleDateFormat("yyyy-MM-dd");

        try {
            Date dateFromUser = fromUser.parse(inputString); // Parse it to the exisitng date pattern and return Date type
            String dateMyFormat = myFormat.format(dateFromUser); // format it to the date pattern you prefer
            System.out.println(dateMyFormat); // outputs : 2009-05-19

        } catch (ParseException e) {

This outputs : 2009-05-19

Add padding on view programmatically

Context contect=MainActivity.this;
TextView tview=new TextView(context);

Python return statement error " 'return' outside function"

Use quit() in this context. break expects to be inside a loop, and return expects to be inside a function.

HTML5 image icon to input placeholder

  1. You can set it as background-image and use text-indent or a padding to shift the text to the right.
  2. You can break it up into two elements.

Honestly, I would avoid usage of HTML5/CSS3 without a good fallback. There are just too many people using old browsers that don't support all the new fancy stuff. It will take a while before we can drop the fallback, unfortunately :(

The first method I mentioned is the safest and easiest. Both ways requires Javascript to hide the icon.


input#search {
    background-image: url(bg.jpg);
    background-repeat: no-repeat;
    text-indent: 20px;


<input type="text" id="search" name="search" onchange="hideIcon(this);" value="search" />


function hideIcon(self) { = 'none';

September 25h, 2013

I can't believe I said "Both ways requires JavaScript to hide the icon.", because this is not entirely true.

The most common timing to hide placeholder text is on change, as suggested in this answer. For icons however it's okay to hide them on focus which can be done in CSS with the active pseudo-class.

#search:active { background-image: none; }

Heck, using CSS3 you can make it fade away!

November 5th, 2013

Of course, there's the CSS3 ::before pseudo-elements too. Beware of browser support though!

            Chrome  Firefox     IE      Opera   Safari
:before     (yes)   1.0         8.0     4       4.0
::before    (yes)   1.5         9.0     7       4.0

Programmatically navigate using react router V4

The easiest way to get it done:



  • You may want to pass the history prop from parent component down to the component you want to invoke the action if its not available.

Using JAXB to unmarshal/marshal a List<String>

In case anyone of you wants to write a list wrapper for lists containing elements of multiple classes and want to give an individual XmlElement name according to the Class type without Writing X Wrapper classes you could use the @XmlMixed annotation. By doing so JAXB names the items of the list according to the value set by the @XmlRootElement. When doing so you have to specify which classes could possibly be in the list using @XmlSeeAlso


Possible Classes in the list

public class User {/*...*/}

public class LogEntry {/*...*/}

Wrapper class

@XmlSeeAlso({User.class, LogEntry.class})
public static class JaxbList<T>{

    protected List<T> records;

    public JaxbList(){}

    public JaxbList(List<T> list){

    public List<T> getRecords(){
        return records;


List l = new List();
l.add(new User("userA"));
l.add(new LogEntry(new UserB()));

XStream xStream = new XStream();
String result = xStream.toXML(l);



Alternatevily you could specify the XmlElement names directly inside the wrapper class using the @XmlElementRef annotation

@XmlSeeAlso({User.class, LogEntry.class})
public static class JaxbList<T>{

    protected List<T> records;

    public JaxbList(){}

    public JaxbList(List<T> list){

        @XmlElementRef(name="item", type=Object.class),
        @XmlElementRef(name="user", type=User.class),
        @XmlElementRef(name="entry", type=LogEntry.class)
    public List<T> getRecords(){
        return records;

How do I pick 2 random items from a Python set?

Use the random module:

import random
random.sample(set([1, 2, 3, 4, 5, 6]), 2)

This samples the two values without replacement (so the two values are different).

What is an OS kernel ? How does it differ from an operating system?

The Operating System is a generic name given to all of the elements (user interface, libraries, resources) which make up the system as a whole.

The kernel is "brain" of the operating system, which controls everything from access to the hard disk to memory management. Whenever you want to do anything, it goes though the kernel.

100% width Twitter Bootstrap 3 template

You're right using div.container-fluid and you also need a div.row child. Then, the content must be placed inside without any grid columns. If you have a look at the docs you can find this text:

  • Rows must be placed within a .container (fixed-width) or .container-fluid (full-width) for proper alignment and padding.
  • Use rows to create horizontal groups of columns.

Not using grid columns it's ok as stated here:

  • Content should be placed within columns, and only columns may be immediate children of rows.

And looking at this example, you can read this text:

Full width, single column: No grid classes are necessary for full-width elements.

Here's a live example showing some elements using the correct layout. This way you don't need any custom CSS or hack.

Android: Force EditText to remove focus?

You can also include android:windowSoftInputMode="stateAlwaysHidden" in your manifest action section.

This is equivalent to :


but in XML way.

FYI, you can also hide the keyboard with codes:

// hide virtual keyboard
InputMethodManager imm = (InputMethodManager)getSystemService(Context.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(mYourEditText.getWindowToken(), 0);

Refreshing data in RecyclerView and keeping its scroll position

The top answer by @DawnYu works, but the recyclerview will first scroll to the top, then go back to the intended scroll position causing a "flicker like" reaction which isn't pleasant.

To refresh the recyclerView, especially after coming from another activity, without flickering, and maintaining the scroll position, you need to do the following.

  1. Ensure you are updating you recycler view using DiffUtil. Read more about that here:
  2. Onresume of your activity, or at the point you want to update your activity, load data to your recyclerview. Using the diffUtil, only the updates will be made on the recyclerview while maintaining it position.

Hope this helps.

Passing a local variable from one function to another

You can very easily use this to re-use the value of the variable in another function.

// Use this in source window.var1= oEvent.getSource().getBindingContext();

// Get value of var1 in destination var var2= window.var1;

How to count lines in a document?

wc -l <filename>

This will give you number of lines and filename in output.


wc -l 24-11-2019-04-33-01-url_creator.log


63 24-11-2019-04-33-01-url_creator.log


wc -l <filename>|cut -d\ -f 1

to get only number of lines in output.


wc -l 24-11-2019-04-33-01-url_creator.log|cut -d\ -f 1



Simple 3x3 matrix inverse code (C++)

With all due respect to our unknown (yahoo) poster, I look at code like that and just die a little inside. Alphabet soup is just so insanely difficult to debug. A single typo anywhere in there can really ruin your whole day. Sadly, this particular example lacked variables with underscores. It's so much more fun when we have a_b-c_d*e_f-g_h. Especially when using a font where _ and - have the same pixel length.

Taking up Suvesh Pratapa on his suggestion, I note:

Given 3x3 matrix:
       y0x0  y0x1  y0x2
       y1x0  y1x1  y1x2
       y2x0  y2x1  y2x2
Declared as double matrix [/*Y=*/3] [/*X=*/3];

(A) When taking a minor of a 3x3 array, we have 4 values of interest. The lower X/Y index is always 0 or 1. The higher X/Y index is always 1 or 2. Always! Therefore:

double determinantOfMinor( int          theRowHeightY,
                           int          theColumnWidthX,
                           const double theMatrix [/*Y=*/3] [/*X=*/3] )
  int x1 = theColumnWidthX == 0 ? 1 : 0;  /* always either 0 or 1 */
  int x2 = theColumnWidthX == 2 ? 1 : 2;  /* always either 1 or 2 */
  int y1 = theRowHeightY   == 0 ? 1 : 0;  /* always either 0 or 1 */
  int y2 = theRowHeightY   == 2 ? 1 : 2;  /* always either 1 or 2 */

  return ( theMatrix [y1] [x1]  *  theMatrix [y2] [x2] )
      -  ( theMatrix [y1] [x2]  *  theMatrix [y2] [x1] );

(B) Determinant is now: (Note the minus sign!)

double determinant( const double theMatrix [/*Y=*/3] [/*X=*/3] )
  return ( theMatrix [0] [0]  *  determinantOfMinor( 0, 0, theMatrix ) )
      -  ( theMatrix [0] [1]  *  determinantOfMinor( 0, 1, theMatrix ) )
      +  ( theMatrix [0] [2]  *  determinantOfMinor( 0, 2, theMatrix ) );

(C) And the inverse is now:

bool inverse( const double theMatrix [/*Y=*/3] [/*X=*/3],
                    double theOutput [/*Y=*/3] [/*X=*/3] )
  double det = determinant( theMatrix );

    /* Arbitrary for now.  This should be something nicer... */
  if ( ABS(det) < 1e-2 )
    memset( theOutput, 0, sizeof theOutput );
    return false;

  double oneOverDeterminant = 1.0 / det;

  for (   int y = 0;  y < 3;  y ++ )
    for ( int x = 0;  x < 3;  x ++   )
        /* Rule is inverse = 1/det * minor of the TRANSPOSE matrix.  *
         * Note (y,x) becomes (x,y) INTENTIONALLY here!              */
      theOutput [y] [x]
        = determinantOfMinor( x, y, theMatrix ) * oneOverDeterminant;

        /* (y0,x1)  (y1,x0)  (y1,x2)  and (y2,x1)  all need to be negated. */
      if( 1 == ((x + y) % 2) )
        theOutput [y] [x] = - theOutput [y] [x];

  return true;

And round it out with a little lower-quality testing code:

void printMatrix( const double theMatrix [/*Y=*/3] [/*X=*/3] )
  for ( int y = 0;  y < 3;  y ++ )
    cout << "[  ";
    for ( int x = 0;  x < 3;  x ++   )
      cout << theMatrix [y] [x] << "  ";
    cout << "]" << endl;
  cout << endl;

void matrixMultiply(  const double theMatrixA [/*Y=*/3] [/*X=*/3],
                      const double theMatrixB [/*Y=*/3] [/*X=*/3],
                            double theOutput  [/*Y=*/3] [/*X=*/3]  )
  for (   int y = 0;  y < 3;  y ++ )
    for ( int x = 0;  x < 3;  x ++   )
      theOutput [y] [x] = 0;
      for ( int i = 0;  i < 3;  i ++ )
        theOutput [y] [x] +=  theMatrixA [y] [i] * theMatrixB [i] [x];

main(int argc, char **argv)
  if ( argc > 1 )
    SRANDOM( atoi( argv[1] ) );

  double m[3][3] = { { RANDOM_D(0,1e3), RANDOM_D(0,1e3), RANDOM_D(0,1e3) },
                     { RANDOM_D(0,1e3), RANDOM_D(0,1e3), RANDOM_D(0,1e3) },
                     { RANDOM_D(0,1e3), RANDOM_D(0,1e3), RANDOM_D(0,1e3) } };
  double o[3][3], mm[3][3];

  if ( argc <= 2 )
    cout << fixed << setprecision(3);

  cout << endl << endl;

  SHOW( determinant(m) );
  cout << endl << endl;

  BOUT( inverse(m, o) );
  cout << endl << endl;

  matrixMultiply (m, o, mm );
  cout << endl << endl;


You may also want to detect very large determinants as round-off errors will affect your accuracy!

Command to open file with git

while you are working in some whatever project and you want to make a minor change you can use git default editor, however you'd probably need a little script that parse the file generated by command below

git config -l

then the variable code.editor holds the value /Applications/ -n -w

which you can open using os.system()

Could not obtain information about Windows NT group user

Just solved this problem. In my case it was domain controller is not accessible, because both dns servers was google dns.

I just add to checklist for this problem:

  • check domain controller is accessible

Resize on div element

I've created jquery plugin jquery.resize it use resizeObserver if supported or solution based on marcj/css-element-queries scroll event, no setTimeout/setInterval.

You use just

 jQuery('div').on('resize', function() { /* What ever */ });

or as resizer plugin

jQuery('div').resizer(function() { /* What ever */ });

I've created this for jQuery Terminal and extracted into separated repo and npm package, but in a mean time I switched to hidden iframe because I had problems with resize if element was inside iframe. I may update the plugin accordingly. You can look at iframe based resizer plugin in jQuery Terminal source code.

EDIT: new version use iframe and resize on it's window object because the previous solutions was not working when page was inside iframe.

EDIT2: Because the fallback use iframe you can't use it with form controls or images, you need to add it to the wrapper element.

EDIT3:: there is better solution using resizeObserver polyfill that use mutation observer (if resizeObserver is not supported) and work even in IE. It also have TypeScript typings.

How do I write stderr to a file while using "tee" with a pipe?

If you're using zsh, you can use multiple redirections, so you don't even need tee:

./cmd 1>&1 2>&2 1>out_file 2>err_file

Here you're simply redirecting each stream to itself and the target file.

Full example

% (echo "out"; echo "err">/dev/stderr) 1>&1 2>&2 1>/tmp/out_file 2>/tmp/err_file
% cat /tmp/out_file
% cat /tmp/err_file

Note that this requires the MULTIOS option to be set (which is the default).


Perform implicit tees or cats when multiple redirections are attempted (see Redirection).

Updating address bar with new URL without hash or reloading the page

var newurl = window.location.protocol + "//" + + window.location.pathname + '?foo=bar';

Unable to set data attribute using jQuery Data() API

I was having serious problems with

.data('property', value);

It was not setting the data-property attribute.

Started using jQuery's .attr():

Get the value of an attribute for the first element in the set of matched elements or set one or more attributes for every matched element.

.attr('property', value)

to set the value and


to retrieve the value.

Now it just works!

How to get the name of a class without the package?


Returns the simple name of the underlying class as given in the source code. Returns an empty string if the underlying class is anonymous.

The simple name of an array is the simple name of the component type with "[]" appended. In particular the simple name of an array whose component type is anonymous is "[]".

It is actually stripping the package information from the name, but this is hidden from you.

How to implement a custom AlertDialog View

This worked for me:

dialog.setView(dialog.getLayoutInflater().inflate(R.layout.custom_dialog_layout, null));

How do I get list of all tables in a database using TSQL?

Well you can use sys.objects to get all database objects.

 select * from sys.objects where type_desc='USER_TABLE' order by name


--  For all tables

  --- For user defined tables

  --- For Views

Android SDK location

Update v3.3

enter image description here


Android Studio 3.1 update, some of the icon images have changed. Click this icon in Android Studio.

enter image description here


Click this icon in Android Studio for the Android SDK manager

enter image description here

And your Android SDK Location will be here enter image description here

Removing "bullets" from unordered list <ul> li a:before, li .item:before, li .separator:before {
  content: "\2022";
  font-family: FontAwesome;
  margin-right: 10px;
  display: inline;
  vertical-align: middle;
  font-size: 1.6em;
  font-weight: normal;

Is present in your site's CSS, looks like it's coming from a compiled CSS file from within your application. Perhaps from a plugin. Changing the name of the "menu" class you are using should resolve the issue.

Visual for you -

You are trying to add a non-nullable field 'new_field' to userprofile without a default

Do you already have database entries in the table UserProfile? If so, when you add new columns the DB doesn't know what to set it to because it can't be NULL. Therefore it asks you what you want to set those fields in the column new_fields to. I had to delete all the rows from this table to solve the problem.

(I know this was answered some time ago, but I just ran into this problem and this was my solution. Hopefully it will help anyone new that sees this)

Merge up to a specific commit

Run below command into the current branch folder to merge from this <commit-id> to current branch, --no-commit do not make a new commit automatically

git merge --no-commit <commit-id>

git merge --continue can only be run after the merge has resulted in conflicts.

git merge --abort Abort the current conflict resolution process, and try to reconstruct the pre-merge state.

Random color generator

Using ES6's Array.from() method, I created this solution:

function randomColor() {
  return "#"+ Array.from({length: 6},()=> Math.floor(Math.random()*16).toString(16)).join("");

The other implementations I've seen need to ensure that if the hexadecimal value has leading zeros, the number still contains six digits.

K._'s answer used ES6's padStart for this:

function randomColor() {
  return `#${Math.floor(Math.random() * 0x1000000).toString(16).padStart(6, 0)}`

The other good single-line solution I've seen is

function randomColor() {
  return '#'+ ('000000' + (Math.random()*0xFFFFFF<<0).toString(16)).slice(-6);

Raw SQL Query without DbSet - Entity Framework Core

In Core 2.1 you can do something like this:

protected override void OnModelCreating(ModelBuilder modelBuilder)

and then define you SQL Procedure, like:

public async Task<List<Ranks>> GetRanks(string value1, Nullable<decimal> value2)
    SqlParameter value1Input = new SqlParameter("@Param1", value1?? (object)DBNull.Value);
    SqlParameter value2Input = new SqlParameter("@Param2", value2?? (object)DBNull.Value);

    List<Ranks> getRanks = await this.Query<Ranks>().FromSql("STORED_PROCEDURE @Param1, @Param2", value1Input, value2Input).ToListAsync();

    return getRanks;

This way Ranks model will not be created in your DB.

Now in your controller/action you can call:

List<Ranks> gettingRanks = _DbContext.GetRanks(value1,value2).Result.ToListAsync();

This way you can call Raw SQL Procedures.

Seeding the random number generator in Javascript

Combining some of the previous answers, this is the seedable random function you are looking for:

Math.seed = function(s) {
    var mask = 0xffffffff;
    var m_w  = (123456789 + s) & mask;
    var m_z  = (987654321 - s) & mask;

    return function() {
      m_z = (36969 * (m_z & 65535) + (m_z >>> 16)) & mask;
      m_w = (18000 * (m_w & 65535) + (m_w >>> 16)) & mask;

      var result = ((m_z << 16) + (m_w & 65535)) >>> 0;
      result /= 4294967296;
      return result;

var myRandomFunction = Math.seed(1234);
var randomNumber = myRandomFunction();

Inserting Data into Hive Table

Use this -

create table dummy_table_name as select * from source_table_name;

This will create the new table with existing data available on source_table_name.

Multiple Updates in MySQL

There is a setting you can alter called 'multi statement' that disables MySQL's 'safety mechanism' implemented to prevent (more than one) injection command. Typical to MySQL's 'brilliant' implementation, it also prevents user from doing efficient queries.

Here ( is some info on the C implementation of the setting.

If you're using PHP, you can use mysqli to do multi statements (I think php has shipped with mysqli for a while now)

$con = new mysqli('localhost','user1','password','my_database');
$query = "Update MyTable SET col1='some value' WHERE id=1 LIMIT 1;";
$query .= "UPDATE MyTable SET col1='other value' WHERE id=2 LIMIT 1;";

Hope that helps.

Regex: Check if string contains at least one digit

Another possible solution, in case you're looking for all the words in a given string, which contain a number


  • \w* - Matches 0 or more instances of [A-Za-z0-9_]
  • \d{1,} - Matches 1 or more instances of a number
  • \w* - Matches 0 or more instances of [A-Za-z0-9_]

The whole point in \w* is to allow not having a character in the beginning or at the end of a word. This enables capturing the first and last words in the text.

If the goal here is to only get the numbers without the words, you can omit both \w*.

Given the string

Hello world 1 4m very happy to be here, my name is W1lly W0nk4


1 4m W1lly W0nk4

Check this example in regexr -

CSS vertical-align: text-bottom;

Sometimes you can play with padding and margin top, add line-height, etc.

See fiddle.

Style and text forked from @aspirinemaga

    border:1px solid red;

Can't bind to 'routerLink' since it isn't a known property

I am running tests for my Angular app and encountered error Can't bind to 'routerLink' since it isn't a known property of 'a' as well.

I thought it might be useful to show my Angular dependencies:

    "@angular/animations": "^8.2.14",
    "@angular/common": "^8.2.14",
    "@angular/compiler": "^8.2.14",
    "@angular/core": "^8.2.14",
    "@angular/forms": "^8.2.14",
    "@angular/router": "^8.2.14",

The issue was in my spec file. I compared to another similar component spec file and found that I was missing RouterTestingModule in imports, e.g.

      declarations: [
      imports: [ReactiveFormsModule, HttpClientTestingModule, RouterTestingModule],
      providers: [...]

How do you add a JToken to an JObject?

I think you're getting confused about what can hold what in JSON.Net.

  • A JToken is a generic representation of a JSON value of any kind. It could be a string, object, array, property, etc.
  • A JProperty is a single JToken value paired with a name. It can only be added to a JObject, and its value cannot be another JProperty.
  • A JObject is a collection of JProperties. It cannot hold any other kind of JToken directly.

In your code, you are attempting to add a JObject (the one containing the "banana" data) to a JProperty ("orange") which already has a value (a JObject containing {"colour":"orange","size":"large"}). As you saw, this will result in an error.

What you really want to do is add a JProperty called "banana" to the JObject which contains the other fruit JProperties. Here is the revised code:

JObject foodJsonObj = JObject.Parse(jsonText);
JObject fruits = foodJsonObj["food"]["fruit"] as JObject;
fruits.Add("banana", JObject.Parse(@"{""colour"":""yellow"",""size"":""medium""}"));

Round up to Second Decimal Place in Python

x = math.ceil(x * 100.0) / 100.0

How to find all serial devices (ttyS, ttyUSB, ..) on Linux without opening them?

The serial communication manager library has many API and features targeted for the task you want. If the device is a USB-UART its VID/PID can be used. If the device is BT-SPP than platform specific APIs can be used. Take a look at this project for serial port programming:

Dictionary returning a default value if the key does not exist

I know this is an old post and I do favor extension methods, but here's a simple class I use from time to time to handle dictionaries when I need default values.

I wish this were just part of the base Dictionary class.

public class DictionaryWithDefault<TKey, TValue> : Dictionary<TKey, TValue>
  TValue _default;
  public TValue DefaultValue {
    get { return _default; }
    set { _default = value; }
  public DictionaryWithDefault() : base() { }
  public DictionaryWithDefault(TValue defaultValue) : base() {
    _default = defaultValue;
  public new TValue this[TKey key]
    get { 
      TValue t;
      return base.TryGetValue(key, out t) ? t : _default;
    set { base[key] = value; }

Beware, however. By subclassing and using new (since override is not available on the native Dictionary type), if a DictionaryWithDefault object is upcast to a plain Dictionary, calling the indexer will use the base Dictionary implementation (throwing an exception if missing) rather than the subclass's implementation.

How do you run your own code alongside Tkinter's event loop?

When writing your own loop, as in the simulation (I assume), you need to call the update function which does what the mainloop does: updates the window with your changes, but you do it in your loop.

def task():
   # do something

while 1:

Using HttpClient and HttpPost in Android with post parameters

I've just checked and i have the same code as you and it works perferctly. The only difference is how i fill my List for the params :

I use a : ArrayList<BasicNameValuePair> params

and fill it this way :

 params.add(new BasicNameValuePair("apikey", apikey);

I do not use any JSONObject to send params to the webservices.

Are you obliged to use the JSONObject ?

Sort hash by key, return hash in Ruby

@ordered = {}
@unordered.keys.sort.each do |key|
  @ordered[key] = @unordered[key]

Hiding elements in responsive layout?

I have a couple of clarifications to add here:

1) The list shown (visible-phone, visible-tablet, etc.) is deprecated in Bootstrap 3. The new values are:

  • visible-xs-*
  • visible-sm-*
  • visible-md-*
  • visible-lg-*
  • hidden-xs-*
  • hidden-sm-*
  • hidden-md-*
  • hidden-lg-*

The asterisk translates to the following for each (I show only visible-xs-* below):

  • visible-xs-block
  • visible-xs-inline
  • visible-xs-inline-block

2) When you use these classes, you don't add a period in front (as confusingly shown in part of the answer above).

For example:

<div class="visible-md-block col-md-6 text-right text-muted">
   <h5>Copyright &copy; 2014 Jazimov</h5>

3) You can use visible-* and hidden-* (for example, visible-xs and hidden-xs) but these have been deprecated in Bootstrap 3.2.0.

For more details and the latest specs, go here and search for "visible":

How to a convert a date to a number and back again in MATLAB


>> datestr(40189)
ans =

Unfortunately, Excel starts counting at 1-Jan-1900. Find out how to convert serial dates from Matlab to Excel by using DATENUM

>> datenum(2010,1,11)
ans =
>> datenum(2010,1,11)-40189
ans =
>> datestr(40189+693960)
ans =

In other words, to convert any serial Excel date, call

datestr(excelSerialDate + 693960)


To get the date in mm/dd/yyyy format, call datestr with the specified format

excelSerialDate = 40189;
datestr(excelSerialDate + 693960,'mm/dd/yyyy')
ans =

Also, if you want to get rid of the leading zero for the month, you can use REGEXPREP to fix things

excelSerialDate = 40189;
regexprep(datestr(excelSerialDate + 693960,'mm/dd/yyyy'),'^0','')
ans =

RegEx to extract all matches from string using RegExp.exec

Here is my answer:

var str = '[me nombre es] : My name is. [Yo puedo] is the right word'; 

var reg = /\[(.*?)\]/g;

var a = str.match(reg);

a = a.toString().replace(/[\[\]]/g, "").split(','));

Possible to perform cross-database queries with PostgreSQL?

Just to add a bit more information.

There is no way to query a database other than the current one. Because PostgreSQL loads database-specific system catalogs, it is uncertain how a cross-database query should even behave.

contrib/dblink allows cross-database queries using function calls. Of course, a client can also make simultaneous connections to different databases and merge the results on the client side.

PostgreSQL FAQ

Leader Not Available Kafka in Console Producer

For anyone trying to run kafka on kubernetes and running into this error, this is what finally solved it for me:

You have to either:

  1. Add hostname to the pod spec, that way kafka can find itself.


  1. If using hostPort, then you need hostNetwork: true and dnsPolicy: ClusterFirstWithHostNet

The reason for this is because Kafka needs to talk to itself, and it decides to use the 'advertised' listener/hostname to find itself, rather than using localhost. Even if you have a Service that points the advertised host name at the pod, it is not visible from within the pod. I do not really know why that is the case, but at least there is a workaround.

apiVersion: extensions/v1beta1
kind: Deployment
  name: zookeeper-cluster1
  namespace: default
    app: zookeeper-cluster1
  replicas: 1
      app: zookeeper-cluster1
        name: zookeeper-cluster1
        app: zookeeper-cluster1
      hostname: zookeeper-cluster1
      - name: zookeeper-cluster1
        image: wurstmeister/zookeeper:latest
        imagePullPolicy: IfNotPresent
        - containerPort: 2181
        - containerPort: 2888
        - containerPort: 3888


apiVersion: v1
kind: Service
  name: zookeeper-cluster1
  namespace: default
    app: zookeeper-cluster1
  type: NodePort
    app: zookeeper-cluster1
  - name: zookeeper-cluster1
    protocol: TCP
    port: 2181
    targetPort: 2181
  - name: zookeeper-follower-cluster1
    protocol: TCP
    port: 2888
    targetPort: 2888
  - name: zookeeper-leader-cluster1
    protocol: TCP
    port: 3888
    targetPort: 3888


apiVersion: extensions/v1beta1
kind: Deployment
  name: kafka-cluster
  namespace: default
    app: kafka-cluster
  replicas: 1
      app: kafka-cluster
        name: kafka-cluster
        app: kafka-cluster
      hostname: kafka-cluster
      - name: kafka-cluster
        image: wurstmeister/kafka:latest
        imagePullPolicy: IfNotPresent
          value: PLAINTEXT://kafka-cluster:9092
          value: zookeeper-cluster1:2181
        - containerPort: 9092


apiVersion: v1
kind: Service
  name: kafka-cluster
  namespace: default
    app: kafka-cluster
  type: NodePort
    app: kafka-cluster
  - name: kafka-cluster
    protocol: TCP
    port: 9092
    targetPort: 9092

When should iteritems() be used instead of items()?

future.utils allows for python 2 and 3 compatibility.

# Python 2 and 3: option 3
from future.utils import iteritems
heights = {'man': 185,'lady': 165}
for (key, value) in iteritems(heights):

>>> ('lady', 165)
>>> ('man', 185)

See this link:

Java: Convert a String (representing an IP) to InetAddress

From the documentation of InetAddress.getByName(String host):

The host name can either be a machine name, such as "", or a textual representation of its IP address. If a literal IP address is supplied, only the validity of the address format is checked.

So you can use it.

Install / upgrade gradle on Mac OS X

Two Method

  • using homebrew auto install:
    • Steps:
      • brew install gradle
    • Pros and cons
      • Pros: easy
      • Cons: (probably) not latest version
  • manually install (for latest version):
    • Pros and cons
      • Pros: use your expected any (or latest) version
      • Cons: need self to do it
    • Steps
      • download latest version binary (gradle-6.0.1) from Gradle | Releases
      • unzip it ( and added gradle path into environment variable PATH
        • normally is edit and add following config into your startup script( ~/.bashrc or ~/.zshrc etc.):
export GRADLE_HOME=/path_to_your_gradle/gradle-6.0.1

some other basic note

Q: How to make PATH take effect immediately?

A: use source:

source ~/.bashrc

it will make/execute your .bashrc, so make PATH become your expected latest values, which include your added gradle path.

Q: How to check PATH is really take effect/working now?

A: use echo to see your added path in indeed in your PATH

?  ~ echo $PATH

you can see we added /Users/crifan/dev/dev_tool/java/gradle/gradle-6.0.1/bin into your PATH

Q: How to verify gradle is installed correctly on my Mac ?

A: use which to make sure can find gradle

?  ~ which gradle

AND to check and see gradle version

?  ~ gradle --version

Gradle 6.0.1

Build time:   2019-11-18 20:25:01 UTC
Revision:     fad121066a68c4701acd362daf4287a7c309a0f5

Kotlin:       1.3.50
Groovy:       2.5.8
Ant:          Apache Ant(TM) version 1.10.7 compiled on September 1 2019
JVM:          1.8.0_112 (Oracle Corporation 25.112-b16)
OS:           Mac OS X 10.14.6 x86_64

this means the (latest) gradle is correctly installed on your mac ^_^.

for more detail please refer my (Chinese) post ?????mac???maven

"message failed to fetch from registry" while trying to install any module

You also need to install software-properties-common for add-apt-repository to work. so it will be

sudo apt-get purge nodejs npm
sudo apt-get install -y python-software-properties python g++ make software-properties-common
sudo add-apt-repository ppa:chris-lea/node.js
sudo apt-get update
sudo apt-get install nodejs

The type java.lang.CharSequence cannot be resolved in package declaration

"Java 8 support for Eclipse Kepler SR2", and the new "JavaSE-1.8" execution environment showed up automatically.

Download this one:- Eclipse kepler SR2

and then follow this link:- Eclipse_Java_8_Support_For_Kepler

how to make jni.h be found?

It needs both jni.h and jni_md.h files, Try this

gcc -I/usr/lib/jvm/jdk1.7.0_07/include \
  -I/usr/lib/jvm/jdk1.7.0_07/include/linux filename.c

This will include both the broad JNI files and the ones necessary for linux

Identifying country by IP address

You can try using - geo location api that returns country among other IP information.

For example with Node.js

const request = require('request-promise')

  .then(response => console.log(JSON.parse(response)))
  .catch(err => console.log(err))

What is the default encoding of the JVM?

There are three "default" encodings:

  • file.encoding:

  • java.nio.Charset:

  • And the encoding of the InputStreamReader:

You can read more about it on this page.

slashes in url variables

You need to escape those but don't just replace it by %2F manually. You can use URLEncoder for this.

Eg URLEncoder.encode(url, "UTF-8")

Then you can say

yourUrl = "www.musicExplained/index.cfm/artist/" + URLEncoder.encode(VariableName, "UTF-8")

Bootstrap : TypeError: $(...).modal is not a function

If you are using any layout page then, move script sections from bottom to head section in layout page. bcz, javascript files should be loaded first. This worked for me

How to kill MySQL connections

No, there is no built-in MySQL command for that. There are various tools and scripts that support it, you can kill some connections manually or restart the server (but that will be slower).

Use SHOW PROCESSLIST to view all connections, and KILL the process ID's you want to kill.

You could edit the timeout setting to have the MySQL daemon kill the inactive processes itself, or raise the connection count. You can even limit the amount of connections per username, so that if the process keeps misbehaving, the only affected process is the process itself and no other clients on your database get locked out.

If you can't connect yourself anymore to the server, you should know that MySQL always reserves 1 extra connection for a user with the SUPER privilege. Unless your offending process is for some reason using a username with that privilege...

Then after you can access your database again, you should fix the process (website) that's spawning that many connections.

Confusing "duplicate identifier" Typescript error message

If you have installed typings separately under typings folder

  "exclude": [

Remove items from one list in another

Solution 1 : You can do like this :

List<car> result = GetSomeOtherList().Except(GetTheList()).ToList();

But in some cases may this solution not work. if it is not work you can use my second solution .

Solution 2 :

List<car> list1 = GetTheList();
List<car> list2 = GetSomeOtherList();

we pretend that list1 is your main list and list2 is your secondry list and you want to get items of list1 without items of list2.

 var result =  list1.Where(p => !list2.Any(x => x.ID == p.ID && x.property1 == p.property1)).ToList();

How to determine if .NET Core is installed

One of the dummies ways to determine if .NET Core is installed on Windows is:

  • Press Windows + R
  • Type cmd
  • On the command prompt, type dotnet --version

dotnet --version

If the .NET Core is installed, we should not get any error in the above steps.

Sort a list of tuples by 2nd item (integer value)

>>> from operator import itemgetter
>>> data = [('abc', 121),('abc', 231),('abc', 148), ('abc',221)]
>>> sorted(data,key=itemgetter(1))
[('abc', 121), ('abc', 148), ('abc', 221), ('abc', 231)]

IMO using itemgetter is more readable in this case than the solution by @cheeken. It is also faster since almost all of the computation will be done on the c side (no pun intended) rather than through the use of lambda.

>python -m timeit -s "from operator import itemgetter; data = [('abc', 121),('abc', 231),('abc', 148), ('abc',221)]" "sorted(data,key=itemgetter(1))"
1000000 loops, best of 3: 1.22 usec per loop

>python -m timeit -s "data = [('abc', 121),('abc', 231),('abc', 148), ('abc',221)]" "sorted(data,key=lambda x: x[1])"
1000000 loops, best of 3: 1.4 usec per loop

How to Check byte array empty or not?

.Net V 4.6 OR C # 6.0

Try This

 if (Attachment?.Length > 0)

Combine Regexp?

1 + 2 + 4 conditions: starts|ends, but not in the middle


is almost the same that:


but this one matches any string without @, sample 'my name is hal9000'

How to format a floating number to fixed width in Python

In python3 the following works:

>>> v=10.4
>>> print('% 6.2f' % v)
>>> print('% 12.1f' % v)
>>> print('%012.1f' % v)

Get parent of current directory from Python script

This worked for me (I am on Ubuntu):

import os

How do I remove the horizontal scrollbar in a div?

Use This chunk of code..

.card::-webkit-scrollbar {
  display: none;

How to run python script on terminal (ubuntu)?

Set the PATH as below:

In the csh shell - type setenv PATH "$PATH:/usr/local/bin/python" and press Enter.

In the bash shell (Linux) - type export PATH="$PATH:/usr/local/bin/python" and press Enter.

In the sh or ksh shell - type PATH="$PATH:/usr/local/bin/python" and press Enter.

Note - /usr/local/bin/python is the path of the Python directory

now run as below:

-bash-4.2$ python

Hello, Python!

How do I create delegates in Objective-C?

In my point of view create separate class for that delegate method and you can use where you want.

in my Custom DropDownClass.h

typedef enum

@protocol DropDownListDelegate <NSObject>
- (void)dropDownDidSelectItemWithString:(NSString*)itemString     DropDownType:(DropDownType)dropDownType;
@interface DropDownViewController : UIViewController
 BOOL isFiltered;
@property (nonatomic, assign) DropDownType dropDownType;
@property (weak) id <DropDownListDelegate> delegate;
@property (strong, nonatomic) NSMutableArray *array1DropDown;
@property (strong, nonatomic) NSMutableArray *array2DropDown;

after that in.m file create array with objects,

 - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath{
CGFloat rowHeight = 44.0f;
return rowHeight;

-(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
return 1;
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
return isFiltered?[self.array1DropDown count]:[self.array2DropDown count];
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *simpleTableIdentifier = @"TableCell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:simpleTableIdentifier];
if (cell == nil) {
    cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:simpleTableIdentifier];

if (self.delegate) {
    if (self.dropDownType == DDCITY) {
        cell.textLabel.text = [self.array1DropDown objectAtIndex:indexPath.row];
    else if (self.dropDownType == DDSTATE) {
        cell.textLabel.text = [self.array2DropDown objectAtIndex:indexPath.row];
return cell;

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
 [self dismissViewControllerAnimated:YES completion:^{
        if(self.dropDownType == DDCITY){
            [self.delegate dropDownDidSelectItemWithString:[self.array1DropDown objectAtIndex:indexPath.row] DropDownType:self.dropDownType];
        else if (self.dropDownType == DDSTATE) {
            [self.delegate dropDownDidSelectItemWithString:[self.array2DropDown objectAtIndex:indexPath.row] DropDownType:self.dropDownType];

Here all are set for Custom delegate class.after that you can use this delegate method where you want.for example...

in my another viewcontroller import after that

create action for calling delegate method like this

- (IBAction)dropDownBtn1Action:(id)sender {
DropDownViewController *vehicleModelDropView = [[DropDownViewController alloc]init];
vehicleModelDropView.dropDownType = DDCITY;
vehicleModelDropView.delegate = self;
[self presentViewController:vehicleModelDropView animated:YES completion:nil];

after that call delegate method like this

- (void)dropDownDidSelectItemWithString:(NSString *)itemString DropDownType:(DropDownType)dropDownType {
switch (dropDownType) {
    case DDCITY:{
        if(itemString.length > 0){
            //Here i am printing the selected row
            [self.dropDownBtn1 setTitle:itemString forState:UIControlStateNormal];
    case DDSTATE: {
        //Here i am printing the selected row
        [self.dropDownBtn2 setTitle:itemString forState:UIControlStateNormal];


WCF, Service attribute value in the ServiceHost directive could not be found

If you have renamed anything verify the (Properties/) AssemblyInfo.cs is correct, as well as the header in the service file.


<%@ ServiceHost Language="C#" Debug="true" Service="Company.Namespace.WcfApp" CodeBehind="WcfApp.svc.cs" %>

Aligning with your namespace in your Service.svc.cs

Create listview in fragment android

you need to give:

public void onActivityCreated(Bundle savedInstanceState)    

inside fragment.

Select multiple columns by labels in pandas

How do I select multiple columns by labels in pandas?

Multiple label-based range slicing is not easily supported with pandas, but position-based slicing is, so let's try that instead:

loc = df.columns.get_loc
df.iloc[:, np.r_[loc('A'):loc('C')+1, loc('E'), loc('G'):loc('I')+1]]

          A         B         C         E         G         H         I
0 -1.666330  0.321260 -1.768185 -0.034774  0.023294  0.533451 -0.241990
1  0.911498  3.408758  0.419618 -0.462590  0.739092  1.103940  0.116119
2  1.243001 -0.867370  1.058194  0.314196  0.887469  0.471137 -1.361059
3 -0.525165  0.676371  0.325831 -1.152202  0.606079  1.002880  2.032663
4  0.706609 -0.424726  0.308808  1.994626  0.626522 -0.033057  1.725315
5  0.879802 -1.961398  0.131694 -0.931951 -0.242822 -1.056038  0.550346
6  0.199072  0.969283  0.347008 -2.611489  0.282920 -0.334618  0.243583
7  1.234059  1.000687  0.863572  0.412544  0.569687 -0.684413 -0.357968
8 -0.299185  0.566009 -0.859453 -0.564557 -0.562524  0.233489 -0.039145
9  0.937637 -2.171174 -1.940916 -1.553634  0.619965 -0.664284 -0.151388

Note that the +1 is added because when using iloc the rightmost index is exclusive.

Comments on Other Solutions

  • filter is a nice and simple method for OP's headers, but this might not generalise well to arbitrary column names.

  • The "location-based" solution with loc is a little closer to the ideal, but you cannot avoid creating intermediate DataFrames (that are eventually thrown out and garbage collected) to compute the final result range -- something that we would ideally like to avoid.

  • Lastly, "pick your columns directly" is good advice as long as you have a manageably small number of columns to pick. It will, however not be applicable in some cases where ranges span dozens (or possibly hundreds) of columns.

How to use a DataAdapter with stored procedure and parameter

Maybe your code is missing this line from the Microsoft example:

MyDataAdapter.SelectCommand.CommandType = CommandType.StoredProcedure

WPF: Setting the Width (and Height) as a Percentage Value

You can put the textboxes inside a grid to do percentage values on the rows or columns of the grid and let the textboxes auto-fill to their parent cells (as they will by default). Example:

        <ColumnDefinition Width="2*" />
        <ColumnDefinition Width="3*" />

    <TextBox Grid.Column="0" />
    <TextBox Grid.Column="1" />

This will make #1 2/5 of the width, and #2 3/5.

Math.random() explanation

The Random class of Java located in the java.util package will serve your purpose better. It has some nextInt() methods that return an integer. The one taking an int argument will generate a number between 0 and that int, the latter not inclusive.

How to check if "Radiobutton" is checked?

You can use switch like this:

XML Layout


                android:text="R1" />

                android:text="R2" />

And JAVA Activity

switch (RG.getCheckedRadioButtonId()) {
            regAuxiliar = ultimoRegistro;
            regAuxiliar = objRegistro;
            regAuxiliar = null; // none selected

You will also need to implement an onClick function with button or setOnCheckedChangeListener function to get required functionality.

How to send email to multiple recipients with addresses stored in Excel?

ToAddress = "[email protected]"
ToAddress1 = "[email protected]"
ToAddress2 = "[email protected]"
MessageSubject = "It works!."
Set ol = CreateObject("Outlook.Application")
Set newMail = ol.CreateItem(olMailItem)
newMail.Subject = MessageSubject

How to color System.out.println output?

Escape sequences must be interpreted by SOMETHING to be converted to color. The standard CMD.EXE used by java when started from the command line, doesn't support this so therefore Java does not.

Laravel 5 call a model function in a blade view

Related to the question in your answer:

You have multiple options to achieve this that are way better:

Let's assume you have a model which you pass to the view:

$model = Model::find(1);

Now in your Model you could have a function:

public function someFunction() {
    // do something

In your view you could call that function directly:


This is nice if you want to do something with the model (the dataset).

If not you can still make a static function in the model:

public static function someStaticFunction($var1, $var2) {
    // do something

And then:


Hope it helps.

How to get the html of a div on another page with jQuery ajax?

Ok, You should "construct" the html and find the .content div.

like this:

   success: function(data){


Code for printf function in C

Here's the GNU version of printf... you can see it passing in stdout to vfprintf:

__printf (const char *format, ...)
   va_list arg;
   int done;

   va_start (arg, format);
   done = vfprintf (stdout, format, arg);
   va_end (arg);

   return done;

See here.

Here's a link to vfprintf... all the formatting 'magic' happens here.

The only thing that's truly 'different' about these functions is that they use varargs to get at arguments in a variable length argument list. Other than that, they're just traditional C. (This is in contrast to Pascal's printf equivalent, which is implemented with specific support in the compiler... at least it was back in the day.)

Highlighting Text Color using Html.fromHtml() in Android?

Alternative solution: Using a WebView instead. Html is easy to work with.

WebView webview = new WebView(this);

String summary = "<html><body>Sorry, <span style=\"background: red;\">Madonna</span> gave no results</body></html>";

webview.loadData(summary, "text/html", "utf-8");

T-SQL: Looping through an array of known values


SET @IDs = @OriginalListOfIDs + ','

SET @IDs = REPLACE(',' + @IDs, ',' + @ID + ',', '')


How to show what a commit did?


git show <commit>


To show what a commit did with stats:

git show <commit> --stat


To show commit log with differences introduced for each commit in a range:

git log -p <commit1> <commit2>

What is <commit>?

Each commit has a unique id we reference here as <commit>. The unique id is an SHA-1 hash – a checksum of the content you’re storing plus a header. #TMI

If you don't know your <commit>:

  1. git log to view the commit history

  2. Find the commit you care about.

How can one grab a stack trace in C?

There's backtrace(), and backtrace_symbols():

From the man page:

#include <execinfo.h>
#include <stdio.h>
void* callstack[128];
int i, frames = backtrace(callstack, 128);
char** strs = backtrace_symbols(callstack, frames);
for (i = 0; i < frames; ++i) {
    printf("%s\n", strs[i]);

One way to use this in a more convenient/OOP way is to save the result of backtrace_symbols() in an exception class constructor. Thus, whenever you throw that type of exception you have the stack trace. Then, just provide a function for printing it out. For example:

class MyException : public std::exception {

    char ** strs;
    MyException( const std::string & message ) {
         int i, frames = backtrace(callstack, 128);
         strs = backtrace_symbols(callstack, frames);

    void printStackTrace() {
        for (i = 0; i < frames; ++i) {
            printf("%s\n", strs[i]);


try {
   throw MyException("Oops!");
} catch ( MyException e ) {

Ta da!

Note: enabling optimization flags may make the resulting stack trace inaccurate. Ideally, one would use this capability with debug flags on and optimization flags off.

phpMyAdmin - configuration?

I had the same problem for days until I noticed (how could I look at it and not read the code :-(..) that is calling config-db.php

** MySql Server version: 5.7.5-m15
** Apache/2.4.10 (Ubuntu)
** phpMyAdmin



Here you need to define your username, password, dbname and others that are showing empty' use default unless you changed their configuration. That solved the issue for me.
U hope it helps you.

Jquery Ajax Loading image

Please note that: ajaxStart / ajaxStop is not working for ajax jsonp request (ajax json request is ok)

I am using jquery 1.7.2 while writing this.

here is one of the reference I found:

System.Collections.Generic.List does not contain a definition for 'Select'

This question's bit old, but, there's a tricky scenario which also leads to this error:

In controller: = //id from querystring
List<string> = GrabDataFromDBByID(>a.ToString());

The above code will lead to an error in this part: .Select(a=>a.ToString()) because of the below reason: You're passing a to a method which in compiler, it doesn't know the type, so there might be several methods with the same name and different parameters let's say:


So to prevent this case, either explicitly cast the ViewBag or create another variable storing it.

SQL Server SELECT into existing table

select *
into existing table database..existingtable
from database..othertables....

If you have used select * into tablename from other tablenames already, next time, to append, you say select * into existing table tablename from other tablenames

Installing Python 2.7 on Windows 8

there is a simple procedure to do it go to controlpanel->system and security ->system->advanced system settings->advanced->environment variables then add new path enter this in your variable path and values

enter image description here

Execute a command in command prompt using excel VBA

The S parameter does not do anything on its own.

/S      Modifies the treatment of string after /C or /K (see below) 
/C      Carries out the command specified by string and then terminates  
/K      Carries out the command specified by string but remains  

Try something like this instead

Call Shell("cmd.exe /S /K" & "perl c:\temp", vbNormalFocus)

You may not even need to add "cmd.exe" to this command unless you want a command window to open up when this is run. Shell should execute the command on its own.

Shell("perl c:\temp")

To wait for the command to finish you will have to do something like @Nate Hekman shows in his answer here

Dim wsh As Object
Set wsh = VBA.CreateObject("WScript.Shell")
Dim waitOnReturn As Boolean: waitOnReturn = True
Dim windowStyle As Integer: windowStyle = 1

wsh.Run "cmd.exe /S /C perl c:\temp", windowStyle, waitOnReturn

Adding gif image in an ImageView in android

I faced problem to use

compile 'pl.droidsonroids.gif:android-gif-drawable:1.1.+'

And also I could not find the jar file to add to my project. So, in order to show gif, I use WebView like this:

WebView webView = (WebView) this.findViewById(;
webView.loadDataWithBaseURL(null, "<html><body><center><img style='align:center;width:250px; height:250px; border-radius:50%' src='file:///android_asset/loading.gif'/></center></body></html>", "text/html", "UTF-8", "");

How to configure "Shorten command line" method for whole project in IntelliJ

The latest 2020 build doesn't have the shorten command line option by default we need to add that option from the configuration.

Run > Edit Configurations > Select the corresponding run configuration and click on Modify options for adding the shorten command-line configuration to the UI. enter image description here

Select the shorten command line option enter image description here

Now choose jar manifest from the shorten command line option enter image description here

Logging framework incompatibility

SLF4J 1.5.11 and 1.6.0 versions are not compatible (see compatibility report) because the argument list of org.slf4j.spi.LocationAwareLogger.log method has been changed (added Object[] p5):

SLF4J 1.5.11:

LocationAwareLogger.log ( org.slf4j.Marker p1, String p2, int p3,
                          String p4, Throwable p5 )

SLF4J 1.6.0:

LocationAwareLogger.log ( org.slf4j.Marker p1, String p2, int p3,
                          String p4, Object[] p5, Throwable p6 )

See compatibility reports for other SLF4J versions on this page.

You can generate such reports by the japi-compliance-checker tool.

enter image description here

How to use PDO to fetch results array in PHP?

There are three ways to fetch multiple rows returned by PDO statement.

The simplest one is just to iterate over PDOStatement itself:

$stmt = $pdo->prepare("SELECT * FROM auction WHERE name LIKE ?")
// iterating over a statement
foreach($stmt as $row) {
    echo $row['name'];

another one is to fetch rows using fetch() method inside a familiar while statement:

$stmt = $pdo->prepare("SELECT * FROM auction WHERE name LIKE ?")
// using while
while($row = $stmt->fetch()) {
    echo $row['name'];

but for the modern web application we should have our datbase iteractions separated from output and thus the most convenient method would be to fetch all rows at once using fetchAll() method:

$stmt = $pdo->prepare("SELECT * FROM auction WHERE name LIKE ?")
// fetching rows into array
$data = $stmt->fetchAll();

or, if you need to preprocess some data first, use the while loop and collect the data into array manually

$result = [];
$stmt = $pdo->prepare("SELECT * FROM auction WHERE name LIKE ?")
// using while
while($row = $stmt->fetch()) {
    $result[] = [
        'newname' => $row['oldname'],
        // etc

and then output them in a template:

<?php foreach($data as $row): ?>
<?php endforeach ?>

Note that PDO supports many sophisticated fetch modes, allowing fetchAll() to return data in many different formats.

'int' object has no attribute '__getitem__'

I had a similar issue recently while working on recursion and nested lists. I declared:


instead of


Note the comma after the number 3

Swift - How to hide back button in navigation item?

You may try with the below code

override func viewDidAppear(_ animated: Bool) {
    self.navigationController?.isNavigationBarHidden = true

How to get first character of a string in SQL?


Aravind Chaterjee
Robin Van Parsee

FROM Dual;

---------                        -----------------
Aravind Chaterjee                AC           
Shivakumar                       S
Robin Van Parsee                 RVP

How to check if String value is Boolean type in Java?

return value.equals("false") || value.equals("true");

Unexpected character encountered while parsing value

If you are using downloading data using url...may need to use

var result = client.DownloadData(url);

Print to the same line and not a new line?

Based on Remi answer for Python 2.7+ use this:

from __future__ import print_function
import time

# status generator
def range_with_status(total):
    """ iterate from 0 to total and show progress in console """
    import sys
    n = 0
    while n < total:
        done = '#' * (n + 1)
        todo = '-' * (total - n - 1)
        s = '<{0}>'.format(done + todo)
        if not todo:
            s += '\n'
        if n > 0:
            s = '\r' + s
        print(s, end='\r')
        yield n
        n += 1

# example for use of status generator
for i in range_with_status(50):

syntaxerror: unexpected character after line continuation character in python


f = open(D\\python\\HW\\2_1 - Copy.cp,"r");


f = open("D:\\python\\HW\\2_1 - Copy.cp", "r")

  1. File path needs to be a string (constant)
  2. need colon in Windows file path
  3. space after comma for better style
  4. ; after statement is allowed but fugly.

What tutorial are you using?

How to use ng-repeat without an html element

Update: If you are using Angular 1.2+, use ng-repeat-start. See @jmagnusson's answer.

Otherwise, how about putting the ng-repeat on tbody? (AFAIK, it is okay to have multiple <tbody>s in a single table.)

<tbody ng-repeat="row in array">
  <tr ng-repeat="item in row">

How to efficiently calculate a running standard deviation?

Here is a literal pure Python translation of the Welford's algorithm implementation from

import math

class RunningStats:

    def __init__(self):
        self.n = 0
        self.old_m = 0
        self.new_m = 0
        self.old_s = 0
        self.new_s = 0

    def clear(self):
        self.n = 0

    def push(self, x):
        self.n += 1

        if self.n == 1:
            self.old_m = self.new_m = x
            self.old_s = 0
            self.new_m = self.old_m + (x - self.old_m) / self.n
            self.new_s = self.old_s + (x - self.old_m) * (x - self.new_m)

            self.old_m = self.new_m
            self.old_s = self.new_s

    def mean(self):
        return self.new_m if self.n else 0.0

    def variance(self):
        return self.new_s / (self.n - 1) if self.n > 1 else 0.0

    def standard_deviation(self):
        return math.sqrt(self.variance())


rs = RunningStats()

mean = rs.mean()
variance = rs.variance()
stdev = rs.standard_deviation()

print(f'Mean: {mean}, Variance: {variance}, Std. Dev.: {stdev}')

Java logical operator short-circuiting

The && and || operators "short-circuit", meaning they don't evaluate the right-hand side if it isn't necessary.

The & and | operators, when used as logical operators, always evaluate both sides.

There is only one case of short-circuiting for each operator, and they are:

  • false && ... - it is not necessary to know what the right-hand side is because the result can only be false regardless of the value there
  • true || ... - it is not necessary to know what the right-hand side is because the result can only be true regardless of the value there

Let's compare the behaviour in a simple example:

public boolean longerThan(String input, int length) {
    return input != null && input.length() > length;

public boolean longerThan(String input, int length) {
    return input != null & input.length() > length;

The 2nd version uses the non-short-circuiting operator & and will throw a NullPointerException if input is null, but the 1st version will return false without an exception.