Programs & Examples On #Computational finance

Response.Redirect with POST instead of Get?

Copy-pasteable code based on Pavlo Neyman's method

RedirectPost(string url, T bodyPayload) and GetPostData() are for those who just want to dump some strongly typed data in the source page and fetch it back in the target one. The data must be serializeable by NewtonSoft Json.NET and you need to reference the library of course.

Just copy-paste into your page(s) or better yet base class for your pages and use it anywhere in you application.

My heart goes out to all of you who still have to use Web Forms in 2019 for whatever reason.

        protected void RedirectPost(string url, IEnumerable<KeyValuePair<string,string>> fields)

            const string template =
<body onload='document.forms[""form""].submit()'>
<form name='form' action='{0}' method='post'>

            var fieldsSection = string.Join(
                    fields.Select(x => $"<input type='hidden' name='{HttpUtility.UrlEncode(x.Key)}' value='{HttpUtility.UrlEncode(x.Value)}'>")

            var html = string.Format(template, HttpUtility.UrlEncode(url), fieldsSection);



        private const string JsonDataFieldName = "_jsonData";

        protected void RedirectPost<T>(string url, T bodyPayload)
            var json = JsonConvert.SerializeObject(bodyPayload, Formatting.Indented);
            //explicit type declaration to prevent recursion
            IEnumerable<KeyValuePair<string, string>> postFields = new List<KeyValuePair<string, string>>()
                {new KeyValuePair<string, string>(JsonDataFieldName, json)};

            RedirectPost(url, postFields);


        protected T GetPostData<T>() where T: class 
            var urlEncodedFieldData = Request.Params[JsonDataFieldName];
            if (string.IsNullOrEmpty(urlEncodedFieldData))
                return null;// default(T);

            var fieldData = HttpUtility.UrlDecode(urlEncodedFieldData);

            var result = JsonConvert.DeserializeObject<T>(fieldData);
            return result;

How to remove listview all items

An other approach after trying the solutions below. When you need it clear, just initialise your list to new clear new list.

List<ModelData> dataLists = new ArrayList<>();
                RaporAdapter adapter = new RaporAdapter(AyrintiliRapor.this, dataLists);

Or set visibility to Gone / Invisible up to need


Why are iframes considered dangerous and a security risk?

The IFRAME element may be a security risk if your site is embedded inside an IFRAME on hostile site. Google "clickjacking" for more details. Note that it does not matter if you use <iframe> or not. The only real protection from this attack is to add HTTP header X-Frame-Options: DENY and hope that the browser knows its job.

In addition, IFRAME element may be a security risk if any page on your site contains an XSS vulnerability which can be exploited. In that case the attacker can expand the XSS attack to any page within the same domain that can be persuaded to load within an <iframe> on the page with XSS vulnerability. This is because content from the same origin (same domain) is allowed to access the parent content DOM (practically execute JavaScript in the "host" document). The only real protection methods from this attack is to add HTTP header X-Frame-Options: DENY and/or always correctly encode all user submitted data (that is, never have an XSS vulnerability on your site - easier said than done).

That's the technical side of the issue. In addition, there's the issue of user interface. If you teach your users to trust that URL bar is supposed to not change when they click links (e.g. your site uses a big iframe with all the actual content), then the users will not notice anything in the future either in case of actual security vulnerability. For example, you could have an XSS vulnerability within your site that allows the attacker to load content from hostile source within your iframe. Nobody could tell the difference because the URL bar still looks identical to previous behavior (never changes) and the content "looks" valid even though it's from hostile domain requesting user credentials.

If somebody claims that using an <iframe> element on your site is dangerous and causes a security risk, he does not understand what <iframe> element does, or he is speaking about possibility of <iframe> related vulnerabilities in browsers. Security of <iframe src="..."> tag is equal to <img src="..." or <a href="..."> as long there are no vulnerabilities in the browser. And if there's a suitable vulnerability, it might be possible to trigger it even without using <iframe>, <img> or <a> element, so it's not worth considering for this issue.

However, be warned that content from <iframe> can initiate top level navigation by default. That is, content within the <iframe> is allowed to automatically open a link over current page location (the new location will be visible in the address bar). The only way to avoid that is to add sandbox attribute without value allow-top-navigation. For example, <iframe sandbox="allow-forms allow-scripts" ...>. Unfortunately, sandbox also disables all plugins, always. For example, Youtube content cannot be sandboxed because Flash player is still required to view all Youtube content. No browser supports using plugins and disallowing top level navigation at the same time.

Note that X-Frame-Options: DENY also protects from rendering performance side-channel attack that can read content cross-origin (also known as "Pixel perfect Timing Attacks").

How to check if a file exists before creating a new file

Looked around a bit, and the only thing I find is using the open system call. It is the only function I found that allows you to create a file in a way that will fail if it already exists

#include <fcntl.h>
#include <errno.h>

int fd=open(filename, O_WRONLY | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
if (fd < 0) {
  /* file exists or otherwise uncreatable
     you might want to check errno*/
}else {
  /* File is open to writing */

Note that you have to give permissions since you are creating a file.

This also removes any race conditions there might be

How to represent multiple conditions in a shell if statement?

Be careful if you have spaces in your string variables and you check for existence. Be sure to quote them properly.

if [ ! "${somepath}" ] || [ ! "${otherstring}" ] || [ ! "${barstring}" ] ; then

Disable arrow key scrolling in users browser

For maintainability, I would attach the "blocking" handler on the element itself (in your case, the canvas).

theCanvas.onkeydown = function (e) {
    if (e.key === 'ArrowUp' || e.key === 'ArrowDown') {

Why not simply do window.event.preventDefault()? MDN states:

window.event is a proprietary Microsoft Internet Explorer property which is only available while a DOM event handler is being called. Its value is the Event object currently being handled.

Further readings:

adb shell command to make Android package uninstall dialog appear

In my case, I do an adb shell pm list packages to see first what are the packages/apps installed in my Android device or emulator, then upon locating the desired package/app, I do an adb shell pm uninstall -k

How to split data into training/testing sets using sample function

If you type:


If will launch a help menu to explain what the parameters of the sample function mean.

I am not an expert, but here is some code I have:

data <- data.frame(matrix(rnorm(400), nrow=100))
splitdata <- split(data[1:nrow(data),],sample(rep(1:4,as.integer(nrow(data)/4))))
test <- splitdata[[1]]
train <- rbind(splitdata[[1]],splitdata[[2]],splitdata[[3]])

This will give you 75% train and 25% test.

Objective-C - Remove last character from string

If it's an NSMutableString (which I would recommend since you're changing it dynamically), you can use:

[myString deleteCharactersInRange:NSMakeRange([myRequestString length]-1, 1)];

Python List & for-each access (Find/Replace in built-in list)

Python is not Java, nor C/C++ -- you need to stop thinking that way to really utilize the power of Python.

Python does not have pass-by-value, nor pass-by-reference, but instead uses pass-by-name (or pass-by-object) -- in other words, nearly everything is bound to a name that you can then use (the two obvious exceptions being tuple- and list-indexing).

When you do spam = "green", you have bound the name spam to the string object "green"; if you then do eggs = spam you have not copied anything, you have not made reference pointers; you have simply bound another name, eggs, to the same object ("green" in this case). If you then bind spam to something else (spam = 3.14159) eggs will still be bound to "green".

When a for-loop executes, it takes the name you give it, and binds it in turn to each object in the iterable while running the loop; when you call a function, it takes the names in the function header and binds them to the arguments passed; reassigning a name is actually rebinding a name (it can take a while to absorb this -- it did for me, anyway).

With for-loops utilizing lists, there are two basic ways to assign back to the list:

for i, item in enumerate(some_list):
    some_list[i] = process(item)


new_list = []
for item in some_list:
some_list[:] = new_list

Notice the [:] on that last some_list -- it is causing a mutation of some_list's elements (setting the entire thing to new_list's elements) instead of rebinding the name some_list to new_list. Is this important? It depends! If you have other names besides some_list bound to the same list object, and you want them to see the updates, then you need to use the slicing method; if you don't, or if you do not want them to see the updates, then rebind -- some_list = new_list.

Extract a substring using PowerShell

The Substring method provides us a way to extract a particular string from the original string based on a starting position and length. If only one argument is provided, it is taken to be the starting position, and the remainder of the string is outputted.

PS > "test_string".Substring(0,4)
PS > "test_string".Substring(4)
_stringPS >

link text

But this is easier...

 $s = 'Hello World is in here Hello World!'
 $p = 'Hello World'
 $s -match $p

And finally, to recurse through a directory selecting only the .txt files and searching for occurrence of "Hello World":

dir -rec -filter *.txt | Select-String 'Hello World'

Call a stored procedure with parameter in c#

The .NET Data Providers consist of a number of classes used to connect to a data source, execute commands, and return recordsets. The Command Object in ADO.NET provides a number of Execute methods that can be used to perform the SQL queries in a variety of fashions.

A stored procedure is a pre-compiled executable object that contains one or more SQL statements. In many cases stored procedures accept input parameters and return multiple values . Parameter values can be supplied if a stored procedure is written to accept them. A sample stored procedure with accepting input parameter is given below :


The above stored procedure is accepting a country name (@COUNTRY VARCHAR(20)) as parameter and return all the publishers from the input country. Once the CommandType is set to StoredProcedure, you can use the Parameters collection to define parameters.

  command.CommandType = CommandType.StoredProcedure;
  param = new SqlParameter("@COUNTRY", "Germany");
  param.Direction = ParameterDirection.Input;
  param.DbType = DbType.String;

The above code passing country parameter to the stored procedure from C# application.

using System;
using System.Data;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace WindowsFormsApplication1
    public partial class Form1 : Form
        public Form1()

        private void button1_Click(object sender, EventArgs e)
            string connetionString = null;
            SqlConnection connection ;
            SqlDataAdapter adapter ;
            SqlCommand command = new SqlCommand();
            SqlParameter param ;
            DataSet ds = new DataSet();

            int i = 0;

            connetionString = "Data Source=servername;Initial Catalog=PUBS;User ID=sa;Password=yourpassword";
            connection = new SqlConnection(connetionString);

            command.Connection = connection;
            command.CommandType = CommandType.StoredProcedure;
            command.CommandText = "SPCOUNTRY";

            param = new SqlParameter("@COUNTRY", "Germany");
            param.Direction = ParameterDirection.Input;
            param.DbType = DbType.String;

            adapter = new SqlDataAdapter(command);

            for (i = 0; i <= ds.Tables[0].Rows.Count - 1; i++)
                MessageBox.Show (ds.Tables[0].Rows[i][0].ToString ());


Completely remove MariaDB or MySQL from CentOS 7 or RHEL 7


sudo systemctl stop mysqld.service && sudo yum remove -y mariadb mariadb-server && sudo rm -rf /var/lib/mysql /etc/my.cnf


sudo service mysql stop && sudo apt-get remove mariadb mariadb-server && sudo rm -rf /var/lib/mysql /etc/my.cnf

Change the URL in the browser without loading the new page using JavaScript

I was wondering if it will posible as long as the parent path in the page is same, only something new is appended to it.

So like let's say the user is at the page: Then the browser can let me do location.append = new.html and the page becomes: and the browser does not change it.

Or just allow the person to change get parameter, so let's location.get = me=1&page=1.

So original page becomes and it does not refresh.

The problem with # is that the data is not cached (at least I don't think so) when hash is changed. So it is like each time a new page is being loaded, whereas back- and forward buttons in a non-Ajax page are able to cache data and do not spend time on re-loading the data.

From what I saw, the Yahoo history thing already loads all of the data at once. It does not seem to be doing any Ajax requests. So when a div is used to handle different method overtime, that data is not stored for each history state.

Creating files in C++

#include <iostream>
#include <fstream>

int main() {
  std::ofstream o("Hello.txt");

  o << "Hello, World\n" << std::endl;

  return 0;

LINQ to SQL Left Outer Join

Not quite - since each "left" row in a left-outer-join will match 0-n "right" rows (in the second table), where-as yours matches only 0-1. To do a left outer join, you need SelectMany and DefaultIfEmpty, for example:

var query = from c in db.Customers
            join o in db.Orders
               on c.CustomerID equals o.CustomerID into sr
            from x in sr.DefaultIfEmpty()
            select new {
               CustomerID = c.CustomerID, ContactName = c.ContactName,
               OrderID = x == null ? -1 : x.OrderID };   

(or via the extension methods)

Declare an empty two-dimensional array in Javascript?

What's wrong with

var arr2 = new Array(10,20);
    arr2[0,0] = 5;
    arr2[0,1] = 2
    console.log("sum is   " + (arr2[0,0] +  arr2[0,1]))

should read out "sum is 7"

How to use a variable for the database name in T-SQL?

Put the entire script into a template string, with {SERVERNAME} placeholders. Then edit the string using:


and then run it with


It's hard to believe that, in the course of three years, nobody noticed that my code doesn't work!

You can't EXEC multiple batches. GO is a batch separator, not a T-SQL statement. It's necessary to build three separate strings, and then to EXEC each one after substitution.

I suppose one could do something "clever" by breaking the single template string into multiple rows by splitting on GO; I've done that in ADO.NET code.

And where did I get the word "SERVERNAME" from?

Here's some code that I just tested (and which works):








Cant get text of a DropDownList in code - can get value but not text

add list using

<asp:ListItem Value="United States" Text="Canada"></asp:ListItem>

and then try


I found your mistake.

<asp:ListItem>United States</asp:ListItem> 

change this to

<asp:ListItem>United States1</asp:ListItem> 

Then you will got the actual value.

What was the issue is, there are two same values in your dropdown, when page postback, it take first value as selected and give the result accordingly. if you noticed when after postback United State Value is selected

#1055 - Expression of SELECT list is not in GROUP BY clause and contains nonaggregated column this is incompatible with sql_mode=only_full_group_by

Base ond defualt config of 5.7.5 ONLY_FULL_GROUP_BY You should use all the not aggregate column in your group by

select libelle,credit_initial,disponible_v,sum(montant) as montant 
FROM fiche,annee,type 
where type.id_type=annee.id_type 
and annee.id_annee=fiche.id_annee 
and annee = year(current_timestamp) 
GROUP BY libelle,credit_initial,disponible_v order by libelle asc

Popup window in PHP?

For a popup javascript is required. Put this in your header:

function myFunction()
alert("I am an alert box!"); // this is the message in ""

And this in your body:

<input type="button" onclick="myFunction()" value="Show alert box">

When the button is pressed a box pops up with the message set in the header.

This can be put in any html or php file without the php tags.


To display it using php try this:

<?php echo '<script>myfunction()</script>'; ?>

It may not be 100% correct but the principle is the same.

To display different messages you can either create lots of functions or you can pass a variable in to the function when you call it.

How to retrieve a single file from a specific revision in Git?

Using git show

To complete your own answer, the syntax is indeed

git show object
git show $REV:$FILE
git show somebranch:from/the/root/myfile.txt
git show HEAD^^^:test/

The command takes the usual style of revision, meaning you can use any of the following:

  1. branch name (as suggested by ash)
  2. HEAD + x number of ^ characters
  3. The SHA1 hash of a given revision
  4. The first few (maybe 5) characters of a given SHA1 hash

Tip It's important to remember that when using "git show", always specify a path from the root of the repository, not your current directory position.

(Although Mike Morearty mentions that, at least with git, you can specify a relative path by putting "./" at the beginning of the path. For example:

git show HEAD^^:./


Using git restore

With Git 2.23+ (August 2019), you can also use git restore which replaces the confusing git checkout command

git restore -s <SHA1>     -- afile
git restore -s somebranch -- afile

That would restore on the working tree only the file as present in the "source" (-s) commit SHA1 or branch somebranch.
To restore also the index:

git restore -s <SHA1> -SW -- afile

(-SW: short for --staged --worktree)

Using low-level git plumbing commands

Before git1.5.x, this was done with some plumbing:

git ls-tree <rev>
show a list of one or more 'blob' objects within a commit

git cat-file blob <file-SHA1>
cat a file as it has been committed within a specific revision (similar to svn cat). use git ls-tree to retrieve the value of a given file-sha1

git cat-file -p $(git-ls-tree $REV $file | cut -d " " -f 3 | cut -f 1)::

git-ls-tree lists the object ID for $file in revision $REV, this is cut out of the output and used as an argument to git-cat-file, which should really be called git-cat-object, and simply dumps that object to stdout.

Note: since Git 2.11 (Q4 2016), you can apply a content filter to the git cat-file output.

See commit 3214594, commit 7bcf341 (09 Sep 2016), commit 7bcf341 (09 Sep 2016), and commit b9e62f6, commit 16dcc29 (24 Aug 2016) by Johannes Schindelin (dscho).
(Merged by Junio C Hamano -- gitster -- in commit 7889ed2, 21 Sep 2016)

git config diff.txt.textconv "tr A-Za-z N-ZA-Mn-za-m <"
git cat-file --textconv --batch

Note: "git cat-file --textconv" started segfaulting recently (2017), which has been corrected in Git 2.15 (Q4 2017)

See commit cc0ea7c (21 Sep 2017) by Jeff King (peff).
(Merged by Junio C Hamano -- gitster -- in commit bfbc2fc, 28 Sep 2017)

How to Right-align flex item?

Here you go. Set justify-content: space-between on the flex container.

.main { _x000D_
    display: flex; _x000D_
    justify-content: space-between;_x000D_
.a, .b, .c { background: #efefef; border: 1px solid #999; }_x000D_
.b { text-align: center; }
<h2>With title</h2>_x000D_
<div class="main">_x000D_
    <div class="a"><a href="#">Home</a></div>_x000D_
    <div class="b"><a href="#">Some title centered</a></div>_x000D_
    <div class="c"><a href="#">Contact</a></div>_x000D_
<h2>Without title</h2>_x000D_
<div class="main">_x000D_
    <div class="a"><a href="#">Home</a></div>_x000D_
<!--     <div class="b"><a href="#">Some title centered</a></div> -->_x000D_
    <div class="c"><a href="#">Contact</a></div>_x000D_

Parsing JSON Array within JSON Object

line 2 should be

for (int i = 0; i < jsonMainArr.size(); i++) {  // **line 2**

For line 3, I'm having to do

    JSONObject childJSONObject = (JSONObject) new JSONParser().parse(jsonMainArr.get(i).toString());

How to get history on react-router v4?

Basing on this answer if you need history object only in order to navigate to other component:

import { useHistory } from "react-router-dom";

function HomeButton() {
  const history = useHistory();

  function handleClick() {

  return (
    <button type="button" onClick={handleClick}>
      Go home

Get characters after last / in url

You could explode based on "/", and return the last entry:

print end( explode( "/", "" ) );

That's based on blowing the string apart, something that isn't necessary if you know the pattern of the string itself will not soon be changing. You could, alternatively, use a regular expression to locate that value at the end of the string:

$url = "";

if ( preg_match( "/\d+$/", $url, $matches ) ) {
    print $matches[0];

Installing lxml module in python

If you're running python3, you'll have to do:

pip3 install lxml

Multipart forms from C# client

This is cut and pasted from some sample code I wrote, hopefully it should give the basics. It only supports File data and form-data at the moment.

public class PostData

    private List<PostDataParam> m_Params;

    public List<PostDataParam> Params
        get { return m_Params; }
        set { m_Params = value; }

    public PostData()
        m_Params = new List<PostDataParam>();

        // Add sample param
        m_Params.Add(new PostDataParam("email", "MyEmail", PostDataParamType.Field));

    /// <summary>
    /// Returns the parameters array formatted for multi-part/form data
    /// </summary>
    /// <returns></returns>
    public string GetPostData()
        // Get boundary, default is --AaB03x
        string boundary = ConfigurationManager.AppSettings["ContentBoundary"].ToString();

        StringBuilder sb = new StringBuilder();
        foreach (PostDataParam p in m_Params)

            if (p.Type == PostDataParamType.File)
                sb.AppendLine(string.Format("Content-Disposition: file; name=\"{0}\"; filename=\"{1}\"", p.Name, p.FileName));
                sb.AppendLine("Content-Type: text/plain");
                sb.AppendLine(string.Format("Content-Disposition: form-data; name=\"{0}\"", p.Name));


        return sb.ToString();           

public enum PostDataParamType

public class PostDataParam

    public PostDataParam(string name, string value, PostDataParamType type)
        Name = name;
        Value = value;
        Type = type;

    public string Name;
    public string FileName;
    public string Value;
    public PostDataParamType Type;

To send the data you then need to:

HttpWebRequest oRequest = null;
oRequest = (HttpWebRequest)HttpWebRequest.Create(oURL.URL);
oRequest.ContentType = "multipart/form-data";                       
oRequest.Method = "POST";
PostData pData = new PostData();

byte[] buffer = encoding.GetBytes(pData.GetPostData());

// Set content length of our data
oRequest.ContentLength = buffer.Length;

// Dump our buffered postdata to the stream, booyah
oStream = oRequest.GetRequestStream();
oStream.Write(buffer, 0, buffer.Length);

// get the response
oResponse = (HttpWebResponse)oRequest.GetResponse();

Hope thats clear, i've cut and pasted from a few sources to get that tidier.

Best way to concatenate List of String objects?

Next variation on Peter Lawrey's answer without initialization of a new string every loop turn

String concatList(List<String> sList, String separator)
    Iterator<String> iter = sList.iterator();
    StringBuilder sb = new StringBuilder();

    while (iter.hasNext())
        sb.append( iter.hasNext() ? separator : "");
    return sb.toString();

ASP.NET MVC Dropdown List From SelectList

Try this, just an example:

u.UserTypeOptions = new SelectList(new[]
        new { ID="1", Name="name1" },
        new { ID="2", Name="name2" },
        new { ID="3", Name="name3" },
    }, "ID", "Name", 1);


u.UserTypeOptions = new SelectList(new List<SelectListItem>
        new SelectListItem { Selected = true, Text = string.Empty, Value = "-1"},
        new SelectListItem { Selected = false, Text = "Homeowner", Value = "2"},
        new SelectListItem { Selected = false, Text = "Contractor", Value = "3"},

Convert array values from string to int?

An alternative shorter method could be:

$r = explode(',', $s);
foreach ($r as &$i) $i = (int) $i;

It has the same performance as Method 3.

How to convert JSON object to JavaScript array?

function json2array(json){
    var result = [];
    var keys = Object.keys(json);
    return result;

See this complete explanation:

MD5 is 128 bits but why is it 32 characters?

I wanted summerize some of the answers into one post.

First, don't think of the MD5 hash as a character string but as a hex number. Therefore, each digit is a hex digit (0-15 or 0-F) and represents four bits, not eight.

Taking that further, one byte or eight bits are represented by two hex digits, e.g. b'1111 1111' = 0xFF = 255.

MD5 hashes are 128 bits in length and generally represented by 32 hex digits.

SHA-1 hashes are 160 bits in length and generally represented by 40 hex digits.

For the SHA-2 family, I think the hash length can be one of a pre-determined set. So SHA-512 can be represented by 128 hex digits.

Again, this post is just based on previous answers.

Combining border-top,border-right,border-left,border-bottom in CSS

I can relate to the problem, there should be a shorthand like...

border: 1px solid red top bottom left;

Of course that doesn't work! Kobi's answer gave me an idea. Let's say you want to do top, bottom and left, but not right. Instead of doing border-top: border-left: border-bottom: (three statements) you could do two like this, the zero cancels out the right side.

border: 1px dashed yellow;
border-width:1px 0 1px 1px;

Two statements instead of three, small improvement :-D

Select rows where column is null

You want to know if the column is null

select * from foo where bar is null

If you want to check for some value not equal to something and the column also contains null values you will not get the columns with null in it

does not work:

select * from foo where bar <> 'value'

does work:

select * from foo where bar <> 'value' or bar is null

in Oracle (don't know on other DBMS) some people use this

select * from foo where NVL(bar,'n/a') <> 'value'

if I read the answer from tdammers correctly then in MS SQL Server this is like that

select * from foo where ISNULL(bar,'n/a') <> 'value'

in my opinion it is a bit of a hack and the moment 'value' becomes a variable the statement tends to become buggy if the variable contains 'n/a'.

How to submit an HTML form without redirection

See jQuery's post function.

I would create a button, and set an onClickListener ($('#button').on('click', function(){});), and send the data in the function.

Also, see the preventDefault function, of jQuery!

Tri-state Check box in HTML?

Here other Example with simple jQuery and property data-checked:

  .click(function(e) {_x000D_
    var el = $(this);_x000D_
    switch ('checked')) {_x000D_
      // unchecked, going indeterminate_x000D_
      case 0:_x000D_'checked', 1);_x000D_
        el.prop('indeterminate', true);_x000D_
        // indeterminate, going checked_x000D_
      case 1:_x000D_'checked', 2);_x000D_
        el.prop('indeterminate', false);_x000D_
        el.prop('checked', true);_x000D_
        // checked, going unchecked_x000D_
      default:_x000D_'checked', 0);_x000D_
        el.prop('indeterminate', false);_x000D_
        el.prop('checked', false);_x000D_
<script src=""></script>_x000D_
<label><input type="checkbox" name="checkbox" value="" checked id="checkbox"> Tri-State Checkbox </label>

Dynamically replace img src attribute with jQuery

This is what you wanna do:

var oldSrc = '';
var newSrc = '';
$('img[src="' + oldSrc + '"]').attr('src', newSrc);

Jquery, set value of td in a table?

Try the code below :

$('#detailInfo').html('your value')

How permission can be checked at runtime without throwing SecurityException?

You can use Context.checkCallingorSelfPermission() function for this. Here is an example:

private boolean checkWriteExternalPermission()
    String permission = android.Manifest.permission.WRITE_EXTERNAL_STORAGE;
    int res = getContext().checkCallingOrSelfPermission(permission);
    return (res == PackageManager.PERMISSION_GRANTED);            

If file exists then delete the file

IF both POS_History_bim_data_*.zip and POS_History_bim_data_*.zip.trg exists in  Y:\ExternalData\RSIDest\ Folder then Delete File Y:\ExternalData\RSIDest\Target_slpos_unzip_done.dat

How to check internet access on Android? InetAddress never times out

Found at and modified (!) from this link :

In your manifest file add at least:

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

You probably already have the INTERNET permission if you are accessing it. Then a boolean function that allows to test for connectivity is:

private boolean checkInternetConnection() {
    ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    // test for connection
    if (cm.getActiveNetworkInfo() != null
            && cm.getActiveNetworkInfo().isAvailable()
            && cm.getActiveNetworkInfo().isConnected()) {
        return true;
    } else {
        Log.v(TAG, "Internet Connection Not Present");
        return false;

Why does NULL = NULL evaluate to false in SQL server

Think of the null as "unknown" in that case (or "does not exist"). In either of those cases, you can't say that they are equal, because you don't know the value of either of them. So, null=null evaluates to not true (false or null, depending on your system), because you don't know the values to say that they ARE equal. This behavior is defined in the ANSI SQL-92 standard.

EDIT: This depends on your ansi_nulls setting. if you have ANSI_NULLS off, this WILL evaluate to true. Run the following code for an example...

set ansi_nulls off

if null = null
    print 'true'
    print 'false'

set ansi_nulls ON

if null = null
    print 'true'
    print 'false'

How to add a delay for a 2 or 3 seconds

For 2.3 seconds you should do:


Curl command without using cache

The -H 'Cache-Control: no-cache' argument is not guaranteed to work because the remote server or any proxy layers in between can ignore it. If it doesn't work, you can do it the old-fashioned way, by adding a unique querystring parameter. Usually, the servers/proxies will think it's a unique URL and not use the cache.

curl ""

You have to use a different querystring value every time, though. Otherwise, the server/proxies will match the cache again. To automatically generate a different querystring parameter every time, you can use date +%s, which will return the seconds since epoch.

curl "$(date +%s)"

How to prevent gcc optimizing some statements in C?

You can use

#pragma GCC push_options
#pragma GCC optimize ("O0")

your code

#pragma GCC pop_options

to disable optimizations since GCC 4.4.

See the GCC documentation if you need more details.

Define an alias in fish shell

To properly load functions from ~/.config/fish/functions

You may set only ONE function inside file and name file the same as function name + add .fish extension.

This way changing file contents reload functions in opened terminals (note some delay may occur ~1-5s)

That way if you edit either by commandline

function name; function_content; end


funcsave name

you have user defined functions in console and custom made in the same order.

How to insert values into the database table using VBA in MS access

  1. Remove this line of code: For i = 1 To DatDiff. A For loop must have the word NEXT
  2. Also, remove this line of code: StrSQL = StrSQL & "SELECT 'Test'" because its making Access look at your final SQL statement like this; INSERT INTO Test (Start_Date) VALUES ('" & InDate & "' );SELECT 'Test' Notice the semicolon in the middle of the SQL statement (should always be at the end. its by the way not required. you can also omit it). also, there is no space between the semicolon and the key word SELECT

in summary: remove those two lines of code above and your insert statement will work fine. You can the modify the code it later to suit your specific needs. And by the way, some times, you have to enclose dates in pounds signs like #

Updating version numbers of modules in a multi-module Maven project

versions:update-child-modules sounds like what you're looking for. You could do versions:set as mentioned, but this is a light-weight way to update the parent version numbers. For the child modules, it's my opinion that you should remove the <version> definitions, since they will inherit the parent module's version number.

Insert string at specified position

Use the stringInsert function rather than the putinplace function. I was using the later function to parse a mysql query. Although the output looked alright, the query resulted in a error which took me a while to track down. The following is my version of the stringInsert function requiring only one parameter.

function stringInsert($str,$insertstr,$pos)
    $str = substr($str, 0, $pos) . $insertstr . substr($str, $pos);
    return $str;

LinearLayout not expanding inside a ScrollView

I know this post is very old, For those who don't want to use android:fillViewport="true" because it sometimes doesn't bring up the edittext above keyboard. Use Relative layout instead of LinearLayout it solves the purpose.

How to find the Number of CPU Cores via .NET/C#?

There are several different pieces of information relating to processors that you could get:

  1. Number of physical processors
  2. Number of cores
  3. Number of logical processors.

These can all be different; in the case of a machine with 2 dual-core hyper-threading-enabled processors, there are 2 physical processors, 4 cores, and 8 logical processors.

The number of logical processors is available through the Environment class, but the other information is only available through WMI (and you may have to install some hotfixes or service packs to get it on some systems):

Make sure to add a reference in your project to System.Management.dll In .NET Core, this is available (for Windows only) as a NuGet package.

Physical Processors:

foreach (var item in new System.Management.ManagementObjectSearcher("Select * from Win32_ComputerSystem").Get())
    Console.WriteLine("Number Of Physical Processors: {0} ", item["NumberOfProcessors"]);


int coreCount = 0;
foreach (var item in new System.Management.ManagementObjectSearcher("Select * from Win32_Processor").Get())
    coreCount += int.Parse(item["NumberOfCores"].ToString());
Console.WriteLine("Number Of Cores: {0}", coreCount);

Logical Processors:

Console.WriteLine("Number Of Logical Processors: {0}", Environment.ProcessorCount);


foreach (var item in new System.Management.ManagementObjectSearcher("Select * from Win32_ComputerSystem").Get())
    Console.WriteLine("Number Of Logical Processors: {0}", item["NumberOfLogicalProcessors"]);

Processors excluded from Windows:

You can also use Windows API calls in setupapi.dll to discover processors that have been excluded from Windows (e.g. through boot settings) and aren't detectable using the above means. The code below gives the total number of logical processors (I haven't been able to figure out how to differentiate physical from logical processors) that exist, including those that have been excluded from Windows:

static void Main(string[] args)
    int deviceCount = 0;
    IntPtr deviceList = IntPtr.Zero;
    // GUID for processor classid
    Guid processorGuid = new Guid("{50127dc3-0f36-415e-a6cc-4cb3be910b65}");

        // get a list of all processor devices
        deviceList = SetupDiGetClassDevs(ref processorGuid, "ACPI", IntPtr.Zero, (int)DIGCF.PRESENT);
        // attempt to process each item in the list
        for (int deviceNumber = 0; ; deviceNumber++)
            SP_DEVINFO_DATA deviceInfo = new SP_DEVINFO_DATA();
            deviceInfo.cbSize = Marshal.SizeOf(deviceInfo);

            // attempt to read the device info from the list, if this fails, we're at the end of the list
            if (!SetupDiEnumDeviceInfo(deviceList, deviceNumber, ref deviceInfo))
                deviceCount = deviceNumber;
        if (deviceList != IntPtr.Zero) { SetupDiDestroyDeviceInfoList(deviceList); }
    Console.WriteLine("Number of cores: {0}", deviceCount);

[DllImport("setupapi.dll", SetLastError = true)]
private static extern IntPtr SetupDiGetClassDevs(ref Guid ClassGuid,
    [MarshalAs(UnmanagedType.LPStr)]String enumerator,
    IntPtr hwndParent,
    Int32 Flags);

[DllImport("setupapi.dll", SetLastError = true)]
private static extern Int32 SetupDiDestroyDeviceInfoList(IntPtr DeviceInfoSet);

[DllImport("setupapi.dll", SetLastError = true)]
private static extern bool SetupDiEnumDeviceInfo(IntPtr DeviceInfoSet,
    Int32 MemberIndex,
    ref SP_DEVINFO_DATA DeviceInterfaceData);

private struct SP_DEVINFO_DATA
    public int cbSize;
    public Guid ClassGuid;
    public uint DevInst;
    public IntPtr Reserved;

private enum DIGCF
    DEFAULT = 0x1,
    PRESENT = 0x2,
    ALLCLASSES = 0x4,
    PROFILE = 0x8,

Sieve of Eratosthenes - Finding Primes Python

I realise this isn't really answering the question of how to generate primes quickly, but perhaps some will find this alternative interesting: because python provides lazy evaluation via generators, eratosthenes' sieve can be implemented exactly as stated:

def intsfrom(n):
    while True:
        yield n
        n += 1

def sieve(ilist):
    p = next(ilist)
    yield p
    for q in sieve(n for n in ilist if n%p != 0):
        yield q

    for p in sieve(intsfrom(2)):
        print p,

    print ''
except RuntimeError as e:
    print e

The try block is there because the algorithm runs until it blows the stack and without the try block the backtrace is displayed pushing the actual output you want to see off screen.

How to activate virtualenv?

1- open powershell and navigate to your application folder 2- enter your virtualenv folder ex : cd .\venv\Scripts\ 3- active virtualenv by type .\activate

Why does the C preprocessor interpret the word "linux" as the constant "1"?

In the Old Days (pre-ANSI), predefining symbols such as unix and vax was a way to allow code to detect at compile time what system it was being compiled for. There was no official language standard back then (beyond the reference material at the back of the first edition of K&R), and C code of any complexity was typically a complex maze of #ifdefs to allow for differences between systems. These macro definitions were generally set by the compiler itself, not defined in a library header file. Since there were no real rules about which identifiers could be used by the implementation and which were reserved for programmers, compiler writers felt free to use simple names like unix and assumed that programmers would simply avoid using those names for their own purposes.

The 1989 ANSI C standard introduced rules restricting what symbols an implementation could legally predefine. A macro predefined by the compiler could only have a name starting with two underscores, or with an underscore followed by an uppercase letter, leaving programmers free to use identifiers not matching that pattern and not used in the standard library.

As a result, any compiler that predefines unix or linux is non-conforming, since it will fail to compile perfectly legal code that uses something like int linux = 5;.

As it happens, gcc is non-conforming by default -- but it can be made to conform (reasonably well) with the right command-line options:

gcc -std=c90 -pedantic ... # or -std=c89 or -ansi
gcc -std=c99 -pedantic
gcc -std=c11 -pedantic

See the gcc manual for more details.

gcc will be phasing out these definitions in future releases, so you shouldn't write code that depends on them. If your program needs to know whether it's being compiled for a Linux target or not it can check whether __linux__ is defined (assuming you're using gcc or a compiler that's compatible with it). See the GNU C preprocessor manual for more information.

A largely irrelevant aside: the "Best One Liner" winner of the 1987 International Obfuscated C Code Contest, by David Korn (yes, the author of the Korn Shell) took advantage of the predefined unix macro:

main() { printf(&unix["\021%six\012\0"],(unix)["have"]+"fun"-0x60);}

It prints "unix", but for reasons that have absolutely nothing to do with the spelling of the macro name.

C# using Sendkey function to send a key to another application

If notepad is already started, you should write:

// import the function in your class
[DllImport ("User32.dll")]
static extern int SetForegroundWindow(IntPtr point);


Process p = Process.GetProcessesByName("notepad").FirstOrDefault();
if (p != null)
    IntPtr h = p.MainWindowHandle;

GetProcessesByName returns an array of processes, so you should get the first one (or find the one you want).

If you want to start notepad and send the key, you should write:

Process p = Process.Start("notepad.exe");
IntPtr h = p.MainWindowHandle;

The only situation in which the code may not work is when notepad is started as Administrator and your application is not.

How can I read and parse CSV files in C++?

Here is a ready-to use function if all you need is to load a data file of doubles (no integers, no text).

#include <sstream>
#include <fstream>
#include <iterator>
#include <string>
#include <vector>
#include <algorithm>

using namespace std;

 * Parse a CSV data file and fill the 2d STL vector "data".
 * Limits: only "pure datas" of doubles, not encapsulated by " and without \n inside.
 * Further no formatting in the data (e.g. scientific notation)
 * It however handles both dots and commas as decimal separators and removes thousand separator.
 * returnCodes[0]: file access 0-> ok 1-> not able to read; 2-> decimal separator equal to comma separator
 * returnCodes[1]: number of records
 * returnCodes[2]: number of fields. -1 If rows have different field size
readCsvData (vector <vector <double>>& data, const string& filename, const string& delimiter, const string& decseparator){

 int vv[3] = { 0,0,0 };
 vector<int> returnCodes(&vv[0], &vv[0]+3);

 string rowstring, stringtoken;
 double doubletoken;
 int rowcount=0;
 int fieldcount=0;

 ifstream iFile(filename, ios_base::in);
 if (!iFile.is_open()){
   returnCodes[0] = 1;
   return returnCodes;
 while (getline(iFile, rowstring)) {
    if (rowstring=="") continue; // empty line
    rowcount ++; //let's start with 1
    if(delimiter == decseparator){
      returnCodes[0] = 2;
      return returnCodes;
    if(decseparator != "."){
     // remove dots (used as thousand separators)
     string::iterator end_pos = remove(rowstring.begin(), rowstring.end(), '.');
     rowstring.erase(end_pos, rowstring.end());
     // replace decimal separator with dots.
     replace(rowstring.begin(), rowstring.end(),decseparator.c_str()[0], '.'); 
    } else {
     // remove commas (used as thousand separators)
     string::iterator end_pos = remove(rowstring.begin(), rowstring.end(), ',');
     rowstring.erase(end_pos, rowstring.end());
    // tokenize..
    vector<double> tokens;
    // Skip delimiters at beginning.
    string::size_type lastPos = rowstring.find_first_not_of(delimiter, 0);
    // Find first "non-delimiter".
    string::size_type pos     = rowstring.find_first_of(delimiter, lastPos);
    while (string::npos != pos || string::npos != lastPos){
        // Found a token, convert it to double add it to the vector.
        stringtoken = rowstring.substr(lastPos, pos - lastPos);
        if (stringtoken == "") {
    } else {
          istringstream totalSString(stringtoken);
      totalSString >> doubletoken;
        // Skip delimiters.  Note the "not_of"
        lastPos = rowstring.find_first_not_of(delimiter, pos);
        // Find next "non-delimiter"
        pos = rowstring.find_first_of(delimiter, lastPos);
    if(rowcount == 1){
      fieldcount = tokens.size();
      returnCodes[2] = tokens.size();
    } else {
      if ( tokens.size() != fieldcount){
    returnCodes[2] = -1;
 returnCodes[1] = rowcount;
 return returnCodes;

What is a LAMP stack?

Lamp stack stands for Linux Apache Mysql PHP

there is also Mean Stack MongoDB ExpressJS AngularJS NodeJS

How to return data from promise

You have to return a promise instead of a variable. So in your function just return:

return relationsManagerResource.GetParentId(nodeId)

And later resolve the returned promise. Or you can make another deferred and resolve theParentId with it.

How to select lines between two marker patterns which may occur multiple times with awk/sed

something like this works for me:



/^abc$/ {

/^mno$/ {
    print "s="s;

!/^abc|mno$/ {
    if (record==1) {
        s = s"\n"$0

using: awk -f file.awk data...

edit: O_o fedorqui solution is way better/prettier than mine.

Is bool a native C type?

/* Many years ago, when the earth was still cooling, we used this: */

typedef enum
    false = ( 1 == 0 ),
    true = ( ! false )
} bool;

/* It has always worked for me. */

Which Ruby version am I really running?

The ruby version 1.8.7 seems to be your system ruby.

Normally you can choose the ruby version you'd like, if you are using rvm with following. Simple change into your directory in a new terminal and type in:

rvm use 2.0.0

You can find more details about rvm here: Open the website and scroll down, you will see a few helpful links. "Setting up default rubies" for example could help you.

Update: To set the ruby as default:

rvm use 2.0.0 --default

What is the basic difference between the Factory and Abstract Factory Design Patterns?

I think we can understand the difference between these two by seeing a Java8 example code:

  interface Something{}

  interface OneWhoCanProvideSomething {
     Something getSomething();

  interface OneWhoCanProvideCreatorsOfSomething{
     OneWhoCanProvideSomething getCreator();

public class AbstractFactoryExample {

    public static void main(String[] args) {
        //I need something
        //Let's create one
        Something something = new Something() {};

        //Or ask someone (FACTORY pattern)
        OneWhoCanProvideSomething oneWhoCanProvideSomethingOfTypeA = () -> null;
        OneWhoCanProvideSomething oneWhoCanProvideSomethingOfTypeB = () -> null;

        //Or ask someone who knows soemone who can create something (ABSTRACT FACTORY pattern)
        OneWhoCanProvideCreatorsOfSomething oneWhoCanProvideCreatorsOfSomething = () -> null;

        //Same thing, but you don't need to write you own interfaces
        Supplier<Something> supplierOfSomething = () -> null;
        Supplier<Supplier<Something>> supplierOfSupplier = () -> null;


Now the question is which way of creation should you use and why: The first way (no pattern, just plain constructor): creating by yourself is not a good idea, you have to do all the work, and your client code is tied to the particular implementation.

The second way (using Factory pattern): provides you the benefit that you can pass any type of implementation, which can provide different type of something based on some condition (maybe a parameter passed to creational method).

The third way (using Abstract Factory pattern): This gives you more flexibility. You can find different types of creators of something based on some condition (maybe a parameter passed).

Note that you can always get away with Factory pattern by combining two conditions together (which slightly increases code complexity, and coupling), I guess that's why we rarely see real life use cases of Abstract Factory pattern.

How to call a .NET Webservice from Android using KSOAP2?

If more than one result is expected, then the getResponse() method will return a Vector containing the various responses.

In which case the offending code becomes:

Object result = envelope.getResponse();

// treat result as a vector
String resultText = null;
if (result instanceof Vector)
    SoapPrimitive element0 = (SoapPrimitive)((Vector) result).elementAt(0);
    resultText = element0.toString();


Answer based on the ksoap2-android (mosabua fork)

How to set cornerRadius for only top-left and top-right corner of a UIView?

A lovely extension to reuse Yunus Nedim Mehel solution

Swift 2.3

extension UIView {
func roundCornersWithLayerMask(cornerRadii: CGFloat, corners: UIRectCorner) {
    let path = UIBezierPath(roundedRect: bounds,
                            byRoundingCorners: corners,
                            cornerRadii: CGSize(width: cornerRadii, height: cornerRadii))
    let maskLayer = CAShapeLayer()
    maskLayer.path = path.CGPath
    layer.mask = maskLayer
} }


let view = UIView()

The import cannot be resolved

I too had the same issue. Got it resolved by compiling with the latest sdk tool versions.(Play services,build tools etc). Sample build.gradle is shown below for reference.

    apply plugin: ''

android {
    compileSdkVersion 23
    buildToolsVersion "23.0.1"

    defaultConfig {
        applicationId ""
        minSdkVersion 14
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), ''

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile ''
    compile ''

Use :hover to modify the css of another class?

There are two approaches you can take, to have a hovered element affect (E) another element (F):

  1. F is a child-element of E, or
  2. F is a later-sibling (or sibling's descendant) element of E (in that E appears in the mark-up/DOM before F):

To illustrate the first of these options (F as a descendant/child of E):

.item:hover .wrapper {
    color: #fff;
    background-color: #000;

To demonstrate the second option, F being a sibling element of E:

.item:hover ~ .wrapper {
    color: #fff;
    background-color: #000;

In this example, if .wrapper was an immediate sibling of .item (with no other elements between the two) you could also use .item:hover + .wrapper.

JS Fiddle demonstration.


Remove empty lines in a text file via grep

with awk, just check for number of fields. no need regex

$ more file




$ awk 'NF' file

How to set default values for Angular 2 component properties?

Here is the best solution for this. (ANGULAR All Version)

Addressing solution: To set a default value for @Input variable. If no value passed to that input variable then It will take the default value.

I have provided solution for this kind of similar question. You can find the full solution from here

export class CarComponent implements OnInit {
  private _defaultCar: car = {
    // default isCar is true
    isCar: true,
    // default wheels  will be 4
    wheels: 4

  @Input() newCar: car = {};

  constructor() {}

  ngOnInit(): void {

   // this will concate both the objects and the object declared later (ie.. ...this.newCar )
   // will overwrite the default value. ONLY AND ONLY IF DEFAULT VALUE IS PRESENT

    this.newCar = { ...this._defaultCar, ...this.newCar };
   //  console.log(this.newCar);

How to turn on WCF tracing?

The following configuration taken from MSDN can be applied to enable tracing on your WCF service.

      <source name="System.ServiceModel"
              switchValue="Information, ActivityTracing"
              propagateActivity="true" >
             <add name="xml"/>
      <source name="System.ServiceModel.MessageLogging">
            <add name="xml"/>
      <source name="myUserTraceSource"
              switchValue="Information, ActivityTracing">
            <add name="xml"/>
        <add name="xml"
             initializeData="Error.svclog" />

To view the log file, you can use "C:\Program Files\Microsoft SDKs\Windows\v7.0A\bin\SvcTraceViewer.exe".

If "SvcTraceViewer.exe" is not on your system, you can download it from the "Microsoft Windows SDK for Windows 7 and .NET Framework 4" package here:

Windows SDK Download

You don't have to install the entire thing, just the ".NET Development / Tools" part.

When/if it bombs out during installation with a non-sensical error, Petopas' answer to Windows 7 SDK Installation Failure solved my issue.

less than 10 add 0 to number

I was bored and playing around JSPerf trying to beat the currently selected answer prepending a zero no matter what and using slice(-2). It's a clever approach but the performance gets a lot worse as the string gets longer.

For numbers zero to ten (one and two character strings) I was able to beat by about ten percent, and the fastest approach was much better when dealing with longer strings by using charAt so it doesn't have to traverse the whole string.

This follow is not quit as simple as slice(-2) but is 86%-89% faster when used across mostly 3 digit numbers (3 character strings).

var prepended = ( 1 === string.length && string.charAt( 0 ) !== "0" ) ? '0' + string : string;

When and Why to use abstract classes/methods?

Typically one uses an abstract class to provide some incomplete functionality that will be fleshed out by concrete subclasses. It may provide methods that are used by its subclasses; it may also represent an intermediate node in the class hierarchy, to represent a common grouping of concrete subclasses, distinguishing them in some way from other subclasses of its superclass. Since an interface can't derive from a class, this is another situation where a class (abstract or otherwise) would be necessary, versus an interface.

A good rule of thumb is that only leaf nodes of a class hierarchy should ever be instantiated. Making non-leaf nodes abstract is an easy way of ensuring that.

Why is using onClick() in HTML a bad practice?

If you are using jQuery then:


 <a id="openMap" href="/map/">link</a>


$(document).ready(function() {
        popup('/map/', 300, 300, 'map');
        return false;

This has the benefit of still working without JS, or if the user middle clicks the link.

It also means that I could handle generic popups by rewriting again to:


 <a class="popup" href="/map/">link</a>


$(document).ready(function() {
        popup($(this).attr("href"), 300, 300, 'map');
        return false;

This would let you add a popup to any link by just giving it the popup class.

This idea could be extended even further like so:


 <a class="popup" data-width="300" data-height="300" href="/map/">link</a>


$(document).ready(function() {
        popup($(this).attr("href"), $(this).data('width'), $(this).data('height'), 'map');
        return false;

I can now use the same bit of code for lots of popups on my whole site without having to write loads of onclick stuff! Yay for reusability!

It also means that if later on I decide that popups are bad practice, (which they are!) and that I want to replace them with a lightbox style modal window, I can change:

popup($(this).attr("href"), $(this).data('width'), $(this).data('height'), 'map');


myAmazingModalWindow($(this).attr("href"), $(this).data('width'), $(this).data('height'), 'map');

and all my popups on my whole site are now working totally differently. I could even do feature detection to decide what to do on a popup, or store a users preference to allow them or not. With the inline onclick, this requires a huge copy and pasting effort.

How to view table contents in Mysql Workbench GUI?

After displaying the first 1000 records, you can page through them by clicking on the icon beside "Fetch rows:" in the header of the result grid.

Match exact string

It depends. You could


But that would not match the following string: 'the first 3 letters of the alphabet are abc. not abc123'

I think you would want to use \b (word boundaries):

var str = 'the first 3 letters of the alphabet are abc. not abc123';_x000D_
var pat = /\b(abc)\b/g;_x000D_

Live example:

If the former solution works for you, I would advise against using it.

That means you may have something like the following:

var strs = ['abc', 'abc1', 'abc2']
for (var i = 0; i < strs.length; i++) {
    if (strs[i] == 'abc') {
        //do something 
    else {
        //do something else

While you could use

if (str[i].match(/^abc$/g)) {
    //do something 

It would be considerably more resource-intensive. For me, a general rule of thumb is for a simple string comparison use a conditional expression, for a more dynamic pattern use a regular expression.

More on JavaScript regexes:

SSL Connection / Connection Reset with IISExpress

The 'Digicert certificate installation checker' is often helpful in situations like this.

I was able to verify the SSL cert being attempted was the one I was expecting by comparing the serial number.

enter image description here

For me @Jason Kleban answer was the actual problem, but this can be a very useful utility to check your basic assertions about what certificate is being loaded.

Threads vs Processes in Linux

Linux uses a 1-1 threading model, with (to the kernel) no distinction between processes and threads -- everything is simply a runnable task. *

On Linux, the system call clone clones a task, with a configurable level of sharing, among which are:

  • CLONE_FILES: share the same file descriptor table (instead of creating a copy)
  • CLONE_PARENT: don't set up a parent-child relationship between the new task and the old (otherwise, child's getppid() = parent's getpid())
  • CLONE_VM: share the same memory space (instead of creating a COW copy)

fork() calls clone(least sharing) and pthread_create() calls clone(most sharing). **

forking costs a tiny bit more than pthread_createing because of copying tables and creating COW mappings for memory, but the Linux kernel developers have tried (and succeeded) at minimizing those costs.

Switching between tasks, if they share the same memory space and various tables, will be a tiny bit cheaper than if they aren't shared, because the data may already be loaded in cache. However, switching tasks is still very fast even if nothing is shared -- this is something else that Linux kernel developers try to ensure (and succeed at ensuring).

In fact, if you are on a multi-processor system, not sharing may actually be beneficial to performance: if each task is running on a different processor, synchronizing shared memory is expensive.

* Simplified. CLONE_THREAD causes signals delivery to be shared (which needs CLONE_SIGHAND, which shares the signal handler table).

** Simplified. There exist both SYS_fork and SYS_clone syscalls, but in the kernel, the sys_fork and sys_clone are both very thin wrappers around the same do_fork function, which itself is a thin wrapper around copy_process. Yes, the terms process, thread, and task are used rather interchangeably in the Linux kernel...

Get the client IP address using PHP

In PHP 5.3 or greater, you can get it like this:

$ip = getenv('HTTP_CLIENT_IP')?:

OSError - Errno 13 Permission denied

supplementing @falsetru's answer : run id in the terminal to get your user_id and group_id

Go the directory/partition where you are facing the challenge. Open terminal, type id then press enter. This will show you your user_id and group_id

then type

chown -R user-id:group-id .

Replace user-id and group-id

. at the end indicates current partition / repository

// chown -R 1001:1001 . (that was my case)

Good examples of python-memcache (memcached) being used in Python?

It's fairly simple. You write values using keys and expiry times. You get values using keys. You can expire keys from the system.

Most clients follow the same rules. You can read the generic instructions and best practices on the memcached homepage.

If you really want to dig into it, I'd look at the source. Here's the header comment:

client module for memcached (memory cache daemon)


See U{the MemCached homepage<>} for more about memcached.

Usage summary

This should give you a feel for how this module operates::

    import memcache
    mc = memcache.Client([''], debug=0)

    mc.set("some_key", "Some value")
    value = mc.get("some_key")

    mc.set("another_key", 3)

    mc.set("key", "1")   # note that the key used for incr/decr must be a string.

The standard way to use memcache with a database is like this::

    key = derive_key(obj)
    obj = mc.get(key)
    if not obj:
        obj = backend_api.get(...)
        mc.set(key, obj)

    # we now have obj, and future passes through this code
    # will use the object from the cache.

Detailed Documentation

More detailed documentation is available in the L{Client} class.

How to set a variable inside a loop for /F

I know this isn't what's asked but I benefited from this method, when trying to set a variable within a "loop". Uses an array. Alternative implementation option.



set Services[0]=SERVICE1
set Services[1]=SERVICE2
set Services[2]=SERVICE3

set "i=0"

if defined Services[%i%] (
    set SERVICE=!Services[%i%]!

    echo CurrentService: !SERVICE!

    set /a "i+=1"
    GOTO :ServicesLoop

1114 (HY000): The table is full

This error also appears if the partition on which tmpdir resides fills up (due to an alter table or other

How to call javascript function from code-behind

If the order of the execution is not important and you need both some javascript AND some codebehind to be fired on an asp element, heres what you can do.

What you can take away from my example: I have a div covering the ASP control that I want both javascript and codebehind to be ran from. The div's onClick method AND the calendar's OnSelectionChanged event both get fired this way.

In this example, i am using an ASP Calendar control, and im controlling it from both javascript and codebehind:

Front end code:

        <div onclick="showHideModal();">
                OnSelectionChanged="DatepickerDateChange" ID="DatepickerCalendar" runat="server" 
                BorderWidth="1px" DayNameFormat="Shortest" Font-Names="Verdana" 
                Font-Size="8pt" ShowGridLines="true" BackColor="#B8C9E1" BorderColor="#003E51" Width="100%"> 
                <OtherMonthDayStyle ForeColor="#6C5D34"> </OtherMonthDayStyle> 
                <DayHeaderStyle  ForeColor="black" BackColor="#D19000"> </DayHeaderStyle>
                <TitleStyle BackColor="#B8C9E1" ForeColor="Black"> </TitleStyle> 
                <DayStyle BackColor="White"> </DayStyle> 
                <SelectedDayStyle BackColor="#003E51" Font-Bold="True"> </SelectedDayStyle> 


        protected void DatepickerDateChange(object sender, EventArgs e)
            if (toFromPicked.Value == "MainContent_fromDate")
                fromDate.Text = DatepickerCalendar.SelectedDate.ToShortDateString();
                toDate.Text = DatepickerCalendar.SelectedDate.ToShortDateString();

Get the difference between dates in terms of weeks, months, quarters, and years

Here's a solution:

dates <- c("14.01.2013", "26.03.2014")

# Date format:
dates2 <- strptime(dates, format = "%d.%m.%Y")

dif <- diff(as.numeric(dates2)) # difference in seconds

dif/(60 * 60 * 24 * 7) # weeks
[1] 62.28571
dif/(60 * 60 * 24 * 30) # months
[1] 14.53333
dif/(60 * 60 * 24 * 30 * 3) # quartes
[1] 4.844444
dif/(60 * 60 * 24 * 365) # years
[1] 1.194521

Request string without GET arguments

You can use $_SERVER['REQUEST_URI'] to get requested path. Then, you'll need to remove the parameters...

$uri_parts = explode('?', $_SERVER['REQUEST_URI'], 2);

Then, add in the hostname and protocol.

echo 'http://' . $_SERVER['HTTP_HOST'] . $uri_parts[0];

You'll have to detect protocol as well, if you mix http: and https://. That I leave as an exercise for you. $_SERVER['REQUEST_SCHEME'] returns the protocol.

Putting it all together:

     . explode('?', $_SERVER['REQUEST_URI'], 2)[0];

...returns, for example: Documentation:

  • $_SERVER — Server and execution environment information
  • explode — Split a string by a string
  • parse_url — Parse a URL and return its components (possibly a better solution)

Is there a way to make text unselectable on an HTML page?

There are many occasions when turning off selectability enhances the user experience.

For instance allowing the user to copy a block of text on the page without copying the text of any interface elements associated with it (that would become interspersed within the text being copied).

Redirecting to URL in Flask

You can use like this:

import os
from flask import Flask

app = Flask(__name__)

def hello():
     # Redirect from here, replace your custom site url ""
    return redirect("", code=200)

if __name__ == '__main__':
    # Bind to PORT if defined, otherwise default to 5000.
    port = int(os.environ.get('PORT', 5000))'', port=port)

Here is the referenced link to this code.

PYTHONPATH vs. sys.path

Neither hacking PYTHONPATH nor sys.path is a good idea due to the before mentioned reasons. And for linking the current project into the site-packages folder there is actually a better way than python develop, as explained here:

pip install --editable path/to/project

If you don't already have a in your project's root folder, this one is good enough to start with:

from setuptools import setup


To answer your question

In Sql Server joins syntax OUTER is optional

It is mentioned in msdn article :

So following list shows join equivalent syntaxes with and without OUTER


Other equivalent syntaxes


Strongly Recommend Dotnet Mob Artice : Joins in Sql Server enter image description here

xpath find if node exists

A variation when using xpath in Java using count():

int numberofbodies = Integer.parseInt((String) xPath.evaluate("count(/html/body)", doc));
if( numberofbodies==0) {
    // body node missing

How to make grep only match if the entire line matches?

    $ cat venky

    $ cat venky | grep "ABB.log" | grep -v "ABB.log\."

    $ cat venky | grep "ABB.log.122" | grep -v "ABB.log.122\."

How to view the SQL queries issued by JPA?

With Spring Boot simply add: to This will show the query but without the actual parameters (you will see ? instead of each parameter).

Format a message using MessageFormat.format() in Java

Just be sure you have used double apostrophe ('')

String text = java.text.MessageFormat.format("You''re about to delete {0} rows.", 5);


Within a String, a pair of single quotes can be used to quote any arbitrary characters except single quotes. For example, pattern string "'{0}'" represents string "{0}", not a FormatElement. ...

Any unmatched quote is treated as closed at the end of the given pattern. For example, pattern string "'{0}" is treated as pattern "'{0}'".


How to view the committed files you have not pushed yet?

Here you'll find your answer:

Using Git how do I find changes between local and remote

For the lazy:

  1. Use "git log origin..HEAD"
  2. Use "git fetch" followed by "git log HEAD..origin". You can cherry-pick individual commits using the listed commit ids.

The above assumes, of course, that "origin" is the name of your remote tracking branch (which it is if you've used clone with default options).

php: loop through json array

First you have to decode your json :

$array = json_decode($the_json_code);

Then after the json decoded you have to do the foreach

foreach ($array as $key => $jsons) { // This will search in the 2 jsons
     foreach($jsons as $key => $value) {
         echo $value; // This will show jsut the value f each key like "var1" will print 9
                       // And then goes print 16,16,8 ...

If you want something specific just ask for a key like this. Put this between the last foreach.

if($key == 'var1'){
 echo $value;

What is REST? Slightly confused

REST is a software design pattern typically used for web applications. In layman's terms this means that it is a commonly used idea used in many different projects. It stands for REpresentational State Transfer. The basic idea of REST is treating objects on the server-side (as in rows in a database table) as resources than can be created or destroyed.

The most basic way of thinking about REST is as a way of formatting the URLs of your web applications. For example, if your resource was called "posts", then:

/posts Would be how a user would access ALL the posts, for displaying.

/posts/:id Would be how a user would access and view an individual post, retrieved based on their unique id.

/posts/new Would be how you would display a form for creating a new post.

Sending a POST request to /users would be how you would actually create a new post on the database level.

Sending a PUT request to /users/:id would be how you would update the attributes of a given post, again identified by a unique id.

Sending a DELETE request to /users/:id would be how you would delete a given post, again identified by a unique id.

As I understand it, the REST pattern was mainly popularized (for web apps) by the Ruby on Rails framework, which puts a big emphasis on RESTful routes. I could be wrong about that though.

I may not be the most qualified to talk about it, but this is how I've learned it (specifically for Rails development).

When someone refers to a "REST api," generally what they mean is an api that uses RESTful urls for retrieving data.

Drag and drop a DLL to the GAC ("assembly") in windows server 2008 .net 4.0

Other alternatives to an installer and gacutil are GUI tools like Gac Manager or GACAdmin. Or if you like PowerShell you could use PowerShell GAC from which I am the author.

Show/Hide Div on Scroll

$(window).scroll(function () {
  var Bottom = $(window).height() + $(window).scrollTop() >= $(document).height();
if(Bottom )

Reading string from input with space character?

Here is an example of how you can get input containing spaces by using the fgets function.

#include <stdio.h>

int main()
    char name[100];
    printf("Enter your name: ");
    fgets(name, 100, stdin); 
    printf("Your Name is: %s", name);
    return 0;

What is the Windows equivalent of the diff command?

The reason you getting the error with COMP is that the utility assumes the files that you are comparing are of the same size. To overcome that you can use th '/n' option with which you can specify the number of lines you want to compare. (see the options supported by comp by typing 'comp /?' on the command line. so your command would look like :

C:\>comp "filepath1" "filepath2" /a /l /n=(the number of lines you want to compare) /c 

This should solve your problem if you wanna stick to using COMP. But this will be a problem for really large files.

Though comp is an option, but I feel it is primitive and FC is a better option. you can use FORFILES and FC together to probably make a really good filecompare utility if you require one on a frequent basis.

FC is used this way for ref:

C:\>fc /c(case insensistive) /lbn(number of errors allowed before you wanna stop compare) /n(display line number) "filename1" "filename2"

there are many options available which you can see by 'fc /?' hope this helps

How do I parse a string to a float or int?

Users codelogic and harley are correct, but keep in mind if you know the string is an integer (for example, 545) you can call int("545") without first casting to float.

If your strings are in a list, you could use the map function as well.

>>> x = ["545.0", "545.6", "999.2"]
>>> map(float, x)
[545.0, 545.60000000000002, 999.20000000000005]

It is only good if they're all the same type.

Using Powershell to stop a service remotely without WMI or remoting

Another option; use invoke-command:

$cred = Get-Credential
$server = 'MyRemoteComputer'
$service = 'My Service Name' 

invoke-command -Credential $cred -ComputerName $server -ScriptBlock {
    stop-service $service 
} -ArgumentList $service

NB: to use this option you'll need PowerShell to be installed on the remote machine and for the firewall to allow requests through, and for the Windows Remote Management service to be running on the target machine. You can configure the firewall by running the following script directly on the target machine (one off task): Enable-PSRemoting -force.

get all characters to right of last dash


Create a simple HTTP server with Java?

The easiest is Simple there is a tutorial, no WEB-INF not Servlet API no dependencies. Just a simple lightweight HTTP server in a single JAR.

sudo service mongodb restart gives "unrecognized service error" in ubuntu 14.0.4

I installed mongo server on Debian Jessie using manual from official site.

It didn't started after recommended command sudo service mongod restart with the same error - mongodb: unrecognized service.

After looking into installed package contents, I noticed that it contains only Systemd service unit, but no SystemV init script:

# dpkg -L mongodb-org-server

But my system was running on SysV init:

# stat /proc/1/exe
File: '/proc/1/exe' -> '/sbin/init'

So, there are 2 options now:

How to convert a String to long in javascript?

JavaScript has a Number type which is a 64 bit floating point number*.

If you're looking to convert a string to a number, use

  1. either parseInt or parseFloat. If using parseInt, I'd recommend always passing the radix too.
  2. use the Unary + operator e.g. +"123456"
  3. use the Number constructor e.g. var n = Number("12343")

*there are situations where the number will internally be held as an integer.

How would you implement an LRU cache in Java?

Have a look at ConcurrentSkipListMap. It should give you log(n) time for testing and removing an element if it is already contained in the cache, and constant time for re-adding it.

You'd just need some counter etc and wrapper element to force ordering of the LRU order and ensure recent stuff is discarded when the cache is full.

How to find Google's IP address?

The following IP address ranges belong to Google: - - - - - - -

Like many popular Web sites, Google utilizes multiple Internet servers to handle incoming requests to its Web site. Instead of entering into the browser, a person can enter http:// followed by one of the above addresses, for example:


HTML input time in 24 format

<!DOCTYPE html>_x000D_
        Time: <input type="time" id="myTime" value="16:32:55">_x000D_
 <p>Click the button to get the time of the time field.</p>_x000D_
 <button onclick="myFunction()">Try it</button>_x000D_
 <p id="demo"></p>_x000D_
     function myFunction() {_x000D_
         var x = document.getElementById("myTime").value;_x000D_
         document.getElementById("demo").innerHTML = x;_x000D_

I found that by setting value field (not just what is given below) time input will be internally converted into the 24hr format.

Using multiple delimiters in awk

The delimiter can be a regular expression.

awk -F'[/=]' '{print $3 "\t" $5 "\t" $8}' file


tc0001   tomcat7.1  
tc0001   tomcat7.2  
tc0001   tomcat7.5

What is the difference between, and localhost?

In current version of Jekyll, it defaults to
This is good, if you are connected to a network but do not want anyone else to access your application.

However it may happen that you want to see how your application runs on a mobile or from some other laptop/computer.

In that case, you can use

jekyll serve --host

This binds your application to the host & next use following to connect to it from some other host

http://host's IP adress/4000 

Leave only two decimal places after the dot

Try this:

double result = Math.Round(24.576938593,2);

Output: 24.57

Recursive search and replace in text files on Mac and Linux

I used this format - but...I found I had to run it three or more times to get it to actually change every instance which I found extremely strange. Running it once would change some in each file but not all. Running exactly the same string two-four times would catch all instances.

find . -type f -name '*.txt' -exec sed -i '' s/thistext/newtext/ {} +

Python: finding lowest integer

list1 = [10,-4,5,2,33,4,7,8,2,3,5,8,99,-34]




for x in list1:
    if x>max_v:
        print('X is {0} and max is {1}'.format(x,max_v))
for x in list1:
    if x<min_v:
        print('X is {0} and min is {1}'.format(x,min_v))

print('Max values is ' + str(max_v))
print('Min values is ' + str(min_v))

How do you truncate all tables in a database using TSQL?

It is a little late but it might help someone. I created a procedure sometimes back which does the following using T-SQL:

  1. Store all constraints in a Temporary table
  2. Drop All Constraints
  3. Truncate all tables with exception of some tables, which does not need truncation
  4. Recreate all Constraints.

I have listed it on my blog here

How to prevent multiple definitions in C?

If you have added test.c to your Code::Blocks project, the definition will be seen twice - once via the #include and once by the linker. You need to:

  • remove the #include "test.c"
  • create a file test.h which contains the declaration: void test();
  • include the file test.h in main.c

Check if not nil and not empty in Rails shortcut?

There's a method that does this for you:

def show
  @city =

The present? method tests for not-nil plus has content. Empty strings, strings consisting of spaces or tabs, are considered not present.

Since this pattern is so common there's even a shortcut in ActiveRecord:

def show
  @city =

This is roughly equivalent.

As a note, testing vs nil is almost always redundant. There are only two logically false values in Ruby: nil and false. Unless it's possible for a variable to be literal false, this would be sufficient:

if (variable)
  # ...

This is preferable to the usual if (!variable.nil?) or if (variable != nil) stuff that shows up occasionally. Ruby tends to wards a more reductionist type of expression.

One reason you'd want to compare vs. nil is if you have a tri-state variable that can be true, false or nil and you need to distinguish between the last two states.

Not unique table/alias

Your query contains columns which could be present with the same name in more than one table you are referencing, hence the not unique error. It's best if you make the references explicit and/or use table aliases when joining.


    SELECT pa.ProjectID, p.Project_Title, a.Account_ID, a.Username, a.Access_Type, c.First_Name, c.Last_Name
      FROM Project_Assigned pa
INNER JOIN Account a
        ON pa.AccountID = a.Account_ID
INNER JOIN Project p
        ON pa.ProjectID = p.Project_ID
INNER JOIN Clients c
        ON a.Account_ID = c.Account_ID
     WHERE a.Access_Type = 'Client';

Properties private set;

Maybe I'm misunderstanding, but if you want truly readonly Ids why not use an actual readonly field?

public class Person
   public Person(int id)
      m_id = id;

   readonly int m_id;
   public int Id { get { return m_id; } }

Check div is hidden using jquery

Did you notice your typo, $car2 instead of #car2 ?

Anyway, :hidden seems to be working as expected, try it here.

DIV table colspan: how?

You can do this ( where data-x has the appropriate display:xxxx set ):

<!-- TH -->
<div data-tr>
    <div data-th style="width:25%">TH</div>
    <div data-th style="width:50%">

         <div data-table style="width:100%">
             <div data-tr>
                 <div data-th style="width:25%">TH</div>
                 <div data-th style="width:25%">TH</div>
                 <div data-th style="width:25%">TH</div>
                 <div data-th style="width:25%">TH</div>

    <div data-th style="width:25%">TH</div>

<!-- TD -->
<div data-tr>
    <div data-td style="width:25%">TD</div>
    <div data-th style="width:50%">

         <div data-table style="width:100%">
             <div data-tr>
                 <div data-td style="width:25%">TD</div>
                 <div data-td style="width:25%">TD</div>
                 <div data-td style="width:25%">TD</div>
                 <div data-td style="width:25%">TD</div>
             <div data-tr>

    <div data-td style="width:25%">TD</div>

Recommended Fonts for Programming?

I like Fixedsys in Visual Studio. It's a classic. No anti-aliasing blur.

Fixedsys Typeface

How to use the command update-alternatives --config java

There are many other binaries that need to be linked so I think it's much better to try something like sudo update-alternatives --all and choosing the right alternatives for everything else besides java and javac.

Convert image from PIL to openCV format

The code commented works as well, just choose which do you prefer

import numpy as np
from PIL import Image

def convert_from_cv2_to_image(img: np.ndarray) -> Image:
    # return Image.fromarray(cv2.cvtColor(img, cv2.COLOR_BGR2RGB))
    return Image.fromarray(img)

def convert_from_image_to_cv2(img: Image) -> np.ndarray:
    # return cv2.cvtColor(numpy.array(img), cv2.COLOR_RGB2BGR)
    return np.asarray(img)

Gmail: 530 5.5.1 Authentication Required. Learn more at

You need to go here

then select Gmail and then select device. then click on Generate. Simply Copy & Paste password which is generated by Google.

Generating a UUID in Postgres for Insert statement?

Without extensions (cheat)

SELECT uuid_in(md5(random()::text || clock_timestamp()::text)::cstring);

output>> c2d29867-3d0b-d497-9191-18a9d8ee7830

(works at least in 8.4)

  • Thanks to @Erwin Brandstetter for clock_timestamp() explanation.

If you need a valid v4 UUID

SELECT uuid_in(overlay(overlay(md5(random()::text || ':' || clock_timestamp()::text) placing '4' from 13) placing to_hex(floor(random()*(11-8+1) + 8)::int)::text from 17)::cstring);

enter image description here * Thanks to @Denis Stafichuk @Karsten and @autronix

Also, in modern Postgres, you can simply cast:

SELECT md5(random()::text || clock_timestamp()::text)::uuid

Build Eclipse Java Project from Command Line

The normal apporoach works the other way around: You create your build based upon maven or ant and then use integrations for your IDE of choice so that you are independent from it, which is esp. important when you try to bring new team members up to speed or use a contious integration server for automated builds. I recommend to use maven and let it do the heavy lifting for you. Create a pom file and generate the eclipse project via mvn eclipse:eclipse. HTH

How to compare files from two different branches?

Use commit hashes as this:

git diff <hash1> <hash2> <filename>

where hash1 can be any commit from any branch, the same for hash2.

flutter remove back button on appbar

The AppBar widget has a property called automaticallyImplyLeading. By default it's value is true. If you don't want flutter automatically build the back button for you then just make the property false.

appBar: AppBar(
  title: Text("YOUR_APPBAR_TITLE"), 
  automaticallyImplyLeading: false,

To add your custom back button

appBar: AppBar(
  title: Text("YOUR_APPBAR_TITLE"), 
  automaticallyImplyLeading: false,
  leading: YOUR_CUSTOM_WIDGET(),

How can I clear the content of a file?

This is what I did to clear the contents of the file without creating a new file as I didn't want the file to display new time of creation even when the application just updated its contents.

FileStream fileStream = File.Open(<path>, FileMode.Open);

 * Set the length of filestream to 0 and flush it to the physical file.
 * Flushing the stream is important because this ensures that
 * the changes to the stream trickle down to the physical file.
fileStream.Close(); // This flushes the content, too.

How to center absolute div horizontally using CSS?

Although above answers are correct but to make it simple for newbies, all you need to do is set margin, left and right. following code will do it provided that width is set and position is absolute:

margin: 0 auto;
left: 0;
right: 0;


.centeredBox {_x000D_
    margin: 0 auto;_x000D_
    left: 0;_x000D_
    right: 0;_x000D_
   /** Position should be absolute */_x000D_
    position: absolute;_x000D_
    /** And box must have a width, any width */_x000D_
    width: 40%;_x000D_
    background: #faebd7;_x000D_
<div class="centeredBox">Centered Box</div>

How to debug Angular JavaScript Code

Since the add-ons don't work anymore, the most helpful set of tools I've found is using Visual Studio/IE because you can set breakpoints in your JS and inspect your data that way. Of course Chrome and Firefox have much better dev tools in general. Also, good ol' console.log() has been super helpful!

How to have conditional elements and keep DRY with Facebook React's JSX?

I made recently to safely render elements only if the predicate passes.

{renderIf(1 + 1 === 2)(


const ifUniverseIsWorking = renderIf(1 + 1 === 2);



How do I find out my MySQL URL, host, port and username?

If you're already logged into the command line client try this:

mysql> select user();

It will output something similar to this:

| user()         |
| root@localhost |
1 row in set (0.41 sec)

In my example above, I was logged in as root from localhost.

To find port number and other interesting settings use this command:

mysql> show variables;

Change a Rails application to production

This would now be

rails server -e production

Or, more compact

rails s -e production

It works for rails 3+ projects.

java.lang.ClassNotFoundException: org.springframework.web.context.ContextLoaderListener

If everything mentioned above does not work try the following. It worked for me.

Remove your project from the server > Restart server > Add your project to server > Restart server.

Detailed Instruction:

1. Right click on server > Add and Remove
2. Select your project > Remove > Finish
3. Restart your server
4. Right click on server > Add and Remove
5. Select your project > Add > Finish
6. Restart your server again.

Expression must be a modifiable lvalue

The assignment operator has lower precedence than &&, so your condition is equivalent to:

if ((match == 0 && k) = m)

But the left-hand side of this is an rvalue, namely the boolean resulting from the evaluation of the sub­expression match == 0 && k, so you cannot assign to it.

By contrast, comparison has higher precedence, so match == 0 && k == m is equivalent to:

if ((match == 0) && (k == m))

How can prepared statements protect from SQL injection attacks?

The key phrase is need not be correctly escaped. That means that you don't to worry about people trying to throw in dashes, apostrophes, quotes, etc...

It is all handled for you.

Sort divs in jQuery based on attribute 'data-sort'?

I used this to sort a gallery of images where the sort array would be altered by an ajax call. Hopefully it can be useful to someone.

var myArray = ['2', '3', '1'];_x000D_
var elArray = [];_x000D_
$('.imgs').each(function() {_x000D_
    elArray[$(this).data('image-id')] = $(this);_x000D_
   $('#container').append(elArray[value]); _x000D_
<script src=""></script>_x000D_
<div id='container'>_x000D_
   <div class="imgs" data-image-id='1'>1</div>_x000D_
   <div class="imgs" data-image-id='2'>2</div>_x000D_
   <div class="imgs" data-image-id='3'>3</div>_x000D_


How do I convert a string to enum in TypeScript?


enum MyEnum {

Sample usage

const parsed = Parser.parseEnum('FiRsT', MyEnum);
// parsed = MyEnum.First 

const parsedInvalid= Parser.parseEnum('other', MyEnum);
// parsedInvalid = undefined

Ignore case sensitive parse

class Parser {
    public static parseEnum<T>(value: string, enumType: T): T[keyof T] | undefined {
        if (!value) {
            return undefined;

        for (const property in enumType) {
            const enumMember = enumType[property];
            if (typeof enumMember === 'string') {
                if (enumMember.toUpperCase() === value.toUpperCase()) {
                    const key = enumMember as string as keyof typeof enumType;
                    return enumType[key];
        return undefined;

How to show row number in Access query like ROW_NUMBER in SQL

by VB function:

Dim m_RowNr(3) as Variant
Function RowNr(ByVal strQName As String, ByVal vUniqValue) As Long
' m_RowNr(3)
' 0 - Nr
' 1 - Query Name
' 2 - last date_time
' 3 - UniqValue

If Not m_RowNr(1) = strQName Then
  m_RowNr(0) = 1
  m_RowNr(1) = strQName
ElseIf DateDiff("s", m_RowNr(2), Now) > 9 Then
  m_RowNr(0) = 1
ElseIf Not m_RowNr(3) = vUniqValue Then
  m_RowNr(0) = m_RowNr(0) + 1
End If

m_RowNr(2) = Now
m_RowNr(3) = vUniqValue
RowNr = m_RowNr(0)

End Function

Usage(without sorting option):

SELECT RowNr('title_of_query_or_any_unique_text', as Nr,A.*
From table A
Order By

if sorting required or multiple tables join then create intermediate table:

 SELECT RowNr('title_of_query_or_any_unique_text', as Nr,A.*
 INTO table_with_Nr
 From table A
 Order By

Why does javascript replace only first instance when using replace?

You can use:

String.prototype.replaceAll = function(search, replace) {
if (replace === undefined) {
    return this.toString();
return this.split(search).join(replace);

How to remove an element slowly with jQuery?

You mean like



How to check if a character in a string is a digit or letter

import java.util.*;

public class String_char 

    public static void main(String arg[]){   

        Scanner in = new Scanner(;
        System.out.println("Enter the value");
        String data;
        data =;

        int len = data.length();
        for (int i = 0 ; i < len ; i++){
            char ch = data.charAt(i);

            if ((ch >= '0' && ch <= '9')){
                System.out.println("Number ");
            else if((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z')){

how to implement a pop up dialog box in iOS

Since the release of iOS 8, UIAlertView is now deprecated; UIAlertController is the replacement.

Here is a sample of how it looks in Swift:

let alert = UIAlertController(title: "Hello!", message: "Message", preferredStyle: UIAlertControllerStyle.alert)
let alertAction = UIAlertAction(title: "OK!", style: UIAlertActionStyle.default)
    (UIAlertAction) -> Void in
present(alert, animated: true)
    () -> Void in

As you can see, the API allows us to implement callbacks for both the action and when we are presenting the alert, which is quite handy!

Updated for Swift 4.2

let alert = UIAlertController(title: "Hello!", message: "Message", preferredStyle: .alert)
let alertAction = UIAlertAction(title: "OK!", style: .default)
            (UIAlertAction) -> Void in
        present(alert, animated: true)
            () -> Void in

What's the CMake syntax to set and use variables?

When writing CMake scripts there is a lot you need to know about the syntax and how to use variables in CMake.

The Syntax

Strings using set():

  • set(MyString "Some Text")
  • set(MyStringWithVar "Some other Text: ${MyString}")
  • set(MyStringWithQuot "Some quote: \"${MyStringWithVar}\"")

Or with string():

  • string(APPEND MyStringWithContent " ${MyString}")

Lists using set():

  • set(MyList "a" "b" "c")
  • set(MyList ${MyList} "d")

Or better with list():

  • list(APPEND MyList "a" "b" "c")
  • list(APPEND MyList "d")

Lists of File Names:

  • set(MySourcesList "" "File with")
  • list(APPEND MySourcesList "" "File with")
  • add_excutable(MyExeTarget ${MySourcesList})

The Documentation

The Scope or "What value does my variable have?"

First there are the "Normal Variables" and things you need to know about their scope:

  • Normal variables are visible to the CMakeLists.txt they are set in and everything called from there (add_subdirectory(), include(), macro() and function()).
  • The add_subdirectory() and function() commands are special, because they open-up their own scope.
    • Meaning variables set(...) there are only visible there and they make a copy of all normal variables of the scope level they are called from (called parent scope).
    • So if you are in a sub-directory or a function you can modify an already existing variable in the parent scope with set(... PARENT_SCOPE)
    • You can make use of this e.g. in functions by passing the variable name as a function parameter. An example would be function(xyz _resultVar) is setting set(${_resultVar} 1 PARENT_SCOPE)
  • On the other hand everything you set in include() or macro() scripts will modify variables directly in the scope of where they are called from.

Second there is the "Global Variables Cache". Things you need to know about the Cache:

  • If no normal variable with the given name is defined in the current scope, CMake will look for a matching Cache entry.
  • Cache values are stored in the CMakeCache.txt file in your binary output directory.
  • The values in the Cache can be modified in CMake's GUI application before they are generated. Therefore they - in comparison to normal variables - have a type and a docstring. I normally don't use the GUI so I use set(... CACHE INTERNAL "") to set my global and persistant values.

    Please note that the INTERNAL cache variable type does imply FORCE

  • In a CMake script you can only change existing Cache entries if you use the set(... CACHE ... FORCE) syntax. This behavior is made use of e.g. by CMake itself, because it normally does not force Cache entries itself and therefore you can pre-define it with another value.

  • You can use the command line to set entries in the Cache with the syntax cmake -D var:type=value, just cmake -D var=value or with cmake -C CMakeInitialCache.cmake.
  • You can unset entries in the Cache with unset(... CACHE).

The Cache is global and you can set them virtually anywhere in your CMake scripts. But I would recommend you think twice about where to use Cache variables (they are global and they are persistant). I normally prefer the set_property(GLOBAL PROPERTY ...) and set_property(GLOBAL APPEND PROPERTY ...) syntax to define my own non-persistant global variables.

Variable Pitfalls and "How to debug variable changes?"

To avoid pitfalls you should know the following about variables:

  • Local variables do hide cached variables if both have the same name
  • The find_... commands - if successful - do write their results as cached variables "so that no call will search again"
  • Lists in CMake are just strings with semicolons delimiters and therefore the quotation-marks are important
    • set(MyVar a b c) is "a;b;c" and set(MyVar "a b c") is "a b c"
    • The recommendation is that you always use quotation marks with the one exception when you want to give a list as list
    • Generally prefer the list() command for handling lists
  • The whole scope issue described above. Especially it's recommended to use functions() instead of macros() because you don't want your local variables to show up in the parent scope.
  • A lot of variables used by CMake are set with the project() and enable_language() calls. So it could get important to set some variables before those commands are used.
  • Environment variables may differ from where CMake generated the make environment and when the the make files are put to use.
    • A change in an environment variable does not re-trigger the generation process.
    • Especially a generated IDE environment may differ from your command line, so it's recommended to transfer your environment variables into something that is cached.

Sometimes only debugging variables helps. The following may help you:

  • Simply use old printf debugging style by using the message() command. There also some ready to use modules shipped with CMake itself: CMakePrintHelpers.cmake, CMakePrintSystemInformation.cmake
  • Look into CMakeCache.txt file in your binary output directory. This file is even generated if the actual generation of your make environment fails.
  • Use variable_watch() to see where your variables are read/written/removed.
  • Look into the directory properties CACHE_VARIABLES and VARIABLES
  • Call cmake --trace ... to see the CMake's complete parsing process. That's sort of the last reserve, because it generates a lot of output.

Special Syntax

  • Environment Variables
    • You can can read $ENV{...} and write set(ENV{...} ...) environment variables
  • Generator Expressions
    • Generator expressions $<...> are only evaluated when CMake's generator writes the make environment (it comparison to normal variables that are replaced "in-place" by the parser)
    • Very handy e.g. in compiler/linker command lines and in multi-configuration environments
  • References
    • With ${${...}} you can give variable names in a variable and reference its content.
    • Often used when giving a variable name as function/macro parameter.
  • Constant Values (see if() command)
    • With if(MyVariable) you can directly check a variable for true/false (no need here for the enclosing ${...})
    • True if the constant is 1, ON, YES, TRUE, Y, or a non-zero number.
    • False if the constant is 0, OFF, NO, FALSE, N, IGNORE, NOTFOUND, the empty string, or ends in the suffix -NOTFOUND.
    • This syntax is often use for something like if(MSVC), but it can be confusing for someone who does not know this syntax shortcut.
  • Recursive substitutions
    • You can construct variable names using variables. After CMake has substituted the variables, it will check again if the result is a variable itself. This is very powerful feature used in CMake itself e.g. as sort of a template set(CMAKE_${lang}_COMPILER ...)
    • But be aware this can give you a headache in if() commands. Here is an example where CMAKE_CXX_COMPILER_ID is "MSVC" and MSVC is "1":
      • if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC") is true, because it evaluates to if("1" STREQUAL "1")
      • if(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC") is false, because it evaluates to if("MSVC" STREQUAL "1")
      • So the best solution here would be - see above - to directly check for if(MSVC)
    • The good news is that this was fixed in CMake 3.1 with the introduction of policy CMP0054. I would recommend to always set cmake_policy(SET CMP0054 NEW) to "only interpret if() arguments as variables or keywords when unquoted."
  • The option() command
    • Mainly just cached strings that only can be ON or OFF and they allow some special handling like e.g. dependencies
    • But be aware, don't mistake the option with the set command. The value given to option is really only the "initial value" (transferred once to the cache during the first configuration step) and is afterwards meant to be changed by the user through CMake's GUI.


Unable to ping vmware guest from another vmware guest

I would like to add, that yes. While using the NAT adapter settings in Vmware and turning off windows firewall I was able to ping other guest machines in my test environment.

Sidenote: Best practice would be to implement a hardware firewall in larger environments and turn off windows firewall on the Domain Controller.

.gitignore is ignored by Git

Just remove the folder or file, which was committed previously in Git, by the following command. Then gitignore file will reflect the correct files.

    git rm -r -f "folder or files insides"

Angularjs: input[text] ngChange fires while the value is changing

This post shows an example of a directive that delays the model changes to an input until the blur event fires.

Here is a fiddle that shows the ng-change working with the new ng-model-on-blur directive. Note this is a slight tweak to the original fiddle.

If you add the directive to your code you would change your binding to this:

<input type="text" ng-model="name" ng-model-onblur ng-change="update()" />

Here is the directive:

// override the default input to update on blur
angular.module('app', []).directive('ngModelOnblur', function() {
    return {
        restrict: 'A',
        require: 'ngModel',
        priority: 1, // needed for angular 1.2.x
        link: function(scope, elm, attr, ngModelCtrl) {
            if (attr.type === 'radio' || attr.type === 'checkbox') return;

            elm.bind('blur', function() {
                scope.$apply(function() {

Note: as @wjin mentions in the comments below this feature is supported directly in Angular 1.3 (currently in beta) via ngModelOptions. See the docs for more info.

UIScrollView not scrolling

After failing with the provided answers in this thread, I stumbled upon this article with the solution.

There are two things not intuitive about setting up the scrollview with autolayout:

  1. The constraints you set up as margin between the contentview and scrollview do not influence the size of the contentview. They really are margins. And to make it work, the contentview should have a fixed size.
  2. The trick to the fixed size is that you can set the width of the contentview equal to that of the scrollview's parent. Just select both views in the tree on the left and add the equal widths constraint.

This is the gist of that article. For a complete explanation, including illustrations, check it out.

htaccess redirect to https://www

RewriteEngine On 
RewriteCond %{SERVER_PORT} 80 
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R]

window.location.href not working

if anyone faced problem even after using return false; . then use the below.

setTimeout(function(){document.location.href = "index.php"},500);

Java Regex to Validate Full Name allow only Spaces and Letters

My personal choice is: ^\p{L}+[\p{L}\p{Pd}\p{Zs}']*\p{L}+$|^\p{L}+$, Where:

^\p{L}+ - It should start with 1 or more letters.

[\p{Pd}\p{Zs}'\p{L}]* - It can have letters, space character (including invisible), dash or hyphen characters and ' in any order 0 or more times.

\p{L}+$ - It should finish with 1 or more letters.

|^\p{L}+$ - Or it just should contain 1 or more letters (It is done to support single letter names).

Support for dots (full stops) was dropped, as in British English it can be dropped in Mr or Mrs, for example.

How do I install Java on Mac OSX allowing version switching?

This answer extends on Jayson's excellent answer with some more opinionated guidance on the best approach for your use case:

  • SDKMAN is the best solution for most users. It's easy to use, doesn't have any weird configuration, and makes managing multiple versions for lots of other Java ecosystem projects easy as well.
  • Downloading Java versions via Homebrew and switching versions via jenv is a good option, but requires more work. For example, the Homebrew commands in this highly upvoted answer don't work anymore. jenv is slightly harder to setup, the plugins aren't well documented, and the README says the project is looking for a new maintainer. jenv is still a great project, solves the job, and the community should be thankful for the wonderful contribution. SDKMAN is just the better option cause it's so great.
  • Jabba is written is a multi-platform solution that provides the same interface on Mac, Windows, and PC (it's written in Go and that's what allows it to be multiplatform). If you care about a multiplatform solution, this is a huge selling point. If you only care about running multiple versions on your Mac, then you don't need a multiplatform solution. SDKMAN's support for tens of popular SDKs is what you're missing out on if you go with Jabba.

Managing versions manually is probably the worst option. If you decide to manually switch versions, you can use this Bash code instead of Jayson's verbose code (code snippet from the homebrew-openjdk README:

jdk() {
        export JAVA_HOME=$(/usr/libexec/java_home -v"$version");
        java -version

Jayson's answer provides the basic commands for SDKMAN and jenv. Here's more info on SDKMAN and more info on jenv if you'd like more background on these tools.

Difference between <context:annotation-config> and <context:component-scan>

I found this nice summary of which annotations are picked up by which declarations. By studying it you will find that <context:component-scan/> recognizes a superset of annotations recognized by <context:annotation-config/>, namely:

  • @Component, @Service, @Repository, @Controller, @Endpoint
  • @Configuration, @Bean, @Lazy, @Scope, @Order, @Primary, @Profile, @DependsOn, @Import, @ImportResource

As you can see <context:component-scan/> logically extends <context:annotation-config/> with CLASSPATH component scanning and Java @Configuration features.

Pushing to Git returning Error Code 403 fatal: HTTP request failed

None of the above answers worked for my enterprise GitHub account. Follow these steps for pushing via ssh key generation way.

Create a repo by visiting your git account.

Generate ssh key:

ssh-keygen -t rsa -C "[email protected]"

Copy the contents of the file ~/.ssh/ to your SSH keys in your GitHub account settings. Test SSH key:

ssh -T [email protected]
clone the repo:
git clone git://

Now cd to your git clone folder and do:

git remote set-url origin [email protected]:username/your-repository.git

Now try editing a file (try the README) and then do:

git add -A
git commit -am "my update msg"
git push -u origin master

Update: new git version seems to recommend not to have any file while new repo is created. Hence make aa blank repo.

The type 'string' must be a non-nullable type in order to use it as parameter T in the generic type or method 'System.Nullable<T>'

Please note that in upcoming version of C# which is 8, the answers are not true.

All the reference types are non-nullable by default and you can actually do the following:

public string? MyNullableString; 
this.MyNullableString = null; //Valid


public string MyNonNullableString; 
this.MyNonNullableString = null; //Not Valid and you'll receive compiler warning. 

The important thing here is to show the intent of your code. If the "intent" is that the reference type can be null, then mark it so otherwise assigning null value to non-nullable would result in compiler warning.

More info

Excel VBA If cell.Value =... then

You can use the Like operator with a wildcard to determine whether a given substring exists in a string, for example:

If cell.Value Like "*Word1*" Then
ElseIf cell.Value Like "*Word2*" Then
End If

In this example the * character in "*Word1*" is a wildcard character which matches zero or more characters.

NOTE: The Like operator is case-sensitive, so "Word1" Like "word1" is false, more information can be found on this MSDN page.

Using the grep and cut delimiter command (in bash shell scripting UNIX) - and kind of "reversing" it?

You don't need to change the delimiter to display the right part of the string with cut.

The -f switch of the cut command is the n-TH element separated by your delimiter : :, so you can just type :

 grep puddle2_1557936 | cut -d ":" -f2

Another solutions (adapt it a bit) if you want fun :

Using :

grep -oP 'puddle2_1557936:\K.*' <<< 'puddle2_1557936:/home/rogers.williams/folderz/puddle2'                                                                        

or still with look around

grep -oP '(?<=puddle2_1557936:).*' <<< 'puddle2_1557936:/home/rogers.williams/folderz/puddle2'                                                                    

or with :

perl -lne '/puddle2_1557936:(.*)/ and print $1' <<< 'puddle2_1557936:/home/rogers.williams/folderz/puddle2'                                                      

or using (thanks to glenn jackman)

ruby -F: -ane '/puddle2_1557936/ and puts $F[1]' <<< 'puddle2_1557936:/home/rogers.williams/folderz/puddle2'

or with :

awk -F'puddle2_1557936:' '{print $2}'  <<< 'puddle2_1557936:/home/rogers.williams/folderz/puddle2'

or with :

python -c 'import sys; print(sys.argv[1].split("puddle2_1557936:")[1])' 'puddle2_1557936:/home/rogers.williams/folderz/puddle2'

or using only :

IFS=: read _ a <<< "puddle2_1557936:/home/rogers.williams/folderz/puddle2"
echo "$a"

or using in a :

var x = 'puddle2_1557936:/home/rogers.williams/folderz/puddle2'

or using in a :

php -r 'preg_match("/puddle2_1557936:(.*)/", $argv[1], $m); echo "$m[1]\n";' 'puddle2_1557936:/home/rogers.williams/folderz/puddle2' 


INSTALL_FAILED_NO_MATCHING_ABIS is when you are trying to install an app that has native libraries and it doesn't have a native library for your cpu architecture. For example if you compiled an app for armv7 and are trying to install it on an emulator that uses the Intel architecture instead it will not work.

Using Xamarin on Visual Studio 2015. Fix this issue by:

  1. Open your xamarin .sln
  2. Right click your android project
  3. Click properties
  4. Click Android Options
  5. Click the 'Advanced' tab
  6. Under "Supported architectures" make the following checked:

    1. armeabi-v7a
    2. x86
  7. save

  8. F5 (build)

Edit: This solution has been reported as working on Visual Studio 2017 as well.

Edit 2: This solution has been reported as working on Visual Studio 2017 for Mac as well.

fatal: could not read Username for '': No such file or directory

Note that if you are getting this error instead:

fatal: could not read Username for '': No error

Then you need to update your Git to version 2.16 or later.

Using awk to print all columns from the nth to the last

If you want formatted text, chain your commands with echo and use $0 to print the last field.


for i in {8..11}; do
   s3="str with spaces $i"
   echo -n "$s1 $s2" | awk '{printf "|%3d|%6s",$1,$2}'
   echo -en "$s3" | awk '{printf "|%-19s|\n", $0}'


|  8|  str8|str with spaces 8  |
|  9|  str9|str with spaces 9  |
| 10| str10|str with spaces 10 |
| 11| str11|str with spaces 11 |

Show Current Location and Update Location in MKMapView in Swift

For Swift 2, you should change it to the following:

func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    let location = locations.last

    let center = CLLocationCoordinate2D(latitude: location!.coordinate.latitude, longitude: location!.coordinate.longitude)
    let region = MKCoordinateRegion(center: center, span: MKCoordinateSpan(latitudeDelta: 0.01, longitudeDelta: 0.01)), animated: true)

get client time zone from browser

Look at this repository pageloom it is helpful

download jstz.min.js and add a function to your html page

<script language="javascript">
    function getTimezoneName() {
        timezone = jstz.determine()

and call this function from your display tag

Install pdo for postgres Ubuntu

If you are using PHP 5.6, the command is:

sudo apt-get install php5.6-pgsql

fs.writeFile in a promise, asynchronous-synchronous stuff

As of 2019...

...the correct answer is to use async/await with the native fs promises module included in node. Upgrade to Node.js 10 or 11 (already supported by major cloud providers) and do this:

const fs = require('fs').promises;

// This must run inside a function marked `async`:
const file = await fs.readFile('filename.txt', 'utf8');
await fs.writeFile('filename.txt', 'test');

Do not use third-party packages and do not write your own wrappers, that's not necessary anymore.

No longer experimental

Before Node 11.14.0, you would still get a warning that this feature is experimental, but it works just fine and it's the way to go in the future. Since 11.14.0, the feature is no longer experimental and is production-ready.

What if I prefer import instead of require?

It works, too - but only in Node.js versions where this feature is not marked as experimental.

import { promises as fs } from 'fs';

(async () => {
    await fs.writeFile('./test.txt', 'test', 'utf8');

Python: How to pip install opencv2 with specific version 2.4.9?

The following command line pip install opencv-python== works properly. Use one of the versions presented to you. May be:,,,,,,, or, etc.

To make sure, you can see my screenshot.screenshot

Bootstrap modal z-index

Resolved this issue for vue, by adding to the options an id: 'alertBox' so now every modal container has its parent set to something like alertBox__id0whatver which can easily be changed with css:

div[id*="alertBox"] { background: red; }

(meaning if id name contains ( *= ) 'alertBox' it will be applied.

nginx: how to create an alias url route?

server {
  root /path/to/root;
  location / {
    # bla bla
  location /demo {
    alias /path/to/root/production/folder/here;

If you need to use try_files inside /demo you'll need to replace alias with a root and do a rewrite because of the bug explained here

Python WindowsError: [Error 123] The filename, directory name, or volume label syntax is incorrect:

I was facing same error with Django Rest Framework, It was nothing to do with UI, still was getting this error. I applied below solution, worked for me.

  • Restarted Machine.
  • Restarted Virtual Environment.

Allow only numeric value in textbox using Javascript

This code uses the event object's .keyCode property to check the characters typed into a given field. If the key pressed is a number, do nothing; otherwise, if it's a letter, alert "Error". If it is neither of these things, it returns false.


    <input type="text" id="txt" />


(function(a) {
    a.onkeypress = function(e) {
        if (e.keyCode >= 49 && e.keyCode <= 57) {}
        else {
            if (e.keyCode >= 97 && e.keyCode <= 122) {
                // return false;
            } else return false;

function $(id) {
    return document.getElementById(id);

For a result:

Mind you that the .keyCode result for .onkeypress, .onkeydown, and .onkeyup differ from each other.

How to check if that data already exist in the database during update (Mongoose And Express)

For anybody falling on this old solution. There is a better way from the mongoose docs.

var s = new Schema({ name: { type: String, unique: true }});
s.path('name').index({ unique: true });

Compare two Byte Arrays? (Java)

Since I wanted to compare two arrays for a unit Test and I arrived on this answer I thought I could share.

You can also do it with:

public void testTwoArrays() {
  byte[] array = new BigInteger("1111000011110001", 2).toByteArray();
  byte[] secondArray = new BigInteger("1111000011110001", 2).toByteArray();

  Assert.assertArrayEquals(array, secondArray);

And you could check on Comparing arrays in JUnit assertions for more infos.

Clearing an HTML file upload field via JavaScript

This jQuery worked for me in IE11, Chrome 53, and Firefox 49:

cloned = $("#fileInput").clone(true);

How do I upgrade the Python installation in Windows 10?

Just install python newest version's installer it will automatically detect your python version and will say upgrade python and starts upgrading

How to make RatingBar to show five stars


Configure the number of Stars in the XML file... No need to provide it in Styles or Activity/Fragment .... IMPORTANT: Make sure you Put the WIDTH as Wrap content and weights are not enabled

Find files in created between a date range

Try this:

find /var/tmp -mtime +2 -a -mtime -8 -ls

to find files older than 2 days but not older than 8 days.

Error: EPERM: operation not permitted, unlink 'D:\Sources\**\node_modules\fsevents\node_modules\abbrev\package.json'

I wanted to run npm install from within my external hard drive as this is where i saved my code workspace. Windows 10 OS.

But I was getting the same error as the original post.None of the previous answers worked for me, I tried all of them:

  1. uninstalling nodejs then re-installing
  2. uninstalling nodejs then downgrading/installing a lower version of nodejs.
  3. npm install -force
  4. deleting the folders from C:\Users{YourUsername}\AppData\Roaming ... npm and npm-cache then re-installing.
  5. npm cache clean --force
  6. npm cache clean
  7. npm install --g or npm install --global

What worked for me was this:

  1. copy the folder from C:\Program Files\nodejs to D:\Program Files\nodejs
  2. Then go to Control Panel\System and Security\System
  3. Advanced System Settings
  4. Environment Variables
  5. System Variables
  6. Double click Path
  7. Add a new path
  8. D:\Program Files\nodejs
  9. Click ok
  10. restart PC.
  11. try npm install from within D: Drive

Change / Add syntax highlighting for a language in Sublime 2/3

This is my recipe

Note: This isn't exactly what OP is asking. These instructions will help you change the colors of items (comments, keywords, etc) that are defined syntax matching rules. For example, use these instructions to change so that all code comments are colored blue instead of green.

I believe the OP is asking how to define this as an item to be colored when found in a JavaScript source file.

  1. Install Package: PackageResourceViewer

  2. Ctrl+Shift+P > [PackageResourceViewer: Open Resource] > [Color Scheme - Default] > [Marina.sublime-color-scheme] (or whichever color scheme you use)

  3. The above command will open a new tab to the file "Marina.sublime-color-scheme".

    • For me, this file was located in my roaming profile %appdata% (C:\Users\walter\AppData\Roaming\Sublime Text 3\Packages\Color Scheme - Default\) .
    • However, if I browse to that path in Windows Explorer, [Color Scheme - Default] is not of a child-dir of [Packages] dir. I suspect that PackageResourceViewer is doing some virtualization.

optional step: On the new color-scheme tab: Ctrl+Shift+P > [Set Syntax: JSON]

  1. Search for the rule you want to change. I wanted to make comments be move visible, so I searched for "Comment"

    • I found it in the "rules" section
            "name": "Comment",
            "scope": "comment, punctuation.definition.comment",
            "foreground": "var(blue6)"
  1. Search for the string "blue6": to find the color variable definitions section. I found it in the "variables" section.

  2. Pick a new color using a tool like .

  3. Either define a new color variable, or overwrite the color setting for blue6.

    • Warning: overwriting blue6 will affect all other text-elements in that color scheme which also use blue6 ("Punctuation" "Accessor").
  4. Save your file, the changes will be applied instantly to any open files/tabs.


Sublime will handle any of these color styles. Possibly more.

hsla = hue, saturation, lightness, alpha rgba = red, green, blue, alpha

hsla(151, 100%, 41%, 1) - last param is the alpha level (transparency) 1 = opaque, 0.5 = half-transparent, 0 = full-transparent

hsl(151, 100%, 41%) - no alpha channel

rgba(0, 209, 108, 1) - rgb with an alpha channel

rgb(0, 209, 108) - no alpha channel

Moving average or running mean

There is a comment by mab buried in one of the answers above which has this method. bottleneck has move_mean which is a simple moving average:

import numpy as np
import bottleneck as bn

a = np.arange(10) + np.random.random(10)

mva = bn.move_mean(a, window=2, min_count=1)

min_count is a handy parameter that will basically take the moving average up to that point in your array. If you don't set min_count, it will equal window, and everything up to window points will be nan.

Is Visual Studio Community a 30 day trial?

I'm using Visual Studio Professional licensed over the MAPS Action Pack subscription. Since the new version of the Microsoft Partner Center one have to add the subscribed user to the partner benefit software.

Partner Center->Benefits->Visual Studio Subscriptions->Add user

After that one have to sign out and reenter the credentials in the account settings of VS.

Connection pooling options with JDBC: DBCP vs C3P0

Another alternative is HikariCP.

Here is the comparison benchmark

How to force a list to be vertical using html css

Hope this is your structure:

        <div ><img.. /><p>text</p></div>
        <div ><img.. /><p>text</p></div>
        <div ><img.. /><p>text</p></div>

By default, it will be add one after another row:


if you want to make it vertical, just add float left to li, give width and height, make sure that content will not break the width:

|  |  |
|  |  |

   width:300px; /* adjust */
   height:150px; /* adjust */
   padding: 5px; /*adjust*/

How to convert latitude or longitude to meters?

Based on average distance for degress in the Earth.

1° = 111km;

Converting this for radians and dividing for meters, take's a magic number for the RAD, in meters: 0.000008998719243599958;


const RAD = 0.000008998719243599958;
Math.sqrt(Math.pow(lat1 - lat2, 2) + Math.pow(long1 - long2, 2)) / RAD;

HTTP Basic Authentication - what's the expected web browser experience?

To help everyone avoid confusion, I will reformulate the question in two parts.

First : "how can make an authenticated HTTP request with a browser, using BASIC auth?".

In the browser you can do a http basic auth first by waiting the prompt to come, or by editing the URL if you follow this format: http://myusername:[email protected]

NB: the curl command mentionned in the question is perfectly fine, if you have a command-line and curl installed. ;)


Also according to the CURL manual page


  Curl also supports user and password in HTTP URLs, thus you can pick a file

      curl http://name:[email protected]/full/path/to/file

  or specify user and password separately like in

      curl -u name:passwd http://machine.domain/full/path/to/file

  HTTP offers many different methods of authentication and curl supports
  several: Basic, Digest, NTLM and Negotiate (SPNEGO). Without telling which
  method to use, curl defaults to Basic. You can also ask curl to pick the
  most secure ones out of the ones that the server accepts for the given URL,
  by using --anyauth.

  NOTE! According to the URL specification, HTTP URLs can not contain a user
  and password, so that style will not work when using curl via a proxy, even
  though curl allows it at other times. When using a proxy, you _must_ use
  the -u style for user and password.

The second and real question is "However, on, I'm not getting an authorization prompt at all, just a page that says I'm not authorized. Did somesite not implement the Basic Auth workflow correctly, or is there something else I need to do?"

The curl documentation says the -u option supports many method of authentication, Basic being the default.

Node.js: what is ENOSPC error and how to solve?

This sounds very odd, but yes, a system reboot or killall node solves the problem for me.

What event handler to use for ComboBox Item Selected (Selected Item not necessarily changed)

You can use "ComboBoxItem.PreviewMouseDown" event. So each time when mouse is down on some item this event will be fired.

To add this event in XAML use "ComboBox.ItemContainerStyle" like in next example:

   <ComboBox x:Name="MyBox"
        ItemsSource="{Binding MyList}"
        SelectedValue="{Binding MyItem, Mode=OneWayToSource}" >
                <EventSetter Event="ComboBoxItem.PreviewMouseDown"

and handle it as usual

void cmbItem_PreviewMouseDown(object sender, MouseButtonEventArgs e)
    // your item selection code here...

Thanks to MSDN

JQuery Event for user pressing enter in a textbox?

Another subtle variation. I went for a slight separation of powers, so I have a plugin to enable catching the enter key, then I just bind to events normally:

(function($) { $.fn.catchEnter = function(sel) {  
    return this.each(function() { 
            if(e.keyCode == 13)

And then in use:

$('.input[type="text"]').catchEnter().on('enterkey',function(ev) { });

This variation allows you to use event delegation (to bind to elements you haven't created yet).

$('body').catchEnter('.onelineInput').on('enterkey',function(ev) { /*process input */ });

Detecting installed programs via registry

An application does not need to have any registry entry. In fact, many applications do not need to be installed at all. U3 USB sticks are a good example; the programs on them just run from the file system.

As noted, most good applications can be found via their uninstall registry key though. This is actually a pair of keys, per-user and per-machine (HKCU/HKLM - Piskvor mentioned only the HKLM one). It does not (always) give you the install directory, though.

If it's in HKCU, then you have to realise that HKEY_CURRENT_USER really means "Current User". Other users have their own HKCU entries, and their own installed software. You can't find that. Reading every HKEY_USERS hive is a disaster on corporate networks with roaming profiles. You really don't want to fetch 1000 accounts from your remote [US|China|Europe] office.

Even if an application is installed, and you know where, it may not have the same "version" notion you have. The best source is the "version" resource in the executables. That's indeed a plural, so you have to find all of them, extract version resources from all and in case of a conflict decid on something reasonable.

So - good luck. There are dozes of ways to fail.

Where to place and how to read configuration resource files in servlet based application?

It just needs to be in the classpath (aka make sure it ends up under /WEB-INF/classes in the .war as part of the build).

What is the Simplest Way to Reverse an ArrayList?

Not the simplest way but if you're a fan of recursion you might be interested in the following method to reverse an ArrayList:

public ArrayList<Object> reverse(ArrayList<Object> list) {
    if(list.size() > 1) {                   
        Object value = list.remove(0);
    return list;

Or non-recursively:

public ArrayList<Object> reverse(ArrayList<Object> list) {
    for(int i = 0, j = list.size() - 1; i < j; i++) {
        list.add(i, list.remove(j));
    return list;

how to compare the Java Byte[] array?

They are returning false because you are testing for object identity rather than value equality. This returns false because your arrays are actually different objects in memory.

If you want to test for value equality should use the handy comparison functions in java.util.Arrays


import java.util.Arrays;



Java Enum return Int

If you need to get the int value, just have a getter for the value in your ENUM:

private enum DownloadType {
    private final int value;

    private DownloadType(int value) {
        this.value = value;

    public int getValue() {
        return value;

public static void main(String[] args) {
    System.out.println(DownloadType.AUDIO.getValue());           //returns 1
    System.out.println(DownloadType.VIDEO.getValue());           //returns 2
    System.out.println(DownloadType.AUDIO_AND_VIDEO.getValue()); //returns 3

Or you could simple use the ordinal() method, which would return the position of the enum constant in the enum.

private enum DownloadType {
    //rest of the code

System.out.println(DownloadType.AUDIO.ordinal());            //returns 0
System.out.println(DownloadType.VIDEO.ordinal());            //returns 1
System.out.println(DownloadType.AUDIO_AND_VIDEO.ordinal()); //returns 2

Return True, False and None in Python

It's impossible to say without seeing your actual code. Likely the reason is a code path through your function that doesn't execute a return statement. When the code goes down that path, the function ends with no value returned, and so returns None.

Updated: It sounds like your code looks like this:

def b(self, p, data): 
    current = p 
    if == data: 
        return True 
    elif == 1:
        return False 
        self.b(, data)

That else clause is your None path. You need to return the value that the recursive call returns:

        return self.b(, data)

BTW: using recursion for iterative programs like this is not a good idea in Python. Use iteration instead. Also, you have no clear termination condition.

Make a link use POST instead of GET

HTML + JQuery: A link that submits a hidden form with POST.

Since I spent a lot of time to understand all these answers, and since all of them have some interesting details, here is the combined version that finally worked for me and which I prefer for its simplicity.

My approach is again to create a hidden form and to submit it by clicking a link somewhere else in the page. It doesn't matter where in the body of the page the form will be placed.

The code for the form:

<form id="myHiddenFormId" action="myAction.php" method="post" style="display: none">
  <input type="hidden" name="myParameterName" value="myParameterValue">


The display: none hides the form. You can alternatively put it in a div or another element and set the display: none on the element.

The type="hidden" will create an fild that will not be shown but its data will be transmitted to the action eitherways (see W3C). I understand that this is the simplest input type.

The code for the link:

<a href="" onclick="$('#myHiddenFormId').submit(); return false;" title="My link title">My link text</a>


The empty href just targets the same page. But it doesn't really matter in this case since the return false will stop the browser from following the link. You may want to change this behavior of course. In my specific case, the action contained a redirection at the end.

The onclick was used to avoid using href="javascript:..." as noted by mplungjan. The $('#myHiddenFormId').submit(); was used to submit the form (instead of defining a function, since the code is very small).

This link will look exactly like any other <a> element. You can actually use any other element instead of the <a> (for example a <span> or an image).

What is the id( ) function used for?

I have an idea to use value of id() in logging.
It's cheap to get and it's quite short.
In my case I use tornado and id() would like to have an anchor to group messages scattered and mixed over file by web socket.

How to convert map to url query string?

Personally, I'd go for a solution like this, it's incredibly similar to the solution provided by @rzwitserloot, only subtle differences.

This solution is small, simple & clean, it requires very little in terms of dependencies, all of which are a part of the Java Util package.

Map<String, String> map = new HashMap<>();

map.put("param1", "12");
map.put("param2", "cat");

String output = "someUrl?";
output += map.entrySet()
    .map(x -> x.getKey() + "=" + x.getValue() + "&")

System.out.println(output.substring(0, output.length() -1));

Error in installation a R package

There could be a few things happening here. Start by first figuring out your library location:




We already know yours from the info you gave: C:\Program Files\R\R-3.0.1\library

I believe you have a file in there called: 00LOCK. From ?install.packages:

Note that it is possible for the package installation to fail so badly that the lock directory is not removed: this inhibits any further installs to the library directory (or for --pkglock, of the package) until the lock directory is removed manually.

You need to delete that file. If you had the pacman package installed you could have simply used p_unlock() and the 00LOCK file is removed. You can't install pacman now until the 00LOCK file is removed.

To install pacman use:


There may be a second issue. This is where you somehow corrupted MASS. This can occur, in my experience, if you try to update a package while it is in use in another R session. I'm sure there's other ways to cause this as well. To solve this problem try:

  1. Close out of all R sessions (use task manager to ensure you're truly R session free) Ctrl + Alt + Delete
  2. Go to your library location Sys.getenv("R_LIBS_USER"). In your case this is: C:\Program Files\R\R-3.0.1\library
  3. Manually delete the MASS package
  4. Fire up a vanilla session of R
  5. Install MASS via install.packages("MASS")

If any of this works please let me know what worked.