Programs & Examples On #Lfe

LFE stands for Lisp Flavoured Erlang, a lisp syntax front-end to the Erlang compiler.

UnhandledPromiseRejectionWarning: This error originated either by throwing inside of an async function without a catch block

I resolve the problem. It's very simple . if do you checking care the problem may be because the auxiliar variable has whitespace. Why ? I don't know but yus must use the trim() method and will resolve the problem

Visual Studio Code always asking for git credentials

Try installing "Git Credential Manager For Windows" (and following instructions for setting up the credential manager).

When required within an app using Git (e.g. VS Code) it will "magically" open the required dialog for Visual Studio Team Services credential input.

Fetch: POST json data

you can use fill-fetch, which is an extension of fetch. Simply, you can post data as below:

import { fill } from 'fill-fetch';

const fetcher = fill();

fetcher.config.timeout = 3000;
fetcher.config.maxConcurrence = 10;
fetcher.config.baseURL = '';

const res = await'/', { a: 1 }, {
    headers: {
        'bearer': '1234'

Chrome disable SSL checking for sites?

To disable the errors windows related with certificates you can start Chrome from console and use this option: --ignore-certificate-errors.

"C:\Program Files (x86)\Google\Chrome\Application\chrome.exe" --ignore-certificate-errors

You should use it for testing purposes. A more complete list of options is here:

How can I make window.showmodaldialog work in chrome 37?

    (function() {
        window.spawn = window.spawn || function(gen) {
            function continuer(verb, arg) {
                var result;
                try {
                    result = generator[verb](arg);
                } catch (err) {
                    return Promise.reject(err);
                if (result.done) {
                    return result.value;
                } else {
                    return Promise.resolve(result.value).then(onFulfilled, onRejected);
            var generator = gen();
            var onFulfilled = continuer.bind(continuer, 'next');
            var onRejected = continuer.bind(continuer, 'throw');
            return onFulfilled();
        window.showModalDialog = window.showModalDialog || function(url, arg, opt) {
            url = url || ''; //URL of a dialog
            arg = arg || null; //arguments to a dialog
            opt = opt || 'dialogWidth:300px;dialogHeight:200px'; //options: dialogTop;dialogLeft;dialogWidth;dialogHeight or CSS styles
            var caller = showModalDialog.caller.toString();
            var dialog = document.body.appendChild(document.createElement('dialog'));
            dialog.setAttribute('style', opt.replace(/dialog/gi, ''));
            dialog.innerHTML = '<a href="#" id="dialog-close" style="position: absolute; top: 0; right: 4px; font-size: 20px; color: #000; text-decoration: none; outline: none;">&times;</a><iframe id="dialog-body" src="' + url + '" style="border: 0; width: 100%; height: 100%;"></iframe>';
            document.getElementById('dialog-body').contentWindow.dialogArguments = arg;
            document.getElementById('dialog-close').addEventListener('click', function(e) {
            //if using yield
            if(caller.indexOf('yield') >= 0) {
                return new Promise(function(resolve, reject) {
                    dialog.addEventListener('close', function() {
                        var returnValue = document.getElementById('dialog-body').contentWindow.returnValue;
            //if using eval
            var isNext = false;
            var nextStmts = caller.split('\n').filter(function(stmt) {
                if(isNext || stmt.indexOf('showModalDialog(') >= 0)
                    return isNext = true;
                return false;
            dialog.addEventListener('close', function() {
                var returnValue = document.getElementById('dialog-body').contentWindow.returnValue;
                nextStmts[0] = nextStmts[0].replace(/(window\.)?showModalDialog\(.*\)/g, JSON.stringify(returnValue));
                eval('{\n' + nextStmts.join('\n'));
            throw 'Execution stopped until showModalDialog is closed';


The best way to deal with showModalDialog for older application conversions is use to `` inorder to work with show modal dialogs  and if modal dailog has ajax calls you need to create object and set the parameters of function to object and pass below...before that check for browser and set the useragent...example: agentStr = navigator.userAgent; and then check for chrome

var objAcceptReject={}; // create empty object and set the parameters to object and send to the other functions as dialog when opened in chrome breaks the functionality
    function rejectClick(index, transferId) {

     agentStr = navigator.userAgent;

                var msie = ua.indexOf("MSIE ");

                if (msie > 0) // If Internet Explorer, return version number
                    var ret = window.showModalDialog("/abc.jsp?accept=false",window,"dialogHeight:175px;dialogWidth:475px;scroll:no;status:no;help:no");   

                    if (ret=="true") {

                } else if ((agentStr.indexOf("Chrome")) >- 1){
                spawn(function() {

                    var ret = window.showModalDialog("/abcd.jsp?accept=false",window,"dialogHeight:175px;dialogWidth:475px;scroll:no;status:no;help:no");   

                    if (ret=="true") {// create an object and store values in objects and send as parameters


                else {
                    var ret = window.showModalDialog("/xtz.jsp?accept=false",window,"dialogHeight:175px;dialogWidth:475px;scroll:no;status:no;help:no");   

                    if (ret=="true") {

Finding common rows (intersection) in two Pandas dataframes

My understanding is that this question is better answered over in this post.

But briefly, the answer to the OP with this method is simply:

s1 = pd.merge(df1, df2, how='inner', on=['user_id'])

Which gives s1 with 5 columns: user_id and the other two columns from each of df1 and df2.

Using for loop inside of a JSP

You concrete problem is caused because you're mixing discouraged and old school scriptlets <% %> with its successor EL ${}. They do not share the same variable scope. The allFestivals is not available in scriptlet scope and the i is not available in EL scope.

You should install JSTL (<-- click the link for instructions) and declare it in top of JSP as follows:

<%@taglib prefix="c" uri=""%>

and then iterate over the list as follows:

<c:forEach items="${allFestivals}" var="festival">

(beware of possible XSS attack holes, use <c:out> accordingly)

Don't forget to remove the <jsp:useBean> as it has no utter value here when you're using a servlet as model-and-view controller. It would only lead to confusion. See also our servlets wiki page. Further you would do yourself a favour to disable scriptlets by the following entry in web.xml so that you won't accidently use them:


How can I Insert data into SQL Server using VBNet

Function ExtSql(ByVal sql As String) As Boolean
    Dim cnn As SqlConnection
    Dim cmd As SqlCommand
    cnn = New SqlConnection(My.Settings.mySqlConnectionString)
        cmd = New SqlCommand
        cmd.Connection = cnn
        cmd.CommandType = CommandType.Text
        cmd.CommandText = sql
    Catch ex As Exception
        Return False
    End Try
    Return True
End Function

How to fill DataTable with SQL Table

You can make method which return the datatable of given sql query:

public DataTable GetDataTable()
SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["BarManConnectionString"].ConnectionString);
string query = "SELECT * FROM [EventOne] ";

SqlCommand cmd = new SqlCommand(query, conn);

DataTable t1 = new DataTable();
using (SqlDataAdapter a = new SqlDataAdapter(cmd))
return t1;

and now can be used like this:

table = GetDataTable();

How to convert image into byte array and byte array to base64 String in android?

here is another solution...

System.IO.Stream st = new System.IO.StreamReader (picturePath).BaseStream;
byte[] buffer = new byte[4096];

System.IO.MemoryStream m = new System.IO.MemoryStream ();
while (st.Read (buffer,0,buffer.Length) > 0) {
    m.Write (buffer, 0, buffer.Length);
imgView.Tag = m.ToArray ();
st.Close ();
m.Close ();

hope it helps!

MYSQL Sum Query with IF Condition

How about this?

SUM(IF(PaymentType = "credit card", totalamount, 0)) AS CreditCardTotal

How do I compile the asm generated by GCC?

If you have main.s file. you can generate object file by GCC and also as

# gcc -c main.s
# as main.s -o main.o

check this link, it will help you learn some binutils of GCC

Python base64 data decode

i used chardet to detect possible encoding of this data ( if its text ), but get {'confidence': 0.0, 'encoding': None}. Then i tried to use pickle.load and get nothing again. I tried to save this as file , test many different formats and failed here too. Maybe you tell us what type have this 16512 bytes of mysterious data?

How to convert XML to JSON in Python?

Jacob Smullyan wrote a utility called pesterfish which uses effbot's ElementTree to convert XML to JSON.

Convert Xml to Table SQL Server

The sp_xml_preparedocument stored procedure will parse the XML and the OPENXML rowset provider will show you a relational view of the XML data.

For details and more examples check the OPENXML documentation.

As for your question,

SET @XML = '<rows><row>

DECLARE @handle INT  
DECLARE @PrepareXmlStatus INT  

EXEC @PrepareXmlStatus= sp_xml_preparedocument @handle OUTPUT, @XML  

FROM    OPENXML(@handle, '/rows/row', 2)  
    WITH (
    IdInvernadero INT,
    IdProducto INT,
    IdCaracteristica1 INT,
    IdCaracteristica2 INT,
    Cantidad INT,
    Folio INT

EXEC sp_xml_removedocument @handle 

Maven : error in opening zip file when running maven

I had the same problem but previous solutions not work for me. The only solution works for me is the following URL.


Here I explain more about it

Suppose you got an error like below

[ERROR] error: error reading C:\Users\user\.m2\repository\org\jdom\jdom\1.1\jdom-1.1.jar; error in opening zip file

Then you have to follow these steps.

  1. First, delete the existing jar C:\Users\user\.m2\repository\org\jdom\jdom\1.1\jdom-1.1.jar
  2. Then you have to manually download relevant jar from Maven central repository. You can download from this link here
  3. After that, you have to copy that downloaded jar into the previous directory.C:\Users\user\.m2\repository\org\jdom\jdom\1.1\

Then you can build your project using mvn clean install

hope this will help somebody.

Difference of two date time in sql server

So this isn't my answer but I just found this while searching around online for a question like this as well. This guy set up a procedure to calculate hours, minutes and seconds. The link and the code:

--Creating Function
If OBJECT_ID('UFN_HourMinuteSecond') Is Not Null
Drop Function dbo.UFN_HourMinuteSecond
'Create Function dbo.UFN_HourMinuteSecond
@StartDateTime DateTime,
@EndDateTime DateTime
) Returns Varchar(10) 

Declare @Seconds Int,
@Minute Int,
@Hour Int,
@Elapsed Varchar(10)

Select @Seconds = ABS(DateDiff(SECOND ,@StartDateTime,@EndDateTime))

If @Seconds >= 60 
select @Minute = @Seconds/60
select @Seconds = @Seconds%60

If @Minute >= 60
select @hour = @Minute/60
select @Minute = @Minute%60

Goto Final 

Select @Hour = Isnull(@Hour,0), @Minute = IsNull(@Minute,0), @Seconds =               IsNull(@Seconds,0)
select @Elapsed = Cast(@Hour as Varchar) + '':'' + Cast(@Minute as Varchar) + '':'' +     Cast(@Seconds as Varchar)

Return (@Elapsed)

Insert HTML from CSS

Content (for text and not html):

But just to be clear, it is bad practice. Its support throughout browsers is shaky, and it's generally not a good idea. But in cases where you really have to use it, there it is.

How to check if a subclass is an instance of a class at runtime?

if(view instanceof B)

This will return true if view is an instance of B or the subclass A (or any subclass of B for that matter).

Switching a DIV background image with jQuery

Mine is animated:

    opacity: 0
}, 100, function() {
    // Callback
    $(this).css("background-image", "url(" + new_img + ")").promise().done(function(){
        // Callback of the callback :)
            opacity: 1
        }, 600)

Node.js Error: connect ECONNREFUSED

You need to have a server running on port 8080 when you run the code above that simply returns the request back through the response. Copy the code below to a separate file (say 'server.js') and start this server using the node command (node server.js). You can then separately run your code above (node app.js) from a separate command line.

var http = require('http');

http.createServer(function(request, response){

    //The following code will print out the incoming request text

}).listen(8080, '');

console.log('Listening on port 8080...');

Set Session variable using javascript in PHP

Not possible. Because JavaScript is client-side and session is server-side. To do anything related to a PHP session, you have to go to the server.

Xcode Debugger: view value of variable

I agree with other posters that Xcode as a developing environment should include an easy way to debug variables. Well, good news, there IS one!

After searching and not finding a simple answer/tutorial on how to debug variables in Xcode I went to explore with Xcode itself and found this (at least for me) very useful discovery.

How to easily debug your variables in Xcode 4.6.3

In the main screen of Xcode make sure to see the bottom Debug Area by clicking the upper-right corner button showed in the screenshot.

Debug Area button

Debug Area in Xcode 4.6.3

Now set a Breakpoint – the line in your code where you want your program to pause, by clicking the border of your Code Area.


Now in the Debug Area look for this buttons and click the one in the middle. You will notice your area is now divided in two.

Split Debug Area

Should look like this

Now run your application.

When the first Breakpoint is reached during the execution of your program you will see on the left side all your variables available at that breakpoint.

Search Field

You can expand the left arrows on the variable for a greater detail. And even use the search field to isolate that variable you want and see it change on real time as you "Step into" the scope of the Breakpoint.

Step Into

On the right side of your Debug Area you can send to print the variables as you desire using the mouse's right-button click over the desired variable.

Contextual Menu

As you can see, that contextual menu is full of very interesting debugging options. Such as Watch that has been already suggested with typed commands or even Edit Value… that changes the runtime value of your variable!

Count how many rows have the same value

Try this Query

select NUM, count(1) as count 
from tbl 
where num = 1
group by NUM
--having count(1) (You condition)


How to auto-size an iFrame?

On any other element, I would use the scrollHeight of the DOM object and set the height accordingly. I don't know if this would work on an iframe (because they're a bit kooky about everything) but it's certainly worth a try.

Edit: Having had a look around, the popular consensus is setting the height from within the iframe using the offsetHeight:

function setHeight() {
    parent.document.getElementById('the-iframe-id').style.height = document['body'].offsetHeight + 'px';

And attach that to run with the iframe-body's onLoad event.

what happens when you type in a URL in browser

Attention: this is an extremely rough and oversimplified sketch, assuming the simplest possible HTTP request (no HTTPS, no HTTP2, no extras), simplest possible DNS, no proxies, single-stack IPv4, one HTTP request only, a simple HTTP server on the other end, and no problems in any step. This is, for most contemporary intents and purposes, an unrealistic scenario; all of these are far more complex in actual use, and the tech stack has become an order of magnitude more complicated since this was written. With this in mind, the following timeline is still somewhat valid:

  1. browser checks cache; if requested object is in cache and is fresh, skip to #9
  2. browser asks OS for server's IP address
  3. OS makes a DNS lookup and replies the IP address to the browser
  4. browser opens a TCP connection to server (this step is much more complex with HTTPS)
  5. browser sends the HTTP request through TCP connection
  6. browser receives HTTP response and may close the TCP connection, or reuse it for another request
  7. browser checks if the response is a redirect or a conditional response (3xx result status codes), authorization request (401), error (4xx and 5xx), etc.; these are handled differently from normal responses (2xx)
  8. if cacheable, response is stored in cache
  9. browser decodes response (e.g. if it's gzipped)
  10. browser determines what to do with response (e.g. is it a HTML page, is it an image, is it a sound clip?)
  11. browser renders response, or offers a download dialog for unrecognized types

Again, discussion of each of these points have filled countless pages; take this only as a summary, abridged for the sake of clarity. Also, there are many other things happening in parallel to this (processing typed-in address, speculative prefetching, adding page to browser history, displaying progress to user, notifying plugins and extensions, rendering the page while it's downloading, pipelining, connection tracking for keep-alive, cookie management, checking for malicious content etc.) - and the whole operation gets an order of magnitude more complex with HTTPS (certificates and ciphers and pinning, oh my!).

Getting date format m-d-Y H:i:s.u from milliseconds

This is based on answer from ArchCodeMonkey.

But just simplified, if you just want something quick that works.

function DateTime_us_utc(){
    return DateTime::createFromFormat('U.u', number_format(microtime(true), 6, '.', ''));
function DateTime_us(){
    $now = DateTime_us_utc();
    return $now->setTimeZone(new DateTimeZone(date_default_timezone_get()));

So for me then

$now = DateTime_us();
$now->format("m-d-Y H:i:s.u");

Using `window.location.hash.includes` throws “Object doesn't support property or method 'includes'” in IE11

IE11 does implement String.prototype.includes so why not using the official Polyfill?

  if (!String.prototype.includes) {
    String.prototype.includes = function(search, start) {
      if (typeof start !== 'number') {
        start = 0;

      if (start + search.length > this.length) {
        return false;
      } else {
        return this.indexOf(search, start) !== -1;

Source: polyfill source

Find duplicate records in MySQL

select * from table_name t1 inner join (select distinct <attribute list> from table_name as temp)t2 where t1.attribute_name = t2.attribute_name

For your table it would be something like

select * from list l1 inner join (select distinct address from list as list2)l2 where l1.address=l2.address

This query will give you all the distinct address entries in your list table... I am not sure how this will work if you have any primary key values for name, etc..

How to jump to top of browser page

You can set the scrollTop, like this:


Or if you want a little animation instead of a snap to the top:

$('html, body').animate({ scrollTop: 0 }, 'fast');

How to test if a string contains one of the substrings in a list, in pandas?

Here is a one line lambda that also works:

df["TrueFalse"] = df['col1'].apply(lambda x: 1 if any(i in x for i in searchfor) else 0)


searchfor = ['og', 'at']

df = pd.DataFrame([('cat', 1000.0), ('hat', 2000000.0), ('dog', 1000.0), ('fog', 330000.0),('pet', 330000.0)], columns=['col1', 'col2'])

   col1  col2
0   cat 1000.0
1   hat 2000000.0
2   dog 1000.0
3   fog 330000.0
4   pet 330000.0

Apply Lambda:

df["TrueFalse"] = df['col1'].apply(lambda x: 1 if any(i in x for i in searchfor) else 0)


    col1    col2        TrueFalse
0   cat     1000.0      1
1   hat     2000000.0   1
2   dog     1000.0      1
3   fog     330000.0    1
4   pet     330000.0    0

Adding div element to body or document in JavaScript

You can make your div HTML code and set it directly into body(Or any element) with following code:

var divStr = '<div class="text-warning">Some html</div>';
document.getElementsByTagName('body')[0].innerHTML += divStr;

Can pandas automatically recognize dates?

pandas read_csv method is great for parsing dates. Complete documentation at

you can even have the different date parts in different columns and pass the parameter:

parse_dates : boolean, list of ints or names, list of lists, or dict
If True -> try parsing the index. If [1, 2, 3] -> try parsing columns 1, 2, 3 each as a
separate date column. If [[1, 3]] -> combine columns 1 and 3 and parse as a single date
column. {‘foo’ : [1, 3]} -> parse columns 1, 3 as date and call result ‘foo’

The default sensing of dates works great, but it seems to be biased towards north american Date formats. If you live elsewhere you might occasionally be caught by the results. As far as I can remember 1/6/2000 means 6 January in the USA as opposed to 1 Jun where I live. It is smart enough to swing them around if dates like 23/6/2000 are used. Probably safer to stay with YYYYMMDD variations of date though. Apologies to pandas developers,here but i have not tested it with local dates recently.

you can use the date_parser parameter to pass a function to convert your format.

date_parser : function
Function to use for converting a sequence of string columns to an array of datetime
instances. The default uses dateutil.parser.parser to do the conversion.

Coerce multiple columns to factors at once

and, for completeness and with regards to this question asking about changing string columns only, there's mutate_if:

data <- cbind(stringVar = sample(c("foo","bar"),10,replace=TRUE),
              data.frame(matrix(sample(1:40), 10, 10, dimnames = list(1:10, LETTERS[1:10]))),stringsAsFactors=FALSE)     

factoredData = data %>% mutate_if(is.character,funs(factor(.)))

Move existing, uncommitted work to a new branch in Git

The common scenario is the following: I forgot to create the new branch for the new feature, and was doing all the work in the old feature branch. I have commited all the "old" work to the master branch, and I want my new branch to grow from the "master". I have not made a single commit of my new work. Here is the branch structure: "master"->"Old_feature"

git stash 
git checkout master
git checkout -b "New_branch"
git stash apply

How to continue the code on the next line in VBA

In VBA (and VB.NET) the line terminator (carriage return) is used to signal the end of a statement. To break long statements into several lines, you need to

Use the line-continuation character, which is an underscore (_), at the point at which you want the line to break. The underscore must be immediately preceded by a space and immediately followed by a line terminator (carriage return).

(From How to: Break and Combine Statements in Code)

In other words: Whenever the interpreter encounters the sequence <space>_<line terminator>, it is ignored and parsing continues on the next line. Note, that even when ignored, the line continuation still acts as a token separator, so it cannot be used in the middle of a variable name, for example. You also cannot continue a comment by using a line-continuation character.

To break the statement in your question into several lines you could do the following:

U_matrix(i, j, n + 1) = _
     k * b_xyt(xi, yi, tn) / (4 * hx * hy) * U_matrix(i + 1, j + 1, n) + _
     (k * (a_xyt(xi, yi, tn) / hx ^ 2 + d_xyt(xi, yi, tn) / (2 * hx)))

(Leading whitespaces are ignored.)

How to count the number of observations in R like Stata command count

The with function will let you use shorthand column references and sum will count TRUE results from the expression(s).

sum(with(aaa, sex==1 & group1==2))
## [1] 3

sum(with(aaa, sex==1 & group2=="A"))
## [1] 2

As @mnel pointed out, you can also do:

nrow(aaa[aaa$sex==1 & aaa$group1==2,])
## [1] 3

nrow(aaa[aaa$sex==1 & aaa$group2=="A",])
## [1] 2

The benefit of that is that you can do:

## [1] 6

And, the behaviour matches Stata's count almost exactly (syntax notwithstanding).

Meaning of "referencing" and "dereferencing" in C


& is the reference operator. It will refer the memory address to the pointer variable.


int *p;
int a=5;
p=&a; // Here Pointer variable p refers to the address of integer variable a.


Dereference operator * is used by the pointer variable to directly access the value of the variable instead of its memory address.


int *p;
int a=5;
int value=*p; // Value variable will get the value of variable a that pointer variable p pointing to.

Running conda with proxy

I was able to get it working without putting in the username and password:

conda config --set proxy_servers.https https://address:port

Setting the default Java character encoding

Try this :

    new OutputStreamWriter( new FileOutputStream("Your_file_fullpath" ),Charset.forName("UTF8"))

jQuery SVG, why can't I addClass?

Just add the missing prototype constructor to all SVG nodes:

SVGElement.prototype.hasClass = function (className) {
  return new RegExp('(\\s|^)' + className + '(\\s|$)').test(this.getAttribute('class'));

SVGElement.prototype.addClass = function (className) { 
  if (!this.hasClass(className)) {
    this.setAttribute('class', this.getAttribute('class') + ' ' + className);

SVGElement.prototype.removeClass = function (className) {
  var removedClass = this.getAttribute('class').replace(new RegExp('(\\s|^)' + className + '(\\s|$)', 'g'), '$2');
  if (this.hasClass(className)) {
    this.setAttribute('class', removedClass);

You can then use it this way without requiring jQuery:



All credit goes to Todd Moto.

KERNELBASE.dll Exception 0xe0434352 offset 0x000000000000a49d

0xe0434352 is the SEH code for a CLR exception. If you don't understand what that means, stop and read A Crash Course on the Depths of Win32™ Structured Exception Handling. So your process is not handling a CLR exception. Don't shoot the messenger, KERNELBASE.DLL is just the unfortunate victim. The perpetrator is MyApp.exe.

There should be a minidump of the crash in DrWatson folders with a full stack, it will contain everything you need to root cause the issue.

I suggest you wire up, in your myapp.exe code, AppDomain.UnhandledException and Application.ThreadException, as appropriate.

Running a CMD or BAT in silent mode

Use Bat To Exe Converter to do this
(Choose Direct Download Link)

1 - Open Bat to Exe Converter, select your Bat file.
2 - In Option menu select "Invisible Application", then press compile button.


Set div height to fit to the browser using CSS

I do not think you need float.

.container {_x000D_
  width: 100%;_x000D_
  height: 100%;_x000D_
.div1, .div2 {_x000D_
  display: inline-block;_x000D_
  margin: 0;_x000D_
  min-height: 100%;_x000D_
.div1 {_x000D_
  width: 25%;_x000D_
  background-color: green;_x000D_
.div2 {_x000D_
  width: 75%;_x000D_
  background-color: blue;_x000D_
<div class="container">_x000D_
  <div class="div1"></div><!--_x000D_
  --><div class="div2"></div>_x000D_

display: inline-block; is used to display blocks as inline (just like spans but keeping the block effect)

Comments in the html is used because you have 75% + 25% = 100%. The space in-between the divs counts (so you have 75% + 1%? + 25% = 101%, meaning line break)

How do you tell if caps lock is on using JavaScript?

Javascript Code

<script type="text/javascript">
   function isCapLockOn(e){
   kc = e.keyCode?e.keyCode:e.which;
   sk = e.shiftKey?e.shiftKey:((kc == 16)?true:false);
   if(((kc >= 65 && kc <= 90) && !sk)||((kc >= 97 && kc <= 122) && sk))
       document.getElementById('alert').style.visibility = 'visible';
       document.getElementById('alert').style.visibility = 'hidden';

We now need to associate this script using Html

<input type="password" name="txtPassword" onkeypress="isCapLockOn(event)" />
<div id="alert" style="visibility:hidden">Caps Lock is on.</div> 

How Can I Resolve:"can not open 'git-upload-pack' " error in eclipse?

You are using the wrong URL (you are using the URL for the html webpage). Try either of these instead:

  • git://

How can I read SMS messages from the device programmatically in Android?

From API 19 onwards you can make use of the Telephony Class for that; Since hardcored values won't retrieve messages in every devices because the content provider Uri changes from devices and manufacturers.

public void getAllSms(Context context) {

    ContentResolver cr = context.getContentResolver();
    Cursor c = cr.query(Telephony.Sms.CONTENT_URI, null, null, null, null);
    int totalSMS = 0;
    if (c != null) {
        totalSMS = c.getCount();
        if (c.moveToFirst()) {
            for (int j = 0; j < totalSMS; j++) {
                String smsDate = c.getString(c.getColumnIndexOrThrow(Telephony.Sms.DATE));
                String number = c.getString(c.getColumnIndexOrThrow(Telephony.Sms.ADDRESS));
                String body = c.getString(c.getColumnIndexOrThrow(Telephony.Sms.BODY));
                Date dateFormat= new Date(Long.valueOf(smsDate));
                String type;
                switch (Integer.parseInt(c.getString(c.getColumnIndexOrThrow(Telephony.Sms.TYPE)))) {
                    case Telephony.Sms.MESSAGE_TYPE_INBOX:
                        type = "inbox";
                    case Telephony.Sms.MESSAGE_TYPE_SENT:
                        type = "sent";
                    case Telephony.Sms.MESSAGE_TYPE_OUTBOX:
                        type = "outbox";



    } else {
        Toast.makeText(this, "No message to show!", Toast.LENGTH_SHORT).show();

receiving error: 'Error: SSL Error: SELF_SIGNED_CERT_IN_CHAIN' while using npm

Putting this before the command seems to work NODE_TLS_REJECT_UNAUTHORIZED=0. ex: NODE_TLS_REJECT_UNAUTHORIZED=0 npm ...

It would be best to figure out how to make node see self signed certificate as valid. strict-ssl suggestion above didn't work for me for some reason. If you understand the security implications and need a temporary quick fix, this is what I found in some random github issues during Google search of the error.

Conditional WHERE clause with CASE statement in Oracle

You can write the where clause as:

where (case when (:stateCode = '') then (1)
            when (:stateCode != '') and (vw.state_cd in (:stateCode)) then 1
            else 0)
       end) = 1;

Alternatively, remove the case entirely:

where (:stateCode = '') or
      ((:stateCode != '') and vw.state_cd in (:stateCode));

Or, even better:

where (:stateCode = '') or vw.state_cd in (:stateCode)

How do I calculate r-squared using Python and Numpy?

From scipy.stats.linregress source. They use the average sum of squares method.

import numpy as np

x = np.array(x)
y = np.array(y)

# average sum of squares:
ssxm, ssxym, ssyxm, ssym = np.cov(x, y, bias=1).flat

r_num = ssxym
r_den = np.sqrt(ssxm * ssym)
r = r_num / r_den

if r_den == 0.0:
    r = 0.0
    r = r_num / r_den

    if r > 1.0:
        r = 1.0
    elif r < -1.0:
        r = -1.0

How does += (plus equal) work?

...and don't forget what happens when you mix types:

x = 127;
x += " hours "
// x is now a string: "127 hours "
x += 1 === 0;
// x is still a string: "127 hours false"

Java - Getting Data from MySQL database

Something like this would do:

public static void main(String[] args) {

    Connection con = null;
    Statement st = null;
    ResultSet rs = null;

    String url = "jdbc:mysql://localhost/t";
    String user = "";
    String password = "";

    try {
        con = DriverManager.getConnection(url, user, password);
        st = con.createStatement();
        rs = st.executeQuery("SELECT * FROM posts ORDER BY id DESC LIMIT 1;");

        if ( {//get first result
            System.out.println(rs.getString(1));//coloumn 1

    } catch (SQLException ex) {
        Logger lgr = Logger.getLogger(Version.class.getName());
        lgr.log(Level.SEVERE, ex.getMessage(), ex);

    } finally {
        try {
            if (rs != null) {
            if (st != null) {
            if (con != null) {

        } catch (SQLException ex) {
            Logger lgr = Logger.getLogger(Version.class.getName());
            lgr.log(Level.WARNING, ex.getMessage(), ex);

you can iterate over the results with a while like this:

System.out.println(rs.getString("Colomn_Name"));//or getString(1) for coloumn 1 etc

There are many other great tutorial out there like these to list a few:

As for your use of Class.forName("com.mysql.jdbc.Driver").newInstance(); see JDBC connection- Class.forName vs Class.forName().newInstance? which shows how you can just use Class.forName("com.mysql.jdbc.Driver") as its not necessary to initiate it yourself


Postman - How to see request with headers and body data with variables substituted

Even though they are separate windows but the request you send from Postman, it's details should be available in network tab of developer tools. Just make sure you are not sending any other http traffic during that time, just for clarity.

The difference between bracket [ ] and double bracket [[ ]] for accessing the elements of a list or dataframe

In addition:

Following the L I N K of the A N S W E R here.

Here is a little example addressing the following point:

x[i, j] vs x[[i, j]]

df1   <- data.frame(a = 1:3)
df1$b <- list(4:5, 6:7, 8:9)



How do I convert datetime to ISO 8601 in PHP

How to convert from ISO 8601 to unixtimestamp :

// Output : 1326883500

How to convert from unixtimestamp to ISO 8601 (timezone server) :

date_format(date_timestamp_set(new DateTime(), 1326883500), 'c');
// Output : 2012-01-18T11:45:00+01:00

How to convert from unixtimestamp to ISO 8601 (GMT) :

date_format(date_create('@'. 1326883500), 'c') . "\n";
// Output : 2012-01-18T10:45:00+00:00

How to convert from unixtimestamp to ISO 8601 (custom timezone) :

date_format(date_timestamp_set(new DateTime(), 1326883500)->setTimezone(new DateTimeZone('America/New_York')), 'c');
// Output : 2012-01-18T05:45:00-05:00

How can I export the schema of a database in PostgreSQL?

If you only want the create tables, then you can do pg_dump -s databasename | awk 'RS="";/CREATE TABLE[^;]*;/'

What does `set -x` do?

set -x

Prints a trace of simple commands, for commands, case commands, select commands, and arithmetic for commands and their arguments or associated word lists after they are expanded and before they are executed. The value of the PS4 variable is expanded and the resultant value is printed before the command and its expanded arguments.



set -x
echo `expr 10 + 20 `
+ expr 10 + 20
+ echo 30

set +x
echo `expr 10 + 20 `

Above example illustrates the usage of set -x. When it is used, above arithmetic expression has been expanded. We could see how a singe line has been evaluated step by step.

  • First step expr has been evaluated.
  • Second step echo has been evaluated.

To know more about set ? visit this link

when it comes to your shell script,

[ "$DEBUG" == 'true' ] && set -x

Your script might have been printing some additional lines of information when the execution mode selected as DEBUG. Traditionally people used to enable debug mode when a script called with optional argument such as -d

How can I convert string to double in C++?

#include <iostream>
#include <string>
using namespace std;

int main()
    cout << stod("  99.999  ") << endl;

Output: 99.999 (which is double, whitespace was automatically stripped)

Since C++11 converting string to floating-point values (like double) is available with functions:
stof - convert str to a float
stod - convert str to a double
stold - convert str to a long double

I want a function that returns 0 when the string is not numerical.

You can add try catch statement when stod throws an exception.

Javascript: open new page in same window

The second parameter of is a string representing the name of the target window.

Set it to: "_self".

<a href="javascript:q=(document.location.href);void(open(''+escape(q),'_self','resizable,location,menubar,toolbar,scrollbars,status'));">click here</a>

Sidenote: The following question gives an overview of an arguably better way to bind event handlers to HTML links.

What's the best way to replace links with js functions?

javascript - replace dash (hyphen) with a space

var str = "This-is-a-news-item-";
while (str.contains("-")) {
  str = str.replace("-", ' ');

I found that one use of str.replace() would only replace the first hyphen, so I looped thru while the input string still contained any hyphens, and replaced them all.

Concatenating string and integer in python

Modern string formatting:

"{} and {}".format("string", 1)

What is private bytes, virtual bytes, working set?

The definition of the perfmon counters has been broken since the beginning and for some reason appears to be too hard to correct.

A good overview of Windows memory management is available in the video "Mysteries of Memory Management Revealed" on MSDN: It covers more topics than needed to track memory leaks (eg working set management) but gives enough detail in the relevant topics.

To give you a hint of the problem with the perfmon counter descriptions, here is the inside story about private bytes from "Private Bytes Performance Counter -- Beware!" on MSDN:

Q: When is a Private Byte not a Private Byte?

A: When it isn't resident.

The Private Bytes counter reports the commit charge of the process. That is to say, the amount of space that has been allocated in the swap file to hold the contents of the private memory in the event that it is swapped out. Note: I'm avoiding the word "reserved" because of possible confusion with virtual memory in the reserved state which is not committed.

From "Performance Planning" on MSDN:

3.3 Private Bytes

3.3.1 Description

Private memory, is defined as memory allocated for a process which cannot be shared by other processes. This memory is more expensive than shared memory when multiple such processes execute on a machine. Private memory in (traditional) unmanaged dlls usually constitutes of C++ statics and is of the order of 5% of the total working set of the dll.

how to get domain name from URL

Just for knowledge:

''.replace(/^(https?:\/\/)([a-z]{3}[0-9]?\.)?(\w+)(\.[a-zA-Z]{2,3})(\.[a-zA-Z]{2,3})?.*$/, '$3$4$5');

# returns 

How to print Unicode character in Python?

This fixes UTF-8 printing in python:

UTF8Writer = codecs.getwriter('utf8')
sys.stdout = UTF8Writer(sys.stdout)

psql: FATAL: Peer authentication failed for user "dev"


psql -U user_name  -h -d db_name


  • -U is the database user name
  • -h is the hostname/IP of the local server, thus avoiding Unix domain sockets
  • -d is the database name to connect to

This is then evaluated as a "network" connection by Postgresql rather than a Unix domain socket connection, thus not evaluated as a "local" connect as you might see in pg_hba.conf:

local   all             all                                     peer

Issue with virtualenv - cannot activate

If you are using windows, just run .\Scripts\activate. Mind that the backslash plays the trick!

Python pandas: fill a dataframe row by row

df['y'] will set a column

since you want to set a row, use .loc

Note that .ix is equivalent here, yours failed because you tried to assign a dictionary to each element of the row y probably not what you want; converting to a Series tells pandas that you want to align the input (for example you then don't have to to specify all of the elements)

In [7]: df = pandas.DataFrame(columns=['a','b','c','d'], index=['x','y','z'])

In [8]: df.loc['y'] = pandas.Series({'a':1, 'b':5, 'c':2, 'd':3})

In [9]: df
     a    b    c    d
x  NaN  NaN  NaN  NaN
y    1    5    2    3
z  NaN  NaN  NaN  NaN

How to empty a list in C#?

You need the Clear() function on the list, like so.

List<object> myList = new List<object>();

myList.Add(new object()); // Add something to the list

myList.Clear() // Our list is now empty

Python Pandas: Get index of rows which column matches certain value

Simple way is to reset the index of the DataFrame prior to filtering:

df_reset = df.reset_index()

Bit hacky, but it's quick!

Send mail via CMD console

A couple more command-line mailer programs:

Both support SSL too.

How to show current user name in a cell?

if you don't want to create a UDF in VBA or you can't, this could be an alternative.

=Cell("Filename",A1) this will give you the full file name, and from this you could get the user name with something like this:


This Formula runs only from a workbook saved earlier.

You must start from 4th position because of the first slash from the drive.

How do I trap ctrl-c (SIGINT) in a C# console app

This question is very similar to:

Capture console exit C#

Here is how I solved this problem, and dealt with the user hitting the X as well as Ctrl-C. Notice the use of ManualResetEvents. These will cause the main thread to sleep which frees the CPU to process other threads while waiting for either exit, or cleanup. NOTE: It is necessary to set the TerminationCompletedEvent at the end of main. Failure to do so causes unnecessary latency in termination due to the OS timing out while killing the application.

namespace CancelSample
    using System;
    using System.Threading;
    using System.Runtime.InteropServices;

    internal class Program
        /// <summary>
        /// Adds or removes an application-defined HandlerRoutine function from the list of handler functions for the calling process
        /// </summary>
        /// <param name="handler">A pointer to the application-defined HandlerRoutine function to be added or removed. This parameter can be NULL.</param>
        /// <param name="add">If this parameter is TRUE, the handler is added; if it is FALSE, the handler is removed.</param>
        /// <returns>If the function succeeds, the return value is true.</returns>
        private static extern bool SetConsoleCtrlHandler(ConsoleCloseHandler handler, bool add);

        /// <summary>
        /// The console close handler delegate.
        /// </summary>
        /// <param name="closeReason">
        /// The close reason.
        /// </param>
        /// <returns>
        /// True if cleanup is complete, false to run other registered close handlers.
        /// </returns>
        private delegate bool ConsoleCloseHandler(int closeReason);

        /// <summary>
        ///  Event set when the process is terminated.
        /// </summary>
        private static readonly ManualResetEvent TerminationRequestedEvent;

        /// <summary>
        /// Event set when the process terminates.
        /// </summary>
        private static readonly ManualResetEvent TerminationCompletedEvent;

        /// <summary>
        /// Static constructor
        /// </summary>
        static Program()
            // Do this initialization here to avoid polluting Main() with it
            // also this is a great place to initialize multiple static
            // variables.
            TerminationRequestedEvent = new ManualResetEvent(false);
            TerminationCompletedEvent = new ManualResetEvent(false);
            SetConsoleCtrlHandler(OnConsoleCloseEvent, true);

        /// <summary>
        /// The main console entry point.
        /// </summary>
        /// <param name="args">The commandline arguments.</param>
        private static void Main(string[] args)
            // Wait for the termination event
            while (!TerminationRequestedEvent.WaitOne(0))
                // Something to do while waiting

            // Sleep until termination

            // Print a message which represents the operation

            // Set this to terminate immediately (if not set, the OS will
            // eventually kill the process)

        /// <summary>
        /// Method called when the user presses Ctrl-C
        /// </summary>
        /// <param name="reason">The close reason</param>
        private static bool OnConsoleCloseEvent(int reason)
            // Signal termination

            // Wait for cleanup

            // Don't run other handlers, just exit.
            return true;

combining two data frames of different lengths

I don't actually get an error with this.

a <-,50, replace=T),runif(100)), nrow=50))
b <- sample(letters,10, replace=T)
c <- cbind(a,b)

I used letters incase joining all numerics had different functionality (which it didn't). Your 'first data frame', which is actually just a vector', is just repeated 5 times in that 4th column...

But all the comments from the gurus to the question are still relevant :)

What is the command to truncate a SQL Server log file?

Since the answer for me was buried in the comments. For SQL Server 2012 and beyond, you can use the following:

DBCC SHRINKFILE (Database_Log, 1)

PHP fwrite new line

How about you store it like this? Maybe in username:password format, so


Then you can use list($username,$password) = explode(':',file_get_contents('users.txt')); to parse the data on your end.

How do I implement IEnumerable<T>

make mylist into a List<MyObject>, is one option

Command line: search and replace in all filenames matched by grep

I like and used the above solution or a system wide search and replace among thousands of files:

find -name '*.htm?' -print -exec sed -i.bak 's/foo/bar/g' {} \;

I assume with the '*.htm?' instead of .html it searches and finds .htm and .html files alike.

I replace the .bak with the more system wide used tilde (~) to make clean up of backup files easier.

Convert Json Array to normal Java list

Using Java Streams you can just use an IntStream mapping the objects:

JSONArray array = new JSONArray(jsonString);
List<String> result = IntStream.range(0, array.length())

How to convert minutes to Hours and minutes (hh:mm) in java

It can be done like this

        int totalMinutesInt = Integer.valueOf(totalMinutes.toString());

        int hours = totalMinutesInt / 60;
        int hoursToDisplay = hours;

        if (hours > 12) {
            hoursToDisplay = hoursToDisplay - 12;

        int minutesToDisplay = totalMinutesInt - (hours * 60);

        String minToDisplay = null;
        if(minutesToDisplay == 0 ) minToDisplay = "00";     
        else if( minutesToDisplay < 10 ) minToDisplay = "0" + minutesToDisplay ;
        else minToDisplay = "" + minutesToDisplay ;

        String displayValue = hoursToDisplay + ":" + minToDisplay;

        if (hours < 12)
            displayValue = displayValue + " AM";
            displayValue = displayValue + " PM";

        return displayValue;
    } catch (Exception e) {
        LOGGER.error("Error while converting currency.");
    return totalMinutes.toString();

Check if a string is null or empty in XSLT

In some cases, you might want to know when the value is specifically null, which is particularly necessary when using XML which has been serialized from .NET objects. While the accepted answer works for this, it also returns the same result when the string is blank or empty, i.e. '', so you can't differentiate.

        <id>item 1</id>
        <CategoryName xsi:nil="true" />

So you can simply test the attribute.

<xsl:if test="CategoryName/@xsi:nil='true'">
   Hello World.

Sometimes it's necessary to know the exact state and you can't simply check if CategoryName is instantiated, because unlike say Javascript

<xsl:if test="CategoryName">
   Hello World.

Will return true for a null element.

Pass multiple parameters in Html.BeginForm MVC

Another option I like, which can be generalized once I start seeing the code not conform to DRY, is to use one controller that redirects to another controller.

public ActionResult ClientIdSearch(int cid)
  var action = String.Format("Details/{0}", cid);

  return RedirectToAction(action, "Accounts");

I find this allows me to apply my logic in one location and re-use it without have to sprinkle JavaScript in the views to handle this. And, as I mentioned I can then refactor for re-use as I see this getting abused.

Does Python have a ternary conditional operator?

More a tip than an answer (don't need to repeat the obvious for the hundreth time), but I sometimes use it as a oneliner shortcut in such constructs:

if conditionX:

, becomes:

print('yes') if conditionX else print('nah')

Some (many :) may frown upon it as unpythonic (even, ruby-ish :), but I personally find it more natural - i.e. how you'd express it normally, plus a bit more visually appealing in large blocks of code.

generate random double numbers in c++

This solution requires C++11 (or TR1).

#include <random>

int main()
   double lower_bound = 0;
   double upper_bound = 10000;
   std::uniform_real_distribution<double> unif(lower_bound,upper_bound);
   std::default_random_engine re;
   double a_random_double = unif(re);

   return 0;

For more details see John D. Cook's "Random number generation using C++ TR1".

See also Stroustrup's "Random number generation".

document.getElementById(id).focus() is not working for firefox or chrome

Try location.href='#yourId'

Like this:

<button onclick="javascript:location.href='#yourId'">Show</button>

Average of multiple columns

Select Req_ID, sum(R1+R2+R3+R4+R5)/5 as Average
from Request
Group by Req_ID;

"A namespace cannot directly contain members such as fields or methods"

The snippet you're showing doesn't seem to be directly responsible for the error.

This is how you can CAUSE the error:

namespace MyNameSpace

   class MyClass

If you don't immediately see what is "outside" the class, this may be due to misplaced or extra closing bracket(s) }.

How do I check the operating system in Python?

You can get a pretty coarse idea of the OS you're using by checking sys.platform.

Once you have that information you can use it to determine if calling something like os.uname() is appropriate to gather more specific information. You could also use something like Python System Information on unix-like OSes, or pywin32 for Windows.

There's also psutil if you want to do more in-depth inspection without wanting to care about the OS.

Delete element in a slice

In golang's wiki it show some tricks for slice, including delete an element from slice.

Link: enter link description here

For example a is the slice which you want to delete the number i element.

a = append(a[:i], a[i+1:]...)


a = a[:i+copy(a[i:], a[i+1:])]

Warning: mysqli_query() expects at least 2 parameters, 1 given. What?

the mysqli_queryexcepts 2 parameters , first variable is mysqli_connectequivalent variable , second one is the query you have provided

$name1 = mysqli_connect(localhost,tdoylex1_dork,dorkk,tdoylex1_dork);

$name2 = mysqli_query($name1,"SELECT name FROM users ORDER BY RAND() LIMIT 1");

Check if string contains a value in array

You are checking whole string to the array values. So output is always false.

I use both array_filter and strpos in this case.

$urls= array('', '', '');
$string = 'my domain name is';
$check = array_filter($urls, function($url){
    global $string;
    if(strpos($string, $url))
        return true;
echo $check?"found":"not found";

What is the difference between Sprint and Iteration in Scrum and length of each Sprint?

The important thing about a sprint is that: within a sprint the functionality that is to be delivered is fixed.

A sprint is normally an iteration. But you can for example have a 4 week sprint, but have 4 one week "internal" iterations within that sprint.

There is a lot of discussion about the length of sprints. I think that if you do it according to the book they should all be the same length.

We have found that a short first sprint to get the development environment up and running, followed by longer basic functionality sprints, then short sprints towards the end of the project, has worked for us.

What is the difference between T(n) and O(n)?

Short explanation:

If an algorithm is of T(g(n)), it means that the running time of the algorithm as n (input size) gets larger is proportional to g(n).

If an algorithm is of O(g(n)), it means that the running time of the algorithm as n gets larger is at most proportional to g(n).

Normally, even when people talk about O(g(n)) they actually mean T(g(n)) but technically, there is a difference.

More technically:

O(n) represents upper bound. T(n) means tight bound. O(n) represents lower bound.

f(x) = T(g(x)) iff f(x) = O(g(x)) and f(x) = O(g(x))

Basically when we say an algorithm is of O(n), it's also O(n2), O(n1000000), O(2n), ... but a T(n) algorithm is not T(n2).

In fact, since f(n) = T(g(n)) means for sufficiently large values of n, f(n) can be bound within c1g(n) and c2g(n) for some values of c1 and c2, i.e. the growth rate of f is asymptotically equal to g: g can be a lower bound and and an upper bound of f. This directly implies f can be a lower bound and an upper bound of g as well. Consequently,

f(x) = T(g(x)) iff g(x) = T(f(x))

Similarly, to show f(n) = T(g(n)), it's enough to show g is an upper bound of f (i.e. f(n) = O(g(n))) and f is a lower bound of g (i.e. f(n) = O(g(n)) which is the exact same thing as g(n) = O(f(n))). Concisely,

f(x) = T(g(x)) iff f(x) = O(g(x)) and g(x) = O(f(x))

There are also little-oh and little-omega (?) notations representing loose upper and loose lower bounds of a function.

To summarize:

f(x) = O(g(x)) (big-oh) means that the growth rate of f(x) is asymptotically less than or equal to to the growth rate of g(x).

f(x) = O(g(x)) (big-omega) means that the growth rate of f(x) is asymptotically greater than or equal to the growth rate of g(x)

f(x) = o(g(x)) (little-oh) means that the growth rate of f(x) is asymptotically less than the growth rate of g(x).

f(x) = ?(g(x)) (little-omega) means that the growth rate of f(x) is asymptotically greater than the growth rate of g(x)

f(x) = T(g(x)) (theta) means that the growth rate of f(x) is asymptotically equal to the growth rate of g(x)

For a more detailed discussion, you can read the definition on Wikipedia or consult a classic textbook like Introduction to Algorithms by Cormen et al.

Mutex example / tutorial?

The best threads tutorial I know of is here:

I like that it's written about the API, rather than about a particular implementation, and it gives some nice simple examples to help you understand synchronization.

How to search for a file in the CentOS command line

CentOS is Linux, so as in just about all other Unix/Linux systems, you have the find command. To search for files within the current directory:

find -name "filename"

You can also have wildcards inside the quotes, and not just a strict filename. You can also explicitly specify a directory to start searching from as the first argument to find:

find / -name "filename"

will look for "filename" or all the files that match the regex expression in between the quotes, starting from the root directory. You can also use single quotes instead of double quotes, but in most cases you don't need either one, so the above commands will work without any quotes as well. Also, for example, if you're searching for java files and you know they are somewhere in your /home/username, do:

find /home/username -name *.java

There are many more options to the find command and you should do a:

man find

to learn more about it.

One more thing: if you start searching from / and are not root or are not sudo running the command, you might get warnings that you don't have permission to read certain directories. To ignore/remove those, do:

find / -name 'filename' 2>/dev/null

That just redirects the stderr to /dev/null.

JWT (JSON Web Token) automatic prolongation of expiration

Today, lots of people opt for doing session management with JWTs without being aware of what they are giving up for the sake of perceived simplicity. My answer elaborates on the 2nd part of the questions:

What is the real benefit then? Why not have only one token (not JWT) and keep the expiration on the server?

Are there other options? Is using JWT not suited for this scenario?

JWTs are capable of supporting basic session management with some limitations. Being self-describing tokens, they don't require any state on the server-side. This makes them appealing. For instance, if the service doesn't have a persistence layer, it doesn't need to bring one in just for session management.

However, statelessness is also the leading cause of their shortcomings. Since they are only issued once with fixed content and expiration, you can't do things you would like to with a typical session management setup.

Namely, you can't invalidate them on-demand. This means you can't implement a secure logout as there is no way to expire already issued tokens. You also can't implement idle timeout for the same reason. One solution is to keep a blacklist, but that introduces state.

I wrote a post explaining these drawbacks in more detail. To be clear, you can work around these by adding more complexity (sliding sessions, refresh tokens, etc.)

As for other options, if your clients only interact with your service via a browser, I strongly recommend using a cookie-based session management solution. I also compiled a list authentication methods currently widely used on the web.

Why does the 'int' object is not callable error occur when using the sum() function?

This means that somewhere else in your code, you have something like:

sum = 0

Which shadows the builtin sum (which is callable) with an int (which isn't).

how to insert date and time in oracle?

Try this:

...(to_date('2011/04/22 08:30:00', 'yyyy/mm/dd hh24:mi:ss'));

Sql Server 'Saving changes is not permitted' error ? Prevent saving changes that require table re-creation

To change the Prevent saving changes that require the table re-creation option, follow these steps:

Open SQL Server Management Studio (SSMS). On the Tools menu, click Options.

In the navigation pane of the Options window, click Designers.

Select or clear the Prevent saving changes that require the table re-creation check box, and then click OK.

Note: If you disable this option, you are not warned when you save the table that the changes that you made have changed the metadata structure of the table. In this case, data loss may occur when you save the table.

enter image description here

Safari 3rd party cookie iframe trick no longer working?

I had the same problem and today I found a fix that works fine for me. If the user agent contains Safari and no cookies are set, I redirect the user to the OAuth Dialog:

<?php if ( ! count($_COOKIE) > 0 && strpos($_SERVER['HTTP_USER_AGENT'], 'Safari')) { ?>
<script type="text/javascript"> = '';
<?php } ?>

After authentication and asking for permissions the OAuth Dialog will redirect to my URI in the top location. So setting cookies is possible. For all of our canvas and page tab apps I have already included the following script:

<script type="text/javascript">
    if (top.location.href==location.href) top.location.href = 'MY_TAB_URL';

So the user will be redirected again to the Facebook page tab with a valid cookie already set and the signed request is posted again.

Setting graph figure size

A different approach.
On the figure() call specify properties or modify the figure handle properties after h = figure().

This creates a full screen figure based on normalized units.
figure('units','normalized','outerposition',[0 0 1 1])

The units property can be adjusted to inches, centimeters, pixels, etc.

See figure documentation.

How to set a value to a file input in HTML?

You cannot, due to security reasons.


<form name="foo" method="post" enctype="multipart/form-data">
    <input type="file" value="c:/passwords.txt">

You don't want the websites you visit to be able to do this, do you? =)

How to load a xib file in a UIView

You could try:

UIView *firstViewUIView = [[[NSBundle mainBundle] loadNibNamed:@"firstView" owner:self options:nil] firstObject];
[self.view.containerView addSubview:firstViewUIView];

Left padding a String with Zeros

If your string contains numbers only, you can make it an integer and then do padding:

String.format("%010d", Integer.parseInt(mystring));

If not I would like to know how it can be done.

Get int value from enum in C#

Declare it as a static class having public constants:

public static class Question
    public const int Role = 2;
    public const int ProjectFunding = 3;
    public const int TotalEmployee = 4;
    public const int NumberOfServers = 5;
    public const int TopBusinessConcern = 6;

And then you can reference it as Question.Role, and it always evaluates to an int or whatever you define it as.

Error: ANDROID_HOME is not set and "android" command not in your PATH. You must fulfill at least one of these conditions.

ANDROID_HOME is deprecated now instead of using ANDROID_HOME use ANDROID_SDK_ROOT

as per Google android documentation -

ANDROID_SDK_ROOT sets the path to the SDK installation directory. Once set, the value does not typically change, and can be shared by multiple users on the same machine. ANDROID_HOME, which also points to the SDK installation directory, is deprecated.

If you continue to use it, the following rules apply:

  • If ANDROID_HOME is defined and contains a valid SDK installation, its value is used instead of the value in ANDROID_SDK_ROOT.
  • If ANDROID_HOME is not defined, the value in ANDROID_SDK_ROOT is used.
  • If ANDROID_HOME is defined but does not exist or does not contain a valid SDK installation, the value in ANDROID_SDK_ROOT is used instead.

For details follow this Android Documentation link

MySQL/SQL: Group by date only on a Datetime column

Cast the datetime to a date, then GROUP BY using this syntax:

SELECT SUM(foo), DATE(mydate) FROM a_table GROUP BY DATE(a_table.mydate);

Or you can GROUP BY the alias as @orlandu63 suggested:

SELECT SUM(foo), DATE(mydate) DateOnly FROM a_table GROUP BY DateOnly;

Though I don't think it'll make any difference to performance, it is a little clearer.

CSS - Overflow: Scroll; - Always show vertical scroll bar?

This will make the scroll bars always display when there is content within windows that must be scrolled to access, it applies to all windows and all apps on the Mac:

Launch System Preferences from the ? Apple menu Click on the “General” settings panel Look for ‘Show scroll bars’ and select the radiobox next to “Always” Close out of System Preferences when finished

SQL grouping by month and year

For mariaDB you can:

FROM [Order]
DATE_FORMAT(date, '%m-%Y')


How to use data-binding with Fragment

Kotlin syntax:

lateinit var binding: MartianDataBinding
override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View? {
    binding = DataBindingUtil.inflate(inflater, R.layout.martian_data, container, false)
    return binding.root

Can I change a column from NOT NULL to NULL without dropping it?


ALTER TABLE myTable MODIFY myColumn {DataType} NULL

How to convert a time string to seconds?

It looks like you're willing to strip fractions of a second... the problem is you can't use '00' as the hour with %I

>>> time.strptime('00:00:00,000'.split(',')[0],'%H:%M:%S')
time.struct_time(tm_year=1900, tm_mon=1, tm_mday=1, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=0, tm_yday=1, tm_isdst=-1)

Using StringWriter for XML Serialization

It may have been covered elsewhere but simply changing the encoding line of the XML source to 'utf-16' allows the XML to be inserted into a SQL Server 'xml'data type.

using (DataSetTableAdapters.SQSTableAdapter tbl_SQS = new DataSetTableAdapters.SQSTableAdapter())
        bodyXML = @"<?xml version="1.0" encoding="UTF-8" standalone="yes"?><test></test>";
        bodyXMLutf16 = bodyXML.Replace("UTF-8", "UTF-16");
        tbl_SQS.Insert(messageID, receiptHandle, md5OfBody, bodyXMLutf16, sourceType);
    catch (System.Data.SqlClient.SqlException ex)

The result is all of the XML text is inserted into the 'xml' data type field but the 'header' line is removed. What you see in the resulting record is just


Using the serialization method described in the "Answered" entry is a way of including the original header in the target field but the result is that the remaining XML text is enclosed in an XML <string></string> tag.

The table adapter in the code is a class automatically built using the Visual Studio 2013 "Add New Data Source: wizard. The five parameters to the Insert method map to fields in a SQL Server table.

Total memory used by Python process?

I like it, thank you for @bayer. I get a specific process count tool, now.

# Megabyte.
$ ps aux | grep python | awk '{sum=sum+$6}; END {print sum/1024 " MB"}'
87.9492 MB

# Byte.
$ ps aux | grep python | awk '{sum=sum+$6}; END {print sum " KB"}'
90064 KB

Attach my process list.

$ ps aux  | grep python
root       943  0.0  0.1  53252  9524 ?        Ss   Aug19  52:01 /usr/bin/python /usr/local/bin/beaver -c /etc/beaver/beaver.conf -l /var/log/beaver.log -P /var/run/
root       950  0.6  0.4 299680 34220 ?        Sl   Aug19 568:52 /usr/bin/python /usr/local/bin/beaver -c /etc/beaver/beaver.conf -l /var/log/beaver.log -P /var/run/
root      3803  0.2  0.4 315692 36576 ?        S    12:43   0:54 /usr/bin/python /usr/local/bin/beaver -c /etc/beaver/beaver.conf -l /var/log/beaver.log -P /var/run/
jonny    23325  0.0  0.1  47460  9076 pts/0    S+   17:40   0:00 python
jonny    24651  0.0  0.0  13076   924 pts/4    S+   18:06   0:00 grep python


'DataFrame' object has no attribute 'sort'

Pandas Sorting 101

sort has been replaced in v0.20 by DataFrame.sort_values and DataFrame.sort_index. Aside from this, we also have argsort.

Here are some common use cases in sorting, and how to solve them using the sorting functions in the current API. First, the setup.

# Setup
df = pd.DataFrame({'A': list('accab'), 'B': np.random.choice(10, 5)})    
   A  B
0  a  7
1  c  9
2  c  3
3  a  5
4  b  2

Sort by Single Column

For example, to sort df by column "A", use sort_values with a single column name:


   A  B
0  a  7
3  a  5
4  b  2
1  c  9
2  c  3

If you need a fresh RangeIndex, use DataFrame.reset_index.

Sort by Multiple Columns

For example, to sort by both col "A" and "B" in df, you can pass a list to sort_values:

df.sort_values(by=['A', 'B'])

   A  B
3  a  5
0  a  7
4  b  2
2  c  3
1  c  9

Sort By DataFrame Index

df2 = df.sample(frac=1)

   A  B
1  c  9
0  a  7
2  c  3
3  a  5
4  b  2

You can do this using sort_index:


   A  B
0  a  7
1  c  9
2  c  3
3  a  5
4  b  2

# False
# True

Here are some comparable methods with their performance:

%timeit df2.sort_index()                                                                                                                  
%timeit df2.iloc[df2.index.argsort()]                                                                                                     
%timeit df2.reindex(np.sort(df2.index))                                                                                                   

605 µs ± 13.6 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)
610 µs ± 24.2 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)
581 µs ± 7.63 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)

Sort by List of Indices

For example,

idx = df2.index.argsort()
# array([0, 7, 2, 3, 9, 4, 5, 6, 8, 1])

This "sorting" problem is actually a simple indexing problem. Just passing integer labels to iloc will do.


   A  B
1  c  9
0  a  7
2  c  3
3  a  5
4  b  2

Compiler error: "class, interface, or enum expected"

class, interface, or enum expected

The above error is even possible when import statement is miss spelled. A proper statement is "import;"

If by mistake while code writing/editing it is miss written like "t;"

compiler will show "class, interface, or enum expected"

Absolute Positioning & Text Alignment

Try this:

You need to add left: 0 and right: 0 (not supported by IE6). Or specify a width

How do I change the ID of a HTML element with JavaScript?

You can modify the id without having to use getElementById


<div id = 'One' onclick = " = 'Two'; return false;">One</div>

You can see it here:

Tested with Mozilla Firefox 22 and Google Chrome 60.0

Fastest way to convert Image to Byte array

public static class HelperExtensions
    //Convert Image to byte[] array:
    public static byte[] ToByteArray(this Image imageIn)
        var ms = new MemoryStream();
        imageIn.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
        return ms.ToArray();

    //Convert byte[] array to Image:
    public static Image ToImage(this byte[] byteArrayIn)
        var ms = new MemoryStream(byteArrayIn);
        var returnImage = Image.FromStream(ms);
        return returnImage;

Use a content script to access the page context variables and functions

If you wish to inject pure function, instead of text, you can use this method:

function inject(){_x000D_ = 'blue';_x000D_
// this includes the function as text and the barentheses make it run itself._x000D_
var actualCode = "("+inject+")()"; _x000D_
document.documentElement.setAttribute('onreset', actualCode);_x000D_
document.documentElement.dispatchEvent(new CustomEvent('reset'));_x000D_

And you can pass parameters (unfortunatelly no objects and arrays can be stringifyed) to the functions. Add it into the baretheses, like so:

function inject(color){_x000D_ = color;_x000D_
// this includes the function as text and the barentheses make it run itself._x000D_
var color = 'yellow';_x000D_
var actualCode = "("+inject+")("+color+")"; 

Apply .gitignore on an existing repository already tracking large number of files

Here is one way to “untrack” any files that are would otherwise be ignored under the current set of exclude patterns:

(GIT_INDEX_FILE=some-non-existent-file \
git ls-files --exclude-standard --others --directory --ignored -z) |
xargs -0 git rm --cached -r --ignore-unmatch --

This leaves the files in your working directory but removes them from the index.

The trick used here is to provide a non-existent index file to git ls-files so that it thinks there are no tracked files. The shell code above asks for all the files that would be ignored if the index were empty and then removes them from the actual index with git rm.

After the files have been “untracked”, use git status to verify that nothing important was removed (if so adjust your exclude patterns and use git reset -- path to restore the removed index entry). Then make a new commit that leaves out the “crud”.

The “crud” will still be in any old commits. You can use git filter-branch to produce clean versions of the old commits if you really need a clean history (n.b. using git filter-branch will “rewrite history”, so it should not be undertaken lightly if you have any collaborators that have pulled any of your historical commits after the “crud” was first introduced).

How to declare a global variable in React?

Create a file named "config.js" in ./src folder with this content:

module.exports = global.config = {
    i18n: {
        welcome: {
            en: "Welcome",
            fa: "??? ?????"
        // rest of your translation object
    // other global config variables you wish

In your main file "index.js" put this line:

import './config';

Everywhere you need your object use this:


How to get memory usage at runtime using C++?

On linux, if you can afford the run time cost (for debugging), you can use valgrind with the massif tool:

It is heavy weight, but very useful.

Merge two (or more) lists into one, in C# .NET

list4 = list1.Concat(list2).Concat(list3).ToList();

Open mvc view in new window from controller

I've seen where you can do something like this, assuming "NewWindow.cshtml" is in your "Home" folder:

string url = "/Home/NewWindow";
return JavaScript(string.Format("'{0}', '_blank', 'left=100,top=100,width=500,height=500,toolbar=no,resizable=no,scrollable=yes');", url));


return Content("/Home/NewWindow");

If you just want to open views in tabs, you could use JavaScript click events to render your partial views. This would be your controller method for NewWindow.cshtml:

public ActionResult DisplayNewWindow(NewWindowModel nwm) {
    // build model list based on its properties & values
    nwm.Name = "John Doe";
    nwm.Address = "123 Main Street";
    return PartialView("NewWindow", nwm);

Your markup on your page this is calling it would go like this:

<input type="button" id="btnNewWin" value="Open Window" />
<div id="newWinResults" />

And the JavaScript (requires jQuery):

var url = '@Url.Action("NewWindow", "Home")';
$('btnNewWin').on('click', function() {
    var model = "{ 'Name': 'Jane Doe', 'Address': '555 Main Street' }"; // you must build your JSON you intend to pass into the "NewWindowModel" manually
    $('#newWinResults').load(url, model); // may need to do JSON.stringify(model)

Note that this JSON would overwrite what is in that C# function above. I had it there for demonstration purposes on how you could hard-code values, only.

(Adapted from Rendering partial view on button click in ASP.NET MVC)

Java constructor/method with optional parameters?

Why do you want to do that?

However, You can do this:

public void foo(int param1)
    int param2 = 2;
    // rest of code


public void foo(int param1, int param2)
    // rest of code

public void foo(int param1)
    foo(param1, 2);

How to properly overload the << operator for an ostream?

You have declared your function as friend. It's not a member of the class. You should remove Matrix:: from the implementation. friend means that the specified function (which is not a member of the class) can access private member variables. The way you implemented the function is like an instance method for Matrix class which is wrong.

How to save Excel Workbook to Desktop regardless of user?

You've mentioned that they each have their own machines, but if they need to log onto a co-workers machine, and then use the file, saving it through "C:\Users\Public\Desktop\" will make it available to different usernames.

Public Sub SaveToDesktop()
    ThisWorkbook.SaveAs Filename:="C:\Users\Public\Desktop\" & ThisWorkbook.Name & "_copy", _ 
End Sub

I'm not sure whether this would be a requirement, but may help!

How to run a PowerShell script from a batch file

Another easy way to execute a ps script from batch is to simply incorporate it between the ECHO and the Redirection characters,(> and >>), example:

@echo off
set WD=%~dp0
ECHO New-Item -Path . -Name "Test.txt" -ItemType "file" -Value "This is a text string." -Force > "%WD%PSHELLFILE.ps1"
ECHO add-content -path "./Test.txt" -value "`r`nThe End" >> "%WD%PSHELLFILE.ps1"
powershell.exe -ExecutionPolicy Bypass -File "%WD%PSHELLFILE.ps1"
del "%WD%PSHELLFILE.ps1"

Last line deletes the created temp file.

What does on_delete do on Django models?

Using CASCADE means actually telling Django to delete the referenced record. In the poll app example below: When a 'Question' gets deleted it will also delete the Choices this Question has.

e.g Question: How did you hear about us? (Choices: 1. Friends 2. TV Ad 3. Search Engine 4. Email Promotion)

When you delete this question, it will also delete all these four choices from the table. Note that which direction it flows. You don't have to put on_delete=models.CASCADE in Question Model put it in the Choice.

from django.db import models

class Question(models.Model):
    question_text = models.CharField(max_length=200)
    pub_date = models.dateTimeField('date_published')

class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_legth=200)
    votes = models.IntegerField(default=0)

XAMPP Port 80 in use by "Unable to open process" with PID 4

I had the following error message Port 80 in use by "Unable to open process" with PID 4! Apache WILL NOT start without the configured ports free! You need to uninstall/disable/reconfigure the blocking application or reconfigure Apache and the Control Panel to listen on a different port Starting Check-Timer Control Panel Ready

opened the httpd.conf and changed the listen port from 80 to 1234 in both places


Listen 1234

Then go to Config for the xampp control panel and go to service and port setting and changed the port from 80 to 1234

That worked.

printf not printing on console

Add c:\gygwin\bin to PATH environment variable either as a system environment variable or in your eclipse project (properties-> run/debug-> edit)

Docker container will automatically stop after "docker run -d"

Argument order matters

Jersey Beans answer (all 3 examples) worked for me. After quite a bit of trial and error I realized that the order of the arguments matter.

Keeps the container running in the background: docker run -t -d <image-name>

Keeps the container running in the foreground: docker run <image-name> -t -d

It wasn't obvious to me coming from a Powershell background.

Writing an mp4 video using python opencv

This worked for me, I added images.sort() to keep the sequence order:

import cv2
import numpy as np
import os

image_folder = 'data-set-race-01'
video_file = 'race-01.mp4'
image_size = (160, 120)
fps = 24

images = [img for img in os.listdir(image_folder) if img.endswith(".jpg")]

out = cv2.VideoWriter(video_file, cv2.VideoWriter_fourcc(*'MP4V'), fps, image_size)

img_array = []
for filename in images:
    img = cv2.imread(os.path.join(image_folder, filename))


"%%" and "%/%" for the remainder and the quotient

I think it is because % has often be associated with the modulus operator in many programming languages.

It is the case, e.g., in C, C++, C# and Java, and many other languages which derive their syntax from C (C itself took it from B).

HTTP authentication logout via PHP

AFAIK, there's no clean way to implement a "logout" function when using htaccess (i.e. HTTP-based) authentication.

This is because such authentication uses the HTTP error code '401' to tell the browser that credentials are required, at which point the browser prompts the user for the details. From then on, until the browser is closed, it will always send the credentials without further prompting.

How to save and load numpy.array() data properly?

np.fromfile() has a sep= keyword argument:

Separator between items if file is a text file. Empty (“”) separator means the file should be treated as binary. Spaces (” ”) in the separator match zero or more whitespace characters. A separator consisting only of spaces must match at least one whitespace.

The default value of sep="" means that np.fromfile() tries to read it as a binary file rather than a space-separated text file, so you get nonsense values back. If you use np.fromfile('markers.txt', sep=" ") you will get the result you are looking for.

However, as others have pointed out, np.loadtxt() is the preferred way to convert text files to numpy arrays, and unless the file needs to be human-readable it is usually better to use binary formats instead (e.g. np.load()/

Git: How to squash all commits on branch

In case you are okay with an answer involving another branch, try git checkout --orphan <new_branch> It allowed me to simply commit ALL files from previous branch as one commit.

This is something like a git merge squash but not quite the same.

How can I replace a newline (\n) using sed?

This is really simple... I really get irritated when I found the solution. There was just one more back slash missing. This is it:

sed -i "s/\\\\\n//g" filename

Cannot connect to the Docker daemon at unix:/var/run/docker.sock. Is the docker daemon running?

Just Run

sudo dockerd

dockerd is the daemon service for docker containers, because it is not running in background we're not able to take any actions related to the service, which needs be restarted.

Loop through properties in JavaScript object with Lodash

Use _.forOwn().

_.forOwn(obj, function(value, key) { } );

Note that forOwn checks hasOwnProperty, as you usually need to do when looping over an object's properties. forIn does not do this check.

Git command to checkout any branch and overwrite local changes

The new git-switch command (starting in GIT 2.23) also has a flag --discard-changes which should help you. git pull might be necessary afterwards.

Warning: it's still considered to be experimental.

Connecting to remote MySQL server using PHP

It is very easy to connect remote MySQL Server Using PHP, what you have to do is:

  1. Create a MySQL User in remote server.

  2. Give Full privilege to the User.

  3. Connect to the Server using PHP Code (Sample Given Below)

$link = mysql_connect('your_my_sql_servername or IP Address', 'new_user_which_u_created', 'password');
if (!$link) {
    die('Could not connect: ' . mysql_error());

echo 'Connected successfully';

mysql_select_db('sandsbtob',$link) or die ("could not open db".mysql_error());
// we connect to localhost at port 3306

Is there any publicly accessible JSON data source to test with real world data?

Tumblr has a public API that provides JSON. You can get a dump of posts using a simple url like

C: scanf to array

The %d conversion specifier will only convert one decimal integer. It doesn't know that you're passing an array, it can't modify its behavior based on that. The conversion specifier specifies the conversion.

There is no specifier for arrays, you have to do it explicitly. Here's an example with four conversions:

if(scanf("%d %d %d %d", &array[0], &array[1], &array[2], &array[3]) == 4)
  printf("got four numbers\n");

Note that this requires whitespace between the input numbers.

If the id is a single 11-digit number, it's best to treat as a string:

char id[12];

if(scanf("%11s", id) == 1)
  /* inspect the *character* in id[0], compare with '1' or '2' for instance. */

NullInjectorError: No provider for AngularFirestore

I take that to my app.module. After the imports it should be works

providers: [
    { provide: LocationStrategy, useClass: HashLocationStrategy },
    { provide: FirestoreSettingsToken, useValue: {} }

My Version:

Angular CLI: 7.2.4
Node: 10.15.0
Angular: 7.2.5
... common, compiler, compiler-cli, core, forms
... language-service, platform-browser, platform-browser-dynamic
... router

Package                           Version
@angular-devkit/architect         0.12.4
@angular-devkit/build-angular     0.12.4
@angular-devkit/build-optimizer   0.12.4
@angular-devkit/build-webpack     0.12.4
@angular-devkit/core              7.2.4
@angular-devkit/schematics        7.2.4
@angular/animations               8.0.0-beta.4+7.sha-3c7ce82
@angular/cdk                      7.3.2-3ae6eb2
@angular/cli                      7.2.4
@angular/fire                     5.1.1
@angular/flex-layout              7.0.0-beta.23
@angular/material                 7.3.2-3ae6eb2
@ngtools/webpack                  7.2.4
@schematics/angular               7.2.4
@schematics/update                0.12.4
rxjs                              6.3.3
typescript                        3.2.4
webpack                           4.28.4

HTTP 401 - what's an appropriate WWW-Authenticate header value?

No, you'll have to specify the authentication method to use (typically "Basic") and the authentication realm. See for an example request and response.

You might also want to read RFC 2617 - HTTP Authentication: Basic and Digest Access Authentication.

CSS vertical alignment of inline/inline-block elements

Simply floating both elements left achieves the same result.

div {

a {
border:solid black 1px;

span {

How can I get the corresponding table header (th) from a table cell (td)?

You can do it by using the td's index:

var tdIndex = $td.index() + 1;
var $th = $('#table tr').find('th:nth-child(' + tdIndex + ')');

How to check if a date is in a given range?

Convert them into dates or timestamp integers and then just check of $date_from_user is <= $end_date and >= $start_date

Codeigniter unset session

I use the old PHP way..It unsets all session variables and doesn't require to specify each one of them in an array. And after unsetting the variables we destroy the session

How to get the size of a file in MB (Megabytes)?

Since Java 7 you can use java.nio.file.Files.size(Path p).

Path path = Paths.get("C:\\1.txt");

long expectedSizeInMB = 27;
long expectedSizeInBytes = 1024 * 1024 * expectedSizeInMB;

long sizeInBytes = -1;
try {
    sizeInBytes = Files.size(path);
} catch (IOException e) {
    System.err.println("Cannot get the size - " + e);

if (sizeInBytes > expectedSizeInBytes) {
    System.out.println("Bigger than " + expectedSizeInMB + " MB");
} else {
    System.out.println("Not bigger than " + expectedSizeInMB + " MB");

Are multiple `.gitignore`s frowned on?

Pro single

  • Easy to find.

  • Hunting down exclusion rules can be quite difficult if I have multiple gitignore, at several levels in the repo.

  • With multiple files, you also typically wind up with a fair bit of duplication.

Pro multiple

  • Scopes "knowledge" to the part of the file tree where it is needed.

  • Since Git only tracks files, an empty .gitignore is the only way to commit an "empty" directory.

    (And before Git 1.8, the only way to exclude a pattern like my/**.example was to create my/.gitignore in with the pattern **.foo. This reason doesn't apply now, as you can do /my/**/*.example.)

I much prefer a single file, where I can find all the exclusions. I've never missed per-directory .svn, and I won't miss per-directory .gitignore either.

That said, multiple gitignores are quite common. If you do use them, at least be consistent in their use to make them reasonable to work with. For example, you may put them in directories only one level from the root.

Gradient borders

Example for Gradient Border

Using border-image css property

Credits to : border-image in Mozilla

.grad-border {_x000D_
  height: 1px;_x000D_
  width: 85%;_x000D_
  margin: 0 auto;_x000D_
  display: flex;_x000D_
.left-border, .right-border {_x000D_
  width: 50%;_x000D_
  border-bottom: 2px solid #695f52;_x000D_
  display: inline-block;_x000D_
.left-border {_x000D_
  border-image: linear-gradient(270deg, #b3b3b3, #fff) 1;_x000D_
.right-border {_x000D_
  border-image: linear-gradient(90deg, #b3b3b3, #fff) 1;_x000D_
<div class="grad-border">_x000D_
  <div class="left-border"></div>_x000D_
  <div class="right-border"></div>_x000D_

How do you make a LinearLayout scrollable?

Here is how I did it by trial and error.

ScrollView - (the outer wrapper).

    LinearLayout (child-1).

        LinearLayout (child-1a).

        LinearLayout (child-1b).

Since ScrollView can have only one child, that child is a linear layout. Then all the other layout types occur in the first linear layout. I haven't tried to include a relative layout yet, but they drive me nuts so I will wait until my sanity returns.

Show ProgressDialog Android

You should not execute resource intensive tasks in the main thread. It will make the UI unresponsive and you will get an ANR. It seems like you will be doing resource intensive stuff and want the user to see the ProgressDialog. You can take a look at to do resource intensive tasks. It also shows you how to use a ProgressDialog.

Add image in pdf using jspdf

For result in base64, before convert to canvas:

var getBase64ImageUrl = function(url, callback, mine) {

                    var img = new Image();

                    url = url.replace("http://","//");

                    img.setAttribute('crossOrigin', 'anonymous');

                    img.onload = function () {
                        var canvas = document.createElement("canvas");
                        canvas.width =this.width;
                        canvas.height =this.height;

                        var ctx = canvas.getContext("2d");
                        ctx.drawImage(this, 0, 0);

                        var dataURL = canvas.toDataURL(mine || "image/jpeg");

                    img.src = url;

                    img.onerror = function(){

                        console.log('on error')



   getBase64ImageUrl('Koala.jpeg', function(img){
         //img is a base64encode result
         //return img;

          var doc = new jsPDF();
              doc.text(30, 20, 'Hello world!');
              doc.addImage(img, 'JPEG', 15, 40, 180, 160);

Listing only directories in UNIX

du -d1 is perhaps the shortest option. (As long as you don't need to pipe the input to another command.)

Validating parameters to a Bash script

Use '-z' to test for empty strings and '-d to check for directories.

if [[ -z "$@" ]]; then
    echo >&2 "You must supply an argument!"
    exit 1
elif [[ ! -d "$@" ]]; then
    echo >&2 "$@ is not a valid directory!"
    exit 1

Value does not fall within the expected range

This might be due to the fact that you are trying to add a ListBoxItem with a same name to the page.

If you want to refresh the content of the listbox with the newly retrieved values you will have to first manually remove the content of the listbox other wise your loop will try to create lb_1 again and add it to the same list.

Look at here for a similar problem that occured Silverlight: Value does not fall within the expected range exception


Defining static const integer members in class definition

Another way to do this, for integer types anyway, is to define constants as enums in the class:

class test
    enum { N = 10 };

JavaScript before leaving the page

You can use the following one-liner to always ask the user before leaving the page.

window.onbeforeunload = s => "";

To ask the user when something on the page has been modified, see this answer.

ProgressDialog in AsyncTask

Don't know what parameter should I use?

A lot of Developers including have hard time at the beginning writing an AsyncTask because of the ambiguity of the parameters. The big reason is we try to memorize the parameters used in the AsyncTask. The key is Don't memorize. If you can visualize what your task really needs to do then writing the AsyncTask with the correct signature would be a piece of cake.

What is an AsyncTask?

AsyncTask are background task which run in the background thread. It takes an Input, performs Progress and gives Output.

ie AsyncTask<Input,Progress,Output>

Just figure out what your Input, Progress and Output are and you will be good to go.

For example

enter image description here

How does doInbackground() changes with AsyncTask parameters?

enter image description here

How doInBackground() and onPostExecute(),onProgressUpdate() are related?

enter image description here

How can You write this in a code?

 DownloadTask extends AsyncTask<String,Integer,String>{

    public void onPreExecute(){

    public String doInbackGround(String... params)
         // Download code
         int downloadPerc = // calculate that

         return "Download Success";

    public void onPostExecute(String result)

    public void onProgressUpdate(Integer... params)
         // show in spinner, access UI elements


How will you run this Task in Your Activity?

new DownLoadTask().execute("Paradise.mp3");

NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equalsIgnoreCase(java.lang.String)' on a null object reference

called_from must be null. Add a test against that condition like

if (called_from != null && called_from.equalsIgnoreCase("add")) {

or you could use Yoda conditions (per the Advantages in the linked Wikipedia article it can also solve some types of unsafe null behavior they can be described as placing the constant portion of the expression on the left side of the conditional statement)

if ("add".equalsIgnoreCase(called_from)) { // <-- safe if called_from is null

How to set time to a date object in java

Calendar cal = Calendar.getInstance();

Date d = cal.getTime();

Also See

LaTeX "\indent" creating paragraph indentation / tabbing package requirement?

The first line of a paragraph is indented by default, thus whether or not you have \indent there won't make a difference. \indent and \noindent can be used to override default behavior. You can see this by replacing your line with the following:

Now we are engaged in a great civil war.\\
\indent this is indented\\
this isn't indented

\noindent override default indentation (not indented)\\

How to read a specific line using the specific line number from a file in Java?

They are all wrong I just wrote this in about 10 seconds. With this I managed to just call the object.getQuestion("linenumber") in the main method to return whatever line I want.

public class Questions {

File file = new File("Question2Files/triviagame1.txt");

public Questions() {


public String getQuestion(int numLine) throws IOException {
    BufferedReader br = new BufferedReader(new FileReader(file));
    String line = "";
    for(int i = 0; i < numLine; i++) {
        line = br.readLine();
    return line; }}

How to ignore a particular directory or file for tslint?

Starting from tslint v5.8.0 you can set an exclude property under your linterOptions key in your tslint.json file:

  "extends": "tslint:latest",
  "linterOptions": {
      "exclude": [

More information on this here.

Contains case insensitive

From ES2016 you can also use slightly better / easier / more elegant method (case-sensitive):

if (referrer.includes("Ral")) { ... }

or (case-insensitive):

if (referrer.toLowerCase().includes(someString.toLowerCase())) { ... }

Here is some comparison of .indexOf() and .includes():

how to find array size in angularjs

You can find the number of members in a Javascript array by using its length property:

var number = $scope.names.length;

Docs - Array.prototype.length

How can I determine whether a 2D Point is within a Polygon?

Really like the solution posted by Nirg and edited by bobobobo. I just made it javascript friendly and a little more legible for my use:

function insidePoly(poly, pointx, pointy) {
    var i, j;
    var inside = false;
    for (i = 0, j = poly.length - 1; i < poly.length; j = i++) {
        if(((poly[i].y > pointy) != (poly[j].y > pointy)) && (pointx < (poly[j].x-poly[i].x) * (pointy-poly[i].y) / (poly[j].y-poly[i].y) + poly[i].x) ) inside = !inside;
    return inside;

"inconsistent use of tabs and spaces in indentation"

I recently had the same problem and found out that I just needed to convert the .py file's charset to UTF-8 as that's the set Python 3 uses.

BTW, I used 4-space tabs all the time, so the problem wasn't caused by them.

C# DateTime to UTC Time without changing the time

6/1/2011 4:08:40 PM Local
6/1/2011 4:08:40 PM Utc


DateTime dt = DateTime.Now;            
Console.WriteLine("{0} {1}", dt, dt.Kind);
DateTime ut = DateTime.SpecifyKind(dt, DateTimeKind.Utc);
Console.WriteLine("{0} {1}", ut, ut.Kind);

Laravel: Get base url

you can get it from Request, at laravel 5


Winforms issue - Error creating window handle

Well, in my case it was definitely the USER Objects that were out of control. I looked in the Windows Task Manager and sure enough, the USER Objects count was at 10'000 exactly.

I am dynamically embedding property and list sheets in Tab Pages by setting the Parent property of the property or list sheet's container panel to that of the Tab Page. I am conditionally recycling or re-creating the property and list sheet forms depending on the type of collection being listed or class type of the object being inspected.

NB: In Delphi, all controls had an Owner and a Parent property. Even if one changed the Parent property of a control, it would still be disposed by its owner when the owning control got destroyed.

In C# it seems that if a control e.g. a Panel is programmatically reassigned from, say, a Form to a Tab Page by changing the Panel.Parent property, calling Dispose() on the Form won't dispose the Panel, neither will calling Controls.Clear() on the Tab Page. Even a direct call Panel.Dispose() won't actually dispose it, unless its Parent is manually set to null beforehand.

Define the selected option with the old input in Laravel / Blade

<select name="gender" class="form-control" id="gender">
                                <option value="">Select Gender</option>
                                <option value="M" @if (old('gender') == "M") {{ 'selected' }} @endif>Male</option>
                                <option value="F" @if (old('gender') == "F") {{ 'selected' }} @endif>Female</option>

Google Chrome: This setting is enforced by your administrator

I found a better solution on the Chrome product forums by a user called Gary. The original thread is here.

Navigate to C:\Windows\System32\GroupPolicy

Open each subdirectory there and change the *.pol files to *.sav, E.g. registry.pol becomes registry.sav.

Hit Windows-Key + R, type the following in the box and hit enter

reg delete HKEY_LOCAL_MACHINE\SOFTWARE\Google\Chrome

In the command promt window that opens type: Yes and press Enter.

Restart Google Chrome and check whether you can change the search engine.

How to set java_home on Windows 7?

In cmd (temporarily for that cmd window):

set JAVA_HOME="C:\\....\java\jdk1.x.y_zz"

echo %JAVA_HOME%


echo %PATH%

Dynamic LINQ OrderBy on IEnumerable<T> / IQueryable<T>

I was trying to do this but having problems with Kjetil Watnedal's solution because I don't use the inline linq syntax - I prefer method-style syntax. My specific problem was in trying to do dynamic sorting using a custom IComparer.

My solution ended up like this:

Given an IQueryable query like so:

List<DATA__Security__Team> teams = TeamManager.GetTeams();
var query = teams.Where(team => team.ID < 10).AsQueryable();

And given a run-time sort field argument:

string SortField; // Set at run-time to "Name"

The dynamic OrderBy looks like so:

query = query.OrderBy(item => item.GetReflectedPropertyValue(SortField));

And that's using a little helper method called GetReflectedPropertyValue():

public static string GetReflectedPropertyValue(this object subject, string field)
    object reflectedValue = subject.GetType().GetProperty(field).GetValue(subject, null);
    return reflectedValue != null ? reflectedValue.ToString() : "";

One last thing - I mentioned that I wanted the OrderBy to use custom IComparer - because I wanted to do Natural sorting.

To do that, I just alter the OrderBy to:

query = query.OrderBy(item => item.GetReflectedPropertyValue(SortField), new NaturalSortComparer<string>());

See this post for the code for NaturalSortComparer().

Getting the array length of a 2D array in Java

public class Array_2D {
int arr[][];
public Array_2D() {
    Random r=new Random(10);
     arr = new int[5][10];
     for(int i=0;i<5;i++)
         for(int j=0;j<10;j++)
  public void display()
         for(int i=0;i<5;i++)

             for(int j=0;j<10;j++)
                 System.out.print(arr[i][j]+" "); 
     public static void main(String[] args) {
     Array_2D s=new Array_2D();

Delete column from SQLite table

In case anyone needs a (nearly) ready-to-use PHP function, the following is based on this answer:

 * Remove a column from a table.
 * @param string $tableName The table to remove the column from.
 * @param string $columnName The column to remove from the table.
public function DropTableColumn($tableName, $columnName)
    // --
    // Determine all columns except the one to remove.

    $columnNames = array();

    $statement = $pdo->prepare("PRAGMA table_info($tableName);");
    $rows = $statement->fetchAll(PDO::FETCH_OBJ);

    $hasColumn = false;

    foreach ($rows as $row)
        if(strtolower($row->name) !== strtolower($columnName))
            array_push($columnNames, $row->name);
            $hasColumn = true;

    // Column does not exist in table, no need to do anything.
    if ( !$hasColumn ) return;

    // --
    // Actually execute the SQL.

    $columns = implode('`,`', $columnNames);

    $statement = $pdo->exec(
       "CREATE TABLE `t1_backup` AS SELECT `$columns` FROM `$tableName`;
        DROP TABLE `$tableName`;
        ALTER TABLE `t1_backup` RENAME TO `$tableName`;");

In contrast to other answers, the SQL used in this approach seems to preserve the data types of the columns, whereas something like the accepted answer seems to result in all columns to be of type TEXT.

Update 1:

The SQL used has the drawback that autoincrement columns are not preserved.

Expression must be a modifiable L-value

lvalue means "left value" -- it should be assignable. You cannot change the value of text since it is an array, not a pointer.

Either declare it as char pointer (in this case it's better to declare it as const char*):

const char *text;
if(number == 2) 
    text = "awesome"; 
    text = "you fail";

Or use strcpy:

char text[60];
if(number == 2) 
    strcpy(text, "awesome"); 
    strcpy(text, "you fail");

Class is inaccessible due to its protection level

I'm guessing public Method AddMethod(string aName) is defined on a public interface that FBlock implements. Consumers of that interface are not guaranteed to have access to Method.

Unknown SSL protocol error in connection

I get the same problem. With the last version of git and no proxy.

I fixed it:

  • sign in the GitHub
  • enter the interface: "Personal settings", then click "SSH Keys" please confirm whether you have put the '' that generated by the command
  • 'ssh-keygen -t rsa ' on windows into github --> GIT BASH
  • 'Add SSH key' and put the '' into it.

More info: create the key

copy the key

How can change width of dropdown list?

Try this code:

<select name="wgtmsr" id="wgtmsr">
<option value="kg">Kg</option>
<option value="gm">Gm</option>
<option value="pound">Pound</option>
<option value="MetricTon">Metric ton</option>
<option value="litre">Litre</option>
<option value="ounce">Ounce</option>



If you want to change the width of the option you can do this in your css:

#wgtmsr option{

Maybe you have a conflict in your css rules that override the width of your select


How can I put strings in an array, split by new line?

An alternative to Davids answer which is faster (way faster) is to use str_replace and explode.

$arrayOfLines = explode("\n",

What's happening is:
Since line breaks can come in different forms, I str_replace \r\n, \n\r, and \r with \n instead (and original \n are preserved).
Then explode on \n and you have all the lines in an array.

I did a benchmark on the src of this page and split the lines 1000 times in a for loop and:
preg_replace took an avg of 11 seconds
str_replace & explode took an avg of about 1 second

More detail and bencmark info on my forum

Safest way to get last record ID from a table

I think this one will also work:


Best data type for storing currency values in a MySQL database

It is also important to work out how many decimal places maybe required for your calculations.

I worked on a share price application that required the calculation of the price of one million shares. The quoted share price had to be stored to 7 digits of accuracy.

What is the difference between __str__ and __repr__?

In short, the goal of __repr__ is to be unambiguous and __str__ is to be readable.

Here is a good example:

>>> import datetime
>>> today =
>>> str(today)
'2012-03-14 09:21:58.130922'
>>> repr(today)
'datetime.datetime(2012, 3, 14, 9, 21, 58, 130922)'

Read this documentation for repr:


Return a string containing a printable representation of an object. This is the same value yielded by conversions (reverse quotes). It is sometimes useful to be able to access this operation as an ordinary function. For many types, this function makes an attempt to return a string that would yield an object with the same value when passed to eval(), otherwise the representation is a string enclosed in angle brackets that contains the name of the type of the object together with additional information often including the name and address of the object. A class can control what this function returns for its instances by defining a __repr__() method.

Here is the documentation for str:


Return a string containing a nicely printable representation of an object. For strings, this returns the string itself. The difference with repr(object) is that str(object) does not always attempt to return a string that is acceptable to eval(); its goal is to return a printable string. If no argument is given, returns the empty string, ''.

Running an executable in Mac Terminal

To run an executable in mac

1). Move to the path of the file:


2). Run the following command to set the file's executable bit using the chmod command:

chmod +x ./NAME_OF_THE_FILE

3). Run the following command to execute the file:


Once you have run these commands, going ahead you just have to run command 3, while in the files path.

What does `ValueError: cannot reindex from a duplicate axis` mean?

Simple Fix that Worked for Me

Run df.reset_index(inplace=True) before grouping.

Thank you to this github comment for the solution.

Remove inplace if you want it to return the dataframe.

setAttribute('display','none') not working

Try this:

setAttribute("hidden", true);

How can I send the "&" (ampersand) character via AJAX?

You could encode your string using Base64 encoding on the JavaScript side and then decoding it on the server side with PHP (?).

JavaScript (Docu)

var wysiwyg_clean = window.btoa( wysiwyg );

PHP (Docu):

var wysiwyg = base64_decode( $_POST['wysiwyg'] );

CardView background color always white

XML code

        app:cardMaxElevation="6dp" />

From the code

CardView card = findViewById(;

Is it wrong to place the <script> tag after the </body> tag?

IE doesn't allow this anymore (since Version 10, I believe) and will ignore such scripts. FF and Chrome still tolerate them, but there are chances that some day they will drop this as non-standard.

How do I find the distance between two points?

Let's not forget math.hypot:

dist = math.hypot(x2-x1, y2-y1)

Here's hypot as part of a snippet to compute the length of a path defined by a list of (x, y) tuples:

from math import hypot

pts = [

# Py2 syntax - no longer allowed in Py3
# ptdiff = lambda (p1,p2): (p1[0]-p2[0], p1[1]-p2[1])
ptdiff = lambda p1, p2: (p1[0]-p2[0], p1[1]-p2[1])

diffs = (ptdiff(p1, p2) for p1, p2 in zip (pts, pts[1:]))
path = sum(hypot(*d) for d in  diffs)

What's the most useful and complete Java cheat sheet?

This Quick Reference looks pretty good if you're looking for a language reference. It's especially geared towards the user interface portion of the API.

For the complete API, however, I always use the Javadoc. I reference it constantly.

Laravel Update Query

You could use the Laravel query builder, but this is not the best way to do it.

Check Wader's answer below for the Eloquent way - which is better as it allows you to check that there is actually a user that matches the email address, and handle the error if there isn't.

        ->where('email', $userEmail)  // find your user by their email
        ->limit(1)  // optional - to ensure only one record is updated.
        ->update(array('member_type' => $plan));  // update the record in the DB. 

If you have multiple fields to update you can simply add more values to that array at the end.

How can I detect window size with jQuery?

Do you want to detect when the window has been resized?

You can use JQuery's resize to attach a handler.

MVC 4 @Scripts "does not exist"

Try this:

@section Scripts 
    Scripts.Render("~/bundles/jqueryval")  // <- without ampersand at the begin

Finding element's position relative to the document

If you don't mind using jQuery, then you can use offset() function. Refer to documentation if you want to read up more about this function.

Can I run HTML files directly from GitHub, instead of just viewing their source?

You might want to use It supports GitHub, Bitbucket, Gitlab and GitHub gists.



In your case .html extension


Development (throttled)[user]/[repository]/[branch]/[filename.ext]

Production (CDN)[user]/[repository]/[branch]/[filename.ext]

In your case .html extension also supports other services:




Development (throttled)[user]/[repository]/raw/[branch]/[filename.ext]

Production (CDN)[user]/[repository]/raw/[branch]/[filename.ext]




Development (throttled)[user]/[repository]/raw/[branch]/[filename.ext]

Production (CDN)[user]/[repository]/raw/[branch]/[filename.ext]

GitHub gists



Development (throttled)[user]/[gist]/raw/[revision]/[filename.ext]

Production (CDN)[user]/[gist]/raw/[revision]/[filename.ext]

Update: rawgit was discontinued

Get year, month or day from numpy datetime64

Anon's answer works great for me, but I just need to modify the statement for days


days = dates - dates.astype('datetime64[M]') + 1


days = dates.astype('datetime64[D]') - dates.astype('datetime64[M]') + 1

Internet Explorer 11 disable "display intranet sites in compatibility view" via meta tag not working

For those who are building an ASP.NET MVC project, make sure that you add the:

<meta http-equiv="X-UA-Compatible" content="IE=edge">

tag into your Layout (template) page. I just spent two hours debugging and tweaking, only to realize that I had only added that meta tag into my child pages. As soon as I added it to my layout page, the browser loaded in EDGE mode perfectly.

Empty brackets '[]' appearing when using .where

A good bet is to utilize Rails' Arel SQL manager, which explicitly supports case-insensitive ActiveRecord queries:

t = Guide.arel_table Guide.where(t[:title].matches('%attack')) 

Here's an interesting blog post regarding the portability of case-insensitive queries using Arel. It's worth a read to understand the implications of utilizing Arel across databases.

Why do table names in SQL Server start with "dbo"?

It's new to SQL 2005 and offers a simplified way to group objects, especially for the purpose of securing the objects in that "group".

The following link offers a more in depth explanation as to what it is, why we would use it:

Understanding the Difference between Owners and Schemas in SQL Server

Detect if range is empty

Dim cel As Range, hasNoData As Boolean

    hasNoData = True
    For Each cel In Selection
        hasNoData = hasNoData And IsEmpty(cel)

This will return True if no cells in Selection contains any data. For a specific range, just substitute RANGE(...) for Selection.

Should I use @EJB or @Inject

The @EJB is used to inject EJB's only and is available for quite some time now. @Inject can inject any managed bean and is a part of the new CDI specification (since Java EE 6).

In simple cases you can simply change @EJB to @Inject. In more advanced cases (e.g. when you heavily depend on @EJB's attributes like beanName, lookup or beanInterface) than in order to use @Inject you would need to define a @Producer field or method.

These resources might be helpful to understand the differences between @EJB and @Produces and how to get the best of them:

Antonio Goncalves' blog:
CDI Part I

JBoss Weld documentation:
CDI and the Java EE ecosystem

Inject @EJB bean based on conditions

How to use bluetooth to connect two iPhone?

Check out the BeamIt open source project. It will connect via bluetooth and WIFI (although it claims it does not do WIFI) and I have verified that it works well in my projects. It will allow peer to peer contact easily.

As for multiple connections, it is possible, but you will have to edit the BeamIt source code to make it possible. I suggest reading the GameKit programming guide

Visual Studio: LINK : fatal error LNK1181: cannot open input file

I created a bin directory at the project_dir level, then created a release/debug directory inside the bin folder, which solved the problem for me.