Programs & Examples On #Shebang

The #! marker at the beginning of scripts is called a shebang.

Why do you need to put #!/bin/bash at the beginning of a script file?

It can be useful to someone that uses a different system that does not have that library readily available. If that is not declared and you have some functions in your script that are not supported by that system, you should declare #/bin/bash. I've ran into this problem before at work and now I just include it as a practice.

What is the difference between "#!/usr/bin/env bash" and "#!/usr/bin/bash"?

Running a command through /usr/bin/env has the benefit of looking for whatever the default version of the program is in your current environment.

This way, you don't have to look for it in a specific place on the system, as those paths may be in different locations on different systems. As long as it's in your path, it will find it.

One downside is that you will be unable to pass more than one argument (e.g. you will be unable to write /usr/bin/env awk -f) if you wish to support Linux, as POSIX is vague on how the line is to be interpreted, and Linux interprets everything after the first space to denote a single argument. You can use /usr/bin/env -S on some versions of env to get around this, but then the script will become even less portable and break on fairly recent systems (e.g. even Ubuntu 16.04 if not later).

Another downside is that since you aren't calling an explicit executable, it's got the potential for mistakes, and on multiuser systems security problems (if someone managed to get their executable called bash in your path, for example).

#!/usr/bin/env bash #lends you some flexibility on different systems
#!/usr/bin/bash     #gives you explicit control on a given system of what executable is called

In some situations, the first may be preferred (like running python scripts with multiple versions of python, without having to rework the executable line). But in situations where security is the focus, the latter would be preferred, as it limits code injection possibilities.

Should I put #! (shebang) in Python scripts, and what form should it take?

The shebang line in any script determines the script's ability to be executed like a standalone executable without typing python beforehand in the terminal or when double clicking it in a file manager (when configured properly). It isn't necessary but generally put there so when someone sees the file opened in an editor, they immediately know what they're looking at. However, which shebang line you use IS important.

Correct usage for Python 3 scripts is:

#!/usr/bin/env python3

This defaults to version 3.latest. For Python 2.7.latest use python2 in place of python3.

The following should NOT be used (except for the rare case that you are writing code which is compatible with both Python 2.x and 3.x):

#!/usr/bin/env python

The reason for these recommendations, given in PEP 394, is that python can refer either to python2 or python3 on different systems. It currently refers to python2 on most distributions, but that is likely to change at some point.

Also, DO NOT Use:


"python may be installed at /usr/bin/python or /bin/python in those cases, the above #! will fail."

--"#!/usr/bin/env python" vs "#!/usr/local/bin/python"

What is the preferred Bash shebang?


as most scripts do not need specific bash feature and should be written for sh.

Also, this makes scripts work on the BSDs, which do not have bash per default.

What does the line "#!/bin/sh" mean in a UNIX shell script?

When you try to execute a program in unix (one with the executable bit set), the operating system will look at the first few bytes of the file. These form the so-called "magic number", which can be used to decide the format of the program and how to execute it.

#! corresponds to the magic number 0x2321 (look it up in an ascii table). When the system sees that the magic number, it knows that it is dealing with a text script and reads until the next \n (there is a limit, but it escapes me atm). Having identified the interpreter (the first argument after the shebang) it will call the interpreter.

Other files also have magic numbers. Try looking at a bitmap (.BMP) file via less and you will see the first two characters are BM. This magic number denotes that the file is indeed a bitmap.

Why do people write #!/usr/bin/env python on the first line of a Python script?

This is a shell convention that tells the shell which program can execute the script.

#!/usr/bin/env python

resolves to a path to the Python binary.

In log4j, does checking isDebugEnabled before logging improve performance?

In Java 8, you don't have to use isDebugEnabled() to improve the performance.

import java.util.logging.Logger;
Logger.getLogger("hello").info(() -> "Hello " + name);

How much does it cost to develop an iPhone application?

I am a very good iPhone app developer, and I charge over $150 per hour for my services. I have a ton of experience building iPhone apps and their server side components. I have also been called in on several occasions to fix offshore developed apps. Here's my take.

  • Design costs money, good design costs lots of money. Expect several designer weeks of work per app screen. Offshore teams do not do design.
  • Server development and infrastructure is critical if the app is to succeed. A slow server response, or an overloaded server will hamper your app, and crimp sales and satisfaction. The server side of the equation will cost the most and take the most time to develop. Those who offshore their server development will find that quality and uptime are both terrible, in my experience.
  • App development if done right takes time too. A professional developer will ensure all HIG rules are followed, the app is properly structured and contains no known errors, it performs well, and it passes the app store validations. Offshore teams just cut code.

I'm just about to release a shopping app for a client. The design work was done by 2 client in-house designers over 2 weeks, quick because they had all the image assets already. Think 2 people x 10 days x 8 hours = ~$24,000. The server side had to be modified to provide data for the iPhone app. We used their in-house team and in-house platform and in-house API, 2 developers, 4 weeks, or about $50,000 and that's because they already have a web shop and API. Cost them about $400,000 to get there (excluding platform). And I wrote the app side in 3 weeks, given that a lot of my code is duplicated from previous projects, another ~$25,000, the cheapest app I ever did.

Total spent: ~$100,000, and that's insanely cheap!

And they will give this away for free so clients will buy from their store from their iPhones.

For your app, Peter, if you have the servers and the APIs and the design, I'd guess at $30,000 to $60,000 depending on complexity. If you do not have the design, double it. If you do not have the APIs, double again...

Check if an element is present in an array

In lodash you can use _.includes (which also aliases to _.contains)

You can search the whole array:

_.includes([1, 2, 3], 1); // true

You can search the array from a starting index:

_.includes([1, 2, 3], 1, 1);  // false (begins search at index 1)

Search a string:

_.includes('pebbles', 'eb');  // true (string contains eb)

Also works for checking simple arrays of objects:

_.includes({ 'user': 'fred', 'age': 40 }, 'fred');    // true
_.includes({ 'user': 'fred', 'age': false }, false);  // true

One thing to note about the last case is it works for primitives like strings, numbers and booleans but cannot search through arrays or objects

_.includes({ 'user': 'fred', 'age': {} }, {});   // false
_.includes({ 'user': [1,2,3], 'age': {} }, 3);   // false

how to "execute" make file

You don't tend to execute the make file itself, rather you execute make, giving it the make file as an argument:

make -f

If your make file is actually one of the standard names (like makefile or Makefile), you don't even need to specify it. It'll be picked up by default (if you have more than one of these standard names in your build directory, you better look up the make man page to see which takes precedence).

Checkbox angular material checked by default

// in component.ts
checked: boolean = true;
indeterminate:boolean = false;
disabled:boolean = false;

onCheck() {
    this.label = this.checked?'ON':'OFF';

// in component.html`enter code here`
<mat-checkbox class="example-margin" [color]="primary" [(ngModel)]="checked" [(indeterminate)]="indeterminate" [labelPosition]="after" [disabled]="disabled" (change)="onCheck()">

The above code should work fine. Mat checkbox allows you to make it checked/unchecked, disabled, set indeterminate state, do some operation onChange of the state etc. Refer API for more details.

Submitting form and pass data to controller method of type FileStreamResult

here the problem is model binding if you specify a class then the model binding can understand it during the post if it an integer or string then you have to specify the [FromBody] to bind it properly.

make the following changes in FormMethod

using (@Html.BeginForm("myMethod", "Home", FormMethod.Post, new { id = @item.JobId })){


and inside your home controller for binding the string you should specify [FromBody]

using System.Web.Http;
public FileStreamResult myMethod([FromBody]string id)
     // Set a local variable with the incoming data
     string str = id;


FromBody is available in System.Web.Http. make sure you have the reference to that class and added it in the cs file.

How to cherry-pick multiple commits

The simplest way to do this is with the onto option to rebase. Suppose that the branch which current finishes at a is called mybranch and this is the branch that you want to move c-f onto.

# checkout mybranch
git checkout mybranch

# reset it to f (currently includes a)
git reset --hard f

# rebase every commit after b and transplant it onto a
git rebase --onto a b

add class with JavaScript

Here is a method adapted from Jquery 2.1.1 that take a dom element instead of a jquery object (so jquery is not needed). Includes type checks and regex expressions:

function addClass(element, value) {
    // Regex terms
    var rclass = /[\t\r\n\f]/g,
        rnotwhite = (/\S+/g);

    var classes,
        proceed = typeof value === "string" && value;

    if (!proceed) return element;

    classes = (value || "").match(rnotwhite) || [];

    cur = element.nodeType === 1
        && (element.className
                ? (" " + element.className + " ").replace(rclass, " ")
                : " "

    if (!cur) return element;

    var j = 0;

    while ((curClass = classes[j++])) {

        if (cur.indexOf(" " + curClass + " ") < 0) {

            cur += curClass + " ";



    // only assign if different to avoid unneeded rendering.
    finalValue = cur.trim();

    if (element.className !== finalValue) {

        element.className = finalValue;


    return element;

How do I parse command line arguments in Bash?

Mixing positional and flag-based arguments

--param=arg (equals delimited)

Freely mixing flags between positional arguments:

./ dumbo --environment=production -q -d
./ dumbo --environment=production --quiet -d

can be accomplished with a fairly concise approach:

# process flags
while [[ $pointer -le $# ]]; do
   if [[ $param != "-"* ]]; then ((pointer++)) # not a parameter flag so advance pointer
      case $param in
         # paramter-flags with arguments
         -e=*|--environment=*) environment="${param#*=}";;
                  --another=*) another="${param#*=}";;

         # binary flags
         -q|--quiet) quiet=true;;
                 -d) debug=true;;

      # splice out pointer frame from positional list
      [[ $pointer -gt 1 ]] \
         && set -- ${@:1:((pointer - 1))} ${@:((pointer + 1)):$#} \
         || set -- ${@:((pointer + 1)):$#};

# positional remain

--param arg (space delimited)

It's usualy clearer to not mix --flag=value and --flag value styles.

./ dumbo --environment production -q -d

This is a little dicey to read, but is still valid

./ dumbo --environment production --quiet -d


# process flags
while [[ $pointer -le $# ]]; do
   if [[ ${!pointer} != "-"* ]]; then ((pointer++)) # not a parameter flag so advance pointer
      ((pointer_plus = pointer + 1))

      case $param in
         # paramter-flags with arguments
         -e|--environment) environment=${!pointer_plus}; ((slice_len++));;
                --another) another=${!pointer_plus}; ((slice_len++));;

         # binary flags
         -q|--quiet) quiet=true;;
                 -d) debug=true;;

      # splice out pointer frame from positional list
      [[ $pointer -gt 1 ]] \
         && set -- ${@:1:((pointer - 1))} ${@:((pointer + $slice_len)):$#} \
         || set -- ${@:((pointer + $slice_len)):$#};

# positional remain

Jquery button click() function is not working

After making the id unique across the document ,You have to use event delegation

$("#container").on("click", "buttonid", function () {

Running code after Spring Boot starts

Best way you use CommandLineRunner or ApplicationRunner The only difference between is run() method CommandLineRunner accepts array of string and ApplicationRunner accepts ApplicationArugument.

R: `which` statement with multiple conditions

The && function is not vectorized. You need the & function:

EUR <- PCs[which(PCs$V13 < 9 & PCs$V13 > 3), ]

How to check if any value is NaN in a Pandas DataFrame

Since pandas has to find this out for DataFrame.dropna(), I took a look to see how they implement it and discovered that they made use of DataFrame.count(), which counts all non-null values in the DataFrame. Cf. pandas source code. I haven't benchmarked this technique, but I figure the authors of the library are likely to have made a wise choice for how to do it.

How do I pass multiple parameter in URL?

You can pass multiple parameters as "?param1=value1&param2=value2"

But it's not secure. It's vulnerable to Cross Site Scripting (XSS) Attack.

Your parameter can be simply replaced with a script.

Have a look at this article and article

You can make it secure by using API of StringEscapeUtils

static String   escapeHtml(String str) 
          Escapes the characters in a String using HTML entities.

Even using https url for security without above precautions is not a good practice.

Have a look at related SE question:

Is URLEncoder.encode(string, "UTF-8") a poor validation?

Is using 'var' to declare variables optional?

Check out this Fiddle:

function doMe(){

a = "123"; // will be global
var b = "321"; // local to doMe
alert("a:"+a+"  --  b:"+b);

b = "something else"; // still local (not global)
alert("a:"+a+"  --  b:"+b);


alert("a:"+a+"  --  b:"+b); // `b` will not be defined, check console.log

IIS7 folder permissions for web application has the answer. Setting the iis authentication to appliction pool identity will resolve this.

In IIS Authentication, Anonymous Authentication was set to "Specific User". When I changed it to Application Pool, I can access the site.

To set, click on your website in IIS and double-click "Authentication". Right-click on "Anonymous Authentication" and click "Edit..." option. Switch from "Specific User" to "Application pool identity". Now you should be able to set file and folder permissions using the IIS AppPool\{Your App Pool Name}.

Difference between File.separator and slash in paths

Although it doesn't make much difference on the way in, it does on the way back.

Sure you can use either '/' or '\' in new File(String path), but File.getPath() will only give you one of them.

How to create custom exceptions in Java?

public class MyException extends Exception {
        // special exception code goes here

Throw it as:

 throw new MyException ("Something happened")

Catch as:

catch (MyException e)
   // something

How to do this using jQuery - document.getElementById("selectlist").value

It can be done by three different ways,though all them are nearly the same

Javascript way


Jquery way




How do I find out what type each object is in a ArrayList<Object>?

If you expect the data to be numeric in some form, and all you are interested in doing is converting the result to a numeric value, I would suggest:

for (Object o:list) {

CSS override rules and specificity

The important needs to be inside the ;

td.rule2 div {     background-color: #ffff00 !important; } 

in fact i believe this should override it

td.rule2 { background-color: #ffff00 !important; } 

Align DIV's to bottom or baseline

The answer posted by Y. Shoham (using absolute positioning) seems to be the simplest solution in most cases where the container is a fixed height, but if the parent DIV has to contain multiple DIVs and auto adjust it's height based on dynamic content, then there can be a problem. I needed to have two blocks of dynamic content; one aligned to the top of the container and one to the bottom and although I could get the container to adjust to the size of the top DIV, if the DIV aligned to the bottom was taller, it would not resize the container but would extend outside. The method outlined above by romiem using table style positioning, although a bit more complicated, is more robust in this respect and allowed alignment to the bottom and correct auto height of the container.


#container {
        display: table;
        height: auto;

#top {
    display: table-cell;
    height: 100%;

#bottom {
    display: table-cell;
    vertical-align: bottom;
    height: 100%;


<div id=“container”>
    <div id=“top”>Dynamic content aligned to top of #container</div>
    <div id=“bottom”>Dynamic content aligned to botttom of #container</div>


I realise this is not a new answer but I wanted to comment on this approach as it lead me to find my solution but as a newbie I was not allowed to comment, only post.

Interface extends another interface but implements its methods

Why does it implement its methods? How can it implement its methods when an interface can't contain method body? How can it implement the methods when it extends the other interface and not implement it? What is the purpose of an interface implementing another interface?

Interface does not implement the methods of another interface but just extends them. One example where the interface extension is needed is: consider that you have a vehicle interface with two methods moveForward and moveBack but also you need to incorporate the Aircraft which is a vehicle but with some addition methods like moveUp, moveDown so in the end you have:

public interface IVehicle {
  bool moveForward(int x);
  bool moveBack(int x);

and airplane:

public interface IAirplane extends IVehicle {
  bool moveDown(int x);
  bool moveUp(int x);

Loading custom functions in PowerShell

I kept using this all this time

Import-module .\build_functions.ps1 -Force

RestSharp simple complete example


RestResponse response = client.Execute(request);


IRestResponse response = client.Execute(request);

worked for me.

Scale the contents of a div by a percentage?

This cross-browser lib seems safer - just zoom and moz-transform won't cover as many browsers as jquery.transform2d's scale().

For example

$('#div').css({ transform: 'scale(.5)' });


OK - I see people are voting this down without an explanation. The other answer here won't work in old Safari (people running Tiger), and it won't work consistently in some older browsers - that is, it does scale things but it does so in a way that's either very pixellated or shifts the position of the element in a way that doesn't match other browsers.

Or just look at this question, which this one is likely just a dupe of:

complete styles for cross browser CSS zoom

Reading a huge .csv file

what worked for me was and is superfast is

import pandas as pd
import dask.dataframe as dd
import time
df_train = dd.read_csv('../data/train.csv', usecols=[col1, col2])
print("load train: " , time.clock()-t)

Another working solution is:

import pandas as pd 
from tqdm import tqdm

PATH = '../data/train.csv'
chunksize = 500000 
traintypes = {

cols = list(traintypes.keys())

df_list = [] # list to hold the batch dataframe

for df_chunk in tqdm(pd.read_csv(PATH, usecols=cols, dtype=traintypes, chunksize=chunksize)):
    # Can process each chunk of dataframe here
    # clean_data(), feature_engineer(),fit()

    # Alternatively, append the chunk to list and merge all

# Merge all dataframes into one dataframe
X = pd.concat(df_list)

# Delete the dataframe list to release memory
del df_list
del df_chunk

tsql returning a table from a function or store procedure

You need a special type of function known as a table valued function. Below is a somewhat long-winded example that builds a date dimension for a data warehouse. Note the returns clause that defines a table structure. You can insert anything into the table variable (@DateHierarchy in this case) that you want, including building a temporary table and copying the contents into it.

if object_id ('ods.uf_DateHierarchy') is not null
    drop function ods.uf_DateHierarchy

create function ods.uf_DateHierarchy (
       @DateFrom datetime
      ,@DateTo   datetime
) returns @DateHierarchy table (
        DateKey           datetime
       ,DisplayDate       varchar (20)
       ,SemanticDate      datetime
       ,MonthKey          int     
       ,DisplayMonth      varchar (10)
       ,FirstDayOfMonth   datetime
       ,QuarterKey        int
       ,DisplayQuarter    varchar (10)
       ,FirstDayOfQuarter datetime
       ,YearKey           int
       ,DisplayYear       varchar (10)
       ,FirstDayOfYear    datetime
) as begin
    declare @year            int
           ,@quarter         int
           ,@month           int
           ,@day             int
           ,@m1ofqtr         int
           ,@DisplayDate     varchar (20)
           ,@DisplayQuarter  varchar (10)
           ,@DisplayMonth    varchar (10)
           ,@DisplayYear     varchar (10)
           ,@today           datetime
           ,@MonthKey        int
           ,@QuarterKey      int
           ,@YearKey         int
           ,@SemanticDate    datetime
           ,@FirstOfMonth    datetime
           ,@FirstOfQuarter  datetime
           ,@FirstOfYear     datetime
           ,@MStr            varchar (2)
           ,@QStr            varchar (2)
           ,@Ystr            varchar (4)
           ,@DStr            varchar (2)
           ,@DateStr         varchar (10)

    -- === Previous ===================================================
    -- Special placeholder date of 1/1/1800 used to denote 'previous'
    -- so that naive date calculations sort and compare in a sensible
    -- order.
    insert @DateHierarchy (
    ) values (

    -- === Calendar Dates =============================================
    -- These are generated from the date range specified in the input
    -- parameters.
    set @today = @Datefrom
    while @today <= @DateTo begin

        set @year = datepart (yyyy, @today)
        set @month = datepart (mm, @today)
        set @day = datepart (dd, @today)
        set @quarter = case when @month in (1,2,3) then 1
                            when @month in (4,5,6) then 2
                            when @month in (7,8,9) then 3
                            when @month in (10,11,12) then 4
        set @m1ofqtr = @quarter * 3 - 2 

        set @DisplayDate = left (convert (varchar, @today, 113), 11)
        set @SemanticDate = @today
        set @MonthKey = @year * 100 + @month
        set @DisplayMonth = substring (convert (varchar, @today, 113), 4, 8)
        set @Mstr = right ('0' + convert (varchar, @month), 2)
        set @Dstr = right ('0' + convert (varchar, @day), 2)
        set @Ystr = convert (varchar, @year)
        set @DateStr = @Ystr + '-' + @Mstr + '-01'
        set @FirstOfMonth = convert (datetime, @DateStr, 120)
        set @QuarterKey = @year * 10 + @quarter
        set @DisplayQuarter = 'Q' + convert (varchar, @quarter) + ' ' +
                                    convert (varchar, @year)
        set @QStr = right ('0' + convert (varchar, @m1ofqtr), 2)   
        set @DateStr = @Ystr + '-' + @Qstr + '-01' 
        set @FirstOfQuarter = convert (datetime, @DateStr, 120)
        set @YearKey = @year
        set @DisplayYear = convert (varchar, @year)
        set @DateStr = @Ystr + '-01-01'
        set @FirstOfYear = convert (datetime, @DateStr)

        insert @DateHierarchy (
        ) values (

        set @today = dateadd (dd, 1, @today)

    -- === Specials ===================================================
    -- 'Ongoing', 'Error' and 'Not Recorded' set two years apart to
    -- avoid accidental collisions on 'Next Year' calculations.
    insert @DateHierarchy (
    ) values (

    insert @DateHierarchy (
    ) values (

    insert @DateHierarchy (
    ) values (
        ,'Not Recorded'



How to list the certificates stored in a PKCS12 keystore with keytool?

You can also use openssl to accomplish the same thing:

$ openssl pkcs12 -nokeys -info \
    -in </path/to/file.pfx> \
    -passin pass:<pfx's password>

MAC Iteration 2048
MAC verified OK
PKCS7 Encrypted data: pbeWithSHA1And40BitRC2-CBC, Iteration 2048
Certificate bag
Bag Attributes
    localKeyID: XX XX XX XX XX XX XX XX XX XX XX XX XX 48 54 A0 47 88 1D 90
    friendlyName: jedis-server
subject=/C=US/ST=NC/L=Raleigh/O=XXX Security/OU=XXX/CN=something1
issuer=/C=US/ST=NC/L=Raleigh/O=XXX Security/OU=XXXX/CN=something1
PKCS7 Data
Shrouded Keybag: pbeWithSHA1And3-KeyTripleDES-CBC, Iteration 2048

What are good message queue options for nodejs?

Look at node-queue-lib. Perhaps it is enough that you. It support node.js and browsers. Has two delivery strategies: broadcast and round-robin. Only javascript.

Quick example:

var Queue = require('node-queue-lib/queue.core');

var queue = new Queue('Queue name', 'broadcast');

// subscribe on 'Queue name' messages
queue.subscribe(function (err, subscriber) {
    subscriber.on('error', function(err){
    subscriber.on('data', function (data, accept) {
        accept(); // accept process message

// publish message

How to enter in a Docker container already running with a new TTY

docker exec -ti 'CONTAINER_NAME' sh


docker exec -ti 'CONTAINER_ID' sh

Pycharm/Python OpenCV and CV2 install error

I rather use Virtualenv to install such packages rather than the entire system, saves time and effort rather than building from source.

I use virtualenvwrapper

Windows user can download

pip install virtualenvwrapper-win

Linux follow

pip install opencv-python


If processing a video is required

pip install opencv-contrib-python


If you do not need GUI in Opencv

pip install opencv-contrib-python-headless


Spring Could not Resolve placeholder

You are not reading the properties file correctly. The propertySource should pass the parameter as: or Change the annotation to:


However I don't know what your PropertiesConfig file contains, as you're importing that also. Ideally the @PropertySource annotation should have been kept there.

How to convert string to datetime format in pandas python?

Use to_datetime, there is no need for a format string the parser is man/woman enough to handle it:

In [51]:

0   2012-03-28 14:15:00
1   2012-03-28 14:17:28
2   2012-03-28 14:50:50
Name: I_DATE, dtype: datetime64[ns]

To access the date/day/time component use the dt accessor:

In [54]:

0    2012-03-28
1    2012-03-28
2    2012-03-28
dtype: object

In [56]:    

0    14:15:00
1    14:17:28
2    14:50:50
dtype: object

You can use strings to filter as an example:

In [59]:
df = pd.DataFrame({'date':pd.date_range(start = dt.datetime(2015,1,1), end =})
df[(df['date'] > '2015-02-04') & (df['date'] < '2015-02-10')]

35 2015-02-05
36 2015-02-06
37 2015-02-07
38 2015-02-08
39 2015-02-09

The entitlements specified...profile. (0xE8008016). Error iOS 4.2

If you didn't change anything related to certificates (didn't replace or update them) just do a Product -> Clean. It helped me several times. (Xcode 6.2)

Where is Python's sys.path initialized from?

Python really tries hard to intelligently set sys.path. How it is set can get really complicated. The following guide is a watered-down, somewhat-incomplete, somewhat-wrong, but hopefully-useful guide for the rank-and-file python programmer of what happens when python figures out what to use as the initial values of sys.path, sys.executable, sys.exec_prefix, and sys.prefix on a normal python installation.

First, python does its level best to figure out its actual physical location on the filesystem based on what the operating system tells it. If the OS just says "python" is running, it finds itself in $PATH. It resolves any symbolic links. Once it has done this, the path of the executable that it finds is used as the value for sys.executable, no ifs, ands, or buts.

Next, it determines the initial values for sys.exec_prefix and sys.prefix.

If there is a file called pyvenv.cfg in the same directory as sys.executable or one directory up, python looks at it. Different OSes do different things with this file.

One of the values in this config file that python looks for is the configuration option home = <DIRECTORY>. Python will use this directory instead of the directory containing sys.executable when it dynamically sets the initial value of sys.prefix later. If the applocal = true setting appears in the pyvenv.cfg file on Windows, but not the home = <DIRECTORY> setting, then sys.prefix will be set to the directory containing sys.executable.

Next, the PYTHONHOME environment variable is examined. On Linux and Mac, sys.prefix and sys.exec_prefix are set to the PYTHONHOME environment variable, if it exists, superseding any home = <DIRECTORY> setting in pyvenv.cfg. On Windows, sys.prefix and sys.exec_prefix is set to the PYTHONHOME environment variable, if it exists, unless a home = <DIRECTORY> setting is present in pyvenv.cfg, which is used instead.

Otherwise, these sys.prefix and sys.exec_prefix are found by walking backwards from the location of sys.executable, or the home directory given by pyvenv.cfg if any.

If the file lib/python<version>/dyn-load is found in that directory or any of its parent directories, that directory is set to be to be sys.exec_prefix on Linux or Mac. If the file lib/python<version>/ is is found in the directory or any of its subdirectories, that directory is set to be sys.prefix on Linux, Mac, and Windows, with sys.exec_prefix set to the same value as sys.prefix on Windows. This entire step is skipped on Windows if applocal = true is set. Either the directory of sys.executable is used or, if home is set in pyvenv.cfg, that is used instead for the initial value of sys.prefix.

If it can't find these "landmark" files or sys.prefix hasn't been found yet, then python sets sys.prefix to a "fallback" value. Linux and Mac, for example, use pre-compiled defaults as the values of sys.prefix and sys.exec_prefix. Windows waits until sys.path is fully figured out to set a fallback value for sys.prefix.

Then, (what you've all been waiting for,) python determines the initial values that are to be contained in sys.path.

  1. The directory of the script which python is executing is added to sys.path. On Windows, this is always the empty string, which tells python to use the full path where the script is located instead.
  2. The contents of PYTHONPATH environment variable, if set, is added to sys.path, unless you're on Windows and applocal is set to true in pyvenv.cfg.
  3. The zip file path, which is <prefix>/lib/ on Linux/Mac and os.path.join(os.dirname(sys.executable), "") on Windows, is added to sys.path.
  4. If on Windows and no applocal = true was set in pyvenv.cfg, then the contents of the subkeys of the registry key HK_CURRENT_USER\Software\Python\PythonCore\<DLLVersion>\PythonPath\ are added, if any.
  5. If on Windows and no applocal = true was set in pyvenv.cfg, and sys.prefix could not be found, then the core contents of the of the registry key HK_CURRENT_USER\Software\Python\PythonCore\<DLLVersion>\PythonPath\ is added, if it exists;
  6. If on Windows and no applocal = true was set in pyvenv.cfg, then the contents of the subkeys of the registry key HK_LOCAL_MACHINE\Software\Python\PythonCore\<DLLVersion>\PythonPath\ are added, if any.
  7. If on Windows and no applocal = true was set in pyvenv.cfg, and sys.prefix could not be found, then the core contents of the of the registry key HK_CURRENT_USER\Software\Python\PythonCore\<DLLVersion>\PythonPath\ is added, if it exists;
  8. If on Windows, and PYTHONPATH was not set, the prefix was not found, and no registry keys were present, then the relative compile-time value of PYTHONPATH is added; otherwise, this step is ignored.
  9. Paths in the compile-time macro PYTHONPATH are added relative to the dynamically-found sys.prefix.
  10. On Mac and Linux, the value of sys.exec_prefix is added. On Windows, the directory which was used (or would have been used) to search dynamically for sys.prefix is added.

At this stage on Windows, if no prefix was found, then python will try to determine it by searching all the directories in sys.path for the landmark files, as it tried to do with the directory of sys.executable previously, until it finds something. If it doesn't, sys.prefix is left blank.

Finally, after all this, Python loads the site module, which adds stuff yet further to sys.path:

It starts by constructing up to four directories from a head and a tail part. For the head part, it uses sys.prefix and sys.exec_prefix; empty heads are skipped. For the tail part, it uses the empty string and then lib/site-packages (on Windows) or lib/pythonX.Y/site-packages and then lib/site-python (on Unix and Macintosh). For each of the distinct head-tail combinations, it sees if it refers to an existing directory, and if so, adds it to sys.path and also inspects the newly added path for configuration files.

Floating point exception( core dump

Floating Point Exception happens because of an unexpected infinity or NaN. You can track that using gdb, which allows you to see what is going on inside your C program while it runs. For more details:

In a nutshell, these commands might be useful...

gcc -g myprog.c

gdb a.out

gdb core a.out

ddd a.out

Emulate/Simulate iOS in Linux

The only solution I can think of is to install VMWare or any other VT then install OSX on a VM.

It works pretty good for testing.

How to tell Jackson to ignore a field during serialization if its value is null?


should work.

Include.NON_EMPTY indicates that property is serialized if its value is not null and not empty. Include.NON_NULL indicates that property is serialized if its value is not null.

Accessing a resource via codebehind in WPF

I got the resources on C# (Desktop WPF W/ .NET Framework 4.8) using the code below


What is the purpose of the single underscore "_" variable in Python?

_ has 3 main conventional uses in Python:

  1. To hold the result of the last executed expression(/statement) in an interactive interpreter session (see docs). This precedent was set by the standard CPython interpreter, and other interpreters have followed suit

  2. For translation lookup in i18n (see the gettext documentation for example), as in code like

    raise forms.ValidationError(_("Please enter a correct username"))
  3. As a general purpose "throwaway" variable name:

    1. To indicate that part of a function result is being deliberately ignored (Conceptually, it is being discarded.), as in code like:

      label, has_label, _ = text.partition(':')
    2. As part of a function definition (using either def or lambda), where the signature is fixed (e.g. by a callback or parent class API), but this particular function implementation doesn't need all of the parameters, as in code like:

      def callback(_):
          return True

      [For a long time this answer didn't list this use case, but it came up often enough, as noted here, to be worth listing explicitly.]

    This use case can conflict with the translation lookup use case, so it is necessary to avoid using _ as a throwaway variable in any code block that also uses it for i18n translation (many folks prefer a double-underscore, __, as their throwaway variable for exactly this reason).

    Linters often recognize this use case. For example year, month, day = date() will raise a lint warning if day is not used later in the code. The fix, if day is truly not needed, is to write year, month, _ = date(). Same with lambda functions, lambda arg: 1.0 creates a function requiring one argument but not using it, which will be caught by lint. The fix is to write lambda _: 1.0. An unused variable is often hiding a bug/typo (e.g. set day but use dya in the next line).

Creating a new DOM element from an HTML string using built-in DOM methods or Prototype

For the heck of it I thought I'd share this over complicated but yet simple approach I came up with... Maybe someone will find something useful.

/*Creates a new element - By Jamin Szczesny*/
function _new(args){
    ele = document.createElement(args.node);
    delete args.node;
    for(x in args){ 
        if(typeof ele[x]==='string'){
            ele[x] = args[x];
            ele.setAttribute(x, args[x]);
    return ele;

/*You would 'simply' use it like this*/

    style:'position:absolute; left:100px; top:100px;'+
          'width:100px; height:100px; border:2px solid red;'+
          'cursor:pointer; background-color:HoneyDew',
    innerHTML:'My newly created div element!',
    value:'for example only',

Are there any Open Source alternatives to Crystal Reports?

You can use jasper report.

iReport is a very effective tool to develop jasper reports.

It supports almost all the facilities provided by crystal report like formatting, grouping, creation of charts etc.

Refer the link for tutorial:

Exception 'open failed: EACCES (Permission denied)' on Android


When using this deprecated method from Android 29 onwards you will receive the same error: open failed: EACCES (Permission denied)

Resolution here:

getExternalStoragePublicDirectory deprecated in Android Q

End-line characters from lines read from text file, using Python

The idiomatic way to do this in Python is to use rstrip('\n'):

for line in open('myfile.txt'):  # opened in text-mode; all EOLs are converted to '\n'
    line = line.rstrip('\n')

Each of the other alternatives has a gotcha:

  • file('...').read().splitlines() has to load the whole file in memory at once.
  • line = line[:-1] will fail if the last line has no EOL.

What are the advantages and disadvantages of recursion?

Recursion means a function calls repeatedly

It uses system stack to accomplish it's task. As stack uses LIFO approach and when a function is called the controlled is moved to where function is defined which has it is stored in memory with some address, this address is stored in stack

Secondly, it reduces a time complexity of a program.

Though bit off-topic,a bit related. Must read. : Recursion vs Iteration

figure of imshow() is too small

I'm new to python too. Here is something that looks like will do what you want to

axes([0.08, 0.08, 0.94-0.08, 0.94-0.08]) #[left, bottom, width, height]

I believe this decides the size of the canvas.

Correct format specifier to print pointer or address?

You can use %x or %X or %p; all of them are correct.

  • If you use %x, the address is given as lowercase, for example: a3bfbc4
  • If you use %X, the address is given as uppercase, for example: A3BFBC4

Both of these are correct.

If you use %x or %X it's considering six positions for the address, and if you use %p it's considering eight positions for the address. For example:

AutoComplete TextBox in WPF

If you have a small number of values to auto complete, you can simply add them in xaml. Typing will invoke auto-complete, plus you have dropdowns too.

<ComboBox Text="{Binding CheckSeconds, UpdateSourceTrigger=PropertyChanged}"
    <ComboBoxItem Content="60"/>
    <ComboBoxItem Content="120"/>
    <ComboBoxItem Content="180"/>
    <ComboBoxItem Content="300"/>
    <ComboBoxItem Content="900"/>

How to call a button click event from another method

You can easily do it by the following piece of code (assuming that name of your button is btnButton):


What is the Python equivalent of static variables inside a function?

Another (not recommended!) twist on the callable object like, if you don't mind using a funky call signature, would be to do

class foo(object):
    counter = 0;
    def __call__():
        foo.counter += 1
        print "counter is %i" % foo.counter

>>> foo()()
counter is 1
>>> foo()()
counter is 2

Get IP address of an interface on Linux

Try this:

#include <stdio.h>
#include <unistd.h>
#include <string.h> /* for strncpy */

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <netinet/in.h>
#include <net/if.h>
#include <arpa/inet.h>

 int fd;
 struct ifreq ifr;

 fd = socket(AF_INET, SOCK_DGRAM, 0);

 /* I want to get an IPv4 IP address */
 ifr.ifr_addr.sa_family = AF_INET;

 /* I want IP address attached to "eth0" */
 strncpy(ifr.ifr_name, "eth0", IFNAMSIZ-1);

 ioctl(fd, SIOCGIFADDR, &ifr);


 /* display result */
 printf("%s\n", inet_ntoa(((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr));

 return 0;

The code sample is taken from here.

How to darken a background using CSS?

You can use a container for your background, placed as absolute and negative z-index :


<div class="main">
    <div class="bg">         
    Hello World!!!!


.main .bg{

.main:hover .bg{

How to change the bootstrap primary color?

Update 2020 for Bootstrap 4

To change the primary, or any of the theme colors in Bootstrap 4 SASS, set the appropriate variables before importing bootstrap.scss. This allows your custom scss to override the !default values...

$primary: purple;
$danger: red;

@import "bootstrap";


In some cases, you may want to set a new color from another existing Bootstrap variable. For this @import the functions and variables first so they can be referenced in the customizations...

/* import the necessary Bootstrap files */
@import "bootstrap/functions";
@import "bootstrap/variables";

$theme-colors: (
  primary: $purple

/* finally, import Bootstrap */
@import "bootstrap";


Also see: this answer, this answer or changing the button color in (CSS or SASS)

It's also possible to change the primary color with CSS only but it requires a lot of additional CSS since there are many -primary variations (btn-primary, alert-primary, bg-primary, text-primary, table-primary, border-primary, etc...) and some of these classes have slight colors variations on borders, hover, and active states. Therefore, if you must use CSS it's better to use target one component such as changing the primary button color.

These solutions will also work for Bootstrap 5 alpha

In where shall I use isset() and !empty()

isset() tests if a variable is set and not null:

empty() can return true when the variable is set to certain values:


$the_var = 0;

if (isset($the_var)) {
  echo "set";
} else {
  echo "not set";

echo "\n";

if (empty($the_var)) {
  echo "empty";
} else {
  echo "not empty";

Table scroll with HTML and CSS

Works only in Chrome but it can be adapted to other modern browsers. Table falls back to common table with scroll bar in other brws. Uses CSS3 FLEX property.

<table border="1px" class="flexy">
    <caption>Lista Sumnjivih vozila:</caption>
            <td>Opis Sumnje</td>
        <td>Registarski<br>broj vozila</td>

        <td>Osumnjicen tranzit</td>
        <td>23-03-2014 20:48:08</td>
        <td>Raskrsnica kod pumpe<br></td>

        <td>Osumnjicen tranzit</td>
        <td>23-03-2014 20:48:08</td>
        <td>Raskrsnica kod pumpe<br></td>

        <td>Osumnjicen tranzit</td>
        <td>23-03-2014 20:48:08</td>
        <td>Raskrsnica kod pumpe<br></td>

        <td>Osumnjicen tranzit</td>
        <td>23-03-2014 20:48:08</td>
        <td>Raskrsnica kod pumpe<br></td>


Style (CSS 3):

caption {
    display: block;
    line-height: 3em;
    width: 100%;
    -webkit-align-items: stretch;
    border: 1px solid #eee;

       .flexy {
            display: block;
            width: 90%;
            border: 1px solid #eee;
            max-height: 320px;
            overflow: auto;

        .flexy thead {
            display: -webkit-flex;
            -webkit-flex-flow: row;

        .flexy thead tr {
            padding-right: 15px;
            display: -webkit-flex;
            width: 100%;
            -webkit-align-items: stretch;

        .flexy tbody {
            display: -webkit-flex;
            height: 100px;
            overflow: auto;
            -webkit-flex-flow: row wrap;
        .flexy tbody tr{
            display: -webkit-flex;
            width: 100%;

        .flexy tr td {
            width: 15%;

How to make sql-mode="NO_ENGINE_SUBSTITUTION" permanent in MySQL my.cnf

My problem was that I had spaces in between the options on 5.7.20. Removing them so the line looked like


What are the differences between LDAP and Active Directory?

There are lots of systems that support LDAP to talk to them, not just Active Directory.

Sun, IBM, Novell all have directory services that are very effective as LDAP servers.

Easy way of running the same junit test over and over?

This works much easier for me.

public class RepeatTests extends TestCase {

    public static Test suite() {
        TestSuite suite = new TestSuite(RepeatTests.class.getName());

        for (int i = 0; i < 10; i++) {              

        return suite;

HTTP Status 504

Suppose access a proxy server A(eg. nginx), and the server A forwards the request to another server B(eg. tomcat).

If this process continues for a long time (more than the proxy server read timeout setting), A still did not get a completed response of B. It happens.

for nginx, You can configure the proxy_read_timeout(in location) property to solve his.But this is usually not a good idea, if you set the value too high. This may hide the real error.You'd better improve the design to really solve this problem.

What is difference between functional and imperative programming languages?

Functional Programming is a form of declarative programming, which describe the logic of computation and the order of execution is completely de-emphasized.

Problem: I want to change this creature from a horse to a giraffe.

  • Lengthen neck
  • Lengthen legs
  • Apply spots
  • Give the creature a black tongue
  • Remove horse tail

Each item can be run in any order to produce the same result.

Imperative Programming is procedural. State and order is important.

Problem: I want to park my car.

  1. Note the initial state of the garage door
  2. Stop car in driveway
  3. If the garage door is closed, open garage door, remember new state; otherwise continue
  4. Pull car into garage
  5. Close garage door

Each step must be done in order to arrive at desired result. Pulling into the garage while the garage door is closed would result in a broken garage door.

How do you find the sum of all the numbers in an array in Java?

In you can use streams:

int[] a = {10,20,30,40,50};
int sum = IntStream.of(a).sum();
System.out.println("The sum is " + sum);


The sum is 150.

It's in the package


CodeIgniter - File upload required validation

I found a solution that works exactly how I want.

I changed

$this->form_validation->set_rules('name', 'Name', 'trim|required');
$this->form_validation->set_rules('code', 'Code', 'trim|required');
$this->form_validation->set_rules('userfile', 'Document', 'required');


$this->form_validation->set_rules('name', 'Name', 'trim|required');
$this->form_validation->set_rules('code', 'Code', 'trim|required');
if (empty($_FILES['userfile']['name']))
    $this->form_validation->set_rules('userfile', 'Document', 'required');

moment.js 24h format

//Format 24H use HH:mm_x000D_
let currentDate = moment().format('YYYY-MM-DD HH:mm')_x000D_
//example of current time with defined Time zone +1_x000D_
let currentDateTm = moment().utcOffset('+0100').format('YYYY-MM-DD HH:mm')_x000D_
<script src=""></script>

Git push error pre-receive hook declined

Despite the question is specific to gitlab, but similar errors can happen on github, depending how it is set up (usually Github Enterprise).

You need to familiarize yourself with the following concepts:

  • pre-receive hooks
  • organization webhooks
  • Webhooks

Webhooks are more commonly understood than other two items.

The Pre-receive hooks

are scripts that run on the GitHub Enterprise server to enforce policy. When a push occurs, each script runs in an isolated environment to determine whether the push is accepted or rejected.

Organization webhooks:

Webhook events are also sent from your repository to your "organization webhooks". more info.

These are set up in your github enterprise. They are specific to the version of the github enterprise. You may have no visibility because of your access limitations (developer, maintainer, admin, etc).

How to represent a DateTime in Excel

You can set date time values to a cell in XlsIO using one of these options

sheet.Range["A1"].Value2 = DateTime.Now;
sheet.Range["A1"].NumberFormat = "dd/mm/yyyy";

sheet.Range["A2"].DateTime = DateTime.Now;
sheet.Range["A2"].NumberFormat = "[$-409]d-mmm-yy;@";

You can find more information here.

Mockito: InvalidUseOfMatchersException

May be helpful for somebody. Mocked method must be of mocked class, created with mock(MyService.class)

echo that outputs to stderr

Another option that I recently stumbled on is this:

        echo "First error line"
        echo "Second error line"
        echo "Third error line"
    } >&2

This uses only Bash built-ins while making multi-line error output less error prone (since you don't have to remember to add &>2 to every line).

Git submodule push

Note that since git1.7.11 ([ANNOUNCE] Git 1.7.11.rc1 and release note, June 2012) mentions:

"git push --recurse-submodules" learned to optionally look into the histories of submodules bound to the superproject and push them out.

Probably done after this patch and the --on-demand option:


Make sure all submodule commits used by the revisions to be pushed are available on a remote tracking branch.

  • If check is used, it will be checked that all submodule commits that changed in the revisions to be pushed are available on a remote.
    Otherwise the push will be aborted and exit with non-zero status.
  • If on-demand is used, all submodules that changed in the revisions to be pushed will be pushed.
    If on-demand was not able to push all necessary revisions it will also be aborted and exit with non-zero status.

So you could push everything in one go with (from the parent repo) a:

git push --recurse-submodules=on-demand

This option only works for one level of nesting. Changes to the submodule inside of another submodule will not be pushed.

With git 2.7 (January 2016), a simple git push will be enough to push the parent repo... and all its submodules.

See commit d34141c, commit f5c7cd9 (03 Dec 2015), commit f5c7cd9 (03 Dec 2015), and commit b33a15b (17 Nov 2015) by Mike Crowe (mikecrowe).
(Merged by Junio C Hamano -- gitster -- in commit 5d35d72, 21 Dec 2015)

push: add recurseSubmodules config option

The --recurse-submodules command line parameter has existed for some time but it has no config file equivalent.

Following the style of the corresponding parameter for git fetch, let's invent push.recurseSubmodules to provide a default for this parameter.
This also requires the addition of --recurse-submodules=no to allow the configuration to be overridden on the command line when required.

The most straightforward way to implement this appears to be to make push use code in submodule-config in a similar way to fetch.

The git config doc now include:


Make sure all submodule commits used by the revisions to be pushed are available on a remote-tracking branch.

  • If the value is 'check', then Git will verify that all submodule commits that changed in the revisions to be pushed are available on at least one remote of the submodule. If any commits are missing, the push will be aborted and exit with non-zero status.
  • If the value is 'on-demand' then all submodules that changed in the revisions to be pushed will be pushed. If on-demand was not able to push all necessary revisions it will also be aborted and exit with non-zero status. -
  • If the value is 'no' then default behavior of ignoring submodules when pushing is retained.

You may override this configuration at time of push by specifying '--recurse-submodules=check|on-demand|no'.


git config push.recurseSubmodules on-demand
git push

Git 2.12 (Q1 2017)

git push --dry-run --recurse-submodules=on-demand will actually work.

See commit 0301c82, commit 1aa7365 (17 Nov 2016) by Brandon Williams (mbrandonw).
(Merged by Junio C Hamano -- gitster -- in commit 12cf113, 16 Dec 2016)

push run with --dry-run doesn't actually (Git 2.11 Dec. 2016 and lower/before) perform a dry-run when push is configured to push submodules on-demand.
Instead all submodules which need to be pushed are actually pushed to their remotes while any updates for the superproject are performed as a dry-run.
This is a bug and not the intended behaviour of a dry-run.

Teach push to respect the --dry-run option when configured to recursively push submodules 'on-demand'.
This is done by passing the --dry-run flag to the child process which performs a push for a submodules when performing a dry-run.

And still in Git 2.12, you now havea "--recurse-submodules=only" option to push submodules out without pushing the top-level superproject.

See commit 225e8bf, commit 6c656c3, commit 14c01bd (19 Dec 2016) by Brandon Williams (mbrandonw).
(Merged by Junio C Hamano -- gitster -- in commit 792e22e, 31 Jan 2017)

Android- create JSON Array and JSON Object

  public void DataSendReg(String picPath, final String ed2, String ed4, int bty1, String bdatee, String ed1, String cno, String address , String select_item, String select_item1, String height, String weight) {

      final ProgressDialog dialog=new ProgressDialog(SignInAct.this);
      AsyncHttpClient httpClient=new AsyncHttpClient();
      RequestParams params=new RequestParams();
      File pic = new File(picPath);
      try {
      } catch (FileNotFoundException e) {
      params.put("state","Gujarat");,params,new JsonHttpResponseHandler(){
          public void onStart() {

          public void onSuccess(int statusCode, Header[] headers, JSONObject response) {
              try {
                  String done=response.get("msg").toString();
                  if(done.equals("s")) {
                      Toast.makeText(SignInAct.this, "Registration Success Fully", Toast.LENGTH_SHORT).show();
                      startActivity(new Intent(SignInAct.this, LoginAct.class));
                  else  if(done.equals("ex")) {
                      Toast.makeText(SignInAct.this, "email already exist", Toast.LENGTH_SHORT).show();
                  }else Toast.makeText(SignInAct.this, "Registration failed", Toast.LENGTH_SHORT).show();
              } catch (JSONException e) {
                  Toast.makeText(SignInAct.this, "e :: ="+e.getMessage(), Toast.LENGTH_SHORT).show();

          public void onFailure(int statusCode, Header[] headers, Throwable throwable, JSONObject errorResponse) {
              Toast.makeText(SignInAct.this, "Server not Responce", Toast.LENGTH_SHORT).show();

          public void onFinish() {

Android Studio: Gradle - build fails -- Execution failed for task ':dexDebug'

ANDROID STUDIO Users try this:-

You need to add the following to your gradle file dependencies:

compile ''

And then add below line ( multidex support application ) to your manifest's application tag:


Android, Java: HTTP POST Request

Please consider using HttpPost. Adopt from this:

URLConnection connection = new URL("").openConnection();
// Http Method becomes POST

// Encode according to application/x-www-form-urlencoded specification
String content =
    "id=" + URLEncoder.encode ("username") +
    "&num=" + URLEncoder.encode ("password") +
    "&remember=" + URLEncoder.encode ("on") +
    "&output=" + URLEncoder.encode ("xml");
connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); 

// Try this should be the length of you content.
// it is not neccessary equal to 48. 
// content.getBytes().length is not neccessarily equal to content.length() if the String contains non ASCII characters.
connection.setRequestProperty("Content-Length", content.getBytes().length); 

// Write body
OutputStream output = connection.getOutputStream(); 

You will need to catch the exception yourself.

PowerShell script to return members of multiple security groups

This will give you a list of a single group, and the members of each group.


import-module activedirectory

# optional, add a wild card..
# $groups = $groups + "*"

$Groups = Get-ADGroup -filter {Name -like $GroupName} | Select-Object Name

ForEach ($Group in $Groups)
   {write-host " "
    write-host "$($"
    write-host "----------------------------"

    Get-ADGroupMember -identity $($groupname) -recursive | Select-Object samaccountname

write-host "Export Complete"

If you want the friendly name, or other details, add them to the end of the select-object query.

Check If array is null or not in php

This checks if the array is empty

if (!empty($result) {
    // do stuf if array is not empty
} else {
    // do stuf if array is empty

This checks if the array is null or not

if (is_null($result) {
   // do stuf if array is null
} else {
   // do stuf if array is not null

How to create checkbox inside dropdown?

var expanded = false;_x000D_
function showCheckboxes() {_x000D_
  var checkboxes = document.getElementById("checkboxes");_x000D_
  if (!expanded) {_x000D_ = "block";_x000D_
    expanded = true;_x000D_
  } else {_x000D_ = "none";_x000D_
    expanded = false;_x000D_
.multiselect {_x000D_
  width: 200px;_x000D_
.selectBox {_x000D_
  position: relative;_x000D_
.selectBox select {_x000D_
  width: 100%;_x000D_
  font-weight: bold;_x000D_
.overSelect {_x000D_
  position: absolute;_x000D_
  left: 0;_x000D_
  right: 0;_x000D_
  top: 0;_x000D_
  bottom: 0;_x000D_
#checkboxes {_x000D_
  display: none;_x000D_
  border: 1px #dadada solid;_x000D_
#checkboxes label {_x000D_
  display: block;_x000D_
#checkboxes label:hover {_x000D_
  background-color: #1e90ff;_x000D_
  <div class="multiselect">_x000D_
    <div class="selectBox" onclick="showCheckboxes()">_x000D_
        <option>Select an option</option>_x000D_
      <div class="overSelect"></div>_x000D_
    <div id="checkboxes">_x000D_
      <label for="one">_x000D_
        <input type="checkbox" id="one" />First checkbox</label>_x000D_
      <label for="two">_x000D_
        <input type="checkbox" id="two" />Second checkbox</label>_x000D_
      <label for="three">_x000D_
        <input type="checkbox" id="three" />Third checkbox</label>_x000D_

Change icon on click (toggle)

Try this:

  icon = $(this).find("i");

or even better, as Kevin said:

  icon = $(this).find("i");
  icon.toggleClass("icon-circle-arrow-up icon-circle-arrow-down")

Converting an array to a function arguments list

A very readable example from another post on similar topic:

var args = [ 'p0', 'p1', 'p2' ];

function call_me (param0, param1, param2 ) {
    // ...

// Calling the function using the array with apply()
call_me.apply(this, args);

And here a link to the original post that I personally liked for its readability

Select an Option from the Right-Click Menu in Selenium Webdriver - Java

Right click can be achieved using Java script executor as well(in cases where action class is not supported):

JavascriptExecutor js = (JavascriptExecutor) driver;

String javaScript = "var evt = document.createEvent('MouseEvents');"
                + "var RIGHT_CLICK_BUTTON_CODE = 2;"
                + "evt.initMouseEvent('contextmenu', true, true, window, 1, 0, 0, 0, 0, false, false, false, false, RIGHT_CLICK_BUTTON_CODE, null);"
                + "arguments[0].dispatchEvent(evt)";

js.executeScript(javaScript, element);

In Git, what is the difference between origin/master vs origin master?

origin/master is an entity (since it is not a physical branch) representing the state of the master branch on the remote origin.

origin master is the branch master on the remote origin.

So we have these:

  • origin/master ( A representation or a pointer to the remote branch)
  • master - (actual branch)
  • <Your_local_branch> (actual branch)
  • <Your_local_branch4> (actual branch)
  • <Your_local_branch4> (actual branch)

Example (in local branch master):

git fetch # get current state of remote repository
git merge origin/master # merge state of remote master branch into local branch
git push origin master # push local branch master to remote branch master

Get response from PHP file using AJAX

<script type="text/javascript">
        function returnwasset(){
            alert('return sent');
                type: "POST",
                url: "process.php",
                data: somedata;
                dataType:'text'; //or HTML, JSON, etc.
                success: function(response){
                    //echo what the server sent back...

When should I use a table variable vs temporary table in sql server?

Use a table variable if for a very small quantity of data (thousands of bytes)

Use a temporary table for a lot of data

Another way to think about it: if you think you might benefit from an index, automated statistics, or any SQL optimizer goodness, then your data set is probably too large for a table variable.

In my example, I just wanted to put about 20 rows into a format and modify them as a group, before using them to UPDATE / INSERT a permanent table. So a table variable is perfect.

But I am also running SQL to back-fill thousands of rows at a time, and I can definitely say that the temporary tables perform much better than table variables.

This is not unlike how CTE's are a concern for a similar size reason - if the data in the CTE is very small, I find a CTE performs as good as or better than what the optimizer comes up with, but if it is quite large then it hurts you bad.

My understanding is mostly based on, which has a lot more detail.

Count number of times a date occurs and make a graph out of it

The simplest is to do a PivotChart. Select your array of dates (with a header) and create a new Pivot Chart (Insert / PivotChart / Ok) Then on the field list window, drag and drop the date column in the Axis list first and then in the value list first.

Step 1:


Step 2:


Angular - POST uploaded file

In my project , I use the XMLHttpRequest to send multipart/form-data. I think it will fit you to.

and the uploader code

let xhr = new XMLHttpRequest();'POST', '', true);
xhr.withCredentials = true;

Here is example :

How can I use inverse or negative wildcards when pattern matching in a unix/linux shell?

You can also use a pretty simple for loop:

for f in `find . -not -name "*Music*"`
    cp $f /target/dir

How can I declare enums using java

Quite simply as follows:

 * @author The Elite Gentleman
public enum MyEnum {
    ONE("one"), TWO("two")
    private final String value;

    private MyEnum(final String value) {
        this.value = value;

    public String getValue() {
        return value;

    public String toString() {
        // TODO Auto-generated method stub
        return getValue();

For more info, visit Enum Types from Oracle Java Tutorials. Also, bear in mind that enums have private constructor.

Update, since you've updated your post, I've changed my value from an int to a String.
Related: Java String enum.

What is a deadlock?

Let me explain a real world (not actually real) example for a deadlock situation from the crime movies. Imagine a criminal holds an hostage and against that, a cop also holds an hostage who is a friend of the criminal. In this case, criminal is not going to let the hostage go if cop won't let his friend to let go. Also the cop is not going to let the friend of criminal let go, unless the criminal releases the hostage. This is an endless untrustworthy situation, because both sides are insisting the first step from each other.

Criminal & Cop Scene

enter image description here

So simply, when two threads needs two different resources and each of them has the lock of the resource that the other need, it is a deadlock.

Another High Level Explanation of Deadlock : Broken Hearts

You are dating with a girl and one day after an argument, both sides are heart-broken to each other and waiting for an I-am-sorry-and-I-missed-you call. In this situation, both sides want to communicate each other if and only if one of them receives an I-am-sorry call from the other. Because that neither of each is going to start communication and waiting in a passive state, both will wait for the other to start communication which ends up in a deadlock situation.

How to get DataGridView cell value in messagebox?

I added this to the Button of a datagrid to get the values of the cells in the row that the user is clicking:

string DGCell = dataGridView1.Rows[e.RowIndex].Cells[X].Value.ToString();

where X is the cell you want to check. Datagrid column count starts at 1 not 0 in my case. Not sure if it is default of a datagrid or because I am using SQL to populate the info.

How to count the number of columns in a table using SQL?

Maybe something like this:

SELECT count(*) FROM user_tab_columns WHERE table_name = 'FOO'

this will count number of columns in a the table FOO

You can also just

select count(*) from all_tab_columns where owner='BAR' and table_name='FOO';

where the owner is schema and note that Table Names are upper case

Generate random 5 characters string

Here are my random 5 cents ...

$random=function($a, $b) {
        $a, $b)


PHP's new password_hash() (* >= PHP 5.5) function is doing the job for generation of decently long set of uppercase and lowercase characters and numbers.

Two concat. strings before and after password_hash within $random function are suitable for change.

Paramteres for $random() *($a,$b) are actually substr() parameters. :)

NOTE: this doesn't need to be a function, it can be normal variable as well .. as one nasty singleliner, like this:

$random=(substr(str_shuffle(('\\`)/|@'.password_hash(mt_rand(0,999999), PASSWORD_DEFAULT).'!*^&~(')), 0, 5));


How to terminate a Python script

While you should generally prefer sys.exit because it is more "friendly" to other code, all it actually does is raise an exception.

If you are sure that you need to exit a process immediately, and you might be inside of some exception handler which would catch SystemExit, there is another function - os._exit - which terminates immediately at the C level and does not perform any of the normal tear-down of the interpreter; for example, hooks registered with the "atexit" module are not executed.

REST API - file (ie images) processing - best practices

OP here (I am answering this question after two years, the post made by Daniel Cerecedo was not bad at a time, but the web services are developing very fast)

After three years of full-time software development (with focus also on software architecture, project management and microservice architecture) I definitely choose the second way (but with one general endpoint) as the best one.

If you have a special endpoint for images, it gives you much more power over handling those images.

We have the same REST API (Node.js) for both - mobile apps (iOS/android) and frontend (using React). This is 2017, therefore you don't want to store images locally, you want to upload them to some cloud storage (Google cloud, s3, cloudinary, ...), therefore you want some general handling over them.

Our typical flow is, that as soon as you select an image, it starts uploading on background (usually POST on /images endpoint), returning you the ID after uploading. This is really user-friendly, because user choose an image and then typically proceed with some other fields (i.e. address, name, ...), therefore when he hits "send" button, the image is usually already uploaded. He does not wait and watching the screen saying "uploading...".

The same goes for getting images. Especially thanks to mobile phones and limited mobile data, you don't want to send original images, you want to send resized images, so they do not take that much bandwidth (and to make your mobile apps faster, you often don't want to resize it at all, you want the image that fits perfectly into your view). For this reason, good apps are using something like cloudinary (or we do have our own image server for resizing).

Also, if the data are not private, then you send back to app/frontend just URL and it downloads it from cloud storage directly, which is huge saving of bandwidth and processing time for your server. In our bigger apps there are a lot of terabytes downloaded every month, you don't want to handle that directly on each of your REST API server, which is focused on CRUD operation. You want to handle that at one place (our Imageserver, which have caching etc.) or let cloud services handle all of it.

Cons : The only "cons" which you should think of is "not assigned images". User select images and continue with filling other fields, but then he says "nah" and turn off the app or tab, but meanwhile you successfully uploaded the image. This means you have uploaded an image which is not assigned anywhere.

There are several ways of handling this. The most easiest one is "I don't care", which is a relevant one, if this is not happening very often or you even have desire to store every image user send you (for any reason) and you don't want any deletion.

Another one is easy too - you have CRON and i.e. every week and you delete all unassigned images older than one week.

Is there a way to provide named parameters in a function call in JavaScript?

ES2015 and later

In ES2015, parameter destructuring can be used to simulate named parameters. It would require the caller to pass an object, but you can avoid all of the checks inside the function if you also use default parameters:

myFunction({ param1 : 70, param2 : 175});

function myFunction({param1, param2}={}){
  // ...function body...

// Or with defaults, 
function myFunc({
  name = 'Default user',
  age = 'N/A'
}={}) {
  // ...function body...


There is a way to come close to what you want, but it is based on the output of Function.prototype.toString [ES5], which is implementation dependent to some degree, so it might not be cross-browser compatible.

The idea is to parse the parameter names from the string representation of the function so that you can associate the properties of an object with the corresponding parameter.

A function call could then look like

func(a, b, {someArg: ..., someOtherArg: ...});

where a and b are positional arguments and the last argument is an object with named arguments.

For example:

var parameterfy = (function() {
    var pattern = /function[^(]*\(([^)]*)\)/;

    return function(func) {
        // fails horribly for parameterless functions ;)
        var args = func.toString().match(pattern)[1].split(/,\s*/);

        return function() {
            var named_params = arguments[arguments.length - 1];
            if (typeof named_params === 'object') {
                var params = [], 0, -1);
                if (params.length < args.length) {
                    for (var i = params.length, l = args.length; i < l; i++) {
                    return func.apply(this, params);
            return func.apply(null, arguments);

Which you would use as:

var foo = parameterfy(function(a, b, c) {
    console.log('a is ' + a, ' | b is ' + b, ' | c is ' + c);     

foo(1, 2, 3); // a is 1  | b is 2  | c is 3
foo(1, {b:2, c:3}); // a is 1  | b is 2  | c is 3
foo(1, {c:3}); // a is 1  | b is undefined  | c is 3
foo({a: 1, c:3}); // a is 1  | b is undefined  | c is 3 


There are some drawbacks to this approach (you have been warned!):

  • If the last argument is an object, it is treated as a "named argument objects"
  • You will always get as many arguments as you defined in the function, but some of them might have the value undefined (that's different from having no value at all). That means you cannot use arguments.length to test how many arguments have been passed.

Instead of having a function creating the wrapper, you could also have a function which accepts a function and various values as arguments, such as

call(func, a, b, {posArg: ... });

or even extend Function.prototype so that you could do:

foo.execute(a, b, {posArg: ...});

The R %in% operator

You can use all

> all(1:6 %in% 0:36)
[1] TRUE
> all(1:60 %in% 0:36)

On a similar note, if you want to check whether any of the elements is TRUE you can use any

> any(1:6 %in% 0:36)
[1] TRUE
> any(1:60 %in% 0:36)
[1] TRUE
> any(50:60 %in% 0:36)

replace all occurrences in a string

As explained here, you can use:

function replaceall(str,replace,with_this)
    var str_hasil ="";
    var temp;

    for(var i=0;i<str.length;i++) // not need to be equal. it causes the last change: undefined..
        if (str[i] == replace)
            temp = with_this;
                temp = str[i];

        str_hasil += temp;

    return str_hasil;

... which you can then call using:

var str = "50.000.000";

The function will alert "50000000"

Regex for 1 or 2 digits, optional non-alphanumeric, 2 known alphas


\d defines a number and {1,2} means 1 or two of the expression before, \W defines a non word character.

Replace console output in Python

An easy solution is just writing "\r" before the string and not adding a newline; if the string never gets shorter this is sufficient...

sys.stdout.write("\rDoing thing %i" % i)

Slightly more sophisticated is a progress bar... this is something I am using:

def startProgress(title):
    global progress_x
    sys.stdout.write(title + ": [" + "-"*40 + "]" + chr(8)*41)
    progress_x = 0

def progress(x):
    global progress_x
    x = int(x * 40 // 100)
    sys.stdout.write("#" * (x - progress_x))
    progress_x = x

def endProgress():
    sys.stdout.write("#" * (40 - progress_x) + "]\n")

You call startProgress passing the description of the operation, then progress(x) where x is the percentage and finally endProgress()

int object is not iterable?

Don't make it a int(), but make it a range() will solve this problem.

inp = range(input("Enter a number: "))

Sending data through POST request from a node.js server to a node.js server

Posting data is a matter of sending a query string (just like the way you would send it with an URL after the ?) as the request body.

This requires Content-Type and Content-Length headers, so the receiving server knows how to interpret the incoming data. (*)

var querystring = require('querystring');
var http = require('http');

var data = querystring.stringify({
      username: yourUsernameValue,
      password: yourPasswordValue

var options = {
    host: 'my.url',
    port: 80,
    path: '/login',
    method: 'POST',
    headers: {
        'Content-Type': 'application/x-www-form-urlencoded',
        'Content-Length': Buffer.byteLength(data)

var req = http.request(options, function(res) {
    res.on('data', function (chunk) {
        console.log("body: " + chunk);


(*) Sending data requires the Content-Type header to be set correctly, i.e. application/x-www-form-urlencoded for the traditional format that a standard HTML form would use.

It's easy to send JSON (application/json) in exactly the same manner; just JSON.stringify() the data beforehand.

URL-encoded data supports one level of structure (i.e. key and value). JSON is useful when it comes to exchanging data that has a nested structure.

The bottom line is: The server must be able to interpret the content type in question. It could be text/plain or anything else; there is no need to convert data if the receiving server understands it as it is.

Add a charset parameter (e.g. application/json; charset=Windows-1252) if your data is in an unusual character set, i.e. not UTF-8. This can be necessary if you read it from a file, for example.

Negation in Python

Python prefers English keywords to punctuation. Use not x, i.e. not os.path.exists(...). The same thing goes for && and || which are and and or in Python.

How to get the current working directory in Java?

I hope you want to access the current directory including the package i.e. If your Java program is in c:\myApp\com\foo\src\service\ and you want to print until c:\myApp\com\foo\src\service then you can try the following code:

String myCurrentDir = System.getProperty("user.dir")
            + File.separator
            + System.getProperty("")
                    .substring(0, System.getProperty("").lastIndexOf("."))
                    .replace(".", File.separator);

Note: This code is only tested in Windows with Oracle JRE.

How to repeat a char using printf?

i think doing some like this.

void printchar(char c, int n){
     int i;


WebSocket with SSL

1 additional caveat (besides the answer by kanaka/peter): if you use WSS, and the server certificate is not acceptable to the browser, you may not get any browser rendered dialog (like it happens for Web pages). This is because WebSockets is treated as a so-called "subresource", and certificate accept / security exception / whatever dialogs are not rendered for subresources.

Spring Boot - Loading Initial Data

I created a library that facilitates initial/demo data loading in a Spring Boot application. You can find it at

Once the data fixtures starter is on the classpath, it will automatically try to load DICTIONARY data upon application startup (this behavior can be controlled by properties) - all you need to do is to register a bean implementing DataFixture.

I find loading initial data by code superior to loading it using SQL scripts:

  • the logic of your fixtures lives close to your application logic/domain model and it is subject to refactoring as your domain evolves
  • you benefit from incremental demo data updates - imagine a QA environment with some user data (that needs not to be lost after application deploy) but at the same time you want to add data for the new features you developed

Example data fixture:

 * You can have as many fixture classes as you want.
 * @Order annotation is respected for the fixtures belonging to the same set.
 * You can make your demo database to be incrementally updated with fresh data
 * each time the application is redeployed - all you need to do is to write
 * a good condition in `canBeLoaded()` method.
public class InitialDataFixture implements DataFixture {

    private final LanguageRepository languageRepository;

    // ...

    public DataFixtureSet getSet() {
      return DataFixtureSet.DICTIONARY;

     * We want to make sure the fixture is applied once and once only.
     * A more sophisticated condition can be used to create incremental demo data
     * over time without the need to reset the QA database (for example).
    public boolean canBeLoaded() {
      return languageRepository.size() == 0;

     * The actual application of the fixture.
     * Assuming that data fixtures are registered as beans, this method can call
     * other services and/or repositories.
    public void load() {
          new Language("en-US"), new Language("pl-PL")));

The concept is inspired by the Symfony Doctrine Data Fixtures bundle.

Including a groovy script in another groovy

Another way to do this is to define the functions in a groovy class and parse and add the file to the classpath at runtime:

File sourceFile = new File("path_to_file.groovy");
Class groovyClass = new GroovyClassLoader(getClass().getClassLoader()).parseClass(sourceFile);
GroovyObject myObject = (GroovyObject) groovyClass.newInstance();

android EditText - finished typing event

Better way, you can also use EditText onFocusChange listener to check whether user has done editing: (Need not rely on user pressing the Done or Enter button on Soft keyboard)

 ((EditText)findViewById( OnFocusChangeListener() {

    public void onFocusChange(View v, boolean hasFocus) {

      // When focus is lost check that the text field has valid values.

      if (!hasFocus) { {
         // Validate youredittext

Note : For more than one EditText, you can also let your class implement View.OnFocusChangeListener then set the listeners to each of you EditText and validate them as below


    public void onFocusChange(View v, boolean hasFocus) {

      // When focus is lost check that the text field has valid values.

      if (!hasFocus) {
        switch (view.getId()) {
                 // Validate EditText1
                 // Validate EditText2

jQuery: go to URL with target="_blank"

The .ready function is used to insert the attribute once the page has finished loading.

$(document).ready(function() {
     $("class name or id a.your class name").attr({"target" : "_blank"})

ExecutorService that interrupts tasks after a timeout

check if this works for you,

    public <T,S,K,V> ResponseObject<Collection<ResponseObject<T>>> runOnScheduler(ThreadPoolExecutor threadPoolExecutor,
      int parallelismLevel, TimeUnit timeUnit, int timeToCompleteEachTask, Collection<S> collection,
      Map<K,V> context, Task<T,S,K,V> someTask){
      return ResponseObject.<Collection<ResponseObject<T>>>builder().errorCode("500").errorMessage("threadPoolExecutor can not be null").build();
      return ResponseObject.<Collection<ResponseObject<T>>>builder().errorCode("500").errorMessage("Task can not be null").build();
      return ResponseObject.<Collection<ResponseObject<T>>>builder().errorCode("500").errorMessage("input collection can not be empty").build();

    LinkedBlockingQueue<Callable<T>> callableLinkedBlockingQueue = new LinkedBlockingQueue<>(collection.size());
    collection.forEach(value -> {
      callableLinkedBlockingQueue.offer(()->someTask.perform(value,context)); //pass some values in callable. which can be anything.
    LinkedBlockingQueue<Future<T>> futures = new LinkedBlockingQueue<>();

    int count = 0;

    while(count<parallelismLevel && count < callableLinkedBlockingQueue.size()){
      Future<T> f = threadPoolExecutor.submit(callableLinkedBlockingQueue.poll());

    Collection<ResponseObject<T>> responseCollection = new ArrayList<>();

      Future<T> future = futures.poll();
      ResponseObject<T> responseObject = null;
        try {
          T response = future.get(timeToCompleteEachTask, timeUnit);
          responseObject = ResponseObject.<T>builder().data(response).build();
        } catch (InterruptedException e) {
        } catch (ExecutionException e) {
        } catch (TimeoutException e) {
        } finally {
          if (Objects.nonNull(responseObject)) {
          futures.remove(future);//remove this
          Callable<T> callable = getRemainingCallables(callableLinkedBlockingQueue);
            Future<T> f = threadPoolExecutor.submit(callable);

    return ResponseObject.<Collection<ResponseObject<T>>>builder().data(responseCollection).build();

  private <T> Callable<T> getRemainingCallables(LinkedBlockingQueue<Callable<T>> callableLinkedBlockingQueue){
      return callableLinkedBlockingQueue.poll();
    return null;

you can restrict the no of thread uses from scheduler as well as put timeout on the task.

Pandas Split Dataframe into two Dataframes at a specific row

I generally use array split because it's easier simple syntax and scales better with more than 2 partitions.

import numpy as np
partitions = 2
dfs = np.array_split(df, partitions)

np.split(df, [100,200,300], axis=0] wants explicit index numbers which may or may not be desirable.

How to get screen width without (minus) scrollbar?

Try this :

$('body, html').css('overflow', 'hidden');
var screenWidth1 = $(window).width();
$('body, html').css('overflow', 'visible');
var screenWidth2 = $(window).width();
alert(screenWidth1); // Gives the screenwith without scrollbar
alert(screenWidth2); // Gives the screenwith including scrollbar

You can get the screen width by with and without scroll bar by using this code. Here, I have changed the overflow value of body and get the width with and without scrollbar.

How to get the class of the clicked element?


load scripts asynchronously

One reason why your scripts could be loading so slowly is if you were running all of your scripts while loading the page, like this:


instead of:

$(window).load(function() {

This second bit of script waits until the browser has completely loaded all of your Javascript code before it starts executing any of your scripts, making it appear to the user that the page has loaded faster.

If you're looking to enhance the user's experience by decreasing the loading time, I wouldn't go for the "loading screen" option. In my opinion that would be much more annoying than just having the page load more slowly.

Understanding colors on Android (six characters)

Android uses hexadecimal ARGB values, which are formatted as #AARRGGBB. That first pair of letters, the AA, represent the alpha channel. You must convert your decimal opacity values to a hexadecimal value. Here are the steps:

Alpha Hex Value Process

  1. Take your opacity as a decimal value and multiply it by 255. So, if you have a block that is 50% opaque the decimal value would be .5. For example: .5 x 255 = 127.5
  2. The fraction won't convert to hexadecimal, so you must round your number up or down to the nearest whole number. For example: 127.5 rounds up to 128; 55.25 rounds down to 55.
  3. Enter your decimal value in a decimal-to-hexadecimal converter, like, and convert your values.
  4. If you only get back a single value, prefix it with a zero. For example, if you're trying to get 5% opacity and you're going through this process, you'll end up with the hexadecimal value of D. Add a zero in front of it so it appears as 0D.

That's how you find the alpha channel value. I've taken the liberty to put together a list of values for you. Enjoy!

Hex Opacity Values

  • 100% — FF
  • 95% — F2
  • 90% — E6
  • 85% — D9
  • 80% — CC
  • 75% — BF
  • 70% — B3
  • 65% — A6
  • 60% — 99
  • 55% — 8C
  • 50% — 80
  • 45% — 73
  • 40% — 66
  • 35% — 59
  • 30% — 4D
  • 25% — 40
  • 20% — 33
  • 15% — 26
  • 10% — 1A
  • 5% — 0D
  • 0% — 00

Apache VirtualHost 403 Forbidden

If you did everything right, just give the permission home directory like:

sudo chmod o+x $HOME


sudo systemctl restart apache2

Finding the index of elements based on a condition using python list comprehension

  • In Python, you wouldn't use indexes for this at all, but just deal with the values—[value for value in a if value > 2]. Usually dealing with indexes means you're not doing something the best way.

  • If you do need an API similar to Matlab's, you would use numpy, a package for multidimensional arrays and numerical math in Python which is heavily inspired by Matlab. You would be using a numpy array instead of a list.

    >>> import numpy
    >>> a = numpy.array([1, 2, 3, 1, 2, 3])
    >>> a
    array([1, 2, 3, 1, 2, 3])
    >>> numpy.where(a > 2)
    (array([2, 5]),)
    >>> a > 2
    array([False, False,  True, False, False,  True], dtype=bool)
    >>> a[numpy.where(a > 2)]
    array([3, 3])
    >>> a[a > 2]
    array([3, 3])

python ValueError: invalid literal for float()

Watch out for possible unintended literals in your argument

for example you can have a space within your argument, rendering it to a string / literal:

float(' 0.33')

After making sure the unintended space did not make it into the argument, I was left with:


Like this it works like a charm.

Take away is: Pay Attention for unintended literals (e.g. spaces that you didn't see) within your input.

'uint32_t' does not name a type

You need to include stdint.h

 #include <stdint.h>

How to efficiently change image attribute "src" from relative URL to absolute using jQuery?

The replace method in Javascript returns a value, and does not act upon the existing string object. See:

In your example, you will have to do

$(this).attr("src", $(this).attr("src").replace(...))

Escape single quote character for use in an SQLite query

In C# you can use the following to replace the single quote with a double quote:

 string sample = "St. Mary's";
 string escapedSample = sample.Replace("'", "''");

And the output will be:

"St. Mary''s"

And, if you are working with Sqlite directly; you can work with object instead of string and catch special things like DBNull:

private static string MySqlEscape(Object usString)
    if (usString is DBNull)
        return "";
    string sample = Convert.ToString(usString);
    return sample.Replace("'", "''");

How do I do an initial push to a remote repository with Git?

You can try this:

on Server:

adding new group to /etc/group like (example)


create new git repository:

mkdir /srv/git
cd /srv/git
mkdir project_dir
cd project_dir
git --bare init (initial git repository )
chgrp -R mygroup objects/ refs/ (change owner of directory )
chmod -R g+w objects/ refs/ (give permission write)

on Client:

mkdir my_project
cd my_project
touch .gitignore
git init
git add .
git commit -m "Initial commit"
git remote add origin [email protected]:/path/to/my_project.git
git push origin master

(Thanks Josh Lindsey for client side)

after Client, do on Server this commands:

cd /srv/git/project_dir
chmod -R g+w objects/ refs/

If got this error after git pull:

There is no tracking information for the current branch. Please specify which branch you want to merge with. See git-pull(1) for details

git pull <remote> <branch>
If you wish to set tracking information for this branch you can do so with:

git branch --set-upstream new origin/<branch>


git push -u origin master

It will help.

openpyxl - adjust column width size

Here is an answer for Python 3.8 and OpenPyXL 3.0.0.

I tried to avoid using the get_column_letter function but failed.

This solution uses the newly introduced assignment expressions aka "walrus operator":

import openpyxl
from openpyxl.utils import get_column_letter

workbook = openpyxl.load_workbook("myxlfile.xlsx")

worksheet = workbook["Sheet1"]

for i, column_cells in enumerate(worksheet.columns, start=1):
    width = (
        if (length := max(len(str(cell_value) if (cell_value := cell.value) is not None else "")
                          for cell in column_cells)) >= MIN_WIDTH
        else MIN_WIDTH
    worksheet.column_dimensions[get_column_letter(i)].width = width

Fixed page header overlaps in-page anchors

You can do this with jQuery:

var offset = $('.target').offset();
var scrollto = - 50; // fixed_top_bar_height = 50px
$('html, body').animate({scrollTop:scrollto}, 0);

Adding Google Play services version to your app's manifest?

This error can also happen when you've downloaded a new version of Google Play Services and not installed the latest SDK. Thats what happened to me. So, as the others mentioned, if you try to import Google Play Services and then open the console, you'll see a compile error. Try installing all the recent Android SDKs and try again, if this is the case.

lvalue required as left operand of assignment error when using C++

It is just a typo(I guess)-


instead of p +1=p; is required .

As name suggest lvalue expression should be left-hand operand of the assignment operator.

How to check date of last change in stored procedure or function in SQL server

SELECT name, create_date, modify_date 
FROM sys.objects
WHERE type = 'P'
ORDER BY modify_date DESC

The type for a function is FN rather than P for procedure. Or you can filter on the name column.

Undoing a git rebase

I tried all suggestions with reset and reflog without any success. Restoring local history of IntelliJ resolved the problem of lost files

how to get curl to output only http response body (json) and no other headers etc


req=$(curl -s -X GET http://host:8080/some/resource -H "Accept: application/json") 2>&1
echo "${req}"

How to download a file with Node.js (without using third-party libraries)?

As Michelle Tilley said, but with the appropriate control flow:

var http = require('http');
var fs = require('fs');

var download = function(url, dest, cb) {
  var file = fs.createWriteStream(dest);
  http.get(url, function(response) {
    file.on('finish', function() {

Without waiting for the finish event, naive scripts may end up with an incomplete file.

Edit: Thanks to @Augusto Roman for pointing out that cb should be passed to file.close, not called explicitly.

Python Array with String Indices

Even better, try an OrderedDict (assuming you want something like a list). Closer to a list than a regular dict since the keys have an order just like list elements have an order. With a regular dict, the keys have an arbitrary order.

Note that this is available in Python 3 and 2.7. If you want to use with an earlier version of Python you can find installable modules to do that.

Printing reverse of any String without using any predefined function?

Here you go:

public static void main (String[] args) {

private static String reverserString(String src) {
    char[] sArr = src.toCharArray();
    char[] dArr = new char[sArr.length];
    for(int i=sArr.length; i>0; i--) {
        dArr[sArr.length-i] = sArr[i-1];

    return new String(dArr);

How do I make a new line in swift

You can use the following code;

var example: String = "Hello World \r\n This is a new line"

Getting Date or Time only from a DateTime Object

var currentDateTime = dateTime.Now();
var date=currentDateTime.Date;

How to solve "Unresolved inclusion: <iostream>" in a C++ file in Eclipse CDT?

On Windows, with Eclipse CDT Oxygen, none of the solutions described here worked for me. I described what works for me in this other question: Eclipse CDT: Unresolved inclusion of stl header.

How to make System.out.println() shorter

Some interesting alternatives:


PrintStream p = System.out;


PrintWriter p = new PrintWriter(System.out, true);

What should I use to open a url instead of urlopen in urllib3

You should use urllib.reuqest, not urllib3.

import urllib.request   # not urllib - important!

How do I properly set the permgen size?

Don't put the environment configuration in catalina.bat/ Instead you should create a new file in CATALINA_BASE\bin\setenv.bat to keep your customizations separate of tomcat installation.

How do I remove blank elements from an array?

Try this:

puts ["Kathmandu", "Pokhara", "", "Dharan", "Butwal"] - [""]

Bash: Echoing a echo command with a variable in bash

echo "echo "we are now going to work with ${ser}" " >> $servfile

Escape all " within quotes with \. Do this with variables like \$servicetest too:

echo "echo \"we are now going to work with \${ser}\" " >> $servfile    
echo "read -p \"Please enter a service: \" ser " >> $servfile
echo "if [ \$servicetest > /dev/null ];then " >> $servfile

MySQL combine two columns and add into a new column

Create the column:

ALTER TABLE yourtable ADD COLUMN combined VARCHAR(50);

Update the current values:

UPDATE yourtable SET combined = CONCAT(zipcode, ' - ', city, ', ', state);

Update all future values automatically:

CREATE TRIGGER insert_trigger
SET new.combined = CONCAT(new.zipcode, ' - ',, ', ', new.state);

CREATE TRIGGER update_trigger
SET new.combined = CONCAT(new.zipcode, ' - ',, ', ', new.state);

Escaping Double Quotes in Batch Script

For example for Unreal engine Automation tool run from batch file - this worked for me

eg: -cmdline=" -Messaging" -device=device -addcmdline="-SessionId=session -SessionOwner='owner' -SessionName='Build' -dataProviderMode=local -LogCmds='LogCommodity OFF' -execcmds='automation list; runtests tests+separated+by+T1+T2; quit' " -run

Hope this helps someone, worked for me.

Viewing root access files/folders of android on windows

You can use Eclipse DDMS perspective to see connected devices and browse through files, you can also pull and push files to the device. You can also do a bunch of stuff using DDMS, this link explains a little bit more of DDMS uses.


If you just want to copy a database you can locate the database on eclipse DDMS file explorer, select it and then pull the database from the device to your computer.

href="tel:" and mobile numbers

As an additional note, you may also add markup language for pausing or waiting, I learned this from the iPhone iOS which allows numbers to be stored with extension numbers in the same line. A semi-colon establishes a wait, which will show as a next step upon calling the number. This helps to simplify the workflow of calling numbers with extensions in their board. You press the button shown on the bottom left of the iPhone screen when prompted, and the iPhone will dial it automatically.

<a href="tel:+50225079227;1">Call Now</a>

The pause is entered with a comma ",", allowing a short pause of time for each comma. Once the time has passed, the number after the comma will be dialed automatically

<a href="tel:+50225079227,1">Call Now, you will be automaticlaly transferred</a>

HTTP Status 404 - The requested resource (/) is not available

In my case, I've had to click on my project, then go to File > Properties > *servlet name* and click Restart servlet.

How to generate the "create table" sql statement for an existing table in postgreSQL

Here is a query with some edits,

select 'CREATE TABLE ' || a.attrelid::regclass::text || '(' ||
string_agg(a.attname || ' ' || pg_catalog.format_type(a.atttypid, 
        CASE WHEN 
            (SELECT substring(pg_catalog.pg_get_expr(d.adbin, d.adrelid) for 128)
             FROM pg_catalog.pg_attrdef d
             WHERE d.adrelid = a.attrelid AND d.adnum = a.attnum AND a.atthasdef) IS NOT NULL THEN
            ' DEFAULT '|| (SELECT substring(pg_catalog.pg_get_expr(d.adbin, d.adrelid) for 128)
                          FROM pg_catalog.pg_attrdef d
                          WHERE d.adrelid = a.attrelid AND d.adnum = a.attnum AND a.atthasdef)
            '' END
        CASE WHEN a.attnotnull = true THEN 
            ' NOT NULL'
            '' END,E'\n,') || ');' 
FROM pg_catalog.pg_attribute a join pg_class on a.attrelid=pg_class.oid
WHERE a.attrelid::regclass::varchar =  
AND a.attnum > 0 AND NOT a.attisdropped  and pg_class.relkind='r'
group by a.attrelid;

How can I define an interface for an array of objects with Typescript?

You don't need to use an indexer (since it a bit less typesafe). You have two options :

interface EnumServiceItem {
    id: number; label: string; key: any

interface EnumServiceItems extends Array<EnumServiceItem>{}

// Option A 
var result: EnumServiceItem[] = [
    { id: 0, label: 'CId', key: 'contentId' },
    { id: 1, label: 'Modified By', key: 'modifiedBy' },
    { id: 2, label: 'Modified Date', key: 'modified' },
    { id: 3, label: 'Status', key: 'contentStatusId' },
    { id: 4, label: 'Status > Type', key: ['contentStatusId', 'contentTypeId'] },
    { id: 5, label: 'Title', key: 'title' },
    { id: 6, label: 'Type', key: 'contentTypeId' },
    { id: 7, label: 'Type > Status', key: ['contentTypeId', 'contentStatusId'] }

// Option B
var result: EnumServiceItems = [
    { id: 0, label: 'CId', key: 'contentId' },
    { id: 1, label: 'Modified By', key: 'modifiedBy' },
    { id: 2, label: 'Modified Date', key: 'modified' },
    { id: 3, label: 'Status', key: 'contentStatusId' },
    { id: 4, label: 'Status > Type', key: ['contentStatusId', 'contentTypeId'] },
    { id: 5, label: 'Title', key: 'title' },
    { id: 6, label: 'Type', key: 'contentTypeId' },
    { id: 7, label: 'Type > Status', key: ['contentTypeId', 'contentStatusId'] }

Personally I recommend Option A (simpler migration when you are using classes not interfaces).

C++ printing boolean, what is displayed?

The standard streams have a boolalpha flag that determines what gets displayed -- when it's false, they'll display as 0 and 1. When it's true, they'll display as false and true.

There's also an std::boolalpha manipulator to set the flag, so this:

#include <iostream>
#include <iomanip>

int main() {
    std::cout << std::boolalpha;   
    return 0;

...produces output like:


For what it's worth, the actual word produced when boolalpha is set to true is localized--that is, <locale> has a num_put category that handles numeric conversions, so if you imbue a stream with the right locale, it can/will print out true and false as they're represented in that locale. For example,

#include <iostream>
#include <iomanip>
#include <locale>

int main() {

    std::cout << false << "\n";
    std::cout << std::boolalpha;
    std::cout << false << "\n";
    return 0;

...and at least in theory (assuming your compiler/standard library accept "fr" as an identifier for "French") it might print out faux instead of false. I should add, however, that real support for this is uneven at best--even the Dinkumware/Microsoft library (usually quite good in this respect) prints false for every language I've checked.

The names that get used are defined in a numpunct facet though, so if you really want them to print out correctly for particular language, you can create a numpunct facet to do that. For example, one that (I believe) is at least reasonably accurate for French would look like this:

#include <array>
#include <string>
#include <locale>
#include <ios>
#include <iostream>

class my_fr : public std::numpunct< char > {
    char do_decimal_point() const { return ','; }
    char do_thousands_sep() const { return '.'; }
    std::string do_grouping() const { return "\3"; }
    std::string do_truename() const { return "vrai";  }
    std::string do_falsename() const { return "faux"; }

int main() {
    std::cout.imbue(std::locale(std::locale(), new my_fr));

    std::cout << false << "\n";
    std::cout << std::boolalpha;
    std::cout << false << "\n";
    return 0;

And the result is (as you'd probably expect):


Trigger standard HTML5 validation (form) without using submit button?

After some research, I've came up with the following code that should be the answer to your question. (At least it worked for me)

Use this piece of code first. The $(document).ready makes sure the code is executed when the form is loaded into the DOM:


Then just call $('#theIdOfMyForm').submit(); in your code.


If you actually want to show which field the user had wrong in the form then add the following code after event.preventDefault();

$('#theIdOfMyForm :input:visible[required="required"]').each(function()
        // break
        return false;

It will give focus on the first invalid input.

jQuery - multiple $(document).ready ...?

Both will get called, first come first served. Take a look here.

    $("#page-title").html("Document-ready was called!");

    $("#page-title").html("Document-ready 2 was called!");


Document-ready 2 was called!

mysqli_connect(): (HY000/2002): No connection could be made because the target machine actively refused it

For those who came here looking for the answer and didnt type 3306 wrong...If like myself, you have wasted hours with no luck searching for this answer, then possibly this may help.

If you are seeing this: (HY000/2002): No connection could be made because the target machine actively refused it

Then my understanding is that it cant connect for one of the following below. Now which..

1) is your wamp, mamp, etc icon GREEN? Either way, right-click the icon --> click tools --> test both the port used for Apache (typically 80) and for Mariadb (3307?). Should say 'It is correct' for both.

2) Error comes from a .php file. So, check your dbconnect.php.

$servername = "localhost";
$username = "your_username";
$password = "your_pw";
$dbname = "your_dbname";
$port = "3307";

Is your setup correct? Does your user exist? Do they have rights? Does port match the tested port in 1)? Doesn't have to be 3307 and user can be root. You can also left click the green icon --> click MariaDB and view used port as shown in the image below. All good? Positive? ok!

enter image description here

3) Error comes when you login to phpmyadmin. So, check your my.ini.

enter image description here

Open my.ini by left clicking the green icon --> click MariaDB -->

; The following options will be passed to all MariaDB clients
;password = your_password
port = 3307
socket = /tmp/mariadb.sock

; Here follows entries for some specific programs

; The MariaDB server
port = 3307
socket = /tmp/mariadb.sock

Make sure the ports match the port MariaDB is being testing on. Then finally..

port = 3307

At the bottom of my.ini, make sure this port matches as well.

4) 1-3 done? restart your WAMP and cross your fingers!

Remove whitespaces inside a string in javascript

You can use Strings replace method with a regular expression.

"Hello World ".replace(/ /g, "");

The replace() method returns a new string with some or all matches of a pattern replaced by a replacement. The pattern can be a string or a RegExp


  • / / - Regular expression matching spaces

  • g - Global flag; find all matches rather than stopping after the first match

const str = "H    e            l l       o  World! ".replace(/ /g, "");_x000D_
document.getElementById("greeting").innerText = str;
<p id="greeting"><p>

Better way to revert to a previous SVN revision of a file?

I recently had to revert to a particular revision to debug an older build and this worked like magic:

svn up -r 3340 (or what ever your desired revision number)

I had to resolve all conflicts using "tc" option as I did not care about local changes (checked in everything I cared about prior to reverting)

To get back to head revision was simple too:

svn up


Mecki's answer is absolutly perfect, but it's worth adding that FreeBSD also supports SO_REUSEPORT_LB, which mimics Linux' SO_REUSEPORT behaviour - it balances the load; see setsockopt(2)

Comments in Android Layout xml

click the


and write anything you and evrything will be in comments

UILabel is not auto-shrinking text to fit label size

Coming late to the party, but since I had the additional requirement of having one word per line, this one addition did the trick for me:

label.numberOfLines = [labelString componentsSeparatedByString:@" "].count;

Apple Docs say:

Normally, the label text is drawn with the font you specify in the font property. If this property is set to YES, however, and the text in the text property exceeds the label’s bounding rectangle, the receiver starts reducing the font size until the string fits or the minimum font size is reached. In iOS 6 and earlier, this property is effective only when the numberOfLines property is set to 1.

But this is a lie. A lie I tell you! It's true for all iOS versions. Specifically, this is true when using a UILabel within a UICollectionViewCell for which the size is determined by constraints adjusted dynamically at runtime via custom layout (ex. self.menuCollectionViewLayout.itemSize = size).

So when used in conjunction with adjustsFontSizeToFitWidth and minimumScaleFactor, as mentioned in previous answers, programmatically setting numberOfLines based on word count solved the autoshrink problem. Doing something similar based on word count or even character count might produce a "close enough" solution.

How do I connect C# with Postgres?

Here is a walkthrough, Using PostgreSQL in your C# (.NET) application (An introduction):

In this article, I would like to show you the basics of using a PostgreSQL database in your .NET application. The reason why I'm doing this is the lack of PostgreSQL articles on CodeProject despite the fact that it is a very good RDBMS. I have used PostgreSQL back in the days when PHP was my main programming language, and I thought.... well, why not use it in my C# application.

Other than that you will need to give us some specific problems that you are having so that we can help diagnose the problem.

How to find the Git commit that introduced a string in any branch?

git log -S"string_to_search" # options like --source --reverse --all etc

Pay attention not to use spaces between S and "string_to_search". In some setups (git 1.7.1), you'll get an error like:

fatal: ambiguous argument 'string_to_search': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions

Uncaught TypeError: Cannot use 'in' operator to search for 'length' in

The only solution that worked for me and $.each was definitely causing the error. so i used for loop and it's not throwing error anymore.

Example code

            type: 'GET',
            url: '',
            data: { get_param: 'value' },
            success: function (data) {
                for (var i = 0; i < data.length; ++i) {

Why is char[] preferred over String for passwords?

These are all the reasons, one should choose a char[] array instead of String for a password.

1. Since Strings are immutable in Java, if you store the password as plain text it will be available in memory until the Garbage collector clears it, and since String is used in the String pool for reusability there is a pretty high chance that it will remain in memory for a long duration, which poses a security threat.

Since anyone who has access to the memory dump can find the password in clear text, that's another reason you should always use an encrypted password rather than plain text. Since Strings are immutable there is no way the contents of Strings can be changed because any change will produce a new String, while if you use a char[] you can still set all the elements as blank or zero. So storing a password in a character array clearly mitigates the security risk of stealing a password.

2. Java itself recommends using the getPassword() method of JPasswordField which returns a char[], instead of the deprecated getText() method which returns passwords in clear text stating security reasons. It's good to follow advice from the Java team and adhere to standards rather than going against them.

3. With String there is always a risk of printing plain text in a log file or console but if you use an Array you won't print contents of an array, but instead its memory location gets printed. Though not a real reason, it still makes sense.

String strPassword="Unknown";
char[] charPassword= new char[]{'U','n','k','w','o','n'};
System.out.println("String password: " + strPassword);
System.out.println("Character password: " + charPassword);

String password: Unknown
Character password: [C@110b053

Referenced from this blog. I hope this helps.

Force an Android activity to always use landscape mode

Press CTRL+F11 to rotate the screen.

How to get difference between two rows for a column field?

Does SQL Server support analytic functions?

select   rowint,
         value - lag(value) over (order by rowint) diff
from     myTable
order by rowint

Best way to deploy Visual Studio application that can run without installing

First you need to publish the file by:

  1. BUILD -> PUBLISH or by right clicking project on Solution Explorer -> properties -> publish or select project in Solution Explorer and press Alt + Enter NOTE: if you are using Visual Studio 2013 then in properties you have to go to BUILD and then you have to disable define DEBUG constant and define TRACE constant and you are ready to go. Representation

  2. Save your file to a particular folder. Find the produced files (the EXE file and the .config, .manifest, and .application files, along with any DLL files, etc.) - they are all in the same folder and typically in the bin\Debug folder below the project file (.csproj). In Visual Studio they are in the Application Files folder and inside that you just need the .exe and dll files. (You have to delete ClickOnce and other files and then make this folder a zip file and distribute it.)

NOTE: The ClickOnce application does install the project to system, but it has one advantage. You DO NOT require administrative privileges here to run (if your application follows the normal guidelines for which folders to use for application data, etc.).

Change navbar text color Bootstrap

In fact, we can simply use the standard bootstrap text colors, instead of hacking the CSS formats.

Standard Color examples: text-primary, text-secondary, text-success, text-danger, text-warning, text-info

In the Navbar code sample bellow, the text Homepage would be in the orange color (text-warning).

<a class="navbar-brand text-warning" href="/" > Homepage </a>

In the Navbar menu item sample bellow, the text Menu Item would be in the blue color (text-primary).

<a class="dropdown-item text-primary" href="/my-link">Menu Item</a>

Type or namespace name does not exist

Delete the .refresh.dll file if you are under source control. Then rebuild. It should work. This worked for me

Does the Java &= operator apply & or &&?

see 15.22.2 of the JLS. For boolean operands, the & operator is boolean, not bitwise. The only difference between && and & for boolean operands is that for && it is short circuited (meaning that the second operand isn't evaluated if the first operand evaluates to false).

So in your case, if b is a primitive, a = a && b, a = a & b, and a &= b all do the same thing.

JSON array get length

have you tried size() ? Something like :


Hope it helps.

How to use Sublime over SSH

lsyncd seem to be nice alternative to the sshfs approach. If you use "-delay 0" it works in real-time.

Difference between Static and final?

static means there is only one copy of the variable in memory shared by all instances of the class.

The final keyword just means the value can't be changed. Without final, any object can change the value of the variable.

How do I tell Gradle to use specific JDK version?

If you are using JDK 9+, you can do this:

java {
    sourceCompatibility = JavaVersion.VERSION_1_8
    targetCompatibility = JavaVersion.VERSION_1_8

tasks.withType<JavaCompile> {
    options.compilerArgs.addAll(arrayOf("--release", "8"))

You can also see the following related issues:

How to import a csv file using python with headers intact, where first column is a non-numerical

You can use pandas library and reference the rows and columns like this:

import pandas as pd

input = pd.read_csv("path_to_file");

#for accessing ith row:

#for accessing column named X

#for accessing ith row and column named X

Convert Uppercase Letter to Lowercase and First Uppercase in Sentence using CSS

You will not be able to capitalize the first word of each sentence with CSS.

CSS offers text-transform for capitalization, but it only supports capitalize, uppercase and lowercase. None of these will do what you want. You can make use of the selector :first-letter, which will apply any style to the first letter of an element - but not of the subsequent ones.

p {
    text-transform: lowercase;
p:first-letter {
    text-transform: capitalize;
<!-- will become this:
Sample text. some sentence. something else. -->

That is not what you want (and :first-letter is not cross-browser compatible... IE again).
The only way to do what you want is with a kind of programming language (serverside or clientside), like Javascript or PHP. In PHP you have the ucwords function (documented here), which just like CSS capitalizes each letter of each word, but doing some programming magic (check out the comments of the documentation for references), you are able to achieve capitalization of each first letter of each sentence.

The easier solution and you might not want to do PHP is using Javascript. Check out the following page - Capital Letters - for a full blown Javascript example of doing exactly what you want. The Javascript is pretty short and does the capitalization with some String manipulation - you will have no problem adjusting the capitalize-sentences.js to your needs.

In any case: Capitalization should usually be done in the content itself not via Javascript or markup languages. Consider cleaning up your content (your texts) with other means. Microsoft Word for example has built in functions to do just what you want.

What is polymorphism, what is it for, and how is it used?

I know this is an older question with a lot of good answers but I'd like to include a one sentence answer:

Treating a derived type as if it were it's base type.

There are plenty of examples above that show this in action, but I feel this is a good concise answer.

NodeJS / Express: what is "app.use"?

The app object is instantiated on creation of the Express server. It has a middleware stack that can be customized in app.configure()(this is now deprecated in version 4.x).

To setup your middleware, you can invoke app.use(<specific_middleware_layer_here>) for every middleware layer that you want to add (it can be generic to all paths, or triggered only on specific path(s) your server handles), and it will add onto your Express middleware stack. Middleware layers can be added one by one in multiple invocations of use, or even all at once in series with one invocation. See use documentation for more details.

To give an example for conceptual understanding of Express Middleware, here is what my app middleware stack (app.stack) looks like when logging my app object to the console as JSON:

   [ { route: '', handle: [Function] },
     { route: '', handle: [Function: static] },
     { route: '', handle: [Function: bodyParser] },
     { route: '', handle: [Function: cookieParser] },
     { route: '', handle: [Function: session] },
     { route: '', handle: [Function: methodOverride] },
     { route: '', handle: [Function] },
     { route: '', handle: [Function] } ]

As you might be able to deduce, I called app.use(express.bodyParser()), app.use(express.cookieParser()), etc, which added these express middleware 'layers' to the middleware stack. Notice that the routes are blank, meaning that when I added those middleware layers I specified that they be triggered on any route. If I added a custom middleware layer that only triggered on the path /user/:id that would be reflected as a string in the route field of that middleware layer object in the stack printout above.

Each layer is essentially adding a function that specifically handles something to your flow through the middleware.

E.g. by adding bodyParser, you're ensuring your server handles incoming requests through the express middleware. So, now parsing the body of incoming requests is part of the procedure that your middleware takes when handling incoming requests -- all because you called app.use(bodyParser).

Docker - Ubuntu - bash: ping: command not found

Alternatively you can use a Docker image which already has ping installed, e.g. busybox:

docker run --rm busybox ping SERVER_NAME -c 2

How to install latest version of git on CentOS 7.x/6.x

You can use WANDisco's CentOS repository to install Git 2.x: for CentOS 6, for CentOS 7

  1. Install WANDisco repo package:

    yum install
    - or -
    yum install
    - or -
    yum install
  2. Install the latest version of Git 2.x:

    yum install git
  3. Verify the version of Git that was installed:

    git --version

As of 02 Mar. 2020, the latest available version from WANDisco is 2.22.0.

How to copy to clipboard in Vim?

If you are using vim in MAC OSX, unfortunately it comes with older verion, and not complied with clipboard options. Luckily, homebrew can easily solve this problem.

install vim:

brew install vim

install gui verion of vim:

brew install macvim

restart the terminal to take effect.

append the following line to ~/.vimrc
set clipboard=unnamed

now you can copy the line in vim with yy and paste it system-wide.

Updated Method:

I was never satisfied with set clipboard method for years. The biggest drawback is it will mess up your clipboard history, even when you use x for deletion. Here is a better and more elegant solution.

  1. Copy the text [range] of vim into the system clipboard. (Hint: use v or V to select the range first, and then type the colon : to activate the Ex command):
    :[line-range]yank +
    :5,10y * (copy/yank lines 5-10 to the system clipboard * register)

  2. Paste the content from the system clipboard into vim on a new line:
    :put +


  1. If you select a word range, the above will not work. use "*y or "+y to save this visual block to clipboard. However this is hard to type, I am still thinking about alternatives.
  2. :help "* or :help *+ for more informations
  3. brew info vim will be able to see other options for installing vim. Currrently it does not have any other options.

nginx - nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)

In my case, one of the services either Apache, Apache2 or Nginx was already running and due to that I was not able to start the other service.

How to find whether or not a variable is empty in Bash?

I have also seen

if [ "x$variable" = "x" ]; then ...

which is obviously very robust and shell independent.

Also, there is a difference between "empty" and "unset". See How to tell if a string is not defined in a Bash shell script.

How do I install pip on macOS or OS X?

Install python3 first, then use pip3 to install packages.

brew install python

python3 will be installed, and pip is shipped with it. To use pip to install some package, run the following

pip3 install package

Notice it's pip3 because you want to use python3.

Are nested try/except blocks in Python a good programming practice?

According to the documentation, it is better to handle multiple exceptions through tuples or like this:

import sys

    f = open('myfile.txt')
    s = f.readline()
    i = int(s.strip())
except IOError as e:
    print "I/O error({0}): {1}".format(e.errno, e.strerror)
except ValueError:
    print "Could not convert data to an integer."
    print "Unexpected error: ", sys.exc_info()[0]

How to convert char* to wchar_t*?

In your example, wc is a local variable which will be deallocated when the function call ends. This puts you into undefined behavior territory.

The simple fix is this:

const wchar_t *GetWC(const char *c)
    const size_t cSize = strlen(c)+1;
    wchar_t* wc = new wchar_t[cSize];
    mbstowcs (wc, c, cSize);

    return wc;

Note that the calling code will then have to deallocate this memory, otherwise you will have a memory leak.

How to create a multiline UITextfield?

Besides from the multiple line behaviour, the main difference between UITextView and UITextField is that the UITextView does not propose a placeholder. To bypass this limitation, you can use a UITextView with a "fake placeholder."

See this SO question for details: Placeholder in UITextView.

Git push error '[remote rejected] master -> master (branch is currently checked out)'

You can get around this "limitation" by editing the .git/config on the destination server. Add the following to allow a git repository to be pushed to even if it is "checked out":

denyCurrentBranch = warn


denyCurrentBranch = false

The first will allow the push while warning of the possibility to mess up the branch, whereas the second will just quietly allow it.

This can be used to "deploy" code to a server which is not meant for editing. This is not the best approach, but a quick one for deploying code.

Using the GET parameter of a URL in JavaScript

You can use this function

function getParmFromUrl(url, parm) {
    var re = new RegExp(".*[?&]" + parm + "=([^&]+)(&|$)");
    var match = url.match(re);
    return(match ? match[1] : "");

What is the difference between Left, Right, Outer and Inner Joins?

Making it more visible might help. One example:

Table 1:


1               Raony
2               Diogo
3               Eduardo
4               Luiz

Table 2:


3               l1
4               l2
5               l3

What I get when I do:

-Inner join of Table 1 and Table 2: 

    - Inner join returns both tables merged only when the key 
      (ID_STUDENT) exists in both tables


        3               Eduardo          l1
        4               Luiz             l2

-Left join of Table 1 and Table 2:

    - Left join merges both tables with all records form table 1, in 
      other words, there might be non-populated fields from table 2


        1               Raony            -
        2               Diogo            -
        3               Eduardo          l1
        4               Luiz             l2

-Right join of table 1 and table 2:

    - Right join merges both tables with all records from table 2, in 
      other words, there might be non-populated fields from table 1


        3               Eduardo          l1
        4               Luiz             l2
        5               -                l3

-Outter join of table 1 and table 2:

    - Returns all records from both tables, in other words, there
      might be non-populated fields either from table 1 or 2.

        1               Raony            -
        2               Diogo            -
        3               Eduardo          l1
        4               Luiz             l2
        5               -                l3

Replacing all non-alphanumeric characters with empty strings

Guava's CharMatcher provides a concise solution:

output = CharMatcher.javaLetterOrDigit().retainFrom(input);

Example on ToggleButton

    android:textOn="Vibrate on"
    android:textOff="Vibrate off"

Within the Activity that hosts this layout, the following method handles the click event:

public void onToggleClicked(View view) {
    // Is the toggle on?
    boolean on = ((ToggleButton) view).isChecked();

    if (on) {
        // Enable vibrate
    } else {
        // Disable vibrate

How to switch back to 'master' with git?

Will take you to the master branch.

git checkout master

To switch to other branches do (ignore the square brackets, it's just for emphasis purposes)

git checkout [the name of the branch you want to switch to]

To create a new branch use the -b like this (ignore the square brackets, it's just for emphasis purposes)

git checkout -b [the name of the branch you want to create]

Interface defining a constructor signature?

The purpose of an interface is to enforce a certain object signature. It should explicitly not be concerned with how an object works internally. Therefore, a constructor in an interface does not really make sense from a conceptual point of view.

There are some alternatives though:

  • Create an abstract class that acts as a minimal default implementation. That class should have the constructors you expect implementing classes to have.

  • If you don't mind the overkill, use the AbstractFactory pattern and declare a method in the factory class interface that has the required signatures.

  • Pass the GraphicsDeviceManager as a parameter to the Update and Draw methods.

  • Use a Compositional Object Oriented Programming framework to pass the GraphicsDeviceManager into the part of the object that requires it. This is a pretty experimental solution in my opinion.

The situation you describe is not easy to handle in general. A similar case would be entities in a business application that require access to the database.

Dynamically Add Variable Name Value Pairs to JSON Object

I'm assuming each entry in "ips" can have multiple name value pairs - so it's nested. You can achieve this data structure as such:

var ips = {}

function addIpId(ipID, name, value) {
    if (!ips[ipID]) ip[ipID] = {};
    var entries = ip[ipID];
    // you could add a check to ensure the name-value par's not already defined here
    var entries[name] = value;

Dump a list in a pickle file and retrieve it back later

Pickling will serialize your list (convert it, and it's entries to a unique byte string), so you can save it to disk. You can also use pickle to retrieve your original list, loading from the saved file.

So, first build a list, then use pickle.dump to send it to a file...

Python 3.4.1 (default, May 21 2014, 12:39:51) 
[GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.2.79)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> mylist = ['I wish to complain about this parrot what I purchased not half an hour ago from this very boutique.', "Oh yes, the, uh, the Norwegian Blue...What's,uh...What's wrong with it?", "I'll tell you what's wrong with it, my lad. 'E's dead, that's what's wrong with it!", "No, no, 'e's uh,...he's resting."]
>>> import pickle
>>> with open('parrot.pkl', 'wb') as f:
...   pickle.dump(mylist, f)

Then quit and come back later… and open with pickle.load...

Python 3.4.1 (default, May 21 2014, 12:39:51) 
[GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.2.79)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import pickle
>>> with open('parrot.pkl', 'rb') as f:
...   mynewlist = pickle.load(f)
>>> mynewlist
['I wish to complain about this parrot what I purchased not half an hour ago from this very boutique.', "Oh yes, the, uh, the Norwegian Blue...What's,uh...What's wrong with it?", "I'll tell you what's wrong with it, my lad. 'E's dead, that's what's wrong with it!", "No, no, 'e's uh,...he's resting."]

How to change checkbox's border style in CSS?

put it in a div and add border to the div

What is the difference between statically typed and dynamically typed languages?

Statically typed languages like C++, Java and Dynamically typed languages like Python differ only in terms of the execution of the type of the variable. Statically typed languages have static data type for the variable, here the data type is checked during compiling so debugging is much simpler...whereas Dynamically typed languages don't do the same, the data type is checked which executing the program and hence the debugging is bit difficult.

Moreover they have a very small difference and can be related with strongly typed and weakly typed languages. A strongly typed language doesn't allow you to use one type as another eg. C and C++ ...whereas weakly typed languages allow eg.python

Force sidebar height 100% using CSS (with a sticky bottom image)?

use body background if you are using fixed width sidebar give the same width image as your side bar. also put background-repeat:repeat-y in your css codes.

Why does Vim save files with a ~ extension?

You're correct that the .swp file is used by vim for locking and as a recovery file.

Try putting set nobackup in your vimrc if you don't want these files. See the Vim docs for various backup related options if you want the whole scoop, or want to have .bak files instead...

How to upload & Save Files with Desired name

i know what went wrong you see you used "" instead of '' in this

$target_Path = $target_Path.basename( 



How do I get into a non-password protected Java keystore or change the password?

Getting into a non-password protected Java keystore and changing the password can be done with a help of Java programming language itself.

That article contains the code for that:

Android Studio Gradle project "Unable to start the daemon process /initialization of VM"

I had the same problem, what i found was that Android Developer tools doesn't work well with JDK 8. I deleted my current JDK 8 and and installed JDK 7 and worked just like that no increase of heap memory or delete of .gradle folder.