Programs & Examples On #Function interposition

Replacing a function in a dynamic library by providing an alternative definition

Using ffmpeg to change framerate

You may consider using fps filter. It won't change the video playback speed:

ffmpeg -i <input> -filter:v fps=fps=30 <output>

Worked nice for reducing fps from 59.6 to 30.

How to stop app that node.js express 'npm start'

Check with netstat -nptl all processes

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0*               LISTEN      1736/mongod     
tcp        0      0    *               LISTEN      1594/sshd       
tcp6       0      0 :::3977                 :::*                    LISTEN      6231/nodejs     
tcp6       0      0 :::22                   :::*                    LISTEN      1594/sshd       
tcp6       0      0 :::3200                 :::*                    LISTEN      5535/nodejs 

And it simply kills the process by the PID reference.... In my case I want to stop the 6231/nodejs so I execute the following command:

kill -9 6231

Timeout for python requests.get entire response

Set the timeout parameter:

r = requests.get(w, verify=False, timeout=10) # 10 seconds

As long as you don't set stream=True on that request, this will cause the call to requests.get() to timeout if the connection takes more than ten seconds, or if the server doesn't send data for more than ten seconds.

What is the difference between i++ and ++i?

Just for the record, in C++, if you can use either (i.e.) you don't care about the ordering of operations (you just want to increment or decrement and use it later) the prefix operator is more efficient since it doesn't have to create a temporary copy of the object. Unfortunately, most people use posfix (var++) instead of prefix (++var), just because that is what we learned initially. (I was asked about this in an interview). Not sure if this is true in C#, but I assume it would be.

Select rows with same id but different value in another column

Use this

select * from (
 SELECT ARIDNR,LIEFNR,row_number() over 
     (partition by ARIDNR order by ARIDNR) as RowNum) a
where a.RowNum >1

Fastest way to determine if record exists

                         FROM dbo.[YourTable] 
                         WHERE [YourColumn] = [YourValue]) 
            THEN CAST (1 AS BIT) 
            ELSE CAST (0 AS BIT) END

This approach returns a boolean for you.

How to set JAVA_HOME path on Ubuntu?

I normally set paths in


However for Java, I followed instructions at

and it was sufficient for me.

you can also define multiple java_home's and have only one of them active (rest commented).

suppose in your bashrc file, you have

export JAVA_HOME=......jdk1.7

#export JAVA_HOME=......jdk1.8

notice 1.8 is commented. Once you do

source ~/.bashrc

jdk1.7 will be in path.

you can switch them fairly easily this way. There are other more permanent solutions too. The link I posted has that info.

How to fix error with xml2-config not found when installing PHP from sources?

this solution it gonna be ok on Redhat 8.0

sudo yum install libxml2-devel

How can I modify a saved Microsoft Access 2007 or 2010 Import Specification?

Tim Lentine's answer works IF you have yours specs saved. Your question did not specify that, it only stated you had imported the data. His method would not save your specs that way.

The way to save the spec of that current import is to re-open the import, hit "apend" and that will allow you to use your current import settings that MS Access picked up. (This is useful if your want to keep the import specs from an Excel format you worked on prior to importing into MS ACCESS.)

Once you're in the apend option, use Tim's instructions, which is using the advanced option and "Save As." From there, simply click cancel, and you can now import any other similar data to various tables, etc.

What is Android's file system?

since most of the devices use eMMC,the file system android uses is ext4,except for the firmware.refer-

Here is the filesystem on galaxy s4:

  • /system ext4

  • /data ext4

  • /cache ext4

  • /firmware vfat

  • /data/media /mnt/shell/emulated sdcardfs

The detailed output is as follows:

/dev/block/platform/msm_sdcc.1/by-name/system /system ext4 ro,seclabel,relatime, data=ordered 0 0

/dev/block/platform/msm_sdcc.1/by-name/userdata /data ext4 rw,seclabel,nosuid,no dev,noatime,discard,journal_checksum,journal_async_commit,noauto_da_alloc,data=o rdered 0 0

/dev/block/platform/msm_sdcc.1/by-name/cache /cache ext4 rw,seclabel,nosuid,node v,noatime,discard,journal_checksum,journal_async_commit,noauto_da_alloc,data=ord ered 0 0

/dev/block/platform/msm_sdcc.1/by-name/efs /efs ext4 rw,seclabel,nosuid,nodev,no atime,discard,journal_checksum,journal_async_commit,noauto_da_alloc,errors=panic ,data=ordered 0 0

/dev/block/platform/msm_sdcc.1/by-name/persdata /persdata/absolute ext4 rw,secla bel,nosuid,nodev,relatime,data=ordered 0 0

/dev/block/platform/msm_sdcc.1/by-name/apnhlos /firmware vfat ro,context=u:objec t_r:firmware:s0,relatime,uid=1000,gid=1000,fmask=0337,dmask=0227,codepage=cp437, iocharset=iso8859-1,shortname=lower,errors=remount-ro 0 0

/dev/block/platform/msm_sdcc.1/by-name/mdm /firmware-mdm vfat ro,context=u:objec t_r:firmware:s0,relatime,uid=1000,gid=1000,fmask=0337,dmask=0227,codepage=cp437, iocharset=iso8859-1,shortname=lower,errors=remount-ro 0 0

/data/media /mnt/shell/emulated sdcardfs rw,nosuid,nodev,relatime,uid=1023,gid=1 023 0 0

fetch in git doesn't get all branches

Had the same problem today setting up my repo from scratch. I tried everything, nothing worked except removing the origin and re-adding it back again.

git remote rm origin
git remote add origin [email protected]:web3coach/the-blockchain-bar-newsletter-edition.git

git fetch --all
// Ta daaa all branches fetched

Ctrl+click doesn't work in Eclipse Juno

I had the exact same issue while working on a GIT based project. I was able to resolve by changing the way i was importing the project in the workspace.

Wrong way : Import project to workspace from GIT perspective , like right click on the GIT URL and selecting the option import which was not recognizing the project facets.

Right way (which resolved my issue): clone the project in GIT perspective , change to JEE Perspective , then import from file > import > Existing Maven Project .

How to change the ROOT application?

There are three methods:

  • First shutdown your Tomcat from the its bin directory (sh Then delete all the content of your Tomcat webapps folder (rm -fr *). Then rename your WAR file to ROOT.war, and finally start your Tomcat from the bin directory (sh

  • Leave your war file in $CATALINA_BASE/webapps under its original name. Turn off autoDeploy and deployOnStartup in your Host element in the server.xml file. Explicitly define all application Contexts in server.xml, specifying both the path and docBase attributes. You must do this because you have disabled all the Tomcat auto-deploy mechanisms, and Tomcat will not deploy your applications anymore unless it finds their Context in the server.xml.

    second method: in order to make any change to any application, you will have to stop and restart Tomcat.

  • Place your WAR file outside of $CATALINA_BASE/webapps (it must be outside to prevent double deployment). Place a context file named ROOT.xml in $CATALINA_BASE/conf/. The single element in this context file MUST have a docBase attribute pointing to the location of your WAR file. The path element should not be set - it is derived from the name of the .xml file, in this case ROOT.xml. See the documentation for the Context container for details.


Dilemma: when to use Fragments vs Activities:

I use Fragments for better user experience. For example if you have a Button and you want to run let's say a webservice when you click it, I attach a Fragment to the parent Activity.

if (id == {

    ForecastFragment forecastFragment = new ForecastFragment();
    FragmentManager fm = getSupportFragmentManager();
    FragmentTransaction ft = fm.beginTransaction();
    ft.replace(, forecastFragment);

In that way the user won't have to move in another activity.

And secondly I prefer Fragments because you can handle them easily during rotation.

What is the best way to convert an array to a hash in Ruby

Edit: Saw the responses posted while I was writing, Hash[a.flatten] seems the way to go. Must have missed that bit in the documentation when I was thinking through the response. Thought the solutions that I've written can be used as alternatives if required.

The second form is simpler:

a = [[:apple, 1], [:banana, 2]]
h = a.inject({}) { |r, i| r[i.first] = i.last; r }

a = array, h = hash, r = return-value hash (the one we accumulate in), i = item in the array

The neatest way that I can think of doing the first form is something like this:

a = [:apple, 1, :banana, 2]
h = {}
a.each_slice(2) { |i| h[i.first] = i.last }

ALTER TABLE, set null in not null column, PostgreSQL 9.1

First, Set :

How to load a model from an HDF5 file in Keras?

If you stored the complete model, not only the weights, in the HDF5 file, then it is as simple as

from keras.models import load_model
model = load_model('model.h5')

How to get current date in 'YYYY-MM-DD' format in ASP.NET?

<%= DateTime.Now.ToString("yyyy-MM-dd") %>

Assert that a method was called in a Python unit test

Yes if you are using Python 3.3+. You can use the built-in unittest.mock to assert method called. For Python 2.6+ use the rolling backport Mock, which is the same thing.

Here is a quick example in your case:

from unittest.mock import MagicMock
aw = aps.Request("nv1")
aw.Clear = MagicMock()
aw2 = aps.Request("nv2", aw)
assert aw.Clear.called

Convert LocalDateTime to LocalDateTime in UTC

Try this using this method.

convert your LocalDateTime to ZonedDateTime by using the of method and pass system default time zone or you can use ZoneId of your zone like ZoneId.of("Australia/Sydney");

LocalDateTime convertToUtc(LocalDateTime dateTime) {
  ZonedDateTime dateTimeInMyZone = ZonedDateTime.
                                        of(dateTime, ZoneId.systemDefault());

  return dateTimeInMyZone

To convert back to your zone local date time use:

LocalDateTime convertFromUtc(LocalDateTime utcDateTime){
    return ZonedDateTime.
            of(utcDateTime, ZoneId.of("UTC"))

Difference between margin and padding?

Padding is the space between you content and the border. Where as Margin is the space between the border and the other element.

How to split string using delimiter char using T-SQL?

For your specific data, you can use

Select col1, col2, LTRIM(RTRIM(SUBSTRING(
    STUFF(col3, CHARINDEX('|', col3,
    PATINDEX('%|Client Name =%', col3) + 14), 1000, ''),
    PATINDEX('%|Client Name =%', col3) + 14, 1000))) col3
from Table01

EDIT - charindex vs patindex


select col3='Clent ID = 4356hy|Client Name = B B BOB|Client Phone = 667-444-2626|Client Fax = 666-666-0151|Info = INF8888877 -MAC333330554/444400800'
into t1m
from master..spt_values a
cross join master..spt_values b
where a.number < 100
-- (711704 row(s) affected)

set statistics time on

dbcc dropcleanbuffers
dbcc freeproccache
select a=CHARINDEX('|Client Name =', col3) into #tmp1 from t1m
drop table #tmp1

dbcc dropcleanbuffers
dbcc freeproccache
select a=PATINDEX('%|Client Name =%', col3) into #tmp2 from t1m
drop table #tmp2

set statistics time off



 SQL Server Execution Times (1):
   CPU time = 5656 ms,  elapsed time = 6418 ms.
 SQL Server Execution Times (2):
   CPU time = 5813 ms,  elapsed time = 6114 ms.
 SQL Server Execution Times (3):
   CPU time = 5672 ms,  elapsed time = 6108 ms.


 SQL Server Execution Times (1):
   CPU time = 5906 ms,  elapsed time = 6296 ms.
 SQL Server Execution Times (2):
   CPU time = 5860 ms,  elapsed time = 6404 ms.
 SQL Server Execution Times (3):
   CPU time = 6109 ms,  elapsed time = 6301 ms.


The timings for CharIndex and PatIndex for 700k calls are within 3.5% of each other, so I don't think it would matter whichever is used. I use them interchangeably when both can work.

javascript popup alert on link click

just make it function,

<script type="text/javascript">
function AlertIt() {
var answer = confirm ("Please click on OK to continue.")
if (answer)

<a href="javascript:AlertIt();">click me</a>

What is the difference between typeof and instanceof and when should one be used vs. the other?

instanceof also works when callback is a subtype of Function, I think

What's the difference between JavaScript and JScript?

JScript is the Microsoft implementation of Javascript

Have nginx access_log and error_log log to STDOUT and STDERR of master process

When running Nginx in a Docker container, be aware that a volume mounted over the log dir defeats the purpose of creating a softlink between the log files and stdout/stderr in your Dockerfile, as described in @Boeboe 's answer.

In that case you can either create the softlink in your entrypoint (executed after volumes are mounted) or not use a volume at all (e.g. when logs are already collected by a central logging system).

How do I debug "Error: spawn ENOENT" on node.js?

In my case removing node, delete all AppData/Roaming/npm and AppData/Roaming/npm-cache and installing node once again solve the issue.

How do I specify row heights in CSS Grid layout?

One of the Related posts gave me the (simple) answer.

Apparently the auto value on the grid-template-rows property does exactly what I was looking for.

.grid {
    grid-template-columns: 1fr 1.5fr 1fr;
    grid-template-rows: auto auto 1fr 1fr 1fr auto auto;
    height: calc(100vh - 10px);

How to get Java Decompiler / JD / JD-Eclipse running in Eclipse Helios

  1. Download the JD-Eclipse Update Site(
  2. Launch Eclipse,

  3. Click on "Help > Install New Software...",

  4. Click on button "Add..." to add an new repository,

  5. Enter "JD-Eclipse Update Site" and select the local site directory,

  6. Check "Java Decompiler Eclipse Plug-in",

  7. Next, next, next... and restart Eclipse.

Install a Python package into a different directory using pip?

With pip v1.5.6 on Python v2.7.3 (GNU/Linux), option --root allows to specify a global installation prefix, (apparently) irrespective of specific package's options. Try f.i.,

$ pip install --root=/alternative/prefix/path package_name

Your CPU supports instructions that this TensorFlow binary was not compiled to use: AVX AVX2

What worked for me tho is this library

Install this library and do as instructed on the page, it works like a charm!

IEnumerable<object> a = new IEnumerable<object>(); Can I do this?

I wanted to create a new enumerable object or list and be able to add to it.

This comment changes everything. You can't add to a generic IEnumerable<T>. If you want to stay with the interfaces in System.Collections.Generic, you need to use a class that implements ICollection<T> like List<T>.

Google Maps v2 - set both my location and zoom in

Its a late answer but I think it will help. Use this method:

protected void zoomMapInitial(LatLng finalPlace, LatLng currenLoc) {
    try {
        int padding = 200; // Space (in px) between bounding box edges and view edges (applied to all four sides of the bounding box)
        LatLngBounds.Builder bc = new LatLngBounds.Builder();

        googleMap.moveCamera(CameraUpdateFactory.newLatLngBounds(, padding));
    } catch (Exception e) {

Use this method after loading the map. Cheers!

Add CSS class to a div in code behind

What if:

 <asp:Button ID="Button1" runat="server" CssClass="test1 test3 test-test" />

To add or remove a class, instead of overwriting all classes with

   BtnventCss.CssClass = "hom_but_a"

keep the HTML correct:

    string classname = "TestClass";

    // Add a class
    BtnventCss.CssClass = String.Join(" ", Button1
               .Split(' ')
               .Except(new string[]{"",classname})
               .Concat(new string[]{classname})

     // Remove a class
     BtnventCss.CssClass = String.Join(" ", Button1
               .Split(' ')
               .Except(new string[]{"",classname})

This assures

  • The original classnames remain.
  • There are no double classnames
  • There are no disturbing extra spaces

Especially when client-side development is using several classnames on one element.

In your example, use

   string classname = "TestClass";

    // Add a class
    Button1.Attributes.Add("class", String.Join(" ", Button1
               .Split(' ')
               .Except(new string[]{"",classname})
               .Concat(new string[]{classname})

     // Remove a class
     Button1.Attributes.Add("class", String.Join(" ", Button1
               .Split(' ')
               .Except(new string[]{"",classname})

You should wrap this in a method/property ;)

What is the best collation to use for MySQL with PHP?

The accepted answer fairly definitively suggests using utf8_unicode_ci, and whilst for new projects that's great, I wanted to relate my recent contrary experience just in case it saves anyone some time.

Because utf8_general_ci is the default collation for Unicode in MySQL, if you want to use utf8_unicode_ci then you end up having to specify it in a lot of places.

For example, all client connections not only have a default charset (makes sense to me) but also a default collation (i.e. the collation will always default to utf8_general_ci for unicode).

Likely, if you use utf8_unicode_ci for your fields, your scripts that connect to the database will need to be updated to mention the desired collation explicitly -- otherwise queries using text strings can fail when your connection is using the default collation.

The upshot is that when converting an existing system of any size to Unicode/utf8, you may end up being forced to use utf8_general_ci because of the way MySQL handles defaults.

Use images instead of radio buttons

You can use CSS for that.

HTML (only for demo, it is customizable)

<div class="button">
    <input type="radio" name="a" value="a" id="a" />
    <label for="a">a</label>
<div class="button">
    <input type="radio" name="a" value="b" id="b" />
    <label for="b">b</label>
<div class="button">
    <input type="radio" name="a" value="c" id="c" />
    <label for="c">c</label>


input[type="radio"] {
    display: none;
input[type="radio"]:checked + label {
    border: 1px solid red;


Kubernetes Pod fails with CrashLoopBackOff

I faced similar issue "CrashLoopBackOff" when I debugged getting pods and logs of pod. Found out that my command arguments are wrong

angular-cli server - how to specify default port

The answer provided by elwyn is correct. But you should also update protractor config for e2e.

In angular.json,

"serve": {
      "builder": "@angular-devkit/build-angular:dev-server",
      "options": {
        "port": 9000,
        "browserTarget": "app:build"

In e2e/protractor.conf.js

exports.config = {
    allScriptsTimeout: 11000,
    specs: [
    capabilities: {
        'browserName': 'chrome'
    directConnect: true,
    baseUrl: 'http://localhost:9000/'

String formatting: % vs. .format vs. string literal

As a side note, you don't have to take a performance hit to use new style formatting with logging. You can pass any object to logging.debug,, etc. that implements the __str__ magic method. When the logging module has decided that it must emit your message object (whatever it is), it calls str(message_object) before doing so. So you could do something like this:

import logging

class NewStyleLogMessage(object):
    def __init__(self, message, *args, **kwargs):
        self.message = message
        self.args = args
        self.kwargs = kwargs

    def __str__(self):
        args = (i() if callable(i) else i for i in self.args)
        kwargs = dict((k, v() if callable(v) else v) for k, v in self.kwargs.items())

        return self.message.format(*args, **kwargs)

N = NewStyleLogMessage

# Neither one of these messages are formatted (or calculated) until they're
# needed

# Emits "Lazily formatted log entry: 123 foo" in log
logging.debug(N('Lazily formatted log entry: {0} {keyword}', 123, keyword='foo'))

def expensive_func():
    # Do something that takes a long time...
    return 'foo'

# Emits "Expensive log entry: foo" in log
logging.debug(N('Expensive log entry: {keyword}', keyword=expensive_func))

This is all described in the Python 3 documentation ( However, it will work with Python 2.6 as well (

One of the advantages of using this technique, other than the fact that it's formatting-style agnostic, is that it allows for lazy values e.g. the function expensive_func above. This provides a more elegant alternative to the advice being given in the Python docs here:

Get hostname of current request in node.js Express

If you need a fully qualified domain name and have no HTTP request, on Linux, you could use:

var child_process = require("child_process");

child_process.exec("hostname -f", function(err, stdout, stderr) {
  var hostname = stdout.trim();

Redis: How to access Redis log file

You can also login to the redis-cli and use the MONITOR command to see what queries are happening against Redis.

How to search for string in an array

Completing remark to Jimmy Pena's accepted answer

As SeanC points out, this must be a 1-D array.

The following example call demonstrates that the IsInArray() function cannot be called only for 1-dim arrays, but also for "flat" 2-dim arrays:

Sub TestIsInArray()
    Const SearchItem As String = "ghi"
    Debug.Print "SearchItem = '" & SearchItem & "'"
    'a) Test 1-dim array
    Dim Arr As Variant
    Arr = Split("abc,def,ghi,jkl", ",")
    Debug.Print "a) 1-dim array " & vbNewLine & "   " & Join(Arr, "|") & " ~~> " & IsInArray(SearchItem, Arr)
        '//quick tool to create a 2-dim 1-based array
        Dim v As Variant, vals As Variant                                       
        v = Array(Array("abc", "def", "dummy", "jkl", 5), _
                  Array("mno", "pqr", "stu", "ghi", "vwx"))
        v = Application.Index(v, 0, 0)  ' create 2-dim array (2 rows, 5 cols)
    'b) Test "flat" 2-dim arrays
    Debug.Print "b) ""flat"" 2-dim arrays "
    Dim i As Long
    For i = LBound(v) To UBound(v)
        'slice "flat" 2-dim arrays of one row each
        vals = Application.Index(v, i, 0)
        'check for findings
        Debug.Print Format(i, "   0"), Join(vals, "|") & " ~~> " & IsInArray(SearchItem, vals)
    Next i
End Sub
Function IsInArray(stringToBeFound As String, Arr As Variant) As Boolean
'Note: needs a "flat" array, not necessarily a 1-dimensioned array
  IsInArray = (UBound(Filter(Arr, stringToBeFound)) > -1)
End Function

Results in VB Editor's immediate window

SearchItem = 'ghi'
a) 1-dim array 
   abc|def|ghi|jkl ~~> Wahr
b) "flat" 2-dim arrays 
   1          abc|def|dummy|jkl|5         False
   2          mno|pqr|stu|ghi|vwx         True

ReferenceError: Invalid left-hand side in assignment

The same happened for me with eslint module. EsLinter throw Parsing error: Invalid left-hand side in assignment expression for await in second if statement.

if (condition_one) {
  let result = await myFunction()

if (condition_two) {
  let result = await myFunction() // eslint parsing error

As strange as it sounds what fixed this error was to add ; semicolon at the end of line where await occurred.

if (condition_one) {
  let result = await myFunction();

if (condition_two) {
  let result = await myFunction();

Use string value from a cell to access worksheet of same name

This will only work to column Z, but you can drag this horizontally and vertically.


Java Generics With a Class & an Interface - Together

You can't do it with "anonymous" type parameters (ie, wildcards that use ?), but you can do it with "named" type parameters. Simply declare the type parameter at method or class level.

import java.util.List;
interface A{}
interface B{}
public class Test<E extends B & A, T extends List<E>> {
    T t;

Mysql where id is in array

Your query translates to:

SELECT name FROM users WHERE id IN ('Array');

Or something to that affect.

Try using prepared queries instead, something like:

$numbers = explode(',', $string);
$prepare = array_map(function(){ return '?'; }, $numbers);
$statement = mysqli_prepare($link , "SELECT name FROM users WHERE id IN ('".implode(',', $prepare)."')");
if($statement) {
   $ints = array_map(function(){ return 'i'; }, $numbers);
   call_user_func_array("mysqli_stmt_bind_param", array_merge(
      array($statement, implode('', $ints)), $numbers
   $results = mysqli_stmt_execute($statement);
   // do something with results 
   // ...

Python develop vs install

python install is used to install (typically third party) packages that you're not going to develop/modify/debug yourself.

For your own stuff, you want to first install your package and then be able to frequently edit the code without having to re-install the package every time — and that is exactly what python develop does: it installs the package (typically just a source folder) in a way that allows you to conveniently edit your code after it’s installed to the (virtual) environment, and have the changes take effect immediately.

Note that it is highly recommended to use pip install . (install) and pip install -e . (developer install) to install packages, as invoking directly will do the wrong things for many dependencies, such as pull prereleases and incompatible package versions, or make the package hard to uninstall with pip.

How to get list of dates between two dates in mysql select query


select * from 
(select adddate('1970-01-01',t4.i*10000 + t3.i*1000 + t2.i*100 + t1.i*10 + t0.i) selected_date from
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t0,
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t1,
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t2,
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t3,
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t4) v
where selected_date between '2012-02-10' and '2012-02-15'

-for date ranges up to nearly 300 years in the future.

[Corrected following a suggested edit by UrvishAtSynapse.]

How can I check the syntax of Python script without executing it?

for some reason ( I am a py newbie ... ) the -m call did not work ...

so here is a bash wrapper func ...

# ---------------------------------------------------------
# check the python synax for all the *.py files under the
# <<product_version_dir/sfw/python
# ---------------------------------------------------------

    doLog "DEBUG START doCheckPythonSyntax"

    test -z "$sleep_interval" || sleep "$sleep_interval"
    cd $product_version_dir/sfw/python
    # python3 -m compileall "$product_version_dir/sfw/python"

    # foreach *.py file ...
    while read -r f ; do \

        py_name_ext=$(basename $f)

        doLog "python3 -c \"import $py_name\""
        # doLog "python3 -m py_compile $f"

        python3 -c "import $py_name"
        # python3 -m py_compile "$f"
        test $! -ne 0 && sleep 5

    done < <(find "$product_version_dir/sfw/python" -type f -name "*.py")

    doLog "DEBUG STOP  doCheckPythonSyntax"
# eof func doCheckPythonSyntax

call a function in success of datatable ajax call

You can use dataSrc :

Here is a typical example of

var table = $('#example').DataTable( {
    "ajax": {
            "type" : "GET",
            "url" : "ajax.php",
            "dataSrc": function ( json ) {
                //Make your callback here.
    "columns": [
            { "data": "name" },
            { "data": "position" },
            { "data": "office" },
            { "data": "extn" },
            { "data": "start_date" },
            { "data": "salary" }

    } );

Check if a number has a decimal place/is a whole number

Here's an excerpt from my guard library (inspired by Effective JavaScript by David Herman):

var guard = {

    guard: function(x) {
        if (!this.test(x)) {
            throw new TypeError("expected " + this);

    // ...

// ...

var number = Object.create(guard);
number.test = function(x) {
    return typeof x === "number" || x instanceof Number;
number.toString = function() {
    return "number";

var uint32 = Object.create(guard);
uint32.test = function(x) {
    return typeof x === "number" && x === (x >>> 0);
uint32.toString = function() {
    return "uint32";

var decimal = Object.create(guard);
decimal.test = function(x) {
    return number.test(x) && !uint32.test(x);
decimal.toString = function() {
    return "decimal";

uint32.guard(1234);     // fine
uint32.guard(123.4);    // TypeError: expected uint32

decimal.guard(1234);    // TypeError: expected decimal
decimal.guard(123.4);   // fine

How to properly express JPQL "join fetch" with "where" clause as JPA 2 CriteriaQuery?

In JPQL the same is actually true in the spec. The JPA spec does not allow an alias to be given to a fetch join. The issue is that you can easily shoot yourself in the foot with this by restricting the context of the join fetch. It is safer to join twice.

This is normally more an issue with ToMany than ToOnes. For example,

Select e from Employee e 
join fetch e.phones p 
where p.areaCode = '613'

This will incorrectly return all Employees that contain numbers in the '613' area code but will left out phone numbers of other areas in the returned list. This means that an employee that had a phone in the 613 and 416 area codes will loose the 416 phone number, so the object will be corrupted.

Granted, if you know what you are doing, the extra join is not desirable, some JPA providers may allow aliasing the join fetch, and may allow casting the Criteria Fetch to a Join.

Interface or an Abstract Class: which one to use?

The main difference is an abstract class can contain default implementation whereas an interface cannot.

An interface is a contract of behaviour without any implementation.

Prevent linebreak after </div>

<span class="label">My Label:</span>
<span class="text">My text</span>

java.util.Date format SSSSSS: if not microseconds what are the last 3 digits?

I used yet another trick to format date with 6-digit precision (microseconds):

    new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.").format(microseconds/1000)
    +String.format("%06d", microseconds%1000000));

This technique can be extended further, to nanoseconds and up.

How can I find a specific element in a List<T>?

Use a lambda expression

MyClass result = list.Find(x => x.GetId() == "xy");

Note: C# has a built-in syntax for properties. Instead of writing getter and setter methods (as you might be used to from Java), write

private string _id;
public string Id
        return _id;
        _id = value;

value is a contextual keyword known only in the set accessor. It represents the value assigned to the property.

Since this pattern is often used, C# provides auto-implemented properties. They are a short version of the code above; however, the backing variable is hidden and not accessible (it is accessible from within the class in VB, however).

public string Id { get; set; }

You can simply use properties as if you were accessing a field:

var obj = new MyClass();
obj.Id = "xy";       // Calls the setter with "xy" assigned to the value parameter.
string id = obj.Id;  // Calls the getter.

Using properties, you would search for items in the list like this

MyClass result = list.Find(x => x.Id == "xy"); 

You can also use auto-implemented properties if you need a read-only property:

public string Id { get; private set; }

This enables you to set the Id within the class but not from outside. If you need to set it in derived classes as well you can also protect the setter

public string Id { get; protected set; }

And finally, you can declare properties as virtual and override them in deriving classes, allowing you to provide different implementations for getters and setters; just as for ordinary virtual methods.

Since C# 6.0 (Visual Studio 2015, Roslyn) you can write getter-only auto-properties with an inline initializer

public string Id { get; } = "A07"; // Evaluated once when object is initialized.

You can also initialize getter-only properties within the constructor instead. Getter-only auto-properties are true read-only properties, unlike auto-implemented properties with a private setter.

This works also with read-write auto-properties:

public string Id { get; set; } = "A07";

Beginning with C# 6.0 you can also write properties as expression-bodied members

public DateTime Yesterday => DateTime.Date.AddDays(-1); // Evaluated at each call.
// Instead of
public DateTime Yesterday { get { return DateTime.Date.AddDays(-1); } }

See: .NET Compiler Platform ("Roslyn")
         New Language Features in C# 6

Starting with C# 7.0, both, getter and setter, can be written with expression bodies:

public string Name
    get => _name;                                // getter
    set => _name = value;                        // setter

Note that in this case the setter must be an expression. It cannot be a statement. The example above works, because in C# an assignment can be used as an expression or as a statement. The value of an assignment expression is the assigned value where the assignment itself is a side effect. This allows you to assign a value to more than one variable at once: x = y = z = 0 is equivalent to x = (y = (z = 0)) and has the same effect as the statements x = 0; y = 0; z = 0;.

The next version of the language, C# 9.0, probably available in November 2020, will allow read-only (or better initialize-once) properties that you can initialize in an object initializer. This is currently not possible with getter-only properties.

public string Name { get; init; }

var c = new C { Name = "c-sharp" };

I have created a table in hive, I would like to know which directory my table is created in?

To see both of the structure and location (directory) of an any (internal or external)table, we can use table's create statment-

show create table table_name;

How to get the previous url using PHP

$_SERVER['HTTP_REFERER'] is the answer

Call a Vue.js component method from outside the component

Sometimes you want to keep these things contained within your component. Depending on DOM state (the elements you're listening on must exist in DOM when your Vue component is instantiated), you can listen to events on elements outside of your component from within your Vue component. Let's say there is an element outside of your component, and when the user clicks it, you want your component to respond.

In html you have:

<a href="#" id="outsideLink">Launch the component</a>

In your Vue component:

    methods() {
      doSomething() {
        // do something
    created() {
       document.getElementById('outsideLink').addEventListener('click', evt => 

Is <img> element block level or inline level?

For almost all purposes think of them as an inline element with a width set. Basically you are free to dictate how you would like images to display using CSS. I generally set a few image classes like so: {display:block;margin:0 auto;}

img.left {float:left;margin-right:10px;}

img.right  {float:right;margin-left:10px;}

img.border  {border:1px solid #333;}

How to read a line from the console in C?

You might need to use a character by character (getc()) loop to ensure you have no buffer overflows and don't truncate the input.

Spring can you autowire inside an abstract class?

In my case, inside a Spring4 Application, i had to use a classic Abstract Factory Pattern(for which i took the idea from - to create instances each and every time there was a operation to be done.So my code was to be designed like:

public abstract class EO {
    protected SmsNotificationService smsNotificationService;
    protected SendEmailService sendEmailService;
    protected abstract void executeOperation(GenericMessage gMessage);

public final class OperationsExecutor {
    public enum OperationsType {

    private OperationsExecutor() {

    public static Object delegateOperation(OperationsType type, Object obj) 
        switch(type) {
            case ENROLL:
                if (obj == null) {
                    return new EnrollOperation();
                return EnrollOperation.validateRequestParams(obj);
            case CAMPAIGN:
                if (obj == null) {
                    return new CampaignOperation();
                return CampaignOperation.validateRequestParams(obj);
                throw new IllegalArgumentException("OperationsType not supported.");

@Configurable(dependencyCheck = true)
public class CampaignOperation extends EO {
    public void executeOperation(GenericMessage genericMessage) {"This is CAMPAIGN Operation: " + genericMessage);

Initially to inject the dependencies in the abstract class I tried all stereotype annotations like @Component, @Service etc but even though Spring context file had ComponentScanning for the entire package, but somehow while creating instances of Subclasses like CampaignOperation, the Super Abstract class EO was having null for its properties as spring was unable to recognize and inject its dependencies.After much trial and error I used this **@Configurable(dependencyCheck = true)** annotation and finally Spring was able to inject the dependencies and I was able to use the properties in the subclass without cluttering them with too many properties.

<context:annotation-config />
<context:component-scan base-package="" />

I also tried these other references to find a solution:

  6. Using abstract factory with Spring framework
  7. Spring Autowiring not working for Abstract classes
  8. Inject spring dependency in abstract super class
  9. Spring and Abstract class - injecting properties in abstract classes
    1. Spring autowire dependency defined in an abstract class

Please try using **@Configurable(dependencyCheck = true)** and update this post, I might try helping you if you face any problems.

Convert .class to .java

I'm guessing that either the class name is wrong - be sure to use the fully-resolved class name, with all packages - or it's not in the CLASSPATH so javap can't find it.

VB.NET: Clear DataGridView

The mistake that you are making is that you seem to be using a dataset object for storing your data. Each time you use the following code to put data into your dataset you add data to the data already in your dataset.


If you assign the table in your dataset to a DataGridView object in your program by the following code you will get duplicate results because you have not cleared data which is already residing in your dataset and in your dataset table.

myDataGridView.DataSource = myDataSet.Tables(0)

To avoid replicating the data you have to call clear method on your dataset object.


An then assign the table in your dataset to your DataGridView object. The code is like this.

myDataGridView.DataSource = myDataSet.Tables(0)

You can try this code:

' clear previous data
DataGridView2.DataSource = Nothing
DataGridView2.DataMember = Nothing
    adapter1 = New SqlDataAdapter(sql, connection)
    ' clear data already in the dataset
    DataGridView2.DataSource = ds1.Tables(0)
Catch ex As Exception
End Try

jQuery - Check if DOM element already exists

In this case, you may want to check if element exists in current DOM

if you want to check if element exist in DOM tree (is attached to DOM), you can use:

var data = $('#data_1'); 
if(jQuery.contains(document.documentElement, data[0])){
    // #data_1 element attached to DOM
} else {
    // is not attached to DOM

Getting list of parameter names inside python function

import inspect

def func(a,b,c=5):

inspect.getargspec(func)  # inspect.signature(func) in Python 3

(['a', 'b', 'c'], None, None, (5,))

Remove element of a regular array

Here's how I did it...

    public static ElementDefinitionImpl[] RemoveElementDefAt(
        ElementDefinition[] oldList,
        int removeIndex
        ElementDefinitionImpl[] newElementDefList = new ElementDefinitionImpl[ oldList.Length - 1 ];

        int offset = 0;
        for ( int index = 0; index < oldList.Length; index++ )
            ElementDefinitionImpl elementDef = oldList[ index ] as ElementDefinitionImpl;
            if ( index == removeIndex )
                //  This is the one we want to remove, so we won't copy it.  But 
                //  every subsequent elementDef will by shifted down by one.
                offset = -1;
                newElementDefList[ index + offset ] = elementDef;
        return newElementDefList;

GetFiles with multiple extensions

The following retrieves the jpg, tiff and bmp files and gives you an IEnumerable<FileInfo> over which you can iterate:

var files = dinfo.GetFiles("*.jpg")

If you really need an array, simply stick .ToArray() at the end of this.

Could not find a declaration file for module 'module-name'. '/path/to/module-name.js' implicitly has an 'any' type

Could not find a declaration file for module 'busboy'. 'f:/firebase-cloud- 
functions/functions/node_modules/busboy/lib/main.js' implicitly has an ‘any’ 

Try `npm install @types/busboy` if it exists or add a new declaration (.d.ts) 
the file containing `declare module 'busboy';`

In my case it's solved: All you have to do is edit your TypeScript Config file (tsconfig.json) and add a new key-value pair as:

"noImplicitAny": false

Populating a database in a Laravel migration file

Don't put the DB::insert() inside of the Schema::create(), because the create method has to finish making the table before you can insert stuff. Try this instead:

public function up()
    // Create the table
    Schema::create('users', function($table){
        $table->string('email', 255);
        $table->string('password', 64);
        $table->string('token', 255);

    // Insert some stuff
            'email' => '[email protected]',
            'verified' => true

Command / failed with exit code 1

Try this - click on the name of your project on the list of files/folders on the left in Xcode (at the very top of the list). Look at the "Targets" section on the left-hand side of the window to the right. Likely, there's two listed with the second being a "test" item. Right-click on that item and select "delete". Then try to run the project again.

How do I return the response from an asynchronous call?

? For a more general explanation of async behaviour with different examples, please see Why is my variable unaltered after I modify it inside of a function? - Asynchronous code reference

? If you already understand the problem, skip to the possible solutions below.

The problem

The A in Ajax stands for asynchronous . That means sending the request (or rather receiving the response) is taken out of the normal execution flow. In your example, $.ajax returns immediately and the next statement, return result;, is executed before the function you passed as success callback was even called.

Here is an analogy which hopefully makes the difference between synchronous and asynchronous flow clearer:


Imagine you make a phone call to a friend and ask him to look something up for you. Although it might take a while, you wait on the phone and stare into space, until your friend gives you the answer that you needed.

The same is happening when you make a function call containing "normal" code:

function findItem() {
    var item;
    while(item_not_found) {
        // search
    return item;

var item = findItem();

// Do something with item

Even though findItem might take a long time to execute, any code coming after var item = findItem(); has to wait until the function returns the result.


You call your friend again for the same reason. But this time you tell him that you are in a hurry and he should call you back on your mobile phone. You hang up, leave the house, and do whatever you planned to do. Once your friend calls you back, you are dealing with the information he gave to you.

That's exactly what's happening when you do an Ajax request.

findItem(function(item) {
    // Do something with the item

Instead of waiting for the response, the execution continues immediately and the statement after the Ajax call is executed. To get the response eventually, you provide a function to be called once the response was received, a callback (notice something? call back ?). Any statement coming after that call is executed before the callback is called.


Embrace the asynchronous nature of JavaScript! While certain asynchronous operations provide synchronous counterparts (so does "Ajax"), it's generally discouraged to use them, especially in a browser context.

Why is it bad do you ask?

JavaScript runs in the UI thread of the browser and any long-running process will lock the UI, making it unresponsive. Additionally, there is an upper limit on the execution time for JavaScript and the browser will ask the user whether to continue the execution or not.

All of this is a really bad user experience. The user won't be able to tell whether everything is working fine or not. Furthermore, the effect will be worse for users with a slow connection.

In the following we will look at three different solutions that are all building on top of each other:

  • Promises with async/await (ES2017+, available in older browsers if you use a transpiler or regenerator)
  • Callbacks (popular in node)
  • Promises with then() (ES2015+, available in older browsers if you use one of the many promise libraries)

All three are available in current browsers, and node 7+.

ES2017+: Promises with async/await

The ECMAScript version released in 2017 introduced syntax-level support for asynchronous functions. With the help of async and await, you can write asynchronous in a "synchronous style". The code is still asynchronous, but it's easier to read/understand.

async/await builds on top of promises: an async function always returns a promise. await "unwraps" a promise and either result in the value the promise was resolved with or throws an error if the promise was rejected.

Important: You can only use await inside an async function. Right now, top-level await isn't yet supported, so you might have to make an async IIFE (Immediately Invoked Function Expression) to start an async context.

You can read more about async and await on MDN.

Here is an example that builds on top of delay above:

// Using 'superagent' which will return a promise.
var superagent = require('superagent')

// This is isn't declared as `async` because it already returns a promise
function delay() {
  // `delay` returns a promise
  return new Promise(function(resolve, reject) {
    // Only `delay` is able to resolve or reject the promise
    setTimeout(function() {
      resolve(42); // After 3 seconds, resolve the promise with value 42
    }, 3000);

async function getAllBooks() {
  try {
    // GET a list of book IDs of the current user
    var bookIDs = await superagent.get('/user/books');
    // wait for 3 seconds (just for the sake of this example)
    await delay();
    // GET information about each book
    return await superagent.get('/books/ids='+JSON.stringify(bookIDs));
  } catch(error) {
    // If any of the awaited promises was rejected, this catch block
    // would catch the rejection reason
    return null;

// Start an IIFE to use `await` at the top level
(async function(){
  let books = await getAllBooks();

Current browser and node versions support async/await. You can also support older environments by transforming your code to ES5 with the help of regenerator (or tools that use regenerator, such as Babel).

Let functions accept callbacks

A callback is when function 1 is passed to function 2. Function 2 can call function 1 whenever it is ready. In the context of an asynchronous process, the callback will be called whenever the asynchronous process is done. Usually, the result is passed to the callback.

In the example of the question, you can make foo accept a callback and use it as success callback. So this

var result = foo();
// Code that depends on 'result'


foo(function(result) {
    // Code that depends on 'result'

Here we defined the function "inline" but you can pass any function reference:

function myCallback(result) {
    // Code that depends on 'result'


foo itself is defined as follows:

function foo(callback) {
        // ...
        success: callback

callback will refer to the function we pass to foo when we call it and we pass it on to success. I.e. once the Ajax request is successful, $.ajax will call callback and pass the response to the callback (which can be referred to with result, since this is how we defined the callback).

You can also process the response before passing it to the callback:

function foo(callback) {
        // ...
        success: function(response) {
            // For example, filter the response

It's easier to write code using callbacks than it may seem. After all, JavaScript in the browser is heavily event-driven (DOM events). Receiving the Ajax response is nothing else but an event.
Difficulties could arise when you have to work with third-party code, but most problems can be solved by just thinking through the application flow.

ES2015+: Promises with then()

The Promise API is a new feature of ECMAScript 6 (ES2015), but it has good browser support already. There are also many libraries which implement the standard Promises API and provide additional methods to ease the use and composition of asynchronous functions (e.g. bluebird).

Promises are containers for future values. When the promise receives the value (it is resolved) or when it is canceled (rejected), it notifies all of its "listeners" who want to access this value.

The advantage over plain callbacks is that they allow you to decouple your code and they are easier to compose.

Here is an example of using a promise:

function delay() {
  // `delay` returns a promise
  return new Promise(function(resolve, reject) {
    // Only `delay` is able to resolve or reject the promise
    setTimeout(function() {
      resolve(42); // After 3 seconds, resolve the promise with value 42
    }, 3000);

  .then(function(v) { // `delay` returns a promise
    console.log(v); // Log the value once it is resolved
  .catch(function(v) {
    // Or do something else if it is rejected 
    // (it would not happen in this example, since `reject` is not called).

Applied to our Ajax call we could use promises like this:

function ajax(url) {
  return new Promise(function(resolve, reject) {
    var xhr = new XMLHttpRequest();
    xhr.onload = function() {
    xhr.onerror = reject;'GET', url);

  .then(function(result) {
    // Code depending on result
  .catch(function() {
    // An error occurred

Describing all the advantages that promise offer is beyond the scope of this answer, but if you write new code, you should seriously consider them. They provide a great abstraction and separation of your code.

More information about promises: HTML5 rocks - JavaScript Promises

Side note: jQuery's deferred objects

Deferred objects are jQuery's custom implementation of promises (before the Promise API was standardized). They behave almost like promises but expose a slightly different API.

Every Ajax method of jQuery already returns a "deferred object" (actually a promise of a deferred object) which you can just return from your function:

function ajax() {
    return $.ajax(...);

ajax().done(function(result) {
    // Code depending on result
}).fail(function() {
    // An error occurred

Side note: Promise gotchas

Keep in mind that promises and deferred objects are just containers for a future value, they are not the value itself. For example, suppose you had the following:

function checkPassword() {
    return $.ajax({
        url: '/password',
        data: {
            username: $('#username').val(),
            password: $('#password').val()
        type: 'POST',
        dataType: 'json'

if (checkPassword()) {
    // Tell the user they're logged in

This code misunderstands the above asynchrony issues. Specifically, $.ajax() doesn't freeze the code while it checks the '/password' page on your server - it sends a request to the server and while it waits, it immediately returns a jQuery Ajax Deferred object, not the response from the server. That means the if statement is going to always get this Deferred object, treat it as true, and proceed as though the user is logged in. Not good.

But the fix is easy:

.done(function(r) {
    if (r) {
        // Tell the user they're logged in
    } else {
        // Tell the user their password was bad
.fail(function(x) {
    // Tell the user something bad happened

Not recommended: Synchronous "Ajax" calls

As I mentioned, some(!) asynchronous operations have synchronous counterparts. I don't advocate their use, but for completeness' sake, here is how you would perform a synchronous call:

Without jQuery

If you directly use a XMLHttpRequest object, pass false as third argument to .open.


If you use jQuery, you can set the async option to false. Note that this option is deprecated since jQuery 1.8. You can then either still use a success callback or access the responseText property of the jqXHR object:

function foo() {
    var jqXHR = $.ajax({
        async: false
    return jqXHR.responseText;

If you use any other jQuery Ajax method, such as $.get, $.getJSON, etc., you have to change it to $.ajax (since you can only pass configuration parameters to $.ajax).

Heads up! It is not possible to make a synchronous JSONP request. JSONP by its very nature is always asynchronous (one more reason to not even consider this option).

Why is conversion from string constant to 'char*' valid in C but invalid in C++

It's valid in C for historical reasons. C traditionally specified that the type of a string literal was char * rather than const char *, although it qualified it by saying that you're not actually allowed to modify it.

When you use a cast, you're essentially telling the compiler that you know better than the default type matching rules, and it makes the assignment OK.

Extracting substrings in Go

Go strings are not null terminated, and to remove the last char of a string you can simply do:

s = s[:len(s)-1]

Way to get all alphabetic chars in an array in PHP?

Try this :

function missingCharacter($list) {

        // Create an array with a range from array minimum to maximu
        $newArray = range(min($list), max($list));

        // Find those elements that are present in the $newArray but not in given $list
        return array_diff($newArray, $list);

Reading CSV file and storing values into an array

Hi all, I created a static class for doing this. + column check + quota sign removal

public static class CSV
    public static List<string[]> Import(string file, char csvDelimiter, bool ignoreHeadline, bool removeQuoteSign)
        return ReadCSVFile(file, csvDelimiter, ignoreHeadline, removeQuoteSign);

    private static List<string[]> ReadCSVFile(string filename, char csvDelimiter, bool ignoreHeadline, bool removeQuoteSign)
        string[] result = new string[0];
        List<string[]> lst = new List<string[]>();

        string line;
        int currentLineNumner = 0;
        int columnCount = 0;

        // Read the file and display it line by line.  
        using (System.IO.StreamReader file = new System.IO.StreamReader(filename))
            while ((line = file.ReadLine()) != null)
                string[] strAr = line.Split(csvDelimiter);
                // save column count of dirst line
                if (currentLineNumner == 1)
                    columnCount = strAr.Count();
                    //Check column count of every other lines
                    if (strAr.Count() != columnCount)
                        throw new Exception(string.Format("CSV Import Exception: Wrong column count in line {0}", currentLineNumner));

                if (removeQuoteSign) strAr = RemoveQouteSign(strAr);

                if (ignoreHeadline)
                    if(currentLineNumner !=1) lst.Add(strAr);


        return lst;
    private static string[] RemoveQouteSign(string[] ar)
        for (int i = 0;i< ar.Count() ; i++)
            if (ar[i].StartsWith("\"") || ar[i].StartsWith("'")) ar[i] = ar[i].Substring(1);
            if (ar[i].EndsWith("\"") || ar[i].EndsWith("'")) ar[i] = ar[i].Substring(0,ar[i].Length-1);

        return ar;


Expanding a parent <div> to the height of its children

add a clear:both. assuming that your columns are floating. Depending on how your height is specified parent you may need an overflow:auto;

<div id="parent">
    <div id="childRightCol">
    <div id="childLeftCol">
    <div id="clear" style="clear:both;"></div>

Default value in an mvc view model

In case you need to post the same model to server the solution with having default bool value in constructor would not be viable for you. Let's imagine that you have following model:

public class SearchModel
    public bool IsMale { get; set; }

    public SearchModel()
        IsMale = true;

On view you would have something like this:

@Html.CheckBoxFor(n => n.IsMale)

The problem is when user uncheck this checkbox and post it to the server - you would end up with default value set up in constructor (which in this case is true).

So in this case I would end up with just specifying default value on view:

@Html.CheckBoxFor(n => n.IsMale, new { @checked = "checked" })

Check if a temporary table exists and delete if it exists before creating a temporary table

pmac72 is using GO to break down the query into batches and using an ALTER.

You appear to be running the same batch but running it twice after changing it: DROP... CREATE... edit... DROP... CREATE..

Perhaps post your exact code so we can see what is going on.

java.lang.ClassNotFoundException: Didn't find class on path: dexpathlist

for anyone who comes across this problem now, with android studio 4.0+ you just have to enable java 8 as mentioned here

android {
    defaultConfig {
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8

Styling mat-select in Angular Material

For Angular9+, according to this, you can use:

.mat-select-panel {
    background: red;


Angular Material uses mat-select-content as class name for the select list content. For its styling I would suggest four options.

1. Use ::ng-deep:

Use the /deep/ shadow-piercing descendant combinator to force a style down through the child component tree into all the child component views. The /deep/ combinator works to any depth of nested components, and it applies to both the view children and content children of the component. Use /deep/, >>> and ::ng-deep only with emulated view encapsulation. Emulated is the default and most commonly used view encapsulation. For more information, see the Controlling view encapsulation section. The shadow-piercing descendant combinator is deprecated and support is being removed from major browsers and tools. As such we plan to drop support in Angular (for all 3 of /deep/, >>> and ::ng-deep). Until then ::ng-deep should be preferred for a broader compatibility with the tools.


::ng-deep .mat-select-content{
    background-color: red;
    font-size: 10px;   


2. Use ViewEncapsulation

... component CSS styles are encapsulated into the component's view and don't affect the rest of the application. To control how this encapsulation happens on a per component basis, you can set the view encapsulation mode in the component metadata. Choose from the following modes: .... None means that Angular does no view encapsulation. Angular adds the CSS to the global styles. The scoping rules, isolations, and protections discussed earlier don't apply. This is essentially the same as pasting the component's styles into the HTML.

None value is what you will need to break the encapsulation and set material style from your component. So can set on the component's selector:


  import {ViewEncapsulation } from '@angular/core';
        encapsulation: ViewEncapsulation.None


    background-color: red;
    font-size: 10px;


3. Set class style in style.css

This time you have to 'force' styles with !important too.


   width:2000px !important;
   background-color: red !important;
   font-size: 10px !important;


4. Use inline style

<mat-option style="width:2000px; background-color: red; font-size: 10px;" ...>


Zsh: Conda/Pip installs command not found

I had this problem on my Catalina OSX after I installed my Anaconda distribution as well.

This solution worked for me on macOS Catalina as of October 19, 2019

Step 1. Check if .bash_profile is available on your home folder, if not:

  • Go to Terminal
  • Type cd ~/ to go to your home folder (if you are not on your home folder)
  • Type touch .bash_profile to create your new file under the your home folder

Step 2. Check if file .zshrc is available on your home folder, if not:

  • Go to terminal and type nano ~/.zshrc

  • Type in the following line into the newly created .zshrc file: source ~/.bash_profile

  • Now to save the file in nano just hit ctrl+X.

  • It will prompt "Save modified buffer (ANSWERING "No" WILL DESTROY CHANGES)?". Just type in Y

Step 3. Check if .bash_profile and .zshrc files are created on your home folder. If yes, in terminal type in source ~/.zshrc

How do I do pagination in ASP.NET MVC?

Well, what is the data source? Your action could take a few defaulted arguments, i.e.

ActionResult Search(string query, int startIndex, int pageSize) {...}

defaulted in the routes setup so that startIndex is 0 and pageSize is (say) 20:

        routes.MapRoute("Search", "Search/{query}/{startIndex}",
                            controller = "Home", action = "Search",
                            startIndex = 0, pageSize = 20

To split the feed, you can use LINQ quite easily:

var page = source.Skip(startIndex).Take(pageSize);

(or do a multiplication if you use "pageNumber" rather than "startIndex")

With LINQ-toSQL, EF, etc - this should "compose" down to the database, too.

You should then be able to use action-links to the next page (etc):

<%=Html.ActionLink("next page", "Search", new {
                query, startIndex = startIndex + pageSize, pageSize }) %>

How to merge many PDF files into a single one?

You can also use Ghostscript to merge different PDFs. You can even use it to merge a mix of PDFs, PostScript (PS) and EPS into one single output PDF file:

gs \
  -o merged.pdf \
  -sDEVICE=pdfwrite \
  -dPDFSETTINGS=/prepress \
   input_1.pdf \
   input_2.pdf \
   input_3.eps \ \

However, I agree with other answers: for your use case of merging PDF file types only, pdftk may be the best (and certainly fastest) option.

If processing time is not the main concern, but if the main concern is file size (or a fine-grained control over certain features of the output file), then the Ghostscript way certainly offers more power to you. To highlight a few of the differences:

  • Ghostscript can 'consolidate' the fonts of the input files which leads to a smaller file size of the output. It also can re-sample images, or scale all pages to a different size, or achieve a controlled color conversion from RGB to CMYK (or vice versa) should you need this (but that will require more CLI options than outlined in above command).
  • pdftk will just concatenate each file, and will not convert any colors. If each of your 16 input PDFs contains 5 subsetted fonts, the resulting output will contain 80 subsetted fonts. The resulting PDF's size is (nearly exactly) the sum of the input file bytes.

Authenticate with GitHub using a token

To avoid handing over "the keys to the castle"...

Note that sigmavirus24's response requires you to give Travis a token with fairly wide permissions -- since GitHub only offers tokens with wide scopes like "write all my public repos" or "write all my private repos".

If you want to tighten down access (with a bit more work!) you can use GitHub deployment keys combined with Travis encrypted yaml fields.

Here's a sketch of how the technique works...

First generate an RSA deploy key (via ssh-keygen) called my_key and add it as a deploy key in your github repo settings.


$ password=`openssl rand -hex 32`
$ cat my_key | openssl aes-256-cbc -k "$password" -a  > my_key.enc
$ travis encrypt --add password=$password -r my-github-user/my-repo

Then use the $password file to decrypt your deploy key at integration-time, by adding to your yaml file:

  - openssl aes-256-cbc -k "$password" -d -a -in my_key.enc -out my_deploy_key
  - echo -e "Host\n  IdentityFile /path/to/my_deploy_key" > ~/.ssh/config
  - echo " ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAq2A7hRGmdnm9tUDbO9IDSwBK6TbQa+PXYPCPy6rbTrTtw7PHkccKrpp0yVhp5HdEIcKr6pLlVDBfOLX9QUsyCOV0wzfjIJNlGEYsdlLJizHhbn2mUjvSAHQqZETYP81eFzLQNnPHt4EVVUh7VfDESU84KezmD5QlWpXLmvU31/yMf+Se8xhHTvKSCZIFImWwoG6mbUoWf9nzpIoaSjB+weqqUUmpaaasXVal72J+UX2B+2RPW3RcT0eOzQgqlJL3RKrTJvdsjE3JEAvGq3lGHSZXy28G3skua2SmVi/w4yCE6gbODqnTWlg7+wC604ydGXA8VJiS5ap43JXiUFFAaQ==" > ~/.ssh/known_hosts

Note: the last line pre-populates github's RSA key, which avoids the need for manually accepting at the time of a connection.

How to get element by class name?

you can use


suppose you have some elements and applied a class name 'test', so, you can get elements like as following

var tests = document.getElementsByClassName('test');

its returns an instance NodeList, or its superset: HTMLCollection (FF).

Read more

Corrupted Access .accdb file: "Unrecognized Database Format"

After much struggle with this same issue I was able to solve the problem by installing the 32 bit version of the 2010 Access Database Engine. For some reason the 64bit version generates this error...

Fill remaining vertical space with CSS using display:flex

Here is the codepen demo showing the solution:

Important highlights:

  • all containers from html, body, ... .container, should have the height set to 100%
  • introducing flex to ANY of the flex items will trigger calculation of the items sizes based on flex distribution:
    • if only one cell is set to flex, for example: flex: 1 then this flex item will occupy the remaining of the space
    • if there are more than one with the flex property, the calculation will be more complicated. For example, if the item 1 is set to flex: 1 and the item 2 is se to flex: 2 then the item 2 will take twice more of the remaining space
  • Main Size Property

Changing background color of selected item in recyclerview

Create a selector into Drawable folder:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android=""> 
<item android:state_pressed="true">
         <solid android:color="@color/blue" />

<item android:state_pressed="false">
       <solid android:color="@android:color/transparent" />

Add the property into your xml (where you declare the RecyclerView):


Adding an img element to a div with javascript




and use the below to set the source

elem.src = 'images/hydrangeas.jpg';

CSS way to horizontally align table

Simple. IE6 and above will happily center your table with "margin: 0 auto;" if only the page renders in "standards" mode. To make this happen you need a valid doctype declaration, such as



<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "">

True, IE5.5 and below will still refuse to center the table but perhaps you can live with that, especially if the page is still functional with the table left aligned. I think by now users of IE5.5 and below are fairly used to some odd looking websites - but you still need to ensure that those visual glitches don't render your site unusable.

Happy coding!

EDIT: Sorry, I should perhaps point out that you do not have to have a "strict" doctype to get IE6 and up into "standards" rendering mode. I realised it might seem that way from the doctype examples I posted above. For example, this doctype declaration will of course work equally:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "">

set environment variable in python script

Compact solution (provided you don't need other environment variables):

call('sqsub -np {} /homedir/anotherdir/executable'.format(var1).split(),

Using the env command line tool:

call('env LD_LIBRARY_PATH=my_path sqsub -np {} /homedir/anotherdir/executable'.format(var1).split())

T-SQL: How to Select Values in Value List that are NOT IN the Table?

This Should work with all SQL versions.

SELECT  E.AccessCode ,
        CASE WHEN C.AccessCode IS NOT NULL THEN 'Exist'
             ELSE 'Not Exist'
        END AS [Status]
FROM    ( SELECT    '60552' AS AccessCode
          UNION ALL
          SELECT    '80630'
          UNION ALL
          SELECT    '1611'
          UNION ALL
          SELECT    '0000'
        ) AS E
        LEFT OUTER JOIN dbo.Credentials C ON E.AccessCode = c.AccessCode

Android camera intent

I found a pretty simple way to do this. Use a button to open it using an on click listener to start the function openc(), like this:

String fileloc;
private void openc()
    Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    File f = null;
        f = File.createTempFile("temppic",".jpg",getApplicationContext().getCacheDir());
        if (takePictureIntent.resolveActivity(getPackageManager()) != null)
            takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT,FileProvider.getUriForFile(profile.this, BuildConfig.APPLICATION_ID+".provider",f));
            fileloc = Uri.fromFile(f)+"";
            Log.d("texts", "openc: "+fileloc);
            startActivityForResult(takePictureIntent, 3);
    catch (IOException e) 

protected void onActivityResult(int requestCode, int resultCode, Intent data) 
    super.onActivityResult(requestCode, resultCode, data);
    if(requestCode == 3 && resultCode == RESULT_OK) {
        Log.d("texts", "onActivityResult: "+fileloc);
        // fileloc is the uri of the file so do whatever with it

You can do whatever you want with the uri location string. For instance, I send it to an image cropper to crop the image.

FileNotFoundError: [Errno 2] No such file or directory

with open(fpath, 'rb') as myfile:
    fstr =

I encounter this error because the file is empty. This answer may not a correct answer for this question but should give developers a hint like me.

Cannot use string offset as an array in php

I was fighting a similar problem, so documenting here in case useful.

In a __get() method I was using the given argument as a property, as in (simplified example):

function __get($prop) {
     return $this->$prop;

...i.e. $obj->fred would access the private/protected fred property of the class.

I found that when I needed to reference an array structure within this property it generated the Cannot use String offset as array error. Here's what I did wrong and how to correct it:

function __get($prop) {
     // this is wrong, generates the error
     return $this->$prop['some key'][0];

function __get($prop) {
     // this is correct
     $ref = & $this->$prop;
     return $ref['some key'][0];

Explanation: in the wrong example, php is interpreting ['some key'] as a key to $prop (a string), whereas we need it to dereference $prop in place. In Perl you could do this by specifying with {} but I don't think this is possible in PHP.

Detecting IE11 using CSS Capability/Feature Detection

Perhaps Layout Engine v0.7.0 is a good solution for your situation. It uses browser feature detection and can detect not only IE11 and IE10, but also IE9, IE8, and IE7. It also detects other popular browsers, including some mobile browsers. It adds a class to the html tag, is easy to use, and it's performed well under some fairly deep testing.

Count the number of occurrences of each letter in string

One simple possibility would be to make an array of 26 ints, each is a count for a letter a-z:

int alphacount[26] = {0}; //[0] = 'a', [1] = 'b', etc

Then loop through the string and increment the count for each letter:

for(int i = 0; i<strlen(mystring); i++)      //for the whole length of the string
        alphacount[tolower(mystring[i])-'a']++;  //make the letter lower case (if it's not)
                                                 //then use it as an offset into the array
                                                 //and increment

It's a simple idea that works for A-Z, a-z. If you want to separate by capitals you just need to make the count 52 instead and subtract the correct ASCII offset

Is it possible to run one logrotate check manually?

logrotate -d [your_config_file] invokes debug mode, giving you a verbose description of what would happen, but leaving the log files untouched.

Keep a line of text as a single line - wrap the whole line or none at all

You could also put non-breaking spaces (&nbsp;) in lieu of the spaces so that they're forced to stay together.

How do I wrap this line of text

How can I use std::maps with user-defined types as key?

class key
    int m_value;
    bool operator<(const key& src)const
        return (this->m_value < src.m_value);

int main()
    key key1;
    key key2;
    map<key,int> mymap;
    map<key,int>::iterator iter=mymap.begin();


How to edit an Android app?

First you have to download file x-plore and installed it.. After that open it and find the thoes you want to edit.. After that just rename the file Xyz.apk to After that open that file and you can see some folders.. then just go and edit the app..

How to use jQuery to get the current value of a file input field

In Chrome 8 the path is always 'C:\fakepath\' with the correct file name.

Favicon not showing up in Google Chrome


Clear your cache. And test another browser.

Some where able to get an updated favicon by adding an URL parameter: ?v=1 after the link href which changes the resource link and therefore loads the favicon without cache (thanks @Stanislav).

<link rel="icon" type="image/x-icon" href="favicon.ico?v=2"  />

Favicon Usage

How did you import the favicon? How you should add it.

Normal favicon:

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

PNG/GIF favicon:

<link rel="icon" type="image/gif" href="favicon.gif" />
<link rel="icon" type="image/png" href="favicon.png" />

in the <head> Tag.

Chrome local problem

Another thing could be the problem that chrome can't display favicons, if it's local (not uploaded to a webserver). Only if the file/icon would be in the downloads directory chrome is allowed to load this data - more information about this can be found here: local (file://) website favicon works in Firefox, not in Chrome or Safari- why?


Try to rename it from favicon.{whatever} to {yourfaviconname}.{whatever} but I would suggest you to still have the normal favicon. This has solved my issue on IE.

Base64 approach

Found another solution for this which works great! I simply added my favicon as Base64 Encoded Image directly inside the tag like this:

<link href="data:image/x-icon;base64,AAABAAIAEBAAAAEAIABoBAAAJgAAACAgAAABACAAqBAAAI4EAAAoAAAAEAAAACAAAAABACAAAAAAAAAEAAAAAAAAAAAAAAAAAAAAAAAA////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AIaDgv+Gg4L/hoOC/4aDgv+Gg4L/hoOC/4aDgv+Gg4L/hoOC/4aDgv////8A////AP///wD///8A////AP///wCGg4L/////AP///wD///8A////AP///wD///8A////AP///wCGg4L/////AP///wD///8A////AP///wD///8AhoOC/////wCGg4L/hoOC/4aDgv+Gg4L/hoOC/4aDgv////8AhoOC/////wD///8A////AP///wD///8A////AIaDgv////8A////AP///wD///8A////AP///wD///8A////AIaDgv////8A////AP///wD///8A////AP///wCGg4L/////AHCMqP9wjKj/cIyo/3CMqP9wjKj/cIyo/////wCGg4L/////AP///wD///8A////AP///wD///8AhoOC/////wBTlsIAU5bCAFOWwgBTlsIAU5bCM1OWwnP///8AhoOC/////wD///8A////AP///wD///8A////AP///wD///8AU5bCBlOWwndTlsLHU5bC+FOWwv1TlsLR////AP///wD///8A////AP///wD///8A////AP///wD///8A////AFOWwvtTlsLuU5bCu1OWwlc2k9cANpPXqjaT19H///8A////AP///wD///8A////AP///wD///8A////AP///wBTlsIGNpPXADaT1wA2k9dINpPX8TaT1+40ktpDH4r2tB+K9hL///8A////AP///wD///8A////AP///wD///8A////ADaT1wY2k9e7NpPX/TaT16AfivYGH4r23R+K9u4tg/WQLoL1mP///wD///8A////AP///wD///8A////AP///wA2k9fuNpPX5zaT1zMfivYGH4r23R+K9uwjiPYXLoL1+S6C9W7///8A////AP///wD///8A////AP///wD///8ANpPXLjaT1wAfivYGH4r22x+K9usfivYSLoL1oC6C9esugvUA////AP///wD///8A////AP///wD///8A////AP///wD///8AH4r2zx+K9usfivYSLoL1DC6C9fwugvVXLoL1AP///wD///8A////AP///wD///8A////AP///wD///8A////AB+K9kgfivYMH4r2AC6C9bEugvXhLoL1AC6C9QD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wAugvXyLoL1SC6C9QAugvUA////AP//AADgBwAA7/cAAOgXAADv9wAA6BcAAO+XAAD4HwAA+E8AAPsDAAD8AQAA/AEAAP0DAAD/AwAA/ycAAP/nAAAoAAAAIAAAAEAAAAABACAAAAAAAAAQAAAAAAAAAAAAAAAAAAAAAAAA////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8AhISE/4SEhP+EhIT/hISE/4SEhP+EhIT/hISE/4SEhP+EhIT/hISE/4SEhP+EhIT/hISE/4SEhP+EhIT/hISE/4SEhP+EhIT/hISE/////wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wCEhIT/hISE/4SEhP+EhIT/hISE/4SEhP+EhIT/hISE/4SEhP+EhIT/hISE/4SEhP+EhIT/hISE/4SEhP+EhIT/hISE/4SEhP+EhIT/////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AISEhP+EhIT/////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8AhISE/4SEhP////8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8AhISE/4SEhP////8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wCEhIT/hISE/////wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wCEhIT/hISE/////wD///8AhISE/4SEhP+EhIT/hISE/4SEhP+EhIT/hISE/4SEhP+EhIT/hISE/4SEhP8AAAAA////AISEhP+EhIT/////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AISEhP+EhIT/////AP///wCEhIT/hISE/4SEhP+EhIT/hISE/4SEhP+EhIT/hISE/4SEhP+EhIT/hISE/wAAAAD///8AhISE/4SEhP////8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8AhISE/4SEhP/4+vsA4ujuAOLo7gDi6O4A4ujuAN3k6wDZ4OgA2eDoANng6ADZ4OgA2eDoANng6ADW3uYAJS84APj6+wCEhIT/hISE/////wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wCEhIT/hISE/9Xd5QBwjKgAcIyoRnCMqGRwjKhxcIyogHCMqI9wjKidcIyoq3CMqLlwjKjHcIyo1HCMqLhogpwA/f7+AISEhP+EhIT/////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AISEhP+EhIT/xtHcAHCMqABwjKjAcIyo/3CMqP9wjKj/cIyo/3CMqP9wjKj/cIyo/3CMqP9wjKj/cIyo4EdZawD///8AhISE/4SEhP////8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8AhISE/4SEhP+2xNMAcIyoAHCMqJhwjKjPcIyowHCMqLFwjKijcoymlXSMpIh0jKR6co2mbG+OqGFqj61zXZO4AeXv9gCEhIT/hISE/////wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wCEhIT/hISE/6i5ygDF0dwAIiozACQyPQAoP1AALlBmADhlggBblLkGVJbBPFOWwnxTlsK5U5bC9FOWwv9TlsIp3erzAISEhP+EhIT/////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AAAAAAAAAAAALztHAAAAAAAuU2sAU5bCClOWwkNTlsKAU5bCwFOWwvhTlsL/U5bC/1OWwv9TlsL/U5bC/ViVvVcXOFAAAAAAAAAAAAD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8AAAAAAAAAAAALDhEALVFoAFOWwjpTlsL6U5bC/1OWwv9TlsL/U5bC/1OWwvxTlsLIV5W+i2CRs0xHi71TKYzUnyuM0gIJHi4AAAAAAAAAAAAAAAAA////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wAAAAAAAAAAACtNZABTlsIAU5bCD1OWwv1TlsL6U5bCxFOWwoRVlsBHZJKwDCNObAA8icJAKYzUwimM1P8pjNT/KYzUWCaCxgALLUsAAAAAAAAAAAD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AAAAAAApS2EAU5bCAFOWwgBTlsIAU5bCNVOWwgg+cJEAIT1QABU/XQA1isg4KYzUuymM1P8pjNT/KYzU/ymM1LAti9E0JYvmDhdouAAAAAAAAAAAAP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8AFyk1AE+PuQBTlsIAU5bCAER7nwAmRVoADBojABRFaQAwi80xKYzUsymM1P8pjNT/KYzU/ymM1LgsjNE2MovXFB+K9MUfivbBH4r2BgcdNAARQH8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wAAAAAAAQIDABIgKgAPGiIABRMcABdQeQAti9AqKYzUrCmM1P8pjNT/KYzU/ymM1MAqjNM9HmqmACWK7SIfivbZH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rel="icon" type="image/x-icon" />

Used this page here for this:

Generate favicons

I can really suggest you this page: to create all types of favicons you need.

How to recover Git objects damaged by hard disk failure?

Banengusk was putting me on the right track. For further reference, I want to post the steps I took to fix my repository corruption. I was lucky enough to find all needed objects either in older packs or in repository backups.

# Unpack last non-corrupted pack
$ mv .git/objects/pack .git/objects/pack.old
$ git unpack-objects -r < .git/objects/pack.old/pack-012066c998b2d171913aeb5bf0719fd4655fa7d0.pack
$ git log
fatal: bad object HEAD

$ cat .git/HEAD 
ref: refs/heads/master

$ ls .git/refs/heads/

$ cat .git/packed-refs 
# pack-refs with: peeled 
aa268a069add6d71e162c4e2455c1b690079c8c1 refs/heads/master

$ git fsck --full 
error: HEAD: invalid sha1 pointer aa268a069add6d71e162c4e2455c1b690079c8c1
error: refs/heads/master does not point to a valid object!
missing blob 75405ef0e6f66e48c1ff836786ff110efa33a919
missing blob 27c4611ffbc3c32712a395910a96052a3de67c9b
dangling tree 30473f109d87f4bcde612a2b9a204c3e322cb0dc

# Copy HEAD object from backup of repository
$ cp repobackup/.git/objects/aa/268a069add6d71e162c4e2455c1b690079c8c1 .git/objects/aa
# Now copy all missing objects from backup of repository and run "git fsck --full" afterwards
# Repeat until git fsck --full only reports dangling objects

# Now garbage collect repo
$ git gc
warning: reflog of 'HEAD' references pruned commits
warning: reflog of 'refs/heads/master' references pruned commits
Counting objects: 3992, done.
Delta compression using 2 threads.
fatal: object bf1c4953c0ea4a045bf0975a916b53d247e7ca94 inconsistent object length (6093 vs 415232)
error: failed to run repack

# Check reflogs...
$ git reflog

# ...then clean
$ git reflog expire --expire=0 --all

# Now garbage collect again
$ git gc       
Counting objects: 3992, done.
Delta compression using 2 threads.
Compressing objects: 100% (3970/3970), done.
Writing objects: 100% (3992/3992), done.
Total 3992 (delta 2060), reused 0 (delta 0)
Removing duplicate objects: 100% (256/256), done.
# Done!

"An access token is required to request this resource" while accessing an album / photo with Facebook php sdk

There are 3 things you need.

  1. You need to oAuth with the owner of those photos. (with the 'user_photos' extended permission)

  2. You need the access token (which you get returned in the URL box after the oAuth is done.)

  3. When those are complete you can then access the photos like so

You can find all of the information in more detail here:

android:drawableLeft margin and/or padding

just remake from:

<?xml version="1.0" encoding="utf-8"?>

    <corners android:radius="40dp"/>

    <solid android:color="@android:color/white"/>




            <corners android:radius="40dp"/>

            <solid android:color="@android:color/white"/>



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

public String readLine(int line){
        FileReader tempFileReader = null;
        BufferedReader tempBufferedReader = null;
        try { tempFileReader = new FileReader(textFile); 
        tempBufferedReader = new BufferedReader(tempFileReader);
        } catch (Exception e) { }
        String returnStr = "ERROR";
        for(int i = 0; i < line - 1; i++){
            try { tempBufferedReader.readLine(); } catch (Exception e) { }
        try { returnStr = tempBufferedReader.readLine(); }  catch (Exception e) { }

        return returnStr;

How to write specific CSS for mozilla, chrome and IE

use agent detector and then with your web language create program to create css

for example in python

    useragent = detector()
    if useragent == "Firefox":
         css = "your css"
    return css

How to crop a CvMat in OpenCV?

I understand this question has been answered but perhaps this might be useful to someone...

If you wish to copy the data into a separate cv::Mat object you could use a function similar to this:

void ExtractROI(Mat& inImage, Mat& outImage, Rect roi){
    /* Create the image */
    outImage = Mat(roi.height, roi.width, inImage.type(), Scalar(0));

    /* Populate the image */
    for (int i = roi.y; i < (roi.y+roi.height); i++){
        uchar* inP = inImage.ptr<uchar>(i);
        uchar* outP = outImage.ptr<uchar>(i-roi.y);
        for (int j = roi.x; j < (roi.x+roi.width); j++){
            outP[j-roi.x] = inP[j];

It would be important to note that this would only function properly on single channel images.

Pandas DataFrame concat vs append

Pandas concat vs append vs join vs merge

  • Concat gives the flexibility to join based on the axis( all rows or all columns)

  • Append is the specific case(axis=0, join='outer') of concat

  • Join is based on the indexes (set by set_index) on how variable =['left','right','inner','couter']

  • Merge is based on any particular column each of the two dataframes, this columns are variables on like 'left_on', 'right_on', 'on'

jQuery Uncaught TypeError: Property '$' of object [object Window] is not a function

You can consider to replace default WordPress jQuery script with Google Library by adding something like the following into theme functions.php file:

function modify_jquery() {
    if (!is_admin()) {
        wp_register_script('jquery', '', false, '1.10.2');
add_action('init', 'modify_jquery');

Code taken from here:

Change the "From:" address in Unix "mail"

What allowed me to have a custom reply-to address on an Ubuntu 16.04 with UTF-8 encoding and a file attachment:

Install the mail client:

sudo apt-get install heirloom-mailx

Edit the SMTP configuration:

sudo vim /etc/ssmtp/ssmtp.conf
[email protected]

Send the mail:

sender='[email protected]'
recipient='[email protected]'
today=`date +\%d-\%m-\%Y`
mailSubject='My subject on the '$today
read -r -d '' mailBody << EOM
Find attached the zip file.

mail -s "$mailSubject" -r "Name <$sender>" -S replyto="$sender" -a $zipfile $recipient < <(echo $mailBody)

How to make Bootstrap carousel slider use mobile left/right swipe

If anyone is looking for the angular version of this answer then I would suggest creating a directive would be a great idea.

NOTE: ngx-bootstrap is used.

import { Directive, Host, Self, Optional, Input, Renderer2, OnInit, ElementRef } from '@angular/core';
import { CarouselComponent } from 'ngx-bootstrap/carousel';

  selector: '[appCarouselSwipe]'
export class AppCarouselSwipeDirective implements OnInit {
  @Input() swipeThreshold = 50;
  private start: number;
  private stillMoving: boolean;
  private moveListener: Function;

    @Host() @Self() @Optional() private carousel: CarouselComponent,
    private renderer: Renderer2,
    private element: ElementRef
  ) {

  ngOnInit(): void {
    if ('ontouchstart' in document.documentElement) {
      this.renderer.listen(this.element.nativeElement, 'touchstart', this.onTouchStart.bind(this));
      this.renderer.listen(this.element.nativeElement, 'touchend', this.onTouchEnd.bind(this));

  private onTouchStart(e: TouchEvent): void {
    if (e.touches.length === 1) {
      this.start = e.touches[0].pageX;
      this.stillMoving = true;
      this.moveListener = this.renderer.listen(this.element.nativeElement, 'touchmove', this.onTouchMove.bind(this));

  private onTouchMove(e: TouchEvent): void {
    if (this.stillMoving) {
      const x = e.touches[0].pageX;
      const difference = this.start - x;
      if (Math.abs(difference) >= this.swipeThreshold) {
        if (difference > 0) {
          if (this.carousel.activeSlide < this.carousel.slides.length - 1) {
            this.carousel.activeSlide = this.carousel.activeSlide + 1;
        } else {
          if (this.carousel.activeSlide > 0) {
            this.carousel.activeSlide = this.carousel.activeSlide - 1;

  private onTouchEnd(e: TouchEvent): void {

  private cancelTouch() {
    if (this.moveListener) {
      this.moveListener = undefined;
    this.start = null;
    this.stillMoving = false;

in html:

<carousel appCarouselSwipe>




Call a stored procedure with another in Oracle

Your stored procedures work as coded. The problem is with the last line, it is unable to invoke either of your stored procedures.

Three choices in SQL*Plus are: call, exec, and an anoymous PL/SQL block.

call appears to be a SQL keyword, and is documented in the SQL Reference. The syntax diagram indicates that parentesis are required, even when no arguments are passed to the call routine.

CALL test_sp_1();

An anonymous PL/SQL block is PL/SQL that is not inside a named procedure, function, trigger, etc. It can be used to call your procedure.


Exec is a SQL*Plus command that is a shortcut for the above anonymous block. EXEC <procedure_name> will be passed to the DB server as BEGIN <procedure_name>; END;

Full example:

  2  AS 
  3  BEGIN 
  4      DBMS_OUTPUT.PUT_LINE('Test works'); 
  5  END;
  6  /

Procedure created.

  2  AS
  3  BEGIN
  4      DBMS_OUTPUT.PUT_LINE('Testing'); 
  5      test_sp; 
  6  END;
  7  /

Procedure created.

SQL> CALL test_sp_1();
Test works

Call completed.

SQL> exec test_sp_1
Test works

PL/SQL procedure successfully completed.

SQL> begin
  2      test_sp_1;
  3  end;
  4  /
Test works

PL/SQL procedure successfully completed.


how to format date in Component of angular 5

You can find more information about the date pipe here, such as formats.

If you want to use it in your component, you can simply do

pipe = new DatePipe('en-US'); // Use your own locale

Now, you can simply use its transform method, which will be

const now =;
const myFormattedDate = this.pipe.transform(now, 'short');

Align two divs horizontally side by side center to the page using bootstrap css

Alternative which I did programming Angular:

    <div class="form-row">
        <div class="form-group col-md-7">
        <div class="form-group col-md-5">

Calculating the SUM of (Quantity*Price) from 2 different tables

i think this - including null value = 0

         SUM(nvl(oi.quantity,0) * nvl(p.price,0)) AS total_qty 
    JOIN PRODUCT p ON = oi.productid 
   WHERE oi.orderid = @OrderId 

How is a CRC32 checksum calculated?

Then there is always Rosetta Code, which shows crc32 implemented in dozens of computer languages. and has links to many explanations and implementations.

Getting java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory exception

Adding commons-logging.jar or commons-logging-1.1.jar will solve this...

.htaccess rewrite to redirect root URL to subdirectory

Another alternative if you want to rewrite the URL and hide the original URL:

RewriteEngine on
RewriteRule ^(.*)$ /store/$1 [L]

With this, if you for example type, it will transparently open the file at but without showing to the user the full url.

Can I give a default value to parameters or optional parameters in C# functions?

It is only possible as from C# 4.0

However, when you use a version of C#, prior to 4.0, you can work around this by using overloaded methods:

public void Func( int i, int j )
    Console.WriteLine (String.Format ("i = {0}, j = {1}", i, j));

public void Func( int i )
    Func (i, 4);

public void Func ()
    Func (5);

(Or, you can upgrade to C# 4.0 offcourse).

C# get string from textbox

The TextBox control has a Text property that you can use to get (or set) the text of the textbox.

Equivalent of explode() to work with strings in MySQL

As @arman-p pointed out MYSQL has no explode(). However, I think the solution presented in much more complicated than it needs to be. To do a quick check when you are given a comma delimited list string (e.g, list of the table keys to look for) you do:

    table_key, field_1, field_2, field_3
    field_3 = 'my_field_3_value'
    AND (comma_list = table_key
        OR comma_list LIKE CONCAT(table_key, ',%')
        OR comma_list LIKE CONCAT('%,', table_key, ',%')
        OR comma_list LIKE CONCAT('%,', table_key))

This assumes that you need to also check field_3 on the table too. If you do not need it, do not add that condition.

Android Preventing Double Click On A Button

Setting Clickable to false does not work on the first double click but subsequent double clicks are blocked. It is as though the loading click delegate the first time is slower and the second click is captured before the first completes.

        Button button = contentView.FindViewById<Button>(Resource.Id.buttonIssue);
        button.Clickable = false;
        button.Clickable = true;

Convert pandas.Series from dtype object to float, and errors to nans

Use pd.to_numeric with errors='coerce'

# Setup
s = pd.Series(['1', '2', '3', '4', '.'])

0    1
1    2
2    3
3    4
4    .
dtype: object

pd.to_numeric(s, errors='coerce')

0    1.0
1    2.0
2    3.0
3    4.0
4    NaN
dtype: float64

If you need the NaNs filled in, use Series.fillna.

pd.to_numeric(s, errors='coerce').fillna(0, downcast='infer')

0    1
1    2
2    3
3    4
4    0
dtype: float64

Note, downcast='infer' will attempt to downcast floats to integers where possible. Remove the argument if you don't want that.

From v0.24+, pandas introduces a Nullable Integer type, which allows integers to coexist with NaNs. If you have integers in your column, you can use

# '0.24.1'

pd.to_numeric(s, errors='coerce').astype('Int32')

0      1
1      2
2      3
3      4
4    NaN
dtype: Int32

There are other options to choose from as well, read the docs for more.

Extension for DataFrames

If you need to extend this to DataFrames, you will need to apply it to each row. You can do this using DataFrame.apply.

# Setup.
df = pd.DataFrame({
    'A' : np.random.choice(10, 5), 
    'C' : np.random.choice(10, 5), 
    'B' : ['1', '###', '...', 50, '234'], 
    'D' : ['23', '1', '...', '268', '$$']}

   A    B  C    D
0  5    1  9   23
1  0  ###  3    1
2  3  ...  5  ...
3  3   50  2  268
4  7  234  4   $$


A     int64
B    object
C     int64
D    object
dtype: object

df2 = df.apply(pd.to_numeric, errors='coerce')

   A      B  C      D
0  5    1.0  9   23.0
1  0    NaN  3    1.0
2  3    NaN  5    NaN
3  3   50.0  2  268.0
4  7  234.0  4    NaN


A      int64
B    float64
C      int64
D    float64
dtype: object

You can also do this with DataFrame.transform; although my tests indicate this is marginally slower:

df.transform(pd.to_numeric, errors='coerce')

   A      B  C      D
0  5    1.0  9   23.0
1  0    NaN  3    1.0
2  3    NaN  5    NaN
3  3   50.0  2  268.0
4  7  234.0  4    NaN

If you have many columns (numeric; non-numeric), you can make this a little more performant by applying pd.to_numeric on the non-numeric columns only.


A    False
B     True
C    False
D     True
dtype: bool

cols = df.columns[df.dtypes.eq(object)]
# Actually, `cols` can be any list of columns you need to convert.
# Index(['B', 'D'], dtype='object')

df[cols] = df[cols].apply(pd.to_numeric, errors='coerce')
# Alternatively,
# for c in cols:
#     df[c] = pd.to_numeric(df[c], errors='coerce')


   A      B  C      D
0  5    1.0  9   23.0
1  0    NaN  3    1.0
2  3    NaN  5    NaN
3  3   50.0  2  268.0
4  7  234.0  4    NaN

Applying pd.to_numeric along the columns (i.e., axis=0, the default) should be slightly faster for long DataFrames.

matplotlib set yaxis label size

If you are using the 'pylab' for interactive plotting you can set the labelsize at creation time with pylab.ylabel('Example', fontsize=40).

If you use pyplot programmatically you can either set the fontsize on creation with ax.set_ylabel('Example', fontsize=40) or afterwards with ax.yaxis.label.set_size(40).

The difference between sys.stdout.write and print?

>>> sys.stdout.write(1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: expected a string or other character buffer object
>>> sys.stdout.write("a")
a>>> sys.stdout.write("a") ; print(1)

Observing the example above:

  1. sys.stdout.write won't write non-string object, but print will

  2. sys.stdout.write won't add a new line symbol in the end, but print will

If we dive deeply,

sys.stdout is a file object which can be used for the output of print()

if file argument of print() is not specified, sys.stdout will be used

Copy every nth line from one sheet to another

In A1 of your new sheet, put this:


... and copy down. If you start somewhere other than row 1, change ROW() to ROW(A1) or some other cell on row 1, then copy down again.

If you want to copy the nth line but multiple columns, use the formula:


This can be copied right too.

Spring Boot: Cannot access REST Controller on localhost (404)

Adding to MattR's answer:

As stated in here, @SpringBootApplication automatically inserts the needed annotations: @Configuration, @EnableAutoConfiguration, and also @ComponentScan; however, the @ComponentScan will only look for the components in the same package as the App, in this case your com.nice.application, whereas your controller resides in com.nice.controller. That's why you get 404 because the App didn't find the controller in the application package.

How can I convert a std::string to int?

It's probably a bit of overkill, but boost::lexical_cast<int>( theString ) should to the job quite well.

C# equivalent of the IsNull() function in SQL Server

You Write Two Function

    //When Expression is Number
    public static double? isNull(double? Expression, double? Value)
        if (Expression ==null)
            return Value;
            return Expression;

    //When Expression is string (Can not send Null value in string Expression
    public static string isEmpty(string Expression, string Value)
        if (Expression == "")
            return Value;
            return Expression;

They Work Very Well

How to check if an environment variable exists and get its value?

There is no difference between environment variables and variables in a script. Environment variables are just defined earlier, outside the script, before the script is called. From the script's point of view, a variable is a variable.

You can check if a variable is defined:

if [ -z "$a" ]
    echo "not defined"
    echo "defined"

and then set a default value for undefined variables or do something else.

The -z checks for a zero-length (i.e. empty) string. See man bash and look for the CONDITIONAL EXPRESSIONS section.

You can also use set -u at the beginning of your script to make it fail once it encounters an undefined variable, if you want to avoid having an undefined variable breaking things in creative ways.

Generate UML Class Diagram from Java Project

How about the Omondo Plugin for Eclipse. I have used it and I find it to be quite useful. Although if you are generating diagrams for large sources, you might have to start Eclipse with more memory.

Using Pipes within ngModel on INPUT Elements in Angular

You can't use Template expression operators(pipe, save navigator) within template statement:

(ngModelChange)="Template statements"

(ngModelChange)="item.value | useMyPipeToFormatThatValue=$event"

Like template expressions, template statements use a language that looks like JavaScript. The template statement parser differs from the template expression parser and specifically supports both basic assignment (=) and chaining expressions (with ; or ,).

However, certain JavaScript syntax is not allowed:

  • new
  • increment and decrement operators, ++ and --
  • operator assignment, such as += and -=
  • the bitwise operators | and &
  • the template expression operators

So you should write it as follows:

<input [ngModel]="item.value | useMyPipeToFormatThatValue" 
      (ngModelChange)="item.value=$event" name="inputField" type="text" />

Plunker Example

git rebase merge conflict

Rebasing can be a real headache. You have to resolve the merge conflicts and continue rebasing. For example you can use the merge tool (which differs depending on your settings)

git mergetool

Then add your changes and go on

git rebase --continue

Good luck

How to send json data in the Http request using NSURLRequest

Since my edit to Mike G's answer to modernize the code was rejected 3 to 2 as

This edit was intended to address the author of the post and makes no sense as an edit. It should have been written as a comment or an answer

I'm reposting my edit as a separate answer here. This edit removes the JSONRepresentation dependency with NSJSONSerialization as Rob's comment with 15 upvotes suggests.

    NSArray *objects = [NSArray arrayWithObjects:[[NSUserDefaults standardUserDefaults]valueForKey:@"StoreNickName"],
      [[UIDevice currentDevice] uniqueIdentifier], [dict objectForKey:@"user_question"],     nil];
    NSArray *keys = [NSArray arrayWithObjects:@"nick_name", @"UDID", @"user_question", nil];
    NSDictionary *questionDict = [NSDictionary dictionaryWithObjects:objects forKeys:keys];

    NSDictionary *jsonDict = [NSDictionary dictionaryWithObject:questionDict forKey:@"question"];

    NSLog(@"jsonRequest is %@", jsonRequest);

    NSURL *url = [NSURL URLWithString:@""];

    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url
                 cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];

    NSData *requestData = [NSJSONSerialization dataWithJSONObject:dict options:0 error:nil]; //TODO handle error

    [request setHTTPMethod:@"POST"];
    [request setValue:@"application/json" forHTTPHeaderField:@"Accept"];
    [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
    [request setValue:[NSString stringWithFormat:@"%d", [requestData length]] forHTTPHeaderField:@"Content-Length"];
    [request setHTTPBody: requestData];

    NSURLConnection *connection = [[NSURLConnection alloc]initWithRequest:request delegate:self];
    if (connection) {
     receivedData = [[NSMutableData data] retain];

The receivedData is then handled by:

NSDictionary *jsonDict = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
    NSDictionary *question = [jsonDict objectForKey:@"question"];

How to get the number of characters in a string

I tried to make to do the normalization a bit faster:

    en, _ = glyphSmart(data)

    func glyphSmart(text string) (int, int) {
        gc := 0
        dummy := 0
        for ind, _ := range text {
            dummy = ind
        dummy = 0
        return gc, dummy

Return Bit Value as 1/0 and NOT True/False in SQL Server

Try with this script, maybe will be useful:


Anyway I always would use a value of 1 or 0 (not TRUE or FALSE). Following your example, the update script would be:

Update Table Set BitField=CAST('TRUE' as bit) Where ID=1

CSS How to set div height 100% minus nPx

Here is a working css, tested under Firefox / IE7 / Safari / Chrome / Opera.

* {margin:0px;padding:0px;overflow:hidden}
div {position:absolute}
div#header {top:0px;left:0px;right:0px;height:60px}
div#wrapper {top:60px;left:0px;right:0px;bottom:0px;}
div#left {top:0px;bottom:0px;left:0px;width:50%;overflow-y:auto}
div#right {top:0px;bottom:0px;right:0px;width:50%;overflow-y:auto}

"overflow-y" is not w3c-approved, but every major browser supports it. Your two divs #left and #right will display a vertical scrollbar if their content is too high.

For this to work under IE7, you have to trigger the standards-compliant mode by adding a DOCTYPE :

<style type="text/css">_x000D_
<div id="header"></div>_x000D_
<div id="wrapper">_x000D_
  <div id="left"><div style="height:1000px">high content</div></div>_x000D_
  <div id="right"></div>_x000D_

How to get First and Last record from a sql query?

You might want to try this, could potentially be faster than doing two queries:

select <some columns>
from (
    SELECT <some columns>,
           row_number() over (order by date desc) as rn,
           count(*) over () as total_count
    FROM mytable
    <maybe some joins here>
    WHERE <various conditions>
) t
where rn = 1
   or rn = total_count

UITableViewCell Selected Background Color on Multiple Selection

Swift 5 - This works for me:

 func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

        let selectedCell:UITableViewCell = tableView.cellForRow(at: indexPath as IndexPath)!
        selectedCell.contentView.backgroundColor = .red

    func tableView(_ tableView: UITableView, didDeselectRowAt indexPath: IndexPath) {

        let cellToDeSelect:UITableViewCell = tableView.cellForRow(at: indexPath as IndexPath)!
        cellToDeSelect.contentView.backgroundColor = .clear

is there a 'block until condition becomes true' function in java?

You could use a semaphore.

While the condition is not met, another thread acquires the semaphore.
Your thread would try to acquire it with acquireUninterruptibly()
or tryAcquire(int permits, long timeout, TimeUnit unit) and would be blocked.

When the condition is met, the semaphore is also released and your thread would acquire it.

You could also try using a SynchronousQueue or a CountDownLatch.

Eclipse HotKey: how to switch between tabs?

Switch like Windows in OS (go to window which last had focus)

CTRL-F6 in Eclipse, like ALT-TAB (on windows), brings up a list of tabs/windows available (if you keep the CTRL / ALT key depressed) and highlights the one you will jump to when you let go of this key. You do not have to select the window. If you want to traverse several tabs at once hold down the CTRL button and tap the TAB button. This is identical behaviour to ALT-TAB on Windows.

In this sense, CTRL-SHIFT-F6 in eclipse is the ALT-SHIFT-TAB analog. Personally, I change these bindings in Eclipse to be like Visual Studio. I.e. CTRL-TAB and CTRL-SHIFT-TAB and I do it like this:


Then set "Next Editor"=Ctrl+Tab and "Previous Editor"=Ctrl+Shift+Tab. Don't forget to click "Unbind Command" before setting the new binding.

Switch like browser (go to tab on the right of current tab)

This is CTRL-PageDown to go right, CTRL-PageUp to go left. Frustratingly, when you get to the end of the list of tabs (say far right hand tab) and then try to go right again Eclipse does not cycle round to the first tab (far left) like most browsers would.

How to get a reversed list view on a list in Java?

Guava provides this: Lists.reverse(List)

List<String> letters = ImmutableList.of("a", "b", "c");
List<String> reverseView = Lists.reverse(letters); 
System.out.println(reverseView); // [c, b, a]

Unlike Collections.reverse, this is purely a view... it doesn't alter the ordering of elements in the original list. Additionally, with an original list that is modifiable, changes to both the original list and the view are reflected in the other.

ASP.NET Background image

You can use this if you want to assign a background image on the backend:

divContent.Attributes.Add("style"," background-image:

How to get the current user in ASP.NET MVC

Try HttpContext.Current.User.

Public Shared Property Current() As System.Web.HttpContext
Member of System.Web.HttpContext

Gets or sets the System.Web.HttpContext object for the current HTTP request.

Return Values:
The System.Web.HttpContext for the current HTTP request

List file using ls command in Linux with full path

There is more than one way to do that, the easiest I think would be:

find /mnt/mediashare/net/

also this should work:

(cd /mnt/mediashare/net/; ls | xargs -i echo `pwd`/{})

How to convert HTML to PDF using iTextSharp

Here's the link I used as a guide. Hope this helps!

Converting HTML to PDF using ITextSharp

protected void Page_Load(object sender, EventArgs e)
            string strHtml = string.Empty;
            //HTML File path -
            string htmlFileName = Server.MapPath("~") + "\\files\\" + "ConvertHTMLToPDF.htm";
            //pdf file path. -
            string pdfFileName = Request.PhysicalApplicationPath + "\\files\\" + "ConvertHTMLToPDF.pdf";

            //reading html code from html file
            FileStream fsHTMLDocument = new FileStream(htmlFileName, FileMode.Open, FileAccess.Read);
            StreamReader srHTMLDocument = new StreamReader(fsHTMLDocument);
            strHtml = srHTMLDocument.ReadToEnd();

            strHtml = strHtml.Replace("\r\n", "");
            strHtml = strHtml.Replace("\0", "");

            CreatePDFFromHTMLFile(strHtml, pdfFileName);

            Response.Write("pdf creation successfully with password -");
        catch (Exception ex)
    public void CreatePDFFromHTMLFile(string HtmlStream, string FileName)
            object TargetFile = FileName;
            string ModifiedFileName = string.Empty;
            string FinalFileName = string.Empty;

            /* To add a Password to PDF - */
            TestPDF.HtmlToPdfBuilder builder = new TestPDF.HtmlToPdfBuilder(iTextSharp.text.PageSize.A4);
            TestPDF.HtmlPdfPage first = builder.AddPage();
            byte[] file = builder.RenderPdf();
            File.WriteAllBytes(TargetFile.ToString(), file);

            iTextSharp.text.pdf.PdfReader reader = new iTextSharp.text.pdf.PdfReader(TargetFile.ToString());
            ModifiedFileName = TargetFile.ToString();
            ModifiedFileName = ModifiedFileName.Insert(ModifiedFileName.Length - 4, "1");

            string password = "password";
            iTextSharp.text.pdf.PdfEncryptor.Encrypt(reader, new FileStream(ModifiedFileName, FileMode.Append), iTextSharp.text.pdf.PdfWriter.STRENGTH128BITS, password, "", iTextSharp.text.pdf.PdfWriter.AllowPrinting);
            if (File.Exists(TargetFile.ToString()))
            FinalFileName = ModifiedFileName.Remove(ModifiedFileName.Length - 5, 1);
            File.Copy(ModifiedFileName, FinalFileName);
            if (File.Exists(ModifiedFileName))

        catch (Exception ex)
            throw ex;

You can download the sample file. Just place the html you want to convert in the files folder and run. It will automatically generate the pdf file and place it in the same folder. But in your case, you can specify your html path in the htmlFileName variable.

how to get the 30 days before date from Todays Date

In MS SQL Server, it is:

SELECT getdate() - 30;

SQL Server 2008: TOP 10 and distinct together


SELECT TOP 10, pl.nm, pl.val, pl.txt_val

from dm.labs pl
join mas_data.patients p    
  on =
  where pl.nm like '%LDL%'
  and val is not null


SELECT list is not in GROUP BY clause and contains nonaggregated column .... incompatible with sql_mode=only_full_group_by

Hi instead of taking all columns, just take what you need by using ANY_VALUE(column_name). It is working perfectly. Just check.


SELECT proof_type,any_value("customer_name") as customer_name
FROM `tbl_customer_pod_uploads`
WHERE `load_id` = '78' AND `status` = 'Active' GROUP BY `proof_type`

Display animated GIF in iOS

Another alternative is to use a UIWebView to display the animated GIF. If the GIF is going to be fetched from a server, then this takes care of the fetching. It also works with local GIFs.

1 = false and 0 = true?

There's no good reason for 1 to be true and 0 to be false; that's just the way things have always been notated. So from a logical perspective, the function in your API isn't "wrong", per se.

That said, it's normally not advisable to work against the idioms of whatever language or framework you're using without a damn good reason to do so, so whoever wrote this function was probably pretty bone-headed, assuming it's not simply a bug.

Select max value of each group

select name, max(value)
from out_pumptable
group by name

How do I make a MySQL database run completely in memory?

Additional thoughts :

Ramdisk - setting the temp drive MySQL uses as a RAM disk, very easy to set up.

memcache - memcache server is easy to set up, use it to store the results of your queries for X amount of time.

Vertical Menu in Bootstrap

The question is old now.

But if somebody looks here the trick in the current version is to use the nav-stack class, like so:

  <ul class="nav nav-pills nav-stacked span2">
    <li><a href="#">Home</a></li>
    <li><a href="#">About</a></li>
    <li><a href="#">Contact</a></li>

How to create empty data frame with column names specified in R?


> data.frame(aname=NA, bname=NA)[numeric(0), ]
[1] aname bname
<0 rows> (or 0-length row.names)

RHEL 6 - how to install 'GLIBC_2.14' or 'GLIBC_2.15'?

To install GLIBC_2.14 or GLIBC_2.15, download package from /gnu/libc/ index at

Then follow instructions listed by Timo:

For example glibc-2.14.tar.gz in your case.

  1. tar xvfz glibc-2.14.tar.gz

  2. cd glibc-2.14

  3. mkdir build

  4. cd build

  5. ../configure --prefix=/opt/glibc-2.14

  6. make

  7. sudo make install

  8. export LD_LIBRARY_PATH=/opt/glibc-2.14/lib:$LD_LIBRARY_PATH

How can I convert a .jar to an .exe?

Launch4j works on both Windows and Linux/Mac. But if you're running Linux/Mac, there is a way to embed your jar into a shell script that performs the autolaunch for you, so you have only one runnable file:

MYSELF=`which "$0" 2>/dev/null`
[ $? -gt  0 -a -f "$0" ] && MYSELF="./$0"
# Parse options to determine which ones are for Java and which ones are for the Program
while [ $# -gt 0 ] ; do
    case $1 in
        -Xm*) JAVA_OPT="$JAVA_OPT $1" ;;
        -D*)  JAVA_OPT="$JAVA_OPT $1" ;;
        *)    PROG_OPT="$PROG_OPT $1" ;;
exec java $JAVA_OPT -jar $MYSELF $PROG_OPT

Then you create your runnable file from your jar:

$ cat myrunnablejar.jar > myrunnable
$ chmod +x myrunnable

It works the same way launch4j works: because a jar has a zip format, which header is located at the end of the file. You can have any header you want (either binary executable or, like here, shell script) and run java -jar <myexe>, as <myexe> is a valid zip/jar file.

Take a screenshot via a Python script on Linux

There is a python package for this Autopy

The bitmap module can to screen grabbing (bitmap.capture_screen) It is multiplateform (Windows, Linux, Osx).

SqlServer: Login failed for user

We got this error when reusing the ConnectionString from EntityFramework connection. We have Username and Password in the connection string but didn't specify "Persist Security Info=True". Thus, the credentials were removed from the connection string after establishing the connection (so we reused an incomplete connection string). Of course, we always have to think twice when using this setting, but in this particular case, it was ok.

mysql alphabetical order

You do not need to user where clause while ordering the data alphabetically. here is my code

SELECT * FROM tbl_name ORDER BY field_name

that's it. It return the data in alphabetical order ie; From A to Z. :)

Could not load file or assembly 'System.Data.SQLite'

As someone who's had to deal with quite a few bug reports on Roadkill Wiki with exactly the same issue, this is what you need to do:

  • Are you using x64 or x86? Sqlite comes with DLLs for separate architectures - copy the right one to your bin folder, there are two DLLS for the official provider: System.Data.SQLite.dll System.Data.SQLite.Linq.dll
  • If you can't be bothered hunting around for these assemblies, enable 32 bit mode for your App Pool (a solution for dev machines only usually)
  • If you're hosting on a server, you'll need the Microsoft C++ Runtime redistributable - it's not installed on Server 2008 R2 by default. x64 version, x86 version

It's a real pain in the ass how many hoops you have to jump through when re-distributing the SQLite .NET binaries, my solution for Roadkill in the end was to copy the correct binaries to the ~/bin folder based on the architecture your using. Unfortunately that doesn't solve the C++ runtime issue.

What is the difference between decodeURIComponent and decodeURI?

decodeURIComponent will decode URI special markers such as &, ?, #, etc, decodeURI will not.

How to force deletion of a python object?

The way to close resources are context managers, aka the with statement:

class Foo(object):

  def __init__(self): = None

  def __enter__(self):
    if != 'open':
      print 'opening the bar' = 'open'
    return self # this is bound to the `as` part

  def close(self):
    if != 'closed':
      print 'closing the bar' = 'close'

  def __exit__(self, *err):

if __name__ == '__main__':
  with Foo() as foo:
    print foo,


opening the bar
<__main__.Foo object at 0x17079d0> open
closing the bar

2) Python's objects get deleted when their reference count is 0. In your example the del foo removes the last reference so __del__ is called instantly. The GC has no part in this.

class Foo(object):

    def __del__(self):
        print "deling", self

if __name__ == '__main__':
    import gc
    gc.disable() # no gc
    f = Foo()
    print "before"
    del f # f gets deleted right away
    print "after"


deling <__main__.Foo object at 0xc49690>

The gc has nothing to do with deleting your and most other objects. It's there to clean up when simple reference counting does not work, because of self-references or circular references:

class Foo(object):
    def __init__(self, other=None):
        # make a circular reference = other
        if other is not None:
   = self

    def __del__(self):
        print "deling", self

if __name__ == '__main__':
    import gc
    f = Foo(Foo())
    print "before"
    del f # nothing gets deleted here
    print "after"
    print gc.garbage # The GC knows the two Foos are garbage, but won't delete
                     # them because they have a __del__ method
    print "after gc"
    # break up the cycle and delete the reference from gc.garbage
    del gc.garbage[0].link, gc.garbage[:]
    print "done"


[<__main__.Foo object at 0x22ed8d0>, <__main__.Foo object at 0x22ed950>]
after gc
deling <__main__.Foo object at 0x22ed950>
deling <__main__.Foo object at 0x22ed8d0>

3) Lets see:

class Foo(object):
    def __init__(self):

        raise Exception

    def __del__(self):
        print "deling", self

if __name__ == '__main__':
    f = Foo()


Traceback (most recent call last):
  File "", line 10, in <module>
    f = Foo()
  File "", line 4, in __init__
    raise Exception
deling <__main__.Foo object at 0xa3a910>

Objects are created with __new__ then passed to __init__ as self. After a exception in __init__, the object will typically not have a name (ie the f = part isn't run) so their ref count is 0. This means that the object is deleted normally and __del__ is called.

How to get all values from python enum class?

You can do the following:

[e.value for e in Color]

Android: Pass data(extras) to a fragment

great answer by @Rarw. Try using a bundle to pass information from one fragment to another

How to build a Debian/Ubuntu package from source?

If you're using Ubuntu, check out the pkgcreator project:

Accessing member of base class

You are incorrectly using the super and this keyword. Here is an example of how they work:

class Animal {
    public name: string;
    constructor(name: string) { = name;
    move(meters: number) {
        console.log( + " moved " + meters + "m.");

class Horse extends Animal {
    move() {
        console.log( + " is Galloping...");
        console.log( + " is Galloping...");

var tom: Animal = new Horse("Tommy the Palomino"); = 'horseee'; 

// Outputs:

// horseee is Galloping...
// Tommy the Palomino is Galloping...
// Tommy the Palomino moved 45m.


  1. The first log outputs, this refers to the prototype chain of the object tom, not the object tom self. Because we have added a name property on the Animal.prototype, horseee will be outputted.
  2. The second log outputs, the this keyword refers to the the tom object itself.
  3. The third log is logged using the move method of the Animal base class. This method is called from Horse class move method with the syntax super.move(45);. Using the super keyword in this context will look for a move method on the prototype chain which is found on the Animal prototype.

Remember TS still uses prototypes under the hood and the class and extends keywords are just syntactic sugar over prototypical inheritance.

How to make a node.js application run permanently?

I’ve found forever to do the job perfectly fine.

Assuming you already have npm installed, if not, just do

sudo apt-get install npm

Then install forever

npm install forever --global

Now you can run it like this

forever start app.js

Is header('Content-Type:text/plain'); necessary at all?

no its not like that,here is Example for the support of my answer ---->the clear difference is visible ,when you go for HTTP Compression,which allows you to compress the data while travelling from Server to Client and the Type of this data automatically becomes as "gzip" which Tells browser that bowser got a zipped data and it has to upzip it,this is a example where Type really matters at Bowser.

E: Unable to locate package npm

I ran into the same issue on Debian 9.2, this is what I did to overcome it.


sudo apt install curl
curl -sL | sudo bash -
sudo apt-get install -y nodejs
sudo apt-get install -y npm

Check installed versions

node --version
npm --version

Originally sourced from "How to install Node.js LTS on Debian 9 stretch"

Skip certain tables with mysqldump

Dump all databases with all tables but skip certain tables

on github:


if [ -z "$1" ] ; then
  echo "ERROR: root password Parameter missing."


mkdir $BACKUP_DIR -p


IGNORE="database1.table1, database1.table2, database2.table1,"

# strpos $1 $2 [$3]
# strpos haystack needle [optional offset of an input string]
    local str=${1}
    local offset=${3}
    if [ -n "${offset}" ]; then
        str=`substr "${str}" ${offset}`
    if [ "${#str}" -eq "${#1}" ]; then
        return 0
    echo $((${#str}+${offset}))

for i in */; do
    if [ $i != 'performance_schema/' ] ; then 
    DB=`basename "$i"` 
    #echo "backup $DB->$BACKUP_DIR$DB.sql.lzo"
    mysqlcheck "$DB" $MYSQL_CONN --silent --auto-repair >/tmp/tmp_grep_mysql-backup
    grep -E -B1 "note|warning|support|auto_increment|required|locks" /tmp/tmp_grep_mysql-backup>/tmp/tmp_grep_mysql-backup_not
    grep -v "$(cat /tmp/tmp_grep_mysql-backup_not)" /tmp/tmp_grep_mysql-backup

    for t in $(mysql -NBA -h $DB_host $MYSQL_CONN -D $DB -e 'show tables') 
      found=$(strpos "$IGNORE" "$DB"."$t,")
      if [ "$found" == "" ] ; then 
        echo "DUMPING TABLE: $DB.$t"
        mysqldump -h $DB_host $MYSQL_CONN $DB $t --events --skip-lock-tables | lzop -3 -f -o $BACKUP_DIR/$DB.$t.sql.lzo
        tbl_count=$(( tbl_count + 1 ))
    echo "$tbl_count tables dumped from database '$DB' into dir=$BACKUP_DIR"

With a little help of

It uses lzop which is much faster, see:

rm: cannot remove: Permission denied

The code says everything:

max@serv$ chmod 777 .

Okay, it doesn't say everything.

In UNIX and Linux, the ability to remove a file is not determined by the access bits of that file. It is determined by the access bits of the directory which contains the file.

Think of it this way -- deleting a file doesn't modify that file. You aren't writing to the file, so why should "w" on the file matter? Deleting a file requires editing the directory that points to the file, so you need "w" on the that directory.

Java Process with Input/Output Stream

I think you can use thread like demon-thread for reading your input and your output reader will already be in while loop in main thread so you can read and write at same time.You can modify your program like this:

Thread T=new Thread(new Runnable() {

    public void run() {
            String input = scan.nextLine();
            input += "\n";
            try {
            } catch (IOException e) {
                // TODO Auto-generated catch block


} );

and you can reader will be same as above i.e.

while ((line = reader.readLine ()) != null) {
    System.out.println ("Stdout: " + line);

make your writer as final otherwise it wont be able to accessible by inner class.

How do getters and setters work?

Here is an example to explain the most simple way of using getter and setter in java. One can do this in a more straightforward way but getter and setter have something special that is when using private member of parent class in child class in inheritance. You can make it possible through using getter and setter.

package stackoverflow;

    public class StackoverFlow 


        private int x;

        public int getX()
            return x;

        public int setX(int x)
          return  this.x = x;
         public void showX()
             System.out.println("value of x  "+x);

        public static void main(String[] args) {

            StackoverFlow sto = new StackoverFlow();


Apache Cordova - uninstall globally

This can happen when the cordova was installed globally on a different version of the node.

Being necessary to manually delete yourself as suggested in the previous comment:

which cordova

it will output something like this


then removing by

rm -rf /usr/local/bin/cordova

How to display the value of the bar on each bar with pyplot.barh()?

I needed the bar labels too, note that my y-axis is having a zoomed view using limits on y axis. The default calculations for putting the labels on top of the bar still works using height (use_global_coordinate=False in the example). But I wanted to show that the labels can be put in the bottom of the graph too in zoomed view using global coordinates in matplotlib 3.0.2. Hope it help someone.

def autolabel(rects,data):
Attach a text label above each bar displaying its height
c = 0
initial = 0.091
offset = 0.205
use_global_coordinate = True

if use_global_coordinate:
    for i in data:        
        ax.text(initial+offset*c, 0.05, str(i), horizontalalignment='center',
                verticalalignment='center', transform=ax.transAxes,fontsize=8)
    for rect,i in zip(rects,data):
        height = rect.get_height()
        ax.text(rect.get_x() + rect.get_width()/2., height,str(i),ha='center', va='bottom')

Example output

Getting distance between two points based on latitude/longitude

Edit: Just as a note, if you just need a quick and easy way of finding the distance between two points, I strongly recommend using the approach described in Kurt's answer below instead of re-implementing Haversine -- see his post for rationale.

This answer focuses just on answering the specific bug OP ran into.

It's because in Python, all the trig functions use radians, not degrees.

You can either convert the numbers manually to radians, or use the radians function from the math module:

from math import sin, cos, sqrt, atan2, radians

# approximate radius of earth in km
R = 6373.0

lat1 = radians(52.2296756)
lon1 = radians(21.0122287)
lat2 = radians(52.406374)
lon2 = radians(16.9251681)

dlon = lon2 - lon1
dlat = lat2 - lat1

a = sin(dlat / 2)**2 + cos(lat1) * cos(lat2) * sin(dlon / 2)**2
c = 2 * atan2(sqrt(a), sqrt(1 - a))

distance = R * c

print("Result:", distance)
print("Should be:", 278.546, "km")

The distance is now returning the correct value of 278.545589351 km.

Scrollbar without fixed height/Dynamic height with scrollbar

You will have to specify a fixed height, you cannot use 100% because there is nothing for this to be compared to, as in height=100% of what?

Edited fiddle:

Permission denied error on Github Push

I had this problem too but managed to solve it, the error is that ur computer has saved a git username and password so if you shift to another account the error 403 will appear. Below is the solution For Windows you can find the keys here:

control panel > user accounts > credential manager > Windows credentials > Generic credentials

Next remove the Github keys.

How do you convert a JavaScript date to UTC?

Convert to ISO without changing date/time

var now = new Date(); // Fri Feb 20 2015 19:29:31 GMT+0530 (India Standard Time) 
var isoDate = new Date(now.getTime() - now.getTimezoneOffset() * 60000).toISOString();
//OUTPUT : 2015-02-20T19:29:31.238Z

Convert to ISO with change in date/time(date/time will be changed)

isoDate = new Date(now).toISOString();
//OUTPUT : 2015-02-20T13:59:31.238Z 

Fiddle link

Creating for loop until list.length

The answer depends on what do you need a loop for.

of course you can have a loop similar to Java:

for i in xrange(len(my_list)):

but I never actually used loops like this,

because usually you want to iterate

for obj in my_list

or if you need an index as well

for index, obj in enumerate(my_list)

or you want to produce another collection from a list

map(some_func, my_list)

[somefunc[x] for x in my_list]

also there are itertools module that covers most of iteration related cases

also please take a look at the builtins like any, max, min, all, enumerate

I would say - do not try to write Java-like code in python. There is always a pythonic way to do it.

Set up Python simpleHTTPserver on Windows

From Stack Overflow question What is the Python 3 equivalent of "python -m SimpleHTTPServer":

The following works for me:

python -m http.server [<portNo>]

Because I am using Python 3 the module SimpleHTTPServer has been replaced by http.server, at least in Windows.

How can I do an OrderBy with a dynamic string parameter?

The simplest & the best solution:

mylist.OrderBy(s => s.GetType().GetProperty("PropertyName").GetValue(s));

Removing html5 required attribute with jQuery



If you're interested in further reading take a look here.

Start index for iterating Python list

stdlib will hook you up son!



from collections import deque

a = deque('Monday Tuesday Wednesday Thursday Friday Saturday Sunday'.split(' '))
deque(['Friday', 'Saturday', 'Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday'])

.NET: Simplest way to send POST with data and read response

I know this is an old thread, but hope it helps some one.

public static void SetRequest(string mXml)
    HttpWebRequest webRequest = (HttpWebRequest)HttpWebRequest.CreateHttp("");
    webRequest.Method = "POST";
    webRequest.Headers["SOURCE"] = "WinApp";

    // Decide your encoding here

    //webRequest.ContentType = "application/x-www-form-urlencoded";
    webRequest.ContentType = "text/xml; charset=utf-8";

    // You should setContentLength
    byte[] content = System.Text.Encoding.UTF8.GetBytes(mXml);
    webRequest.ContentLength = content.Length;

    var reqStream = await webRequest.GetRequestStreamAsync();
    reqStream.Write(content, 0, content.Length);

    var res = await httpRequest(webRequest);

PHP Array to JSON Array using json_encode();

I want to add to Michael Berkowski's answer that this can also happen if the array's order is reversed, in which case it's a bit trickier to observe the issue, because in the json object, the order will be ordered ascending.

For example:

    3 => 'a',
    2 => 'b',
    1 => 'c',
    0 => 'd'

Will return:

    0: 'd',
    1: 'c',
    2: 'b',
    3: 'a'

So the solution in this case, is to use array_reverse before encoding it to json

What is the unix command to see how much disk space there is and how much is remaining?

su -sm ./*

You can see every file and folder size (-sm=Mb ; -sk=Kb) in the current directory like a list. This way runs in all Unix/Linux environment.

XMLHttpRequest status 0 (responseText is empty)

I had faced a similar problem. Every thing was okay, the "readystate" was 4, but the "status" was 0. It was because I was using a Apache PHP portable server and my file in which I used the "XMLHttpRequest" object was a html file. I changed the file extension to php and the problem was solved.

Cannot get a text value from a numeric cell “Poi”

Use that code it definitely works and I modified it.

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import org.apache.poi.poifs.filesystem.POIFSFileSystem;

public class TestApp {

    public static void main(String[] args) throws Exception {

        try {

            Class forName = Class.forName("com.mysql.jdbc.Driver");
            Connection con = null;
            con = DriverManager.getConnection("jdbc:mysql://localhost/tables", "root", "root");
            PreparedStatement pstm = null;
            FileInputStream input = new FileInputStream("C:\\Users\\Desktop\\a1.xls");
            POIFSFileSystem fs = new POIFSFileSystem(input);
            Workbook workbook;
            workbook = WorkbookFactory.create(fs);
            Sheet sheet = workbook.getSheetAt(0);
            Row row;
            for (int i = 1; i <= sheet.getLastRowNum(); i++) {
                row = (Row) sheet.getRow(i);
                String name = row.getCell(0).getStringCellValue();
                String add = row.getCell(1).getStringCellValue();

                int  contact = (int) row.getCell(2).getNumericCellValue();

                String email = row.getCell(3).getStringCellValue();

                String sql = "INSERT INTO employee (name, address, contactNo, email) VALUES('" + name + "','" + add + "'," + contact + ",'" + email + "')";
                pstm = (PreparedStatement) con.prepareStatement(sql);
                System.out.println("Import rows " + i);
            System.out.println("Success import excel to mysql table");
        } catch (IOException e) {


How to change href attribute using JavaScript after opening the link in a new window?




onclick="changeLink(); return false;"

to cancel its default action

Count number of occurences for each unique value

If you need to have the number of unique values as an additional column in the data frame containing your values (a column which may represent sample size for example), plyr provides a neat way:

data_frame <- data.frame(v = rep(c(1,2, 2, 2), 25))

data_frame <- ddply(data_frame, .(v), transform, n = length(v))