Programs & Examples On #Ls

A utility in Unix-like systems such as Linux used for listing files and directories.

Linux delete file with size 0

This will delete all the files in a directory (and below) that are size zero.

find /tmp -size  0 -print -delete

If you just want a particular file;

if [ ! -s /tmp/foo ] ; then
  rm /tmp/foo

Unix ls command: show full path when using options

You can combine the find command and the ls command. Use the path (.) and selector (*) to narrow down the files you're after. Surround the find command in back quotes. The argument to -name is doublequote star doublequote in case you can't read it.

ls -lart `find . -type f -name "*" `

How do I list all the files in a directory and subdirectories in reverse chronological order?

find -type f -print0 | xargs -0 ls -t

Drawback: Works only to a certain amount of files. If you have extremly large amounts of files you need something more complicated

How can I generate a list of files with their absolute path in Linux?

Command: ls -1 -d "$PWD/"*

This will give the absolute paths of the file like below.

[root@kubenode1 ssl]# ls -1 -d "$PWD/"*

'ls' is not recognized as an internal or external command, operable program or batch file

I'm fairly certain that the ls command is for Linux, not Windows (I'm assuming you're using Windows as you referred to cmd, which is the command line for the Windows OS).

You should use dir instead, which is the Windows equivalent of ls.

Edit (since this post seems to be getting so many views :) ):

You can't use ls on cmd as it's not shipped with Windows, but you can use it on other terminal programs (such as GitBash). Note, ls might work on some FTP servers if the servers are linux based and the FTP is being used from cmd.

dir on Windows is similar to ls. To find out the various options available, just do dir/?.

If you really want to use ls, you could install 3rd party tools to allow you to run unix commands on Windows. Such a program is Microsoft Windows Subsystem for Linux (link to docs).

How can I list (ls) the 5 last modified files in a directory?

ls -t list files by creation time not last modified time. Use ls -ltc if you want to list files by last modified time from last to first(top to bottom). Thus to list the last n: ls -ltc | head ${n}

How do I list one filename per output line in Linux?

You can also use ls -w1

This allows to set number of columns. From manpage of ls:

   -w, --width=COLS
          set output width to COLS.  0 means no limit

How do I assign ls to an array in Linux Bash?

Whenever possible, you should avoid parsing the output of ls (see Greg's wiki on the subject). Basically, the output of ls will be ambiguous if there are funny characters in any of the filenames. It's also usually a waste of time. In this case, when you execute ls -d */, what happens is that the shell expands */ to a list of subdirectories (which is already exactly what you want), passes that list as arguments to ls -d, which looks at each one, says "yep, that's a directory all right" and prints it (in an inconsistent and sometimes ambiguous format). The ls command isn't doing anything useful!

Well, ok, it is doing one thing that's useful: if there are no subdirectories, */ will get left as is, ls will look for a subdirectory named "*", not find it, print an error message that it doesn't exist (to stderr), and not print the "*/" (to stdout).

The cleaner way to make an array of subdirectory names is to use the glob (*/) without passing it to ls. But in order to avoid putting "*/" in the array if there are no actual subdirectories, you should set nullglob first (again, see Greg's wiki):

shopt -s nullglob
shopt -u nullglob # Turn off nullglob to make sure it doesn't interfere with anything later
echo "${array[@]}"  # Note double-quotes to avoid extra parsing of funny characters in filenames

If you want to print an error message if there are no subdirectories, you're better off doing it yourself:

if (( ${#array[@]} == 0 )); then
    echo "No subdirectories found" >&2

How to get file creation date/time in Bash/Debian?

even better:

lsct () 
    debugfs -R 'stat <'`ls -i "$1" | (read a b;echo -n $a)`'>' `df "$1" | (read a; read a b; echo "$a")` 2> /dev/null | grep --color=auto crtime | ( read a b c d;
    echo $d )

lsct /etc

Wed Jul 20 19:25:48 2016

List of All Folders and Sub-folders

find . -type d > list.txt

Will list all directories and subdirectories under the current path. If you want to list all of the directories under a path other than the current one, change the . to that other path.

If you want to exclude certain directories, you can filter them out with a negative condition:

find . -type d ! -name "~snapshot" > list.txt

Regular Expression usage with ls

You don't say what shell you are using, but they generally don't support regular expressions that way, although there are common *nix CLI tools (grep, sed, etc) that do.

What shells like bash do support is globbing, which uses some similiar characters (eg, *) but is not the same thing.

Newer versions of bash do have a regular expression operator, =~:

for x in `ls`; do 
    if [[ $x =~ .+\..* ]]; then 
        echo $x; 

List files recursively in Linux CLI with path relative to the current directory

Use find:

find . -name \*.txt -print

On systems that use GNU find, like most GNU/Linux distributions, you can leave out the -print.

Unix's 'ls' sort by name

You can try:

ls -lru

-u with -lt: sort by, and show, access time;

ls command: how can I get a recursive full-path listing, one line per file?

Recursive list of all files from current location:

ls -l $(find . -type f)

'ls' in CMD on Windows is not recognized

Use the command dir to list all the directories and files in a directory; ls is a unix command.

To show only file name without the entire directory path

ls whateveryouwant | xargs -n 1 basename

Does that work for you?

Otherwise you can (cd /the/directory && ls) (yes, parentheses intended)

Count number of files within a directory in Linux?

this is one:

ls -l . | egrep -c '^-'


ls -1 | wc -l

Which means: ls: list files in dir

-1: (that's a ONE) only one entry per line. Change it to -1a if you want hidden files too

|: pipe output onto...

wc: "wordcount"

-l: count lines.

Listing only directories using ls in Bash?

If a hidden directory is not needed to be listed, I offer:

ls -l | grep "^d" | awk -F" " '{print $9}'

And if hidden directories are needed to be listed, use:

ls -Al | grep "^d" | awk -F" " '{print $9}'


find -maxdepth 1 -type d | awk -F"./" '{print $2}'

What is more efficient? Using pow to square or just multiply it with itself?

I was also wondering about the performance issue, and was hoping this would be optimised out by the compiler, based on the answer from @EmileCormier. However, I was worried that the test code he showed would still allow the compiler to optimise away the std::pow() call, since the same values were used in the call every time, which would allow the compiler to store the results and re-use it in the loop - this would explain the almost identical run-times for all cases. So I had a look into it too.

Here's the code I used (test_pow.cpp):

#include <iostream>                                                                                                                                                                                                                       
#include <cmath>
#include <chrono>

class Timer {
    explicit Timer () : from (std::chrono::high_resolution_clock::now()) { }

    void start () {
      from = std::chrono::high_resolution_clock::now();

    double elapsed() const {
      return std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::high_resolution_clock::now() - from).count() * 1.0e-6;

    std::chrono::high_resolution_clock::time_point from;

int main (int argc, char* argv[])
  double total;
  Timer timer;

  total = 0.0;
  for (double i = 0.0; i < 1.0; i += 1e-8)
    total += std::pow (i,2);
  std::cout << "std::pow(i,2): " << timer.elapsed() << "s (result = " << total << ")\n";

  total = 0.0;
  for (double i = 0.0; i < 1.0; i += 1e-8)
    total += i*i;
  std::cout << "i*i: " << timer.elapsed() << "s (result = " << total << ")\n";

  std::cout << "\n";

  total = 0.0;
  for (double i = 0.0; i < 1.0; i += 1e-8)
    total += std::pow (i,3);
  std::cout << "std::pow(i,3): " << timer.elapsed() << "s (result = " << total << ")\n";

  total = 0.0;
  for (double i = 0.0; i < 1.0; i += 1e-8)
    total += i*i*i;
  std::cout << "i*i*i: " << timer.elapsed() << "s (result = " << total << ")\n";

  return 0;

This was compiled using:

g++ -std=c++11 [-O2] test_pow.cpp -o test_pow

Basically, the difference is the argument to std::pow() is the loop counter. As I feared, the difference in performance is pronounced. Without the -O2 flag, the results on my system (Arch Linux 64-bit, g++ 4.9.1, Intel i7-4930) were:

std::pow(i,2): 0.001105s (result = 3.33333e+07)
i*i: 0.000352s (result = 3.33333e+07)

std::pow(i,3): 0.006034s (result = 2.5e+07)
i*i*i: 0.000328s (result = 2.5e+07)

With optimisation, the results were equally striking:

std::pow(i,2): 0.000155s (result = 3.33333e+07)
i*i: 0.000106s (result = 3.33333e+07)

std::pow(i,3): 0.006066s (result = 2.5e+07)
i*i*i: 9.7e-05s (result = 2.5e+07)

So it looks like the compiler does at least try to optimise the std::pow(x,2) case, but not the std::pow(x,3) case (it takes ~40 times longer than the std::pow(x,2) case). In all cases, manual expansion performed better - but particularly for the power 3 case (60 times quicker). This is definitely worth bearing in mind if running std::pow() with integer powers greater than 2 in a tight loop...

Regular expression negative lookahead

A negative lookahead says, at this position, the following regex can not match.

Let's take a simplified example:


a      Match: (?!b) succeeds
ac     Match: (?!b) succeeds
ab     No match: (?!b(?!c)) fails
abe    No match: (?!b(?!c)) fails
abc    Match: (?!b(?!c)) succeeds

The last example is a double negation: it allows a b followed by c. The nested negative lookahead becomes a positive lookahead: the c should be present.

In each example, only the a is matched. The lookahead is only a condition, and does not add to the matched text.

getElementById returns null?

It can be caused by:

  1. Invalid HTML syntax (some tag is not closed or similar error)
  2. Duplicate IDs - there are two HTML DOM elements with the same ID
  3. Maybe element you are trying to get by ID is created dynamically (loaded by ajax or created by script)?

Please, post your code.

TypeScript: casting HTMLElement

As of TypeScript 0.9 the lib.d.ts file uses specialized overload signatures that return the correct types for calls to getElementsByTagName.

This means you no longer need to use type assertions to change the type:

// No type assertions needed
var script: HTMLScriptElement = document.getElementsByTagName('script')[0];

MySQL Creating tables with Foreign Keys giving errno: 150

MySQL’s generic “errno 150” message “means that a foreign key constraint was not correctly formed.” As you probably already know if you are reading this page, the generic “errno: 150” error message is really unhelpful. However:

You can get the actual error message by running SHOW ENGINE INNODB STATUS; and then looking for LATEST FOREIGN KEY ERROR in the output.

For example, this attempt to create a foreign key constraint:


(t1_id INTEGER,

fails with the error Can't create table 'test.t2' (errno: 150). That doesn’t tell anyone anything useful other than that it’s a foreign key problem. But run SHOW ENGINE INNODB STATUS; and it will say:

130811 23:36:38 Error in foreign key constraint of table test/t2:
FOREIGN KEY (t1_id) REFERENCES t1 (id)):
Cannot find an index in the referenced table where the
referenced columns appear as the first columns, or column types
in the table and the referenced table do not match for constraint.

It says that the problem is it can’t find an index. SHOW INDEX FROM t1 shows that there aren’t any indexes at all for table t1. Fix that by, say, defining a primary key on t1, and the foreign key constraint will be created successfully.

Best way to track onchange as-you-type in input type="text"?

2018 here, this is what I do:

$(inputs).on('change keydown paste input propertychange click keyup blur',handler);

If you can point out flaws in this approach, I would be grateful.

Is it possible to modify a registry entry via a .bat/.cmd script?

This is how you can modify registry, without yes or no prompt and don't forget to run as administrator

reg add HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\etc\etc   /v Valuename /t REG_SZ /d valuedata  /f 

Below is a real example to set internet explorer as my default browser

reg add HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\Associations\UrlAssociations\https\UserChoice   /v ProgId /t REG_SZ /d IE.HTTPS  /f 

/f Force: Force an update without prompting "Value exists, overwrite Y/N"

/d Data : The actual data to store as a "String", integer etc

/v Value : The value name eg ProgId

/t DataType : REG_SZ (default) | REG_DWORD | REG_EXPAND_SZ | REG_MULTI_SZ

Learn more about Read, Set or Delete registry keys and values, save and restore from a .REG file. from here

ORA-28001: The password has expired

I had same problem, i am trying to login database it appear a message with: "ORA-28001: The password has expired" , I have fixed the problem simple steps command prompt 2.type sqlplus 3.It will ask Enter Password, you can give old password, it will show password has expired ORA-28001 4.It will ask new password and retype password 5.It will change with new password 6.Go to the sql database and try to connect with new password, it will connect.

Selecting with complex criteria from pandas.DataFrame

And remember to use parenthesis!

Keep in mind that & operator takes a precedence over operators such as > or < etc. That is why

4 < 5 & 6 > 4

evaluates to False. Therefore if you're using pd.loc, you need to put brackets around your logical statements, otherwise you get an error. That's why do:

df.loc[(df['A'] > 10) & (df['B'] < 15)]

instead of

df.loc[df['A'] > 10 & df['B'] < 15]

which would result in

TypeError: cannot compare a dtyped [float64] array with a scalar of type [bool]

Can't access

In windows first check under services if world wide web publishing services is running. If not start it.

If you cannot find it switch on IIS features of windows: In 7,8,10 it is under control panel , "turn windows features on or off". Internet Information Services World Wide web services and Internet information Services Hostable Core are required. Not sure if there is another way to get it going on windows, but this worked for me for all browsers. You might need to add localhost or http:/ to the trusted websites also under IE settings.

application/x-www-form-urlencoded or multipart/form-data?

Just a little hint from my side for uploading HTML5 canvas image data:

I am working on a project for a print-shop and had some problems due to uploading images to the server that came from an HTML5 canvas element. I was struggling for at least an hour and I did not get it to save the image correctly on my server.

Once I set the contentType option of my jQuery ajax call to application/x-www-form-urlencoded everything went the right way and the base64-encoded data was interpreted correctly and successfully saved as an image.

Maybe that helps someone!

How to save an activity state using save instance state?

Saving state is a kludge at best as far as I'm concerned. If you need to save persistent data, just use an SQLite database. Android makes it SOOO easy.

Something like this:

import java.util.Date;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class dataHelper {

    private static final String DATABASE_NAME = "autoMate.db";
    private static final int DATABASE_VERSION = 1;

    private Context context;
    private SQLiteDatabase db;
    private OpenHelper oh ;

    public dataHelper(Context context) {
        this.context = context;
        this.oh = new OpenHelper(this.context);
        this.db = oh.getWritableDatabase();

    public void close() {
        db = null;
        oh = null;

    public void setCode(String codeName, Object codeValue, String codeDataType) {
        Cursor codeRow = db.rawQuery("SELECT * FROM code WHERE codeName = '"+  codeName + "'", null);
        String cv = "" ;

        if (codeDataType.toLowerCase().trim().equals("long") == true){
            cv = String.valueOf(codeValue);
        else if (codeDataType.toLowerCase().trim().equals("int") == true)
            cv = String.valueOf(codeValue);
        else if (codeDataType.toLowerCase().trim().equals("date") == true)
            cv = String.valueOf(((Date)codeValue).getTime());
        else if (codeDataType.toLowerCase().trim().equals("boolean") == true)
            cv = String.valueOf(codeValue);

        if(codeRow.getCount() > 0) //exists-- update
            db.execSQL("update code set codeValue = '" + cv +
                "' where codeName = '" + codeName + "'");
        else // does not exist, insert
            db.execSQL("INSERT INTO code (codeName, codeValue, codeDataType) VALUES(" +
                    "'" + codeName + "'," +
                    "'" + cv + "'," +
                    "'" + codeDataType + "')" );

    public Object getCode(String codeName, Object defaultValue){

        //Check to see if it already exists
        String codeValue = "";
        String codeDataType = "";
        boolean found = false;
        Cursor codeRow  = db.rawQuery("SELECT * FROM code WHERE codeName = '"+  codeName + "'", null);
        if (codeRow.moveToFirst())
            codeValue = codeRow.getString(codeRow.getColumnIndex("codeValue"));
            codeDataType = codeRow.getString(codeRow.getColumnIndex("codeDataType"));
            found = true;

        if (found == false)
            return defaultValue;
        else if (codeDataType.toLowerCase().trim().equals("long") == true)
            if (codeValue.equals("") == true)
                return (long)0;
            return Long.parseLong(codeValue);
        else if (codeDataType.toLowerCase().trim().equals("int") == true)
            if (codeValue.equals("") == true)
                return (int)0;
            return Integer.parseInt(codeValue);
        else if (codeDataType.toLowerCase().trim().equals("date") == true)
            if (codeValue.equals("") == true)
                return null;
            return new Date(Long.parseLong(codeValue));
        else if (codeDataType.toLowerCase().trim().equals("boolean") == true)
            if (codeValue.equals("") == true)
                return false;
            return Boolean.parseBoolean(codeValue);
            return (String)codeValue;

    private static class OpenHelper extends SQLiteOpenHelper {

        OpenHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);

        public void onCreate(SQLiteDatabase db) {
            db.execSQL("CREATE TABLE IF  NOT EXISTS code" +
            "(id INTEGER PRIMARY KEY, codeName TEXT, codeValue TEXT, codeDataType TEXT)");

        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

A simple call after that

dataHelper dh = new dataHelper(getBaseContext());
String status = (String) dh.getCode("appState", "safetyDisabled");
Date serviceStart = (Date) dh.getCode("serviceStartTime", null);
dh = null;

Plot a legend outside of the plotting area in base graphics?

Another solution, besides the ondes already mentioned (using layout or par(xpd=TRUE)) is to overlay your plot with a transparent plot over the entire device and then add the legend to that.

The trick is to overlay a (empty) graph over the complete plotting area and adding the legend to that. We can use the par(fig=...) option. First we instruct R to create a new plot over the entire plotting device:

par(fig=c(0, 1, 0, 1), oma=c(0, 0, 0, 0), mar=c(0, 0, 0, 0), new=TRUE)

Setting oma and mar is needed since we want to have the interior of the plot cover the entire device. new=TRUE is needed to prevent R from starting a new device. We can then add the empty plot:

plot(0, 0, type='n', bty='n', xaxt='n', yaxt='n')

And we are ready to add the legend:

legend("bottomright", ...)

will add a legend to the bottom right of the device. Likewise, we can add the legend to the top or right margin. The only thing we need to ensure is that the margin of the original plot is large enough to accomodate the legend.

Putting all this into a function;

add_legend <- function(...) {
  opar <- par(fig=c(0, 1, 0, 1), oma=c(0, 0, 0, 0), 
    mar=c(0, 0, 0, 0), new=TRUE)
  plot(0, 0, type='n', bty='n', xaxt='n', yaxt='n')

And an example. First create the plot making sure we have enough space at the bottom to add the legend:

par(mar = c(5, 4, 1.4, 0.2))
plot(rnorm(50), rnorm(50), col=c("steelblue", "indianred"), pch=20)

Then add the legend

add_legend("topright", legend=c("Foo", "Bar"), pch=20, 
   col=c("steelblue", "indianred"),
   horiz=TRUE, bty='n', cex=0.8)

Resulting in:

Example figure shown legend in top margin

How to Implement Custom Table View Section Headers and Footers with Storyboard

When you return cell's contentView you will have a 2 problems:

  1. crash related to gestures
  2. you don't reusing contentView (every time on viewForHeaderInSection call, you creating new cell)


Wrapper class for table header\footer. It is just container, inherited from UITableViewHeaderFooterView, which holds cell inside

Register class in your UITableView (for example, in viewDidLoad)

- (void)viewDidLoad {
    [super viewDidLoad];
    [self.tableView registerClass:[MGTableViewHeaderWrapperView class] forHeaderFooterViewReuseIdentifier:@"ProfileEditSectionHeader"];

In your UITableViewDelegate:

- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section {
    MGTableViewHeaderWrapperView *view = [tableView dequeueReusableHeaderFooterViewWithIdentifier:@"ProfileEditSectionHeader"];

    // init your custom cell
    ProfileEditSectionTitleTableCell *cell = (ProfileEditSectionTitleTableCell * ) view.cell;
    if (!cell) {
        cell = [tableView dequeueReusableCellWithIdentifier:@"ProfileEditSectionTitleTableCell"];
        view.cell = cell;

    // Do something with your cell

    return view;

How to convert Windows end of line in Unix end of line (CR/LF to LF)

The tr command can also do this:

tr -d '\15\32' < winfile.txt > unixfile.txt

and should be available to you.

You'll need to run tr from within a script, since it cannot work with file names. For example, create a file


for f in `find -iname \*.java`; do
    echo "$f"
    tr -d '\15\32' < "$f" > "$"
    mv "$" "$f"
    recode CP1252...UTF-8 "$f"

Running would process all the java files in the current directory and its subdirectories.

Remove excess whitespace from within a string

If you want to replace only multiple spaces in a string, for Example: "this string have lots of space . " And you expect the answer to be "this string have lots of space", you can use the following solution:

$strng = "this string                        have lots of                        space  .   ";

$strng = trim(preg_replace('/\s+/',' ', $strng));

echo $strng;

How do I parse JSON from a Java HTTPResponse?

Use JSON Simple,

Which has a small foot-print, no dependencies so it's perfect for Android.

You can do something like this,

Object obj=JSONValue.parse(buffer.tString());
JSONArray finalResult=(JSONArray)obj;

batch file to copy files to another location?

robocopy yourfolder yourdestination /MON:0

should do it, although you may need some more options. The switch at the end will re-run robocopy if more than 0 changes are seen.

How to set HTTP headers (for cache-control)?

OWASP recommends the following,

Whenever possible ensure the cache-control HTTP header is set with no-cache, no-store, must-revalidate, private; and that the pragma HTTP header is set with no-cache.

<IfModule mod_headers.c>
    Header set Cache-Control "private, no-cache, no-store, proxy-revalidate, no-transform"
    Header set Pragma "no-cache"

No content to map due to end-of-input jackson parser

I know this is weird but when I changed GetMapping to PostMapping for both client and server side the error disappeared.

Both client and server are Spring boot projects.

Is there a way to return a list of all the image file names from a folder using only Javascript?

IMHO, Edizkan Adil Ata's idea is actually the most proper way. It extracts the URLs of anchor tags and puts them in a different tag. And if you don't want to let the anchors being seen by the page visitor then just .hide() them all with JQuery or display: none; in CSS.

Also you can perform prefetching, like this:

<link rel="prefetch" href="imagefolder/clouds.jpg" />

That way you don't have to hide it and still can extract the path to the image.

Create table (structure) from existing table

This is what I use to clone a table structure (columns only)...

INTO NewTable
FROM TableStructureIWishToClone

Finding first blank row, then writing to it

If you mean the row number after the last row that is used, you can find it with this:

Dim unusedRow As Long
unusedRow = Cells.SpecialCells(xlCellTypeLastCell).Offset(1, 0).Row

If you mean a row that happens to be blank with data after it... it gets more complicated.

Here's a function I wrote which will give you the actual row number of the first row that is blank for the provided worksheet.

Function firstBlankRow(ws As Worksheet) As Long
'returns the row # of the row after the last used row
'Or the first row with no data in it
    Dim rw As Range
    For Each rw In ws.UsedRange.Rows
        If rw.Address = ws.Range(rw.Address).SpecialCells(xlCellTypeBlanks). _
            Address Then

                firstBlankRow = rw.Row
                Exit For
        End If
    If firstBlankRow = 0 Then
        firstBlankRow = ws.Cells.SpecialCells(xlCellTypeLastCell). _
                    Offset(1, 0).Row
    End If
End Function

Usage example: firstblankRow(thisworkbook.Sheets(1)) or pass any worksheet.

Edit: As ooo pointed out, this will error if there are no blank cells in your used range.

How to bind Events on Ajax loaded Content?

If the content is appended after .on() is called, you'll need to create a delegated event on a parent element of the loaded content. This is because event handlers are bound when .on() is called (i.e. usually on page load). If the element doesn't exist when .on() is called, the event will not be bound to it!

Because events propagate up through the DOM, we can solve this by creating a delegated event on a parent element (.parent-element in the example below) that we know exists when the page loads. Here's how:

$('.parent-element').on('click', '.mylink', function(){
  alert ("new link clicked!");

Some more reading on the subject:

"git rebase origin" vs."git rebase origin/master"

You can make a new file under [.git\refs\remotes\origin] with name "HEAD" and put content "ref: refs/remotes/origin/master" to it. This should solve your problem.

It seems that clone from an empty repos will lead to this. Maybe the empty repos do not have HEAD because no commit object exist.

You can use the

git log --remotes --branches --oneline --decorate

to see the difference between each repository, while the "problem" one do not have "origin/HEAD"

Edit: Give a way using command line
You can also use git command line to do this, they have the same result

git symbolic-ref refs/remotes/origin/HEAD refs/remotes/origin/master

Android new Bottom Navigation bar or BottomNavigationView

I think you might looking for this.

Here's a quick snippet to get started:

public class MainActivity extends AppCompatActivity {
    private BottomBar mBottomBar;

    protected void onCreate(Bundle savedInstanceState) {

        // Notice how you don't use the setContentView method here! Just
        // pass your layout to bottom bar, it will be taken care of.
        // Everything will be just like you're used to.
        mBottomBar = BottomBar.bind(this, R.layout.activity_main,

                new BottomBarTab(R.drawable.ic_recents, "Recents"),
                new BottomBarTab(R.drawable.ic_favorites, "Favorites"),
                new BottomBarTab(R.drawable.ic_nearby, "Nearby"),
                new BottomBarTab(R.drawable.ic_friends, "Friends")

        mBottomBar.setOnItemSelectedListener(new OnTabSelectedListener() {
            public void onItemSelected(final int position) {
                // the user selected a new tab

    protected void onSaveInstanceState(Bundle outState) {

Here is reference link.

EDIT New Releases.

The Bottom Navigation View has been in the material design guidelines for some time, but it hasn’t been easy for us to implement it into our apps. Some applications have built their own solutions, whilst others have relied on third-party open-source libraries to get the job done. Now the design support library is seeing the addition of this bottom navigation bar, let’s take a dive into how we can use it!

How to use ?

To begin with we need to update our dependency!

compile ‘’

Design xml.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android=""

    <!-- Content Container -->

        app:menu="@menu/bottom_navigation_main" />


Create menu as per your requirement.

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android=""
        app:showAsAction="ifRoom" />
        app:showAsAction="ifRoom" />
        app:showAsAction="ifRoom" />

Handling Enabled / Disabled states. Make selector file.

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="">
      android:color="@color/colorPrimary" />
      android:color="@color/grey" />

Handle click events.

BottomNavigationView bottomNavigationView = (BottomNavigationView)
        new BottomNavigationView.OnNavigationItemSelectedListener() {
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                switch (item.getItemId()) {
                return false;

Edit : Using Androidx you just need to add below dependencies.

implementation ''


<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android=""

If you want to read more about it's methods and how it works read this.

Surely it will help you.

Is there a function to round a float in C or do I need to write my own?

Just to generalize Rob's answer a little, if you're not doing it on output, you can still use the same interface with sprintf().

I think there is another way to do it, though. You can try ceil() and floor() to round up and down. A nice trick is to add 0.5, so anything over 0.5 rounds up but anything under it rounds down. ceil() and floor() only work on doubles though.

EDIT: Also, for floats, you can use truncf() to truncate floats. The same +0.5 trick should work to do accurate rounding.

How do I make a transparent border with CSS?

You can use "transparent" as a colour. In some versions of IE, that comes up as black, but I've not tested it out since the IE6 days.

Python: Finding differences between elements of a list

I would suggest using

v = np.diff(t)

this is simple and easy to read.

But if you want v to have the same length as t then

v = np.diff([t[0]] + t) # for python 3.x


v = np.diff(t + [t[-1]])

FYI: this will only work for lists.

for numpy arrays

v = np.diff(np.append(t[0], t))

Putting HTML inside Html.ActionLink(), plus No Link Text?

I ended up with a custom extension method. Its worth noting, when trying to place HTML inside of an Anchor object, the link text can be either to the left, or to the right of the inner HTML. For this reason, I opted to provide parameters for left and right inner HTML - the link text is in the middle. Both left and right inner HTML are optional.

Extension Method ActionLinkInnerHtml:

    public static MvcHtmlString ActionLinkInnerHtml(this HtmlHelper helper, string linkText, string actionName, string controllerName, RouteValueDictionary routeValues = null, IDictionary<string, object> htmlAttributes = null, string leftInnerHtml = null, string rightInnerHtml = null)
        var urlHelper = new UrlHelper(helper.ViewContext.RequestContext);
        var url = urlHelper.Action(actionName: actionName, controllerName: controllerName, routeValues: routeValues);

        var builder = new TagBuilder("a");
        builder.InnerHtml = string.Format("{0}{1}{2}", leftInnerHtml, linkText, rightInnerHtml);
        builder.MergeAttribute(key: "href", value: url);

        builder.MergeAttributes(htmlAttributes, replaceExisting: true);

        var mvcHtmlString = MvcHtmlString.Create(builder.ToString());
        return mvcHtmlString;

Example of Usage:

Here is an example of usage. For this example I only wanted the inner html on the right side of the link text...

    linkText: "Hello World"
        , actionName: "SomethingOtherThanIndex"
        , controllerName: "SomethingOtherThanHome"
        , rightInnerHtml: "<span class=\"caret\" />"


this results in the following HTML...

<a href="/SomethingOtherThanHome/SomethingOtherThanIndex">Hello World<span class="caret" /></a>

How to restart adb from root to user mode?

For quick steps just check summary. If interested to know details, go on to read below.

adb is a daemon. Doing ps adb we can see its process.

shell@grouper:/ $ ps adb
shell     133   1     4636   212   ffffffff 00000000 S /sbin/adbd

I just checked what additional property variables it is using when adb is running as root and user.

adb user mode :

shell@grouper:/ $ getprop | grep adb                                         
[init.svc.adbd]: [running]
[persist.sys.usb.config]: [mtp,adb]
[]: [1]
[sys.usb.config]: [mtp,adb]
[sys.usb.state]: [mtp,adb]

adb root mode :

shell@grouper:/ # getprop | grep adb                                         
[init.svc.adbd]: [running]
[persist.sys.usb.config]: [mtp,adb]
[]: [1]
[service.adb.root]: [1]
[sys.usb.config]: [mtp,adb]
[sys.usb.state]: [mtp,adb]

We can see that service.adb.root is a new prop variable that came up when we did adb root.

So, to change back adb to user from root, I went ahead and made this 0

setprop service.adb.root 0

But this did not change anything.

Then I went ahead and killed the process (with an intention to restart the process). The pid of adbd process in my device is 133

kill -9 133

I exited from shell automatically after I had killed the process.

I did adb shell again it was in user mode.


So, we have 3 very simple steps.

  1. Enter adb shell as a root.
  2. setprop service.adb.root 0
  3. kill -9 (pid of adbd)

After these steps just re-enter the shell with adb shell and you are back on your device as a user.

How to redirect user's browser URL to a different page in Nodejs?

In Express you can use


to redirect user from server.

To include a status code 301 or 302 it can be used

res.redirect(301, '');

Passing std::string by Value or Reference

Check this answer for C++11. Basically, if you pass an lvalue the rvalue reference

From this article:

void f1(String s) {
    vector<String> v;
void f2(const String &s) {
    vector<String> v;

"For lvalue argument, ‘f1’ has one extra copy to pass the argument because it is by-value, while ‘f2’ has one extra copy to call push_back. So no difference; for rvalue argument, the compiler has to create a temporary ‘String(L“”)’ and pass the temporary to ‘f1’ or ‘f2’ anyway. Because ‘f2’ can take advantage of move ctor when the argument is a temporary (which is an rvalue), the costs to pass the argument are the same now for ‘f1’ and ‘f2’."

Continuing: " This means in C++11 we can get better performance by using pass-by-value approach when:

  1. The parameter type supports move semantics - All standard library components do in C++11
  2. The cost of move constructor is much cheaper than the copy constructor (both the time and stack usage).
  3. Inside the function, the parameter type will be passed to another function or operation which supports both copy and move.
  4. It is common to pass a temporary as the argument - You can organize you code to do this more.


OTOH, for C++98 it is best to pass by reference - less data gets copied around. Passing const or non const depend of whether you need to change the argument or not.

change cursor from block or rectangle to line?

please Press fn +ins key together

OS X cp command in Terminal - No such file or directory

In my case, I had accidentally named a folder 'samples '. I couldn't see the space when I did 'ls -la'.

Eventually I realized this when I tried tabbing to autocomplete and saw 'samples\ /'.

To fix this I ran

mv samples\  samples

Difference between jQuery parent(), parents() and closest() functions


The .parents() and .closest() methods are similar in that they both traverse up the DOM tree. The differences between the two, though subtle, are significant:


  • Begins with the current element
  • Travels up the DOM tree until it finds a match for the supplied selector
  • The returned jQuery object contains zero or one element


  • Begins with the parent element
  • Travels up the DOM tree to the document's root element, adding each ancestor element to a temporary collection; it then filters that collection based on a selector if one is supplied
  • The returned jQuery object contains zero, one, or multiple elements


  • Given a jQuery object that represents a set of DOM elements, the .parent() method allows us to search through the parents of these elements in the DOM tree and construct a new jQuery object from the matching elements.

Note: The .parents() and .parent() methods are similar, except that the latter only travels a single level up the DOM tree. Also, $("html").parent() method returns a set containing document whereas $("html").parents() returns an empty set.

Here are related threads:

Objective-C: Calling selectors with multiple arguments

iOS users also expect autocapitalization: In a standard text field, the first letter of a sentence in a case-sensitive language is automatically capitalized.

You can decide whether or not to implement such features; there is no dedicated API for any of the features just listed, so providing them is a competitive advantage.

Apple document is saying there is no API available for this feature and some other expected feature in a customkeyboard. so you need to find out your own logic to implement this.

How to start new activity on button click

Take Button in xml first.

        android:text="Your Text"

Make listner of button.

 pre.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            Intent intent = new Intent(MainActivity.this, SecondActivity.class);

Cannot implicitly convert type 'string' to 'System.Threading.Tasks.Task<string>'

    public async Task<string> methodName()
             return Data;


Hope this helps :)

python ignore certificate validation urllib2

In the meantime urllib2 seems to verify server certificates by default. The warning, that was shown in the past disappeared for 2.7.9 and I currently ran into this problem in a test environment with a self signed certificate (and Python 2.7.9).

My evil workaround (don't do this in production!):

import urllib2
import ssl

ctx = ssl.create_default_context()
ctx.check_hostname = False
ctx.verify_mode = ssl.CERT_NONE

urllib2.urlopen("https://your-test-server.local", context=ctx)

According to docs calling SSLContext constructor directly should work, too. I haven't tried that.

Accessing Object Memory Address

While it's true that id(object) gets the object's address in the default CPython implementation, this is generally useless... you can't do anything with the address from pure Python code.

The only time you would actually be able to use the address is from a C extension library... in which case it is trivial to get the object's address since Python objects are always passed around as C pointers.

windows batch file rename

Use REN Command

Ren is for rename

ren ( where the file is located ) ( the new name )


ren C:\Users\&username%\Desktop\aaa.txt bbb.txt

it will change aaa.txt to bbb.txt

Your code will be :

ren (file located)AAA_a001.jpg a001.AAA.jpg

ren (file located)BBB_a002.jpg a002.BBB.jpg

ren (file located)CCC_a003.jpg a003.CCC.jpg

and so on


Hope it helps :D

Initializing a dictionary in python with a key value and no corresponding values

Based on the clarifying comment by @user2989027, I think a good solution is the following:

definition = ['apple', 'ball']
data = {'orange':1, 'pear':2, 'apple':3, 'ball':4}
my_data = {}
for k in definition:
  except KeyError:
print my_data

I tried not to do anything fancy here. I setup my data and an empty dictionary. I then loop through a list of strings that represent potential keys in my data dictionary. I copy each value from data to my_data, but consider the case where data may not have the key that I want.

Angular.js ng-repeat filter by property having one of multiple values (OR of values)

Best way to do this is to use a function:

<div ng-repeat="product in products | filter: myFilter">

$scope.myFilter = function (item) { 
    return item === 'red' || item === 'blue'; 

Alternatively, you can use ngHide or ngShow to dynamically show and hide elements based on a certain criteria.

How do I set path while saving a cookie value in JavaScript?

document.cookie = "cookiename=Some Name; path=/";

This will do

findViewById in Fragment

The best way to implement this is as follows:

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

rootView = inflater.inflate(R.layout.testclassfragment, container, false);
        ImageView imageView = (ImageView) rootView.findViewById(;
        return rootView

In this way, the rootView can be used for each control defined in the xml layout and the code is much cleaner in this way.

Hope this helps :)

Javascript change date into format of (dd/mm/yyyy)

Some JavaScript engines can parse that format directly, which makes the task pretty easy:

function convertDate(inputFormat) {_x000D_
  function pad(s) { return (s < 10) ? '0' + s : s; }_x000D_
  var d = new Date(inputFormat)_x000D_
  return [pad(d.getDate()), pad(d.getMonth()+1), d.getFullYear()].join('/')_x000D_
console.log(convertDate('Mon Nov 19 13:29:40 2012')) // => "19/11/2012"

Django return redirect() with parameters

Firstly, your URL definition does not accept any parameters at all. If you want parameters to be passed from the URL into the view, you need to define them in the urlconf.

Secondly, it's not at all clear what you are expecting to happen to the cleaned_data dictionary. Don't forget you can't redirect to a POST - this is a limitation of HTTP, not Django - so your cleaned_data either needs to be a URL parameter (horrible) or, slightly better, a series of GET parameters - so the URL would be in the form:


and so on. In this case, field1, field2 and field3 are not included in the URLconf definition - they are available in the view via request.GET.

So your urlconf would be:

url(r'^link/(?P<backend>\w+?)/$', my_function)

and the view would look like:

def my_function(request, backend):
   data = request.GET

and the reverse would be (after importing urllib):

return "%s?%s" % (redirect('my_function', args=(backend,)),

Edited after comment

The whole point of using redirect and reverse, as you have been doing, is that you go to the URL - it returns an Http code that causes the browser to redirect to the new URL, and call that.

If you simply want to call the view from within your code, just do it directly - no need to use reverse at all.

That said, if all you want to do is store the data, then just put it in the session:

request.session['temp_data'] = form.cleaned_data

Checking for empty queryset in Django

The most efficient way (before django 1.2) is this:

if orgs.count() == 0:
    # no results
    # alrigh! let's continue...

How to change default language for SQL Server?

@John Woo's accepted answer has some caveats which you should be aware of:

  1. Default language setting of a session is controlled from default language setting of the user login instead which you have used to create the session. SQL Server instance level setting doesn't affect the default language of the session.
  2. Changing default language setting at SQL Server instance level doesn't affects the default language setting of the existing SQL Server logins. It is meant to be inherited only by the new user logins that you create after changing the instance level setting.

So, there is an intermediate level between your SQL Server instance and the session which you can use to control the default language setting for session - login level.

SQL Server Instance level setting -> User login level setting -> Query Session level setting

This can help you in case you want to set default language of all new sessions belonging to some specific user only.

Simply change the default language setting of the target user login as per this link and you are all set. You can also do it from SQL Server Management Studio (SSMS) UI. Below you can see the default language setting in properties window of sa user in SQL Server:

enter image description here

Note: Also, it is important to know that changing the setting doesn't affect the default language of already active sessions from that user login. It will affect only the new sessions created after changing the setting.

How can I use UserDefaults in Swift?

Swift 4 :


    UserDefaults.standard.set(object/value, forKey: "key_name")


    var returnValue: [datatype]? = UserDefaults.standard.object(forKey: "key_name") as? [datatype]



Error Microsoft.Web.Infrastructure, Version=, Culture=neutral, PublicKeyToken=31bf3856ad364e35

I had the same problem and the "Microsoft.Web.Infrastructure.dll" appeared to be missing. I have tried few advises and installed MVC`s etc. and nothing helped. The solution was to install "Web Services Enhancements (WSE) 1.0 SP1 for Microsoft .NET" which includes Microsoft.Web.Infrastructure.dll. Available at:

Add a property to a JavaScript object using a variable as the name?

If you want to add fields to an object dynamically, simplest way to do it is as follows:

 var params= [
{key: "k1", value=1},
{key: "k2", value=2},
{key: "k3", value=3}];

for(i=0; i< params.len; i++) {
  data[params[i].key] = params[i].value

This will create data object which has following fields:

{k1:1, k2:2, k3:3}

Reasons for a 409/Conflict HTTP error when uploading a file to sharepoint using a .NET WebRequest?

I is because you are using predefined variables to naming your filename. change your filename from e.g register.asp to registerUser.asp. That will solve your issue

Load external css file like scripts in jquery which is compatible in ie also

Based on your comment under @Raul's answer, I can think of two ways to include a callback:

  1. Have getScript call the file that loads the css.
  2. Load the contents of the css file with AJAX, and append to <style>. Your callback would be the callback from $.get or whatever you use to load the css file contents.

Javascript: Call a function after specific time period

ECMAScript 6 introduced arrow functions so now the setTimeout() or setInterval() don't have to look like this:

setTimeout(function() { FetchData(); }, 1000)

Instead, you can use annonymous arrow function which looks cleaner, and less confusing:

setTimeout(() => {FetchData();}, 1000)

PostgreSQL Autoincrement

If you want to add sequence to id in the table which already exist you can use:

CREATE SEQUENCE user_id_seq;
ALTER TABLE user ALTER user_id SET DEFAULT NEXTVAL('user_id_seq');

check if a number already exist in a list in python

If you want to have unique elements in your list, then why not use a set, if of course, order does not matter for you: -

>>> s = set()
>>> s.add(2)
>>> s.add(4)
>>> s.add(5)
>>> s.add(2)
>>> s
39: set([2, 4, 5])

If order is a matter of concern, then you can use: -

>>> def addUnique(l, num):
...     if num not in l:
...         l.append(num)
...     return l

You can also find an OrderedSet recipe, which is referred to in Python Documentation

html select scroll bar

Horizontal scrollbars in a HTML Select are not natively supported. However, here's a way to create the appearance of a horizontal scrollbar:

1. First create a css class

<style type="text/css">
   overflow: auto;
   width: 70px; /* adjust this width depending to amount of text to display */
   height: 80px; /* adjust height depending on number of options to display */
   border: 1px silver solid;
 .scrollable select{
   border: none;

2. Wrap the SELECT inside a DIV - also, explicitly set the size to the number of options.

<div class="scrollable">
<select size="6" multiple="multiple">
    <option value="1" selected>option 1 The Long Option</option>
    <option value="2">option 2</option>
    <option value="3">option 3</option>
    <option value="4">option 4</option>
    <option value="5">option 5 Another Longer than the Long Option ;)</option>
    <option value="6">option 6</option>

What is the difference between float and double?

When using floating point numbers you cannot trust that your local tests will be exactly the same as the tests that are done on the server side. The environment and the compiler are probably different on you local system and where the final tests are run. I have seen this problem many times before in some TopCoder competitions especially if you try to compare two floating point numbers.

Gradle finds wrong JAVA_HOME even though it's correctly set

For me an explicit set on the arguments section of the external tools configuration in Eclipse was the problem.

enter image description here

Run PowerShell scripts on remote PC

Can you try the following?

psexec \\server cmd /c "echo . | powershell script.ps1"

How do I use the lines of a file as arguments of a command?

I suggest using:

command $(echo $(tr '\n' ' ' < parameters.cfg))

Simply trim the end-line characters and replace them with spaces, and then push the resulting string as possible separate arguments with echo.

How to rename HTML "browse" button of an input type=file?

Here is the best, simple, short and clean way to "rename" the text of an input with file type and without JQuery, with pure HTML and javascript:

<input id='browse' type='file' style='width:0px'>
<button id='browser' onclick=''>
    *The text you want*

How to change the background color of the options menu?

 <style name="AppThemeLight" parent="Theme.AppCompat.Light.NoActionBar">
    <item name="android:itemBackground">#000000</item>

this works fine for me

Perl: function to trim string leading and trailing whitespace

Apply: s/^\s*//; s/\s+$//; to it. Or use s/^\s+|\s+$//g if you want to be fancy.

Execute method on startup in Spring

With SpringBoot, we can execute a method on startup via @EventListener annotation

public class LoadDataOnStartUp
    public void loadData()
        // do something

Class JavaLaunchHelper is implemented in both ... libinstrument.dylib. One of the two will be used. Which one is undefined

Not sure if this is the cause of the problem, but I got this issue only after installing JVM Monitor.

Uninstalling JVM Monitor solved the issue for me.

Converting a vector<int> to string

Maybe std::ostream_iterator and std::ostringstream:

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

int main()
  std::vector<int> vec;

  std::ostringstream oss;

  if (!vec.empty())
    // Convert all but the last element to avoid a trailing ","
    std::copy(vec.begin(), vec.end()-1,
        std::ostream_iterator<int>(oss, ","));

    // Now add the last element with no delimiter
    oss << vec.back();

  std::cout << oss.str() << std::endl;

Could not locate Gemfile

Make sure you are in the project directory before running bundle install. For example, after running rails new myproject, you will want to cd myproject before running bundle install.

JavaScript/jQuery: replace part of string?

It should be like this

$(this).text($(this).text().replace('N/A, ', ''))

How to trim white space from all elements in array?

Another java 8 lambda option :

String[] array2 =[]::new);

And the ugly but optimized version without new array creation -> array);

Original "array" is modified.

linux script to kill java process

If you just want to kill any/all java processes, then all you need is;

killall java

If, however, you want to kill the wskInterface process in particular, then you're most of the way there, you just need to strip out the process id;

PID=`ps -ef | grep wskInterface | awk '{ print $2 }'`
kill -9 $PID

Should do it, there is probably an easier way though...

Is there a way to get a textarea to stretch to fit its content without using PHP or JavaScript?

This is a very simple solution, but it works for me:

<textarea id="textBox1" name="content" TextMode="MultiLine" onkeyup="setHeight('textBox1');" onkeydown="setHeight('textBox1');">Hello World</textarea>_x000D_
<script type="text/javascript">_x000D_
function setHeight(fieldId){_x000D_
    document.getElementById(fieldId).style.height = document.getElementById(fieldId).scrollHeight+'px';_x000D_

CSS position absolute full width problem

I have similar situation. In my case, it doesn't have a parent with position:relative. Just paste my solution here for those that might need.

position: fixed;
left: 0;
right: 0;

How do I remove an item from a stl vector with a certain value?

Use the global method std::remove with the begin and end iterator, and then use std::vector.erase to actually remove the elements.

Documentation links

std::vector<int> v;

//Vector should contain the elements 1, 2

//Find new end iterator
std::vector<int>::iterator newEnd = std::remove(v.begin(), v.end(), 1);

//Erase the "removed" elements.
v.erase(newEnd, v.end());

//Vector should now only contain 2

Thanks to Jim Buck for pointing out my error.

How do you synchronise projects to GitHub with Android Studio?

For existing project end existing repository with files:

git init
git remote add origin <.git>
git checkout -b master
git branch --set-upstream-to=origin/master master
git pull --allow-unrelated-histories

CSS two div width 50% in one line with line break in file

Wrap them around a div with the following CSS

    white-space: nowrap;

Oracle query to identify columns having special characters

Compare the length using lengthB and length function in oracle.

SELECT * FROM test WHERE length(sampletext) <> lengthb(sampletext)

Crop image in PHP

imagecopyresampled() will take a rectangular area from $src_image of width $src_w and height $src_h at position ($src_x, $src_y) and place it in a rectangular area of $dst_image of width $dst_w and height $dst_h at position ($dst_x, $dst_y).

If the source and destination coordinates and width and heights differ, appropriate stretching or shrinking of the image fragment will be performed. The coordinates refer to the upper left corner.

This function can be used to copy regions within the same image. But if the regions overlap, the results will be unpredictable.

- Edit -

If $src_w and $src_h are smaller than $dst_w and $dst_h respectively, thumb image will be zoomed in. Otherwise it will be zoomed out.

$dst_x = 0;   // X-coordinate of destination point
$dst_y = 0;   // Y-coordinate of destination point
$src_x = 100; // Crop Start X position in original image
$src_y = 100; // Crop Srart Y position in original image
$dst_w = 160; // Thumb width
$dst_h = 120; // Thumb height
$src_w = 260; // Crop end X position in original image
$src_h = 220; // Crop end Y position in original image

// Creating an image with true colors having thumb dimensions (to merge with the original image)
$dst_image = imagecreatetruecolor($dst_w, $dst_h);
// Get original image
$src_image = imagecreatefromjpeg('images/source.jpg');
// Cropping
imagecopyresampled($dst_image, $src_image, $dst_x, $dst_y, $src_x, $src_y, $dst_w, $dst_h, $src_w, $src_h);
// Saving
imagejpeg($dst_image, 'images/crop.jpg');

Iterate through the fields of a struct in Go

Maybe too late :))) but there is another solution that you can find the key and value of structs and iterate over that

package main

import (

type person struct {
    firsName string
    lastName string
    iceCream []string

func main() {
    u := struct {
        myMap    map[int]int
        mySlice  []string
        myPerson person
        myMap:   map[int]int{1: 10, 2: 20},
        mySlice: []string{"red", "green"},
        myPerson: person{
            firsName: "Esmaeil",
            lastName: "Abedi",
            iceCream: []string{"Vanilla", "chocolate"},
    v := reflect.ValueOf(u)
    for i := 0; i < v.NumField(); i++ {
        fmt.Println("\t", v.Field(i))
and there is no *panic* for v.Field(i)

How to use a servlet filter in Java to change an incoming servlet request url?

  1. Implement javax.servlet.Filter.
  2. In doFilter() method, cast the incoming ServletRequest to HttpServletRequest.
  3. Use HttpServletRequest#getRequestURI() to grab the path.
  4. Use straightforward java.lang.String methods like substring(), split(), concat() and so on to extract the part of interest and compose the new path.
  5. Use either ServletRequest#getRequestDispatcher() and then RequestDispatcher#forward() to forward the request/response to the new URL (server-side redirect, not reflected in browser address bar), or cast the incoming ServletResponse to HttpServletResponse and then HttpServletResponse#sendRedirect() to redirect the response to the new URL (client side redirect, reflected in browser address bar).
  6. Register the filter in web.xml on an url-pattern of /* or /Check_License/*, depending on the context path, or if you're on Servlet 3.0 already, use the @WebFilter annotation for that instead.

Don't forget to add a check in the code if the URL needs to be changed and if not, then just call FilterChain#doFilter(), else it will call itself in an infinite loop.

Alternatively you can also just use an existing 3rd party API to do all the work for you, such as Tuckey's UrlRewriteFilter which can be configured the way as you would do with Apache's mod_rewrite.

How to extract numbers from a string in Python?

If you only want to extract only positive integers, try the following:

>>> str = "h3110 23 cat 444.4 rabbit 11 2 dog"
>>> [int(s) for s in str.split() if s.isdigit()]
[23, 11, 2]

I would argue that this is better than the regex example because you don't need another module and it's more readable because you don't need to parse (and learn) the regex mini-language.

This will not recognize floats, negative integers, or integers in hexadecimal format. If you can't accept these limitations, jmnas's answer below will do the trick.

Does Java support structs?

Actually a struct in C++ is a class (e.g. you can define methods there, it can be extended, it works exactly like a class), the only difference is that the default access modfiers are set to public (for classes they are set to private by default).

This is really the only difference in C++, many people don't know that. ; )

Bootstrap Responsive Text Size

Well, my solution is sort of hack, but it works and I am using it.

1vw = 1% of viewport width

1vh = 1% of viewport height

1vmin = 1vw or 1vh, whichever is smaller

1vmax = 1vw or 1vh, whichever is larger

h1 {
  font-size: 5.9vw;
h2 {
  font-size: 3.0vh;
p {
  font-size: 2vmin;

List Git aliases

$ git config --get-regexp alias

How to use to fire and handle HTTP requests?

First a disclaimer beforehand: the posted code snippets are all basic examples. You'll need to handle trivial IOExceptions and RuntimeExceptions like NullPointerException, ArrayIndexOutOfBoundsException and consorts yourself.


We first need to know at least the URL and the charset. The parameters are optional and depend on the functional requirements.

String url = "";
String charset = "UTF-8";  // Or in Java 7 and later, use the constant:
String param1 = "value1";
String param2 = "value2";
// ...

String query = String.format("param1=%s&param2=%s", 
     URLEncoder.encode(param1, charset), 
     URLEncoder.encode(param2, charset));

The query parameters must be in name=value format and be concatenated by &. You would normally also URL-encode the query parameters with the specified charset using URLEncoder#encode().

The String#format() is just for convenience. I prefer it when I would need the String concatenation operator + more than twice.

Firing an HTTP GET request with (optionally) query parameters

It's a trivial task. It's the default request method.

URLConnection connection = new URL(url + "?" + query).openConnection();
connection.setRequestProperty("Accept-Charset", charset);
InputStream response = connection.getInputStream();
// ...

Any query string should be concatenated to the URL using ?. The Accept-Charset header may hint the server what encoding the parameters are in. If you don't send any query string, then you can leave the Accept-Charset header away. If you don't need to set any headers, then you can even use the URL#openStream() shortcut method.

InputStream response = new URL(url).openStream();
// ...

Either way, if the other side is an HttpServlet, then its doGet() method will be called and the parameters will be available by HttpServletRequest#getParameter().

For testing purposes, you can print the response body to stdout as below:

try (Scanner scanner = new Scanner(response)) {
    String responseBody = scanner.useDelimiter("\\A").next();

Firing an HTTP POST request with query parameters

Setting the URLConnection#setDoOutput() to true implicitly sets the request method to POST. The standard HTTP POST as web forms do is of type application/x-www-form-urlencoded wherein the query string is written to the request body.

URLConnection connection = new URL(url).openConnection();
connection.setDoOutput(true); // Triggers POST.
connection.setRequestProperty("Accept-Charset", charset);
connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded;charset=" + charset);

try (OutputStream output = connection.getOutputStream()) {

InputStream response = connection.getInputStream();
// ...

Note: whenever you'd like to submit a HTML form programmatically, don't forget to take the name=value pairs of any <input type="hidden"> elements into the query string and of course also the name=value pair of the <input type="submit"> element which you'd like to "press" programmatically (because that's usually been used in the server side to distinguish if a button was pressed and if so, which one).

You can also cast the obtained URLConnection to HttpURLConnection and use its HttpURLConnection#setRequestMethod() instead. But if you're trying to use the connection for output you still need to set URLConnection#setDoOutput() to true.

HttpURLConnection httpConnection = (HttpURLConnection) new URL(url).openConnection();
// ...

Either way, if the other side is an HttpServlet, then its doPost() method will be called and the parameters will be available by HttpServletRequest#getParameter().

Actually firing the HTTP request

You can fire the HTTP request explicitly with URLConnection#connect(), but the request will automatically be fired on demand when you want to get any information about the HTTP response, such as the response body using URLConnection#getInputStream() and so on. The above examples does exactly that, so the connect() call is in fact superfluous.

Gathering HTTP response information

  1. HTTP response status:

You need an HttpURLConnection here. Cast it first if necessary.

    int status = httpConnection.getResponseCode();
  1. HTTP response headers:

     for (Entry<String, List<String>> header : connection.getHeaderFields().entrySet()) {
         System.out.println(header.getKey() + "=" + header.getValue());
  2. HTTP response encoding:

When the Content-Type contains a charset parameter, then the response body is likely text based and we'd like to process the response body with the server-side specified character encoding then.

    String contentType = connection.getHeaderField("Content-Type");
    String charset = null;

    for (String param : contentType.replace(" ", "").split(";")) {
        if (param.startsWith("charset=")) {
            charset = param.split("=", 2)[1];

    if (charset != null) {
        try (BufferedReader reader = new BufferedReader(new InputStreamReader(response, charset))) {
            for (String line; (line = reader.readLine()) != null;) {
                // ... System.out.println(line) ?
    } else {
        // It's likely binary content, use InputStream/OutputStream.

Maintaining the session

The server side session is usually backed by a cookie. Some web forms require that you're logged in and/or are tracked by a session. You can use the CookieHandler API to maintain cookies. You need to prepare a CookieManager with a CookiePolicy of ACCEPT_ALL before sending all HTTP requests.

// First set the default cookie manager.
CookieHandler.setDefault(new CookieManager(null, CookiePolicy.ACCEPT_ALL));

// All the following subsequent URLConnections will use the same cookie manager.
URLConnection connection = new URL(url).openConnection();
// ...

connection = new URL(url).openConnection();
// ...

connection = new URL(url).openConnection();
// ...

Note that this is known to not always work properly in all circumstances. If it fails for you, then best is to manually gather and set the cookie headers. You basically need to grab all Set-Cookie headers from the response of the login or the first GET request and then pass this through the subsequent requests.

// Gather all cookies on the first request.
URLConnection connection = new URL(url).openConnection();
List<String> cookies = connection.getHeaderFields().get("Set-Cookie");
// ...

// Then use the same cookies on all subsequent requests.
connection = new URL(url).openConnection();
for (String cookie : cookies) {
    connection.addRequestProperty("Cookie", cookie.split(";", 2)[0]);
// ...

The split(";", 2)[0] is there to get rid of cookie attributes which are irrelevant for the server side like expires, path, etc. Alternatively, you could also use cookie.substring(0, cookie.indexOf(';')) instead of split().

Streaming mode

The HttpURLConnection will by default buffer the entire request body before actually sending it, regardless of whether you've set a fixed content length yourself using connection.setRequestProperty("Content-Length", contentLength);. This may cause OutOfMemoryExceptions whenever you concurrently send large POST requests (e.g. uploading files). To avoid this, you would like to set the HttpURLConnection#setFixedLengthStreamingMode().


But if the content length is really not known beforehand, then you can make use of chunked streaming mode by setting the HttpURLConnection#setChunkedStreamingMode() accordingly. This will set the HTTP Transfer-Encoding header to chunked which will force the request body being sent in chunks. The below example will send the body in chunks of 1KB.



It can happen that a request returns an unexpected response, while it works fine with a real web browser. The server side is probably blocking requests based on the User-Agent request header. The URLConnection will by default set it to Java/1.6.0_19 where the last part is obviously the JRE version. You can override this as follows:

connection.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36"); // Do as if you're using Chrome 41 on Windows 7.

Use the User-Agent string from a recent browser.

Error handling

If the HTTP response code is 4nn (Client Error) or 5nn (Server Error), then you may want to read the HttpURLConnection#getErrorStream() to see if the server has sent any useful error information.

InputStream error = ((HttpURLConnection) connection).getErrorStream();

If the HTTP response code is -1, then something went wrong with connection and response handling. The HttpURLConnection implementation is in older JREs somewhat buggy with keeping connections alive. You may want to turn it off by setting the http.keepAlive system property to false. You can do this programmatically in the beginning of your application by:

System.setProperty("http.keepAlive", "false");

Uploading files

You'd normally use multipart/form-data encoding for mixed POST content (binary and character data). The encoding is in more detail described in RFC2388.

String param = "value";
File textFile = new File("/path/to/file.txt");
File binaryFile = new File("/path/to/file.bin");
String boundary = Long.toHexString(System.currentTimeMillis()); // Just generate some unique random value.
String CRLF = "\r\n"; // Line separator required by multipart/form-data.
URLConnection connection = new URL(url).openConnection();
connection.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);

try (
    OutputStream output = connection.getOutputStream();
    PrintWriter writer = new PrintWriter(new OutputStreamWriter(output, charset), true);
) {
    // Send normal param.
    writer.append("--" + boundary).append(CRLF);
    writer.append("Content-Disposition: form-data; name=\"param\"").append(CRLF);
    writer.append("Content-Type: text/plain; charset=" + charset).append(CRLF);

    // Send text file.
    writer.append("--" + boundary).append(CRLF);
    writer.append("Content-Disposition: form-data; name=\"textFile\"; filename=\"" + textFile.getName() + "\"").append(CRLF);
    writer.append("Content-Type: text/plain; charset=" + charset).append(CRLF); // Text file itself must be saved in this charset!
    Files.copy(textFile.toPath(), output);
    output.flush(); // Important before continuing with writer!
    writer.append(CRLF).flush(); // CRLF is important! It indicates end of boundary.

    // Send binary file.
    writer.append("--" + boundary).append(CRLF);
    writer.append("Content-Disposition: form-data; name=\"binaryFile\"; filename=\"" + binaryFile.getName() + "\"").append(CRLF);
    writer.append("Content-Type: " + URLConnection.guessContentTypeFromName(binaryFile.getName())).append(CRLF);
    writer.append("Content-Transfer-Encoding: binary").append(CRLF);
    Files.copy(binaryFile.toPath(), output);
    output.flush(); // Important before continuing with writer!
    writer.append(CRLF).flush(); // CRLF is important! It indicates end of boundary.

    // End of multipart/form-data.
    writer.append("--" + boundary + "--").append(CRLF).flush();

If the other side is an HttpServlet, then its doPost() method will be called and the parts will be available by HttpServletRequest#getPart() (note, thus not getParameter() and so on!). The getPart() method is however relatively new, it's introduced in Servlet 3.0 (Glassfish 3, Tomcat 7, etc). Prior to Servlet 3.0, your best choice is using Apache Commons FileUpload to parse a multipart/form-data request. Also see this answer for examples of both the FileUpload and the Servelt 3.0 approaches.

Dealing with untrusted or misconfigured HTTPS sites

Sometimes you need to connect an HTTPS URL, perhaps because you're writing a web scraper. In that case, you may likely face a Not trusted server certificate on some HTTPS sites who doesn't keep their SSL certificates up to date, or a No subject alternative DNS name matching [hostname] found or handshake alert: unrecognized_name on some misconfigured HTTPS sites.

The following one-time-run static initializer in your web scraper class should make HttpsURLConnection more lenient as to those HTTPS sites and thus not throw those exceptions anymore.

static {
    TrustManager[] trustAllCertificates = new TrustManager[] {
        new X509TrustManager() {
            public X509Certificate[] getAcceptedIssuers() {
                return null; // Not relevant.
            public void checkClientTrusted(X509Certificate[] certs, String authType) {
                // Do nothing. Just allow them all.
            public void checkServerTrusted(X509Certificate[] certs, String authType) {
                // Do nothing. Just allow them all.

    HostnameVerifier trustAllHostnames = new HostnameVerifier() {
        public boolean verify(String hostname, SSLSession session) {
            return true; // Just allow them all.

    try {
        System.setProperty("jsse.enableSNIExtension", "false");
        SSLContext sc = SSLContext.getInstance("SSL");
        sc.init(null, trustAllCertificates, new SecureRandom());
    catch (GeneralSecurityException e) {
        throw new ExceptionInInitializerError(e);

Last words

The Apache HttpComponents HttpClient is much more convenient in this all :)

Parsing and extracting HTML

If all you want is parsing and extracting data from HTML, then better use a HTML parser like Jsoup

How to retrieve raw post data from HttpServletRequest in java

This worked for me: (notice that java 8 is required)

String requestData = request.getReader().lines().collect(Collectors.joining());
UserJsonParser u = gson.fromJson(requestData, UserJsonParser.class);

UserJsonParse is a class that shows gson how to parse the json formant.

class is like that:

public class UserJsonParser {

    private String username;
    private String name;
    private String lastname;
    private String mail;
    private String pass1;
//then put setters and getters

the json string that is parsed is like that:

$jsonData: {    "username": "testuser",    "pass1": "clave1234" }

The rest of values (mail, lastname, name) are set to null

What is the purpose of a question mark after a type (for example: int? myVariable)?

Nullable Types

Nullable types are instances of the System.Nullable struct. A nullable type can represent the normal range of values for its underlying value type, plus an additional null value. For example, a [Nullable<Int32>], pronounced "Nullable of Int32," can be assigned any value from -2147483648 to 2147483647, or it can be assigned the null value. A [Nullable<bool>] can be assigned the values true or false, or null. The ability to assign null to numeric and Boolean types is particularly useful when dealing with databases and other data types containing elements that may not be assigned a value. For example, a Boolean field in a database can store the values true or false, or it may be undefined.

Eclipse EGit Checkout conflict with files: - EGit doesn't want to continue

I guess the best way to do this is like this :

  1. Store all your changes in a separate branch.
  2. Then do a hard reset on the local master.
  3. Then merge back your changes from the locally created branch
  4. Then commit and push your changes.

That how I resolve mine, whenever it happens.

How to check if a file exists in the Documents directory in Swift?

Nowadays (2016) Apple recommends more and more to use the URL related API of NSURL, NSFileManager etc.

To get the documents directory in iOS and Swift 2 use

let documentDirectoryURL = try! NSFileManager.defaultManager().URLForDirectory(.DocumentDirectory, 
                                 inDomain: .UserDomainMask, 
                        appropriateForURL: nil, 
                                   create: true)

The try! is safe in this case because this standard directory is guaranteed to exist.

Then append the appropriate path component for example an sqlite file

let databaseURL = documentDirectoryURL.URLByAppendingPathComponent("MyDataBase.sqlite")

Now check if the file exists with checkResourceIsReachableAndReturnError of NSURL.

let fileExists = databaseURL.checkResourceIsReachableAndReturnError(nil)

If you need the error pass the NSError pointer to the parameter.

var error : NSError?
let fileExists = databaseURL.checkResourceIsReachableAndReturnError(&error)
if !fileExists { print(error) }

Swift 3+:

let documentDirectoryURL = try! FileManager.default.url(for: .documentDirectory, 
                                in: .userDomainMask, 
                    appropriateFor: nil, 
                            create: true)

let databaseURL = documentDirectoryURL.appendingPathComponent("MyDataBase.sqlite")

checkResourceIsReachable is marked as can throw

do {
    let fileExists = try databaseURL.checkResourceIsReachable()
    // handle the boolean result
} catch let error as NSError {

To consider only the boolean return value and ignore the error use the nil-coalescing operator

let fileExists = (try? databaseURL.checkResourceIsReachable()) ?? false

Format numbers in JavaScript similar to C#

Here's another version:

$.fn.digits = function () {
    return this.each(function () {
        var value = $(this).text();
        var decimal = "";
        if (value) {
            var pos = value.indexOf(".");
            if (pos >= 0) {
                decimal = value.substring(pos);
                value = value.substring(0, pos);
            if (value) {
                value = value.replace(/(\d)(?=(\d\d\d)+(?!\d))/g, "$1,");
                if (!String.isNullOrEmpty(decimal)) value = (value + decimal);
        else {
            value = $(this).val()
            if (value) {
                var pos = value.indexOf(".");
                if (pos >= 0) {
                    decimal = value.substring(pos);
                    value = value.substring(0, pos);
                if (value) {
                    value = value.replace(/(\d)(?=(\d\d\d)+(?!\d))/g, "$1,");
                    if (!String.isNullOrEmpty(decimal)) value = (value + decimal);

Check if a key is down?

Is there a way to detect if a key is currently down in JavaScript?

Nope. The only possibility is monitoring each keyup and keydown and remembering.

after some period of time the key begins to repeat, firing off keydown and keyup events like a fiend.

It shouldn't. You'll definitely get keypress repeating, and in many browsers you'll also get repeated keydown, but if keyup repeats, it's a bug.

Unfortunately it is not a completely unheard-of bug: on Linux, Chromium, and Firefox (when it is being run under GTK+, which it is in popular distros such as Ubuntu) both generate repeating keyup-keypress-keydown sequences for held keys, which are impossible to distinguish from someone hammering the key really fast.

Delete all but the most recent X files in bash

Removes all but the 10 latest (most recents) files

ls -t1 | head -n $(echo $(ls -1 | wc -l) - 10 | bc) | xargs rm

If less than 10 files no file is removed and you will have : error head: illegal line count -- 0

To count files with bash

Can you force Visual Studio to always run as an Administrator in Windows 8?

NOTE in recent VS versions (2015+) it seems this extension no longer exists/has this feature.

You can also download VSCommands for VS2012 by Squared Infinity which has a feature to change it to run as admin (as well as some other cool bits and pieces)

enter image description here


One can install the commands from the Visual Studio menu bar using Tools->Extensions and Updates selecting Online and searching for vscommands where then one selects VSCommands for Visual Studio 20XX depending on whether using 2012 or 2013 (or greater going forward) and download and install.

CodeIgniter Disallowed Key Characters

In most of the cases when you have a existing software and you are trying to deploy in a new enviroment this kind of error should be caused by the PHP property


Check if you have enabled in your new enviroment. In other words PHP couldn't read the tags in your code.

Converting BigDecimal to Integer

I found that the above did not work for me. I was pulling a cell value from a JTable but could not cast to double or int etc. My solution:

Object obj = getTable().getValueAt(row, 0);

where row 0 would always be a number. Hope this helps anyone still scrolling!

Check whether user has a Chrome extension installed

A lot of the answers here so far are Chrome only or incur an HTTP overhead penalty. The solution that we are using is a little different:

1. Add a new object to the manifest content_scripts list like so:

  "matches": ["*"],
  "js": [
  "run_at": "document_idle"

This will allow the code in install_notifier.js to run on that site (if you didn't already have permissions there).

2. Send a message to every site in the manifest key above.

Add something like this to install_notifier.js (note that this is using a closure to keep the variables from being global, but that's not strictly necessary):

// Dispatch a message to every URL that's in the manifest to say that the extension is
// installed.  This allows webpages to take action based on the presence of the
// extension and its version. This is only allowed for a small whitelist of
// domains defined in the manifest.
(function () {
  let currentVersion = chrome.runtime.getManifest().version;
    sender: "my-extension",
    message_name: "version",
    message: currentVersion
  }, "*");

Your message could say anything, but it's useful to send the version so you know what you're dealing with. Then...

3. On your website, listen for that message.

Add this to your website somewhere:

window.addEventListener("message", function (event) {
  if (event.source == window && && === "my-extension" && && === "version") {
    console.log("Got the message");

This works in Firefox and Chrome, and doesn't incur HTTP overhead or manipulate the page.

How do I preserve line breaks when getting text from a textarea?

You could set width of div using Javascript and add white-space:pre-wrap to p tag, this break your textarea content at end of each line.

document.querySelector("button").onclick = function gt(){_x000D_
var card = document.createElement('div');_x000D_ = "160px";_x000D_ = "#eee";_x000D_
var post = document.createElement('p');_x000D_
var postText = document.getElementById('post-text').value;_x000D_ = "pre-wrap";_x000D_
<textarea id="post-text" class="form-control" rows="3" placeholder="What's up?" required>_x000D_
Group Schedule:_x000D_
Tuesday practice @ 5th floor (8pm - 11 pm)_x000D_
Thursday practice @ 5th floor (8pm - 11 pm)_x000D_
Sunday practice @ (9pm - 12 am)</textarea>_x000D_

Collections.emptyList() vs. new instance

Be carefully though. If you return Collections.emptyList() and then try to do some changes with it like add() or smth like that, u will have an UnsupportedOperationException() because Collections.emptyList() returns an immutable object.

Should I use PATCH or PUT in my REST API?

The R in REST stands for resource

(Which isn't true, because it stands for Representational, but it's a good trick to remember the importance of Resources in REST).

About PUT /groups/api/v1/groups/{group id}/status/activate: you are not updating an "activate". An "activate" is not a thing, it's a verb. Verbs are never good resources. A rule of thumb: if the action, a verb, is in the URL, it probably is not RESTful.

What are you doing instead? Either you are "adding", "removing" or "updating" an activation on a Group, or if you prefer: manipulating a "status"-resource on a Group. Personally, I'd use "activations" because they are less ambiguous than the concept "status": creating a status is ambiguous, creating an activation is not.

  • POST /groups/{group id}/activation Creates (or requests the creation of) an activation.
  • PATCH /groups/{group id}/activation Updates some details of an existing activation. Since a group has only one activation, we know what activation-resource we are referring to.
  • PUT /groups/{group id}/activation Inserts-or-replaces the old activation. Since a group has only one activation, we know what activation-resource we are referring to.
  • DELETE /groups/{group id}/activation Will cancel, or remove the activation.

This pattern is useful when the "activation" of a Group has side-effects, such as payments being made, mails being sent and so on. Only POST and PATCH may have such side-effects. When e.g. a deletion of an activation needs to, say, notify users over mail, DELETE is not the right choice; in that case you probably want to create a deactivation resource: POST /groups/{group_id}/deactivation.

It is a good idea to follow these guidelines, because this standard contract makes it very clear for your clients, and all the proxies and layers between the client and you, know when it is safe to retry, and when not. Let's say the client is somewhere with flaky wifi, and its user clicks on "deactivate", which triggers a DELETE: If that fails, the client can simply retry, until it gets a 404, 200 or anything else it can handle. But if it triggers a POST to deactivation it knows not to retry: the POST implies this.
Any client now has a contract, which, when followed, will protect against sending out 42 emails "your group has been deactivated", simply because its HTTP-library kept retrying the call to the backend.

Updating a single attribute: use PATCH

PATCH /groups/{group id}

In case you wish to update an attribute. E.g. the "status" could be an attribute on Groups that can be set. An attribute such as "status" is often a good candidate to limit to a whitelist of values. Examples use some undefined JSON-scheme:

PATCH /groups/{group id} { "attributes": { "status": "active" } }
response: 200 OK

PATCH /groups/{group id} { "attributes": { "status": "deleted" } }
response: 406 Not Acceptable

Replacing the resource, without side-effects use PUT.

PUT /groups/{group id}

In case you wish to replace an entire Group. This does not necessarily mean that the server actually creates a new group and throws the old one out, e.g. the ids might remain the same. But for the clients, this is what PUT can mean: the client should assume he gets an entirely new item, based on the server's response.

The client should, in case of a PUT request, always send the entire resource, having all the data that is needed to create a new item: usually the same data as a POST-create would require.

PUT /groups/{group id} { "attributes": { "status": "active" } }
response: 406 Not Acceptable

PUT /groups/{group id} { "attributes": { "name": .... etc. "status": "active" } }
response: 201 Created or 200 OK, depending on whether we made a new one.

A very important requirement is that PUT is idempotent: if you require side-effects when updating a Group (or changing an activation), you should use PATCH. So, when the update results in e.g. sending out a mail, don't use PUT.

Can an AWS Lambda function call another

There are a lot of answers, but none is stressing that calling another lambda function is not recommended solution for synchronous calls and the one that you should be using is really Step Functions

Reasons why it is not recommended solution:

  • you are paying for both functions
  • your code is responsible for retrials

You can also use it for quite complex logic, such as parallel steps and catch failures. Every execution is also being logged out which makes debugging much simpler.

Display current time in 12 hour format with AM/PM

To put your current mobile date and time format in

Feb 9, 2018 10:36:59 PM

Date date = new Date();
 String stringDate = DateFormat.getDateTimeInstance().format(date);

you can show it to your Activity, Fragment, CardView, ListView anywhere by using TextView

` TextView mDateTime;


  Date date = new Date();
  String mStringDate = DateFormat.getDateTimeInstance().format(date);
  mDateTime.setText("My Device Current Date and Time is:"+date);


How to set the authorization header using curl

Be careful that when you using: curl -H "Authorization: token_str"

token_str and Authorization must be separated by white space, otherwise server-side will not get the HTTP_AUTHORIZATION environment.

How to compile and run C in sublime text 3?

try to write a shell script named in your project foler


and make a Build System to compile and execute it:

      "shell_cmd": "make all && ./"

don't forget $chmod +x

do one thing and do it well:)

Checking if a list of objects contains a property with a specific value

myList.Where(item=>item.Name == nameToExtract)

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

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

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

Detailed Instruction:

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

Get immediate first child element

Both these will give you the first child node:

console.log(parentElement.firstChild); // or

If you need the first child that is an element node then use:



Ah, I see your problem now; parentElement is an array.

If you know that getElementsByClassName will only return one result, which it seems you do, you should use [0] to dearray (yes, I made that word up) the element:

var parentElement = document.getElementsByClassName("uniqueClassName")[0];

How to check string length and then select substring in Sql Server

To conditionally check the length of the string, use CASE.

SELECT  CASE WHEN LEN(comments) <= 60 
             THEN comments
             ELSE LEFT(comments, 60) + '...'
        END  As Comments
FROM    myView

How to use Regular Expressions (Regex) in Microsoft Excel both in-cell and loops

To make use of regular expressions directly in Excel formulas the following UDF (user defined function) can be of help. It more or less directly exposes regular expression functionality as an excel function.

How it works

It takes 2-3 parameters.

  1. A text to use the regular expression on.
  2. A regular expression.
  3. A format string specifying how the result should look. It can contain $0, $1, $2, and so on. $0 is the entire match, $1 and up correspond to the respective match groups in the regular expression. Defaults to $0.

Some examples

Extracting an email address:

=regex("Peter Gordon: [email protected], 47", "\w+@\w+\.\w+")
=regex("Peter Gordon: [email protected], 47", "\w+@\w+\.\w+", "$0")

Results in: [email protected]

Extracting several substrings:

=regex("Peter Gordon: [email protected], 47", "^(.+): (.+), (\d+)$", "E-Mail: $2, Name: $1")

Results in: E-Mail: [email protected], Name: Peter Gordon

To take apart a combined string in a single cell into its components in multiple cells:

=regex("Peter Gordon: [email protected], 47", "^(.+): (.+), (\d+)$", "$" & 1)
=regex("Peter Gordon: [email protected], 47", "^(.+): (.+), (\d+)$", "$" & 2)

Results in: Peter Gordon [email protected] ...

How to use

To use this UDF do the following (roughly based on this Microsoft page. They have some good additional info there!):

  1. In Excel in a Macro enabled file ('.xlsm') push ALT+F11 to open the Microsoft Visual Basic for Applications Editor.
  2. Add VBA reference to the Regular Expressions library (shamelessly copied from Portland Runners++ answer):
    1. Click on Tools -> References (please excuse the german screenshot) Tools -> References
    2. Find Microsoft VBScript Regular Expressions 5.5 in the list and tick the checkbox next to it.
    3. Click OK.
  3. Click on Insert Module. If you give your module a different name make sure the Module does not have the same name as the UDF below (e.g. naming the Module Regex and the function regex causes #NAME! errors).

    Second icon in the icon row -> Module

  4. In the big text window in the middle insert the following:

    Function regex(strInput As String, matchPattern As String, Optional ByVal outputPattern As String = "$0") As Variant
        Dim inputRegexObj As New VBScript_RegExp_55.RegExp, outputRegexObj As New VBScript_RegExp_55.RegExp, outReplaceRegexObj As New VBScript_RegExp_55.RegExp
        Dim inputMatches As Object, replaceMatches As Object, replaceMatch As Object
        Dim replaceNumber As Integer
        With inputRegexObj
            .Global = True
            .MultiLine = True
            .IgnoreCase = False
            .Pattern = matchPattern
        End With
        With outputRegexObj
            .Global = True
            .MultiLine = True
            .IgnoreCase = False
            .Pattern = "\$(\d+)"
        End With
        With outReplaceRegexObj
            .Global = True
            .MultiLine = True
            .IgnoreCase = False
        End With
        Set inputMatches = inputRegexObj.Execute(strInput)
        If inputMatches.Count = 0 Then
            regex = False
            Set replaceMatches = outputRegexObj.Execute(outputPattern)
            For Each replaceMatch In replaceMatches
                replaceNumber = replaceMatch.SubMatches(0)
                outReplaceRegexObj.Pattern = "\$" & replaceNumber
                If replaceNumber = 0 Then
                    outputPattern = outReplaceRegexObj.Replace(outputPattern, inputMatches(0).Value)
                    If replaceNumber > inputMatches(0).SubMatches.Count Then
                        'regex = "A to high $ tag found. Largest allowed is $" & inputMatches(0).SubMatches.Count & "."
                        regex = CVErr(xlErrValue)
                        Exit Function
                        outputPattern = outReplaceRegexObj.Replace(outputPattern, inputMatches(0).SubMatches(replaceNumber - 1))
                    End If
                End If
            regex = outputPattern
        End If
    End Function
  5. Save and close the Microsoft Visual Basic for Applications Editor window.

How to import multiple csv files in a single load?

Using Spark 2.0+, we can load multiple CSV files from different directories using df =['directory_1','directory_2','directory_3'.....], header=True). For more information, refer the documentation here

PHP Multiple Checkbox Array

Also remember you can include custom indices to the array sent to the server like this

<form method='post' id='userform' action='thisform.php'>
    <td>Trouble Type</td>
    <input type='checkbox' name='checkboxvar[4]' value='Option One'>4<br>
    <input type='checkbox' name='checkboxvar[6]' value='Option Two'>6<br>
    <input type='checkbox' name='checkboxvar[9]' value='Option Three'>9
<input type='submit' class='buttons'>

This is particularly useful when you want to use the id of individual objects in a server array accounts (for instance) to send data back to the server and recognize same at server

<form method='post' id='userform' action='thisform.php'>
    <td>Trouble Type</td>
    <?php foreach($accounts as $account) { ?>
        <input type='checkbox' name='accounts[<?php echo $account->id ?>]' value='<?php echo $account->name ?>'>
        <?php echo $account->name ?>
    <?php } ?>
<input type='submit' class='buttons'>

if (isset($_POST['accounts'])) 

How do I make a burn down chart in Excel?

Say your data set is in Columns A and B of the first sheet.

  1. On Insert ribbon, pick chart type as "Line with Markers"
  2. Right-click on chart, "Select Data...". Select your data in columns without column labels, so your data range would be something like =Sheet1!$A$2:$B$5.
  3. Profit! I mean you're done :-) You might want to change 'Series1' label Excel generates with an actual book name, you can do so in the above "Select Data" dialog.

You can do this with multiple books too - as long as their "pages remaining" data points are tracked on the same dates (e.g. Book2 data would be in Column C, etc...) Books will be represented by additional series.

How do I add 24 hours to a unix timestamp in php?

A Unix timestamp is simply the number of seconds since January the first 1970, so to add 24 hours to a Unix timestamp we just add the number of seconds in 24 hours. (24 * 60 *60)

time() + 24*60*60;

Replace text in HTML page with jQuery

var replaced = $("body").html().replace(/-1o9-2202/g,'The ALL new string');

for variable:

var replaced = $("body").html().replace(new RegExp("-1o9-2202", "igm"),'The ALL new string');

How to get the size of the current screen in WPF?

As far as I know there is no native WPF function to get dimensions of the current monitor. Instead you could PInvoke native multiple display monitors functions, wrap them in managed class and expose all properties you need to consume them from XAML.

How do I order my SQLITE database in descending order, for an android app?

This a terrible thing! It costs my a few hours! this is my table rows :

private String USER_ID = "user_id";
private String REMEMBER_UN = "remember_un";
private String REMEMBER_PWD = "remember_pwd";
private String HEAD_URL = "head_url";
private String USER_NAME = "user_name";
private String USER_PPU = "user_ppu";
private String CURRENT_TIME = "current_time";

Cursor c = db.rawQuery("SELECT * FROM " + TABLE +" ORDER BY " + CURRENT_TIME + " DESC",null);

Every time when I update the table , I will update the CURRENT_TIME for sort. But I found that it is not work.The result is not sorted what I want. Finally, I found that, the column "current_time" is the default row of sqlite.

The solution is, rename the column "cur_time" instead of "current_time".

How to make Visual Studio copy a DLL file to the output directory?

Use a post-build action in your project, and add the commands to copy the offending DLL. The post-build action are written as a batch script.

The output directory can be referenced as $(OutDir). The project directory is available as $(ProjDir). Try to use relative pathes where applicable, so that you can copy or move your project folder without breaking the post-build action.

Order by multiple columns with Doctrine

The comment for orderBy source code notes: Keys are field and values are the order, being either ASC or DESC.. So you can do orderBy->(['field' => Criteria::ASC]).

HTML checkbox onclick called in Javascript

You can also extract the event code from the HTML, like this :

<input type="checkbox" id="check_all_1" name="check_all_1" title="Select All" />
<label for="check_all_1">Select All</label>

function selectAll(frmElement, chkElement) {
    // ...
document.getElementById("check_all_1").onclick = function() {
    selectAll(document.wizard_form, this);

Failed to open/create the internal network Vagrant on Windows10

Fo me, updating VirtualBox to 5.1.23 fixed the issue. You can download this version for Windows from the official website.

spark submit add multiple jars in classpath

I was trying to connect to mysql from the python code that was executed using spark-submit.

I was using HDP sandbox that was using Ambari. Tried lot of options such as --jars, --driver-class-path, etc, but none worked.


Copy the jar in /usr/local/miniconda/lib/python2.7/site-packages/pyspark/jars/

As of now I'm not sure if it's a solution or a quick hack, but since I'm working on POC so it kind of works for me.

How to check if a std::thread is still running?

Surely have a mutex-wrapped variable initialised to false, that the thread sets to true as the last thing it does before exiting. Is that atomic enough for your needs?

Maven 3 warnings about build.plugins.plugin.version

Search "maven-jar-plugin" in pom.xml and add version tag maven version

Why is Spring's ApplicationContext.getBean considered bad?

I mentioned this in a comment on the other question, but the whole idea of Inversion of Control is to have none of your classes know or care how they get the objects they depend on. This makes it easy to change what type of implementation of a given dependency you use at any time. It also makes the classes easy to test, as you can provide mock implementations of dependencies. Finally, it makes the classes simpler and more focused on their core responsibility.

Calling ApplicationContext.getBean() is not Inversion of Control! While it's still easy to change what implemenation is configured for the given bean name, the class now relies directly on Spring to provide that dependency and can't get it any other way. You can't just make your own mock implementation in a test class and pass that to it yourself. This basically defeats Spring's purpose as a dependency injection container.

Everywhere you want to say:

MyClass myClass = applicationContext.getBean("myClass");

you should instead, for example, declare a method:

public void setMyClass(MyClass myClass) {
   this.myClass = myClass;

And then in your configuration:

<bean id="myClass" class="MyClass">...</bean>

<bean id="myOtherClass" class="MyOtherClass">
   <property name="myClass" ref="myClass"/>

Spring will then automatically inject myClass into myOtherClass.

Declare everything in this way, and at the root of it all have something like:

<bean id="myApplication" class="MyApplication">
   <property name="myCentralClass" ref="myCentralClass"/>
   <property name="myOtherCentralClass" ref="myOtherCentralClass"/>

MyApplication is the most central class, and depends at least indirectly on every other service in your program. When bootstrapping, in your main method, you can call applicationContext.getBean("myApplication") but you should not need to call getBean() anywhere else!

postgresql - sql - count of `true` values

probably, the best approach is to use nullif function.

in general

    count(nullif(myCol = false, true)),  -- count true values
    count(nullif(myCol = true, true)),   -- count false values

or in short

    count(nullif(myCol, true)),  -- count false values
    count(nullif(myCol, false)), -- count true values

How to check the Angular version?

Angular CLI ng v does output few more thing than just the version.

If you only want the version from it the you can add pipe grep and filter for angular like:

ng v | grep 'Angular:'


Angular: #.#.# <-- VERSION

For this, I have an alias which is

alias ngv='ng v | grep 'Angular:''

Then just use ngv

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

And to nicely dump it into a file (on Windows at least) - Git Bash:

$ echo "`git show 60d8bdfc:src/services/`" >>

The " quotes are needed so it preserves newlines.

upstream sent too big header while reading response header from upstream

upstream sent too big header while reading response header from upstream is nginx's generic way of saying "I don't like what I'm seeing"

  1. Your upstream server thread crashed
  2. The upstream server sent an invalid header back
  3. The Notice/Warnings sent back from STDERR overflowed their buffer and both it and STDOUT were closed

3: Look at the error logs above the message, is it streaming with logged lines preceding the message? PHP message: PHP Notice: Undefined index: Example snippet from a loop my log file:

2015/11/23 10:30:02 [error] 32451#0: *580927 FastCGI sent in stderr: "PHP message: PHP Notice:  Undefined index: Firstname in /srv/www/classes/data_convert.php on line 1090
PHP message: PHP Notice:  Undefined index: Lastname in /srv/www/classes/data_convert.php on line 1090
... // 20 lines of same
PHP message: PHP Notice:  Undefined index: Firstname in /srv/www/classes/data_convert.php on line 1090
PHP message: PHP Notice:  Undefined index: Lastname in /srv/www/classes/data_convert.php on line 1090
PHP message: PHP Notice:  Undef
2015/11/23 10:30:02 [error] 32451#0: *580927 FastCGI sent in stderr: "ta_convert.php on line 1090
PHP message: PHP Notice:  Undefined index: Firstname

you can see in the 3rd line from the bottom that the buffer limit was hit, broke, and the next thread wrote in over it. Nginx then closed the connection and returned 502 to the client.

2: log all the headers sent per request, review them and make sure they conform to standards (nginx does not permit anything older than 24 hours to delete/expire a cookie, sending invalid content length because error messages were buffered before the content counted...). getallheaders function call can usually help out in abstracted code situations php get all headers

examples include:

//expire cookie
setcookie ( 'bookmark', '', strtotime('2012-01-01 00:00:00') );
// nginx will refuse this header response, too far past to accept

and this:

header('Content-type: image/jpg');

<?php   //a space was injected into the output above this line
header('Content-length: ' . filesize('image.jpg') );
echo file_get_contents('image.jpg');
// error! the response is now 1-byte longer than header!!

1: verify, or make a script log, to ensure your thread is reaching the correct end point and not exiting before completion.

Could not find 3.2.25 4.0.30 4.1.32 4.2.40 4.2.42 4.3.23 4.4.52 5.0.77 5.0.89 5.2.08 6.1.11 6.1.71 6.5.87

I had the same problem because I had:

compile ''

and I solved changing the version numbers for a '+'. so the lines has to be:

compile ''

Spring 3 RequestMapping: Get path value

This has been here quite a while but posting this. Might be useful for someone.

@RequestMapping( "/{id}/**" )
public void foo( @PathVariable String id, HttpServletRequest request ) {
    String urlTail = new AntPathMatcher()
            .extractPathWithinPattern( "/{id}/**", request.getRequestURI() );

What is the point of the diamond operator (<>) in Java 7?

Your understanding is slightly flawed. The diamond operator is a nice feature as you don't have to repeat yourself. It makes sense to define the type once when you declare the type but just doesn't make sense to define it again on the right side. The DRY principle.

Now to explain all the fuzz about defining types. You are right that the type is removed at runtime but once you want to retrieve something out of a List with type definition you get it back as the type you've defined when declaring the list otherwise it would lose all specific features and have only the Object features except when you'd cast the retrieved object to it's original type which can sometimes be very tricky and result in a ClassCastException.

Using List<String> list = new LinkedList() will get you rawtype warnings.

How do I access my SSH public key?

In UBUNTU +18.04

         ssh-keygen -o -t rsa -b 4096 -C "[email protected]" 

And After that Just Copy And Paste

         cat ~/.ssh/ 


         cat ~/.ssh/

Concatenating variables and strings in React


        const json1 = [
            {id: 1, test: 1},
            {id: 2, test: 2},
            {id: 3, test: 3},
            {id: 4, test: 4},
            {id: 5, test: 5}

        const json2 = [
            {id: 3, test: 6},
            {id: 4, test: 7},
            {id: 5, test: 8},
            {id: 6, test: 9},
            {id: 7, test: 10}


        const finalData1 = json1.concat(json2).reduce(function (index, obj) {
            index[] = Object.assign({}, obj, index[]);
            return index;
        }, []).filter(function (res, obj) {
            return obj;


        let hashData = new Map();

        json1.concat(json2).forEach(function (obj) {
            hashData.set(, Object.assign(hashData.get( || {}, obj))

        const finalData2 = Array.from(hashData.values());

I recommend second example , it is faster.

The program can't start because MSVCR110.dll is missing from your computer

This error appears when you wish to run a software which require the Microsoft Visual C++ Redistributable 2012. Download it fromMicrosoft website as x86 or x64 edition. Depending on the software you wish to install you need to install either the 32 bit or the 64 bit version. Visit the following link:

What does \u003C mean?

That is a unicode character code that, when parsed by JavaScript as a string, is converted into its corresponding character (JavaScript automatically converts any occurrences of \uXXXX into the corresponding Unicode character). For example, your example would be:

Browse Interests{{/i}}</a>\n        </li>\n  {{#logged_in}}\n

As you can see, \u003C changes into < (less-than sign) and \u003E changes into > (greater-than sign).

In addition to the link posted by Raynos, this page from the Unicode website lists a lot of characters (so many that they decided to annoyingly group them) and this page has a (kind of) nice index.

How to show Error & Warning Message Box in .NET/ How to Customize MessageBox

Try details: use any option..

    MessageBox.Show("your message",
    "window title", 
    MessageBoxIcon.Warning // for Warning  
    //MessageBoxIcon.Error // for Error 
    //MessageBoxIcon.Information  // for Information
    //MessageBoxIcon.Question // for Question

How to change color of SVG image using CSS (jQuery SVG image replacement)?

@Drew Baker gave a great solution to solve the problem. The code works properly. However, those who uses AngularJs may find lots of dependency on jQuery. Consequently, I thought it is a good idea to paste for AngularJS users, a code following @Drew Baker's solution.

AngularJs way of the same code

1. Html: use the bellow tag in you html file:

<svg-image src="/icons/my.svg" class="any-class-you-wish"></svg-image>

2. Directive: this will be the directive that you will need to recognise the tag:

'use strict';
  .directive('svgImage', ['$http', function($http) {
    return {
      restrict: 'E',
      link: function(scope, element) {
        var imgURL = element.attr('src');
        // if you want to use ng-include, then
        // instead of the above line write the bellow:
        // var imgURL = element.attr('ng-include');
        var request = $http.get(
          {'Content-Type': 'application/xml'}

        scope.manipulateImgNode = function(data, elem){
          var $svg = angular.element(data)[4];
          var imgClass = elem.attr('class');
          if(typeof(imgClass) !== 'undefined') {
            var classes = imgClass.split(' ');
            for(var i = 0; i < classes.length; ++i){
          return $svg;

          element.replaceWith(scope.manipulateImgNode(data, element));

3. CSS:

    border: 1px solid red;
    height: 300px;
    width:  120px

4. Unit-test with karma-jasmine:

'use strict';

describe('Directive: svgImage', function() {

  var $rootScope, $compile, element, scope, $httpBackend, apiUrl, data;

  beforeEach(function() {

    inject(function($injector) {
      $rootScope = $injector.get('$rootScope');
      $compile = $injector.get('$compile');
      $httpBackend = $injector.get('$httpBackend');
      apiUrl = $injector.get('apiUrl');

    scope = $rootScope.$new();
    element = angular.element('<svg-image src="/icons/icon-man.svg" class="svg"></svg-image>');
    element = $compile(element)(scope);

    spyOn(scope, 'manipulateImgNode').andCallThrough();
    $httpBackend.whenGET(apiUrl + 'me').respond(200, {});

    data = '<?xml version="1.0" encoding="utf-8"?>' +
      '<!-- Generator: Adobe Illustrator 17.0.0, SVG Export Plug-In . SVG Version: 6.00 Build 0)  -->' +
      '<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "">' +
      '<!-- Obj -->' +
      '<!-- Obj -->' +
      '<svg version="1.1" id="Capa_1" xmlns="" xmlns:xlink="" x="0px" y="0px"' +
      'width="64px" height="64px" viewBox="0 0 64 64" enable-background="new 0 0 64 64" xml:space="preserve">' +
        '<g>' +
          '<path fill="#F4A902" d=""/>' +
          '<path fill="#F4A902" d=""/>' +
        '</g>' +
    $httpBackend.expectGET('/icons/icon-man.svg').respond(200, data);

  afterEach(function() {

  it('should call manipulateImgNode atleast once', function () {

  it('should return correct result', function () {
    var result = scope.manipulateImgNode(data, element);

  it('should define classes', function () {
    var result = scope.manipulateImgNode(data, element);
    var classList = ["svg"];

How to write inside a DIV box with javascript

document.getElementById('log').innerHTML += '<br>Some new content!';
<div id="log">initial content</div>

How to tell which commit a tag points to in Git?

From git mailing list, here is the way to get the list of commit hashes for tags with automatic dereferencing for annotated tags:

git for-each-ref --format='%(if)%(*objectname)%(then)%(*objectname)%(else)%(objectname)%(end) %(refname)' refs/tags

Timestamp Difference In Hours for PostgreSQL

Michael Krelin's answer is close is not entirely safe, since it can be wrong in rare situations. The problem is that intervals in PostgreSQL do not have context with regards to things like daylight savings. Intervals store things internally as months, days, and seconds. Months aren't an issue in this case since subtracting two timestamps just use days and seconds but 'days' can be a problem.

If your subtraction involves daylight savings change-overs, a particular day might be considered 23 or 25 hours respectively. The interval will take that into account, which is useful for knowing the amount of days that passed in the symbolic sense but it would give an incorrect number of the actual hours that passed. Epoch on the interval will just multiply all days by 24 hours.

For example, if a full 'short' day passes and an additional hour of the next day, the interval will be recorded as one day and one hour. Which converted to epoch/3600 is 25 hours. But in reality 23 hours + 1 hour should be a total of 24 hours.

So the safer method is:

(EXTRACT(EPOCH FROM current_timestamp) - EXTRACT(EPOCH FROM somedate))/3600

As Michael mentioned in his follow-up comment, you'll also probably want to use floor() or round() to get the result as an integer value.

What is the most efficient way to get first and last line of a text file?

First open the file in read mode.Then use readlines() method to read line by line.All the lines stored in a list.Now you can use list slices to get first and last lines of the file.

    lines = a.readlines()
    if lines:
        first_line = lines[:1]
        last_line = lines[-1]

What is "origin" in Git?

origin is an alias on your system for a particular remote repository. It's not actually a property of that repository.

By doing

git push origin branchname

you're saying to push to the origin repository. There's no requirement to name the remote repository origin: in fact the same repository could have a different alias for another developer.

Remotes are simply an alias that store the URL of repositories. You can see what URL belongs to each remote by using

git remote -v

In the push command, you can use remotes or you can simply use a URL directly. An example that uses the URL:

git push [email protected]:git/git.git master

CSS performance relative to translateZ(0)

If you want implications, in some scenarios Google Chrome performance is horrible with hardware acceleration enabled. Oddly enough, changing the "trick" to -webkit-transform: rotateZ(360deg); worked just fine.

I don't believe we ever figured out why.

Mysql adding user for remote access

An alternative way is to use MySql Workbench. Go to Administration -> Users and privileges -> and change 'localhost' with '%' in 'Limit to Host Matching' (From host) attribute for users you wont to give remote access Or create new user ( Add account button ) with '%' on this attribute instead localhost.

.jar error - could not find or load main class

I Faced the same issue while installing a setup using a jar file. Solution thta worked for me is

  1. open command prompt as administrator
  2. Go to jdk bin directory (Ex.C:\Program Files\Java\jdk1.8.0_73\bin)
  3. now execute java -jar <<jar fully qualified path>>

It worked for me :)

Docker-compose: node_modules not present in a volume after npm install succeeds

If you don't use docker-compose you can do it like this:

FROM node:10

WORKDIR /usr/src/app

RUN npm install -g @angular/cli

COPY package.json ./
RUN npm install


CMD ng serve --port 5000 --host

Then you build it: docker build -t myname . and you run it by adding two volumes, the second one without source: docker run --rm -it -p 5000:5000 -v "$PWD":/usr/src/app/ -v /usr/src/app/node_modules myname

JS file gets a net::ERR_ABORTED 404 (Not Found)

As mentionned in comments: you need a way to send your static files to the client. This can be achieved with a reverse proxy like Nginx, or simply using express.static().

Put all your "static" (css, js, images) files in a folder dedicated to it, different from where you put your "views" (html files in your case). I'll call it static for the example. Once it's done, add this line in your server code:

app.use("/static", express.static('./static/'));

This will effectively serve every file in your "static" folder via the /static route.

Querying your index.js file in the client thus becomes:

<script src="static/index.js"></script>

Recyclerview and handling different type of row inflation

It is quite tricky but that much hard, just copy the below code and you are done

package com.yuvi.sample.main;

import android.content.Context;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import com.yuvi.sample.R;

import java.util.List;

 * Created by yubraj on 6/17/15.

public class NavDrawerAdapter extends RecyclerView.Adapter<NavDrawerAdapter.MainViewHolder> {
    List<MainOption> mainOptionlist;
    Context context;
    private static final int TYPE_PROFILE = 1;
    private static final int TYPE_OPTION_MENU = 2;
    private int selectedPos = 0;
    public NavDrawerAdapter(Context context){
        this.mainOptionlist = MainOption.getDrawableDataList();
        this.context = context;

    public int getItemViewType(int position) {
        return (position == 0? TYPE_PROFILE : TYPE_OPTION_MENU);

    public MainViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        switch (viewType){
            case TYPE_PROFILE:
                return new ProfileViewHolder(LayoutInflater.from(context).inflate(R.layout.row_profile, parent, false));
            case TYPE_OPTION_MENU:
                return new MyViewHolder(LayoutInflater.from(context).inflate(R.layout.row_nav_drawer, parent, false));
        return null;

    public void onBindViewHolder(MainViewHolder holder, int position) {
        if(holder.getItemViewType() == TYPE_PROFILE){
            ProfileViewHolder mholder = (ProfileViewHolder) holder;
        else {
            MyViewHolder mHolder = (MyViewHolder) holder;
            MainOption mo = mainOptionlist.get(position);
            mHolder.itemView.setSelected(selectedPos == position);

    private void setUpProfileView(ProfileViewHolder mholder) {


    public int getItemCount() {
        return mainOptionlist.size();

public class MyViewHolder extends MainViewHolder{
    TextView tv_title;
    ImageView iv_icon;

    public MyViewHolder(View v){
        this.tv_title = (TextView) v.findViewById(;
        this.iv_icon = (ImageView) v.findViewById(;
        v.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                // Redraw the old selection and the new
                selectedPos = getLayoutPosition();
    public class ProfileViewHolder extends MainViewHolder{
        TextView tv_name, login;
        ImageView iv_profile;

        public ProfileViewHolder(View v){
            this.tv_name = (TextView) v.findViewById(;
            this.iv_profile = (ImageView) v.findViewById(;
            this.login = (TextView) v.findViewById(;

    public void trace(String tag, String message){
        Log.d(tag , message);
    public class MainViewHolder extends  RecyclerView.ViewHolder {
        public MainViewHolder(View v) {


enjoy !!!!

Dynamic tabs with user-click chosen components

there is component ready to use (rc5 compatible) ng2-steps which uses Compiler to inject component to step container and service for wiring everything together (data sync)

    import { Directive , Input, OnInit, Compiler , ViewContainerRef } from '@angular/core';

import { StepsService } from './ng2-steps';

export class StepDirective implements OnInit{

  @Input('content') content:any;
  @Input('index') index:string;
  public instance;

    private compiler:Compiler,
    private viewContainerRef:ViewContainerRef,
    private sds:StepsService

      const injector = this.viewContainerRef.injector;
      this.viewContainerRef.createComponent(cmpFactory, 0,  injector);


How to use a SQL SELECT statement with Access VBA

Here is another way to use SQL SELECT statement in VBA:

 sSQL = "SELECT Variable FROM GroupTable WHERE VariableCode = '" & Me.comboBox & "'" 
 Set rs = CurrentDb.OpenRecordset(sSQL)
 On Error GoTo resultsetError 
 dbValue = rs!Variable
 MsgBox dbValue, vbOKOnly, "RS VALUE"
 MsgBox "Error Retrieving value from database",VbOkOnly,"Database Error"

mongodb group values by multiple fields

TLDR Summary

In modern MongoDB releases you can brute force this with $slice just off the basic aggregation result. For "large" results, run parallel queries instead for each grouping ( a demonstration listing is at the end of the answer ), or wait for SERVER-9377 to resolve, which would allow a "limit" to the number of items to $push to an array.

    { "$group": {
        "_id": {
            "addr": "$addr",
            "book": "$book"
        "bookCount": { "$sum": 1 }
    { "$group": {
        "_id": "$_id.addr",
        "books": { 
            "$push": { 
                "book": "$",
                "count": "$bookCount"
        "count": { "$sum": "$bookCount" }
    { "$sort": { "count": -1 } },
    { "$limit": 2 },
    { "$project": {
        "books": { "$slice": [ "$books", 2 ] },
        "count": 1

MongoDB 3.6 Preview

Still not resolving SERVER-9377, but in this release $lookup allows a new "non-correlated" option which takes an "pipeline" expression as an argument instead of the "localFields" and "foreignFields" options. This then allows a "self-join" with another pipeline expression, in which we can apply $limit in order to return the "top-n" results.

  { "$group": {
    "_id": "$addr",
    "count": { "$sum": 1 }
  { "$sort": { "count": -1 } },
  { "$limit": 2 },
  { "$lookup": {
    "from": "books",
    "let": {
      "addr": "$_id"
    "pipeline": [
      { "$match": { 
        "$expr": { "$eq": [ "$addr", "$$addr"] }
      { "$group": {
        "_id": "$book",
        "count": { "$sum": 1 }
      { "$sort": { "count": -1  } },
      { "$limit": 2 }
    "as": "books"

The other addition here is of course the ability to interpolate the variable through $expr using $match to select the matching items in the "join", but the general premise is a "pipeline within a pipeline" where the inner content can be filtered by matches from the parent. Since they are both "pipelines" themselves we can $limit each result separately.

This would be the next best option to running parallel queries, and actually would be better if the $match were allowed and able to use an index in the "sub-pipeline" processing. So which is does not use the "limit to $push" as the referenced issue asks, it actually delivers something that should work better.

Original Content

You seem have stumbled upon the top "N" problem. In a way your problem is fairly easy to solve though not with the exact limiting that you ask for:

    { "$group": {
        "_id": {
            "addr": "$addr",
            "book": "$book"
        "bookCount": { "$sum": 1 }
    { "$group": {
        "_id": "$_id.addr",
        "books": { 
            "$push": { 
                "book": "$",
                "count": "$bookCount"
        "count": { "$sum": "$bookCount" }
    { "$sort": { "count": -1 } },
    { "$limit": 2 }

Now that will give you a result like this:

    "result" : [
                    "_id" : "address1",
                    "books" : [
                                    "book" : "book4",
                                    "count" : 1
                                    "book" : "book5",
                                    "count" : 1
                                    "book" : "book1",
                                    "count" : 3
                    "count" : 5
                    "_id" : "address2",
                    "books" : [
                                    "book" : "book5",
                                    "count" : 1
                                    "book" : "book1",
                                    "count" : 2
                    "count" : 3
    "ok" : 1

So this differs from what you are asking in that, while we do get the top results for the address values the underlying "books" selection is not limited to only a required amount of results.

This turns out to be very difficult to do, but it can be done though the complexity just increases with the number of items you need to match. To keep it simple we can keep this at 2 matches at most:

    { "$group": {
        "_id": {
            "addr": "$addr",
            "book": "$book"
        "bookCount": { "$sum": 1 }
    { "$group": {
        "_id": "$_id.addr",
        "books": { 
            "$push": { 
                "book": "$",
                "count": "$bookCount"
        "count": { "$sum": "$bookCount" }
    { "$sort": { "count": -1 } },
    { "$limit": 2 },
    { "$unwind": "$books" },
    { "$sort": { "count": 1, "books.count": -1 } },
    { "$group": {
        "_id": "$_id",
        "books": { "$push": "$books" },
        "count": { "$first": "$count" }
    { "$project": {
        "_id": {
            "_id": "$_id",
            "books": "$books",
            "count": "$count"
        "newBooks": "$books"
    { "$unwind": "$newBooks" },
    { "$group": {
      "_id": "$_id",
      "num1": { "$first": "$newBooks" }
    { "$project": {
        "_id": "$_id",
        "newBooks": "$_id.books",
        "num1": 1
    { "$unwind": "$newBooks" },
    { "$project": {
        "_id": "$_id",
        "num1": 1,
        "newBooks": 1,
        "seen": { "$eq": [
    { "$match": { "seen": false } },
    { "$group":{
        "_id": "$_id._id",
        "num1": { "$first": "$num1" },
        "num2": { "$first": "$newBooks" },
        "count": { "$first": "$_id.count" }
    { "$project": {
        "num1": 1,
        "num2": 1,
        "count": 1,
        "type": { "$cond": [ 1, [true,false],0 ] }
    { "$unwind": "$type" },
    { "$project": {
        "books": { "$cond": [
        "count": 1
    { "$group": {
        "_id": "$_id",
        "count": { "$first": "$count" },
        "books": { "$push": "$books" }
    { "$sort": { "count": -1 } }

So that will actually give you the top 2 "books" from the top two "address" entries.

But for my money, stay with the first form and then simply "slice" the elements of the array that are returned to take the first "N" elements.

Demonstration Code

The demonstration code is appropriate for usage with current LTS versions of NodeJS from v8.x and v10.x releases. That's mostly for the async/await syntax, but there is nothing really within the general flow that has any such restriction, and adapts with little alteration to plain promises or even back to plain callback implementation.


const { MongoClient } = require('mongodb');
const fs = require('mz/fs');

const uri = 'mongodb://localhost:27017';

const log = data => console.log(JSON.stringify(data, undefined, 2));

(async function() {

  try {
    const client = await MongoClient.connect(uri);

    const db = client.db('bookDemo');
    const books = db.collection('books');

    let { version } = await db.command({ buildInfo: 1 });
    version = parseFloat(version.match(new RegExp(/(?:(?!-).)*/))[0]);

    // Clear and load books
    await books.deleteMany({});

    await books.insertMany(
      (await fs.readFile('books.json'))

    if ( version >= 3.6 ) {

    // Non-correlated pipeline with limits
      let result = await books.aggregate([
        { "$group": {
          "_id": "$addr",
          "count": { "$sum": 1 }
        { "$sort": { "count": -1 } },
        { "$limit": 2 },
        { "$lookup": {
          "from": "books",
          "as": "books",
          "let": { "addr": "$_id" },
          "pipeline": [
            { "$match": {
              "$expr": { "$eq": [ "$addr", "$$addr" ] }
            { "$group": {
              "_id": "$book",
              "count": { "$sum": 1 },
            { "$sort": { "count": -1 } },
            { "$limit": 2 }

      log({ result });

    // Serial result procesing with parallel fetch

    // First get top addr items
    let topaddr = await books.aggregate([
      { "$group": {
        "_id": "$addr",
        "count": { "$sum": 1 }
      { "$sort": { "count": -1 } },
      { "$limit": 2 }

    // Run parallel top books for each addr
    let topbooks = await Promise.all({ _id: addr }) =>
          { "$match": { addr } },
          { "$group": {
            "_id": "$book",
            "count": { "$sum": 1 }
          { "$sort": { "count": -1 } },
          { "$limit": 2 }

    // Merge output
    topaddr =,i) => ({ ...d, books: topbooks[i] }));
    log({ topaddr });


  } catch(e) {
  } finally {



{ "addr": "address1",  "book": "book1"  }
{ "addr": "address2",  "book": "book1"  }
{ "addr": "address1",  "book": "book5"  }
{ "addr": "address3",  "book": "book9"  }
{ "addr": "address2",  "book": "book5"  }
{ "addr": "address2",  "book": "book1"  }
{ "addr": "address1",  "book": "book1"  }
{ "addr": "address15", "book": "book1"  }
{ "addr": "address9",  "book": "book99" }
{ "addr": "address90", "book": "book33" }
{ "addr": "address4",  "book": "book3"  }
{ "addr": "address5",  "book": "book1"  }
{ "addr": "address77", "book": "book11" }
{ "addr": "address1",  "book": "book1"  }

How to redirect siteA to siteB with A or CNAME records

You can only make DNS name pont to a different IP address, so if You you are using virtual hosts redirecting with DNS won't work.

When you enter in your browser it will use DNS to get it's IP address (if it's a CNAME it will continue trying until it gets IP from A record) then it will connect to that IP and send a http request with


somewhere in the http headers.

Best JavaScript compressor

YUI Compressor is the way to go. It has a great compression rate, is well tested and is in use among many top sites, and, well, personally recommended by me.

I've used it for my projects without a single JavaScript error or hiccup. And it has nice documentation.

I've never used its CSS compression capabilities, but they exist as well. CSS compression works just as well.

Note: Although Dean Edwards's /packer/ achieves a better compression rate than YUI Compressor, I ran into a few JavaScript errors when using it.

How to center a component in Material-UI and make it responsive?

With other answers used, xs='auto' did a trick for me.

<Grid container
    style={{ minHeight: "100vh" }}>

    <Grid item xs='auto'>
            buttonText="Log in with Google"

Setting width as a percentage using jQuery

Using the width function:


will turn:

<div id="somediv" />


<div id="somediv" style="width: 70%;"/>

How to get the azure account tenant Id?

My team really got sick of trying to find the tenant ID for our O365 and Azure projects. The devs, the support team, the sales team, everyone needs it at some point and never remembers how to do it.

So we've built this small site in the same vein as Hope you find it useful!

How to find my Microsoft 365, Azure or SharePoint Online tenant ID?

What to do about Eclipse's "No repository found containing: ..." error messages?

Some of the above solutions worked to resolve some of my errors... it seems that after a while update connections just get corrupted and there is no silver-bullet. Managing updates through the marketplace (Help > Marketplace > 'show updates') allowed me to narrow down the packages with failed dependencies.

Here's what I tried (taken from posts above):

  1. switching https to http for software sites
  2. running Eclipse as administrator
  3. 'disabling' obviously outdated software sites
  4. 'enabling' all software sites
  5. adding backslashes to the end of software site urls
  6. uninstalling and re-installing troublesome software

I was still left with some Mylyn wikitext errors despite trying the suggestions here

Eclipse IDE for JavaScript and Web Developers

Version: 2019-09 R (4.13.0) Build id: 20190917-1200

Javascript how to parse JSON array

Just as a heads up...

var data = JSON.parse(responseBody);

has been deprecated.

Postman Learning Center now suggests

var jsonData = pm.response.json();

Can You Get A Users Local LAN IP Address Via JavaScript?

Now supported in internal-ip!

An RTCPeerConnection can be used. In browsers like Chrome where a getUserMedia permission is required, we can just detect available input devices and request for them.

const internalIp = async () => {
    if (!RTCPeerConnection) {
        throw new Error("Not supported.")

    const peerConnection = new RTCPeerConnection({ iceServers: [] })

    peerConnection.createOffer(peerConnection.setLocalDescription.bind(peerConnection), () => { })

    peerConnection.addEventListener("icecandidateerror", (event) => {
        throw new Error(event.errorText)

    return new Promise(async resolve => {
        peerConnection.addEventListener("icecandidate", async ({candidate}) => {
            if (candidate && candidate.candidate) {
                const result = candidate.candidate.split(" ")[4]
                if (result.endsWith(".local")) {
                    const inputDevices = await navigator.mediaDevices.enumerateDevices()
                    const inputDeviceTypes ={ kind }) => kind)

                    const constraints = {}

                    if (inputDeviceTypes.includes("audioinput")) {
               = true
                    } else if (inputDeviceTypes.includes("videoinput")) {
               = true
                    } else {
                        throw new Error("An audio or video input device is required!")

                    const mediaStream = await navigator.mediaDevices.getUserMedia(constraints)
                    mediaStream.getTracks().forEach(track => track.stop())

How do you perform address validation? service is available that provides following services,

1) Address Validation.

2) Address Correction.

3) Address spell correcting.

4) Correct addresses phonetic mistakes. uses USPS and Tiger data as reference data.

For more detail visit below link,

Get the string value from List<String> through loop for display

Use the For-Each loop which came with Java 1.5, and it work on Types which are iterable.

ArrayList<String> data = new ArrayList<String>();

for (String s : data){

 System.out.prinln("Data of "+data.indexOf(s)+" "+s);


How can I write to the console in PHP?

There is also a great Google Chrome extension, PHP Console, with a PHP library that allows you to:

  • See errors and exceptions in the Chrome JavaScript console and in the notification popups.
  • Dump any type of variable.
  • Execute PHP code remotely.
  • Protect access by password.
  • Group console logs by request.
  • Jump to error file:line in your text editor.
  • Copy error/debug data to the clipboard (for testers).

Find child element in AngularJS directive

jQlite (angular's "jQuery" port) doesn't support lookup by classes.

One solution would be to include jQuery in your app.

Another is using QuerySelector or QuerySelectorAll:

link: function(scope, element, attrs) {

We use the first item in the element array, which is the HTML element. element.eq(0) would yield the same.


Using jQuery, Restricting File Size Before Uploading

I encountered the same issue. You have to use ActiveX or Flash (or Java). The good thing is that it doesn't have to be invasive. I have a simple ActiveX method that will return the size of the to-be-uploaded file.

If you go with Flash, you can even do some fancy js/css to cusomize the uploading experience--only using Flash (as a 1x1 "movie") to access it's file uploading features.

How to download file in swift?

Example downloader class without Alamofire:

class Downloader {
    class func load(URL: NSURL) {
        let sessionConfig = NSURLSessionConfiguration.defaultSessionConfiguration()
        let session = NSURLSession(configuration: sessionConfig, delegate: nil, delegateQueue: nil)
        let request = NSMutableURLRequest(URL: URL)
        request.HTTPMethod = "GET"
        let task = session.dataTaskWithRequest(request, completionHandler: { (data: NSData!, response: NSURLResponse!, error: NSError!) -> Void in
            if (error == nil) {
                // Success
                let statusCode = (response as NSHTTPURLResponse).statusCode
                println("Success: \(statusCode)")

                // This is your file-variable:
                // data
            else {
                // Failure
                println("Failure: %@", error.localizedDescription);

This is how to use it in your own code:

class Foo {
    func bar() {
        if var URL = NSURL(string: "") {

Swift 3 Version

Also note to download large files on disk instead instead in memory. see `downloadTask:

class Downloader {
    class func load(url: URL, to localUrl: URL, completion: @escaping () -> ()) {
        let sessionConfig = URLSessionConfiguration.default
        let session = URLSession(configuration: sessionConfig)
        let request = try! URLRequest(url: url, method: .get)

        let task = session.downloadTask(with: request) { (tempLocalUrl, response, error) in
            if let tempLocalUrl = tempLocalUrl, error == nil {
                // Success
                if let statusCode = (response as? HTTPURLResponse)?.statusCode {
                    print("Success: \(statusCode)")

                do {
                    try FileManager.default.copyItem(at: tempLocalUrl, to: localUrl)
                } catch (let writeError) {
                    print("error writing file \(localUrl) : \(writeError)")

            } else {
                print("Failure: %@", error?.localizedDescription);

Get folder name of the file in Python

I'm using 2 ways to get the same response: one of them use:


due to errors that I found in my script I changed to:

Path = filename[:(len(filename)-len(os.path.basename(filename)))]

it's a workaround due to python's '\\'

Expected initializer before function name

Try adding a semi colon to the end of your structure:

 struct sotrudnik {
    string name;
    string speciality;
    string razread;
    int zarplata;
} //Semi colon here

Is there any boolean type in Oracle databases?

No there doesn't exist type boolean,but instead of this you can you 1/0(type number),or 'Y'/'N'(type char),or 'true'/'false' (type varchar2).

How to add elements to an empty array in PHP?

$cart = array();
$cart[] = 11;
$cart[] = 15;

// etc

//Above is correct. but below one is for further understanding

$cart = array();
for($i = 0; $i <= 5; $i++){
          $cart[] = $i;  

//if you write $cart = [$i]; you will only take last $i value as first element in array.

echo "<pre>";
echo "</pre>";

Removing a model in rails (reverse of "rails g model Title...")

Try this

rails destroy model Rating

It will remove model, migration, tests and fixtures

Quadratic and cubic regression in Excel

The LINEST function described in a previous answer is the way to go, but an easier way to show the 3 coefficients of the output is to additionally use the INDEX function. In one cell, type: =INDEX(LINEST(B2:B21,A2:A21^{1,2},TRUE,FALSE),1) (by the way, the B2:B21 and A2:A21 I used are just the same values the first poster who answered this used... of course you'd change these ranges appropriately to match your data). This gives the X^2 coefficient. In an adjacent cell, type the same formula again but change the final 1 to a 2... this gives the X^1 coefficient. Lastly, in the next cell over, again type the same formula but change the last number to a 3... this gives the constant. I did notice that the three coefficients are very close but not quite identical to those derived by using the graphical trendline feature under the charts tab. Also, I discovered that LINEST only seems to work if the X and Y data are in columns (not rows), with no empty cells within the range, so be aware of that if you get a #VALUE error.

How to create multiple output paths in Webpack config

Please don't use any workaround because it will impact build performance.

Webpack File Manager Plugin

Easy to install copy this tag on top of the webpack.config.js

const FileManagerPlugin = require('filemanager-webpack-plugin');


npm install filemanager-webpack-plugin --save-dev

Add the plugin

module.exports = {
    plugins: [
        new FileManagerPlugin({
            onEnd: {
                copy: [
                    {source: 'www', destination: './vinod test 1/'},
                    {source: 'www', destination: './vinod testing 2/'},
                    {source: 'www', destination: './vinod testing 3/'},


enter image description here

How to specify a multi-line shell variable?

I would like to give one additional answer, while the other ones will suffice in most cases.

I wanted to write a string over multiple lines, but its contents needed to be single-line.

sql="                       \
SELECT c1, c2               \
from Table1, ${TABLE2}      \
where ...                   \

I am sorry if this if a bit off-topic (I did not need this for SQL). However, this post comes up among the first results when searching for multi-line shell variables and an additional answer seemed appropriate.

Getting the folder name from a path

Try this:

string filename = @"C:/folder1/folder2/file.txt";
string FolderName = new DirectoryInfo(System.IO.Path.GetDirectoryName(filename)).Name;

How can I use a carriage return in a HTML tooltip?

According to this article on the w3c website:

CDATA is a sequence of characters from the document character set and may include character entities. User agents should interpret attribute values as follows:

  • Replace character entities with characters,
  • Ignore line feeds,
  • Replace each carriage return or tab with a single space.

This means that (at least) CR and LF won't work inside title attribute. I suggest that you use a tooltip plugin. Most of these plugins allow arbitrary HTML to be displayed as an element's tooltip.

How to kill a process running on particular port in Linux?

This is the solution for Windows:

C:\Users\Niroshan>netstat -ano|findstr "PID :8080"

Proto Local Address Foreign Address State PID

taskkill /pid 18264 /f

Java program to find the largest & smallest number in n numbers without using arrays

Try this :

int smallest = Integer.MAX_VALUE;
for(int i=0;i<n;i++)

Transparent background on winforms?

The manner I have used before is to use a wild color (a color no one in their right mind would use) for the BackColor and then set the transparency key to that.

this.BackColor = Color.LimeGreen;
this.TransparencyKey = Color.LimeGreen;

How to decode Unicode escape sequences like "\u00ed" to proper UTF-8 encoded characters?

This is a sledgehammer approach to replacing raw UNICODE with HTML. I haven't seen any other place to put this solution, but I assume others have had this problem.

Apply this str_replace function to the RAW JSON, before doing anything else.

function unicode2html($str){
     return $str;

This won't take as long as you think, and this will replace ANY unicode with HTML.

Of course this can be reduced if you know the unicode types that are being returned in the JSON.

For example my code was getting lots of arrows and dingbat unicode. These are between 8448 an 11263. So my production code looks like:


You can look up the blocks of Unicode by type here: If you know you're translating Arabic or Telegu or whatever, you can just replace those codes, not all 65,000.

You could apply this same sledgehammer to simple encoding:


A failure occurred while executing

In right side of android studio click gradle -> app -> build -> assemble. then android studio will start building, and print you a proper message of the issue.

jQuery select element in parent window

You can also use,

parent.jQuery("#testdiv").attr("style", content from form);

Update Eclipse with Android development tools v. 23

Solution, see:

This solution is the correct way of how you should change the files and keep your Eclipse ADT and not downloading a new one.

How to set bot's status

Use this:

client.user.setActivity("with depression", {
  type: "STREAMING",
  url: ""

Shell command to tar directory excluding certain files/folders

After reading this thread, I did a little testing on RHEL 5 and here are my results for tarring up the abc directory:

This will exclude the directories error and logs and all files under the directories:

tar cvpzf abc.tgz abc/ --exclude='abc/error' --exclude='abc/logs'

Adding a wildcard after the excluded directory will exclude the files but preserve the directories:

tar cvpzf abc.tgz abc/ --exclude='abc/error/*' --exclude='abc/logs/*'

Converting Integer to Long

If the Integer is not null

Integer i;
Long long = Long.valueOf(i);

i will be automatically typecast to a long.

Using valueOf instead of new allows caching of this value (if its small) by the compiler or JVM , resulting in faster code.

Facebook database design?


They use a stack architecture with cached graphs for everything above the MySQL bottom of their stack.

Long Answer:

I did some research on this myself because I was curious how they handle their huge amount of data and search it in a quick way. I've seen people complaining about custom made social network scripts becoming slow when the user base grows. After I did some benchmarking myself with just 10k users and 2.5 million friend connections - not even trying to bother about group permissions and likes and wall posts - it quickly turned out that this approach is flawed. So I've spent some time searching the web on how to do it better and came across this official Facebook article:

I really recommend you to watch the presentation of the first link above before continue reading. It's probably the best explanation of how FB works behind the scenes you can find.

The video and article tells you a few things:

  • They're using MySQL at the very bottom of their stack
  • Above the SQL DB there is the TAO layer which contains at least two levels of caching and is using graphs to describe the connections.
  • I could not find anything on what software / DB they actually use for their cached graphs

Let's take a look at this, friend connections are top left:

enter image description here

Well, this is a graph. :) It doesn't tell you how to build it in SQL, there are several ways to do it but this site has a good amount of different approaches. Attention: Consider that a relational DB is what it is: It's thought to store normalised data, not a graph structure. So it won't perform as good as a specialised graph database.

Also consider that you have to do more complex queries than just friends of friends, for example when you want to filter all locations around a given coordinate that you and your friends of friends like. A graph is the perfect solution here.

I can't tell you how to build it so that it will perform well but it clearly requires some trial and error and benchmarking.

Here is my disappointing test for just findings friends of friends:

DB Schema:

`id` int(11) NOT NULL,
  `user_id` int(11) NOT NULL,
  `friend_id` int(11) NOT NULL

Friends of Friends Query:

        select friend_id
        from friends
        where user_id = 1
    ) union (
        select distinct ff.friend_id
            friends f
            join friends ff on ff.user_id = f.friend_id
        where f.user_id = 1

I really recommend you to create you some sample data with at least 10k user records and each of them having at least 250 friend connections and then run this query. On my machine (i7 4770k, SSD, 16gb RAM) the result was ~0.18 seconds for that query. Maybe it can be optimized, I'm not a DB genius (suggestions are welcome). However, if this scales linear you're already at 1.8 seconds for just 100k users, 18 seconds for 1 million users.

This might still sound OKish for ~100k users but consider that you just fetched friends of friends and didn't do any more complex query like "display me only posts from friends of friends + do the permission check if I'm allowed or NOT allowed to see some of them + do a sub query to check if I liked any of them". You want to let the DB do the check on if you liked a post already or not or you'll have to do in code. Also consider that this is not the only query you run and that your have more than active user at the same time on a more or less popular site.

I think my answer answers the question how Facebook designed their friends relationship very well but I'm sorry that I can't tell you how to implement it in a way it will work fast. Implementing a social network is easy but making sure it performs well is clearly not - IMHO.

I've started experimenting with OrientDB to do the graph-queries and mapping my edges to the underlying SQL DB. If I ever get it done I'll write an article about it.

How to declare Global Variables in Excel VBA to be visible across the Workbook

You can do the following to learn/test the concept:

  1. Open new Excel Workbook and in Excel VBA editor right-click on Modules->Insert->Module

  2. In newly added Module1 add the declaration; Public Global1 As String

  3. in Worksheet VBA Module Sheet1(Sheet1) put the code snippet:

Sub setMe()
      Global1 = "Hello"
End Sub
  1. in Worksheet VBA Module Sheet2(Sheet2) put the code snippet:
Sub showMe()
    Debug.Print (Global1)
End Sub
  1. Run in sequence Sub setMe() and then Sub showMe() to test the global visibility/accessibility of the var Global1

Hope this will help.

Alternative to the HTML Bold tag

Its in CSS you have to set font-weight: bold; as style

Allow Google Chrome to use XMLHttpRequest to load a URL from a local file

Mac version. From terminal run:

open /Applications/Google\ --args --allow-file-access-from-files

How can I "disable" zoom on a mobile web page?

There are a number of approaches here- and though the position is that typically users should not be restricted when it comes to zooming for accessibility purposes, there may be incidences where is it required:

Render the page at the width of the device, dont scale:

<meta name="viewport" content="width=device-width, initial-scale=1.0">

Prevent scaling- and prevent the user from being able to zoom:

<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no">

Removing all zooming, all scaling

<meta name="viewport" content="user-scalable=no, initial-scale=1, maximum-scale=1, minimum-scale=1, width=device-width, height=device-height, target-densitydpi=device-dpi" />

Call an overridden method from super class in typescript

The order of execution is:

  1. A's constructor
  2. B's constructor

The assignment occurs in B's constructor after A's constructor—_super—has been called:

function B() {
    _super.apply(this, arguments);   // MyvirtualMethod called in here
    this.testString = "Test String"; // testString assigned here

So the following happens:

var b = new B();     // undefined
b.MyvirtualMethod(); // "Test String"

You will need to change your code to deal with this. For example, by calling this.MyvirtualMethod() in B's constructor, by creating a factory method to create the object and then execute the function, or by passing the string into A's constructor and working that out somehow... there's lots of possibilities.

What is the difference between onBlur and onChange attribute in HTML?

onChange is when something within a field changes eg, you write something in a text input.

onBlur is when you take focus away from a field eg, you were writing in a text input and you have clicked off it.

So really they are almost the same thing but for onChange to behave the way onBlur does something in that input needs to change.

How to import a module given the full path?

Do you mean load or import?

You can manipulate the sys.path list specify the path to your module, then import your module. For example, given a module at:


You could do:

import sys
sys.path[0:0] = ['/foo'] # puts the /foo directory at the start of your path
import bar