Programs & Examples On #Bash

For questions about scripts written for the Bash command shell. For shell scripts with errors, please check them with the shellcheck program (or in the web shellcheck server at before posting here. Questions about interactive use of Bash are more likely to be on-topic on Super User than on Stack Overflow.

I just assigned a variable, but echo $variable shows something else

Additional to putting the variable in quotation, one could also translate the output of the variable using tr and converting spaces to newlines.

$ echo $var | tr " " "\n"

Although this is a little more convoluted, it does add more diversity with the output as you can substitute any character as the separator between array variables.

Execute a shell function with timeout

This function uses only builtins

  • Maybe consider evaling "$*" instead of running $@ directly depending on your needs

  • It starts a job with the command string specified after the first arg that is the timeout value and monitors the job pid

  • It checks every 1 seconds, bash supports timeouts down to 0.01 so that can be tweaked

  • Also if your script needs stdin, read should rely on a dedicated fd (exec {tofd}<> <(:))

  • Also you might want to tweak the kill signal (the one inside the loop) which is default to -15, you might want -9

## forking is evil
timeout() {
    to=$1; shift
    $@ & local wp=$! start=0
     while kill -0 $wp; do
        read -t 1
        if [ $start -ge $to ]; then
            kill $wp && break

Run text file as commands in Bash

You can use something like this:

for i in `cat foo.txt`
    sudo $i

Though if the commands have arguments (i.e. there is whitespace in the lines) you may have to monkey around with that a bit to protect the whitepace so that the whole string is seen by sudo as a command. But it gives you an idea on how to start.

Command output redirect to file and terminal

It is worth mentioning that 2>&1 means that standard error will be redirected too, together with standard output. So

someCommand | tee someFile

gives you just the standard output in the file, but not the standard error: standard error will appear in console only. To get standard error in the file too, you can use

someCommand 2>&1 | tee someFile

(source: In the shell, what is " 2>&1 "? ). Finally, both the above commands will truncate the file and start clear. If you use a sequence of commands, you may want to get output&error of all of them, one after another. In this case you can use -a flag to "tee" command:

someCommand 2>&1 | tee -a someFile

rm: cannot remove: Permission denied

The code says everything:

max@serv$ chmod 777 .

Okay, it doesn't say everything.

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

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

Subtract two variables in Bash

Alternatively to the suggested 3 methods you can try let which carries out arithmetic operations on variables as follows:




kill a process in bash

This one is violent use with caution :

pkill -9 -e -f processname 

If your process name is "sh" it will also kill "bash"

Regex matching in a Bash if statement

I'd prefer to use [:punct:] for that. Also, a-zA-Z09-9 could be just [:alnum:]:

[[ $TEST =~ ^[[:alnum:][:blank:][:punct:]]+$ ]]

rsync copy over only certain types of files using include option

One more addition: if you need to sync files by its extensions in one dir only (without of recursion) you should use a construction like this:

rsync -auzv --include './' --include '*.ext' --exclude '*' /source/dir/ /destination/dir/

Pay your attention to the dot in the first --include. --no-r does not work in this construction.


Thanks to for the valuable comment!

How to download an entire directory and subdirectories using wget?

wget -r --no-parent URL --user=username --password=password

the last two options are optional if you have the username and password for downloading, otherwise no need to use them.

You can also see more options in the link

How to resolve symbolic links in a shell script

To work around the Mac incompatibility, I came up with

echo `php -r "echo realpath('foo');"`

Not great but cross OS

How to replace an entire line in a text file by line number

On mac I used

sed -i '' -e 's/text-on-line-to-be-changed.*/text-to-replace-the=whole-line/' file-name

How to print / echo environment variables?

On windows, you can print with this command in your CLI C:\Users\dir\env | more

You can view all environment variables set on your system with the env command. The list is long, so pipe the output through more to make it easier to read.

iTerm 2: How to set keyboard shortcuts to jump to beginning/end of line?

Just to help out anyone that is having the same issue but specifically using Zsh shell with iTerm 2. It turns out that Zsh doesn't read /etc/inputrc properly, and so fails to understand any key bindings you set up through the preferences!

To fix this, you need to add some key bindings to your .zshrc file, such as:

# key bindings
bindkey "\e[1~" beginning-of-line
bindkey "\e[4~" end-of-line

Note the backslashes in the example above before the "e", the linked article does not show them, so add them into your .zshrc file when adding bindings.

Insert multiple lines into a file after specified pattern using shell script

Here is a more generic solution based on @rindeal solution which does not work on MacOS/BSD (/r expects a file):

cat << DOC > input.txt
$ cat << EOF | sed '/^cdef$/ r /dev/stdin' input.txt
line 1
line 2

# outputs:
line 1
line 2

This can be used to pipe anything into the file at the given position:

$ date | sed '/^cdef$/ r /dev/stdin' input.txt

# outputs
Tue Mar 17 10:50:15 CET 2020

Also, you could add multiple commands which allows deleting the marker line cdef:

$ date | sed '/^cdef$/ {
  r /dev/stdin
}' input.txt

# outputs
Tue Mar 17 10:53:53 CET 2020

Run bash command on jenkins pipeline

For multi-line shell scripts or those run multiple times, I would create a new bash script file (starting from #!/bin/bash), and simply run it with sh from Jenkinsfile:

sh 'chmod +x ./'
sh './'

recursively use scp but excluding some folders

Although scp supports recursive directory copying with the -r option, it does not support filtering of the files. There are several ways to accomplish your task, but I would probably rely on find, xargs, tar, and ssh instead of scp.

find . -type d -wholename '*bench*/image' \
| xargs tar cf - \
| ssh user@remote tar xf - -C /my/dir

The rsync solution can be made to work, but you are missing some arguments. rsync also needs the r switch to recurse into subdirectories. Also, if you want the same security of scp, you need to do the transfer under ssh. Something like:

rsync -avr -e "ssh -l user" --exclude 'fl_*' ./bench* remote:/my/dir

How can I quickly sum all numbers in a file?

One in tcl:

#!/usr/bin/env tclsh
set sum 0
while {[gets stdin num] >= 0} { incr sum $num }
puts $sum

Select objects based on value of variable in object using jq

I had a similar related question: What if you wanted the original object format back (with key names, e.g. FOO, BAR)?

Jq provides to_entries and from_entries to convert between objects and key-value pair arrays. That along with map around the select

These functions convert between an object and an array of key-value pairs. If to_entries is passed an object, then for each k: v entry in the input, the output array includes {"key": k, "value": v}.

from_entries does the opposite conversion, and with_entries(foo) is a shorthand for to_entries | map(foo) | from_entries, useful for doing some operation to all keys and values of an object. from_entries accepts key, Key, name, Name, value and Value as keys.

jq15 < json 'to_entries | map(select(.value.location=="Stockholm")) | from_entries'

  "FOO": {
    "name": "Donald",
    "location": "Stockholm"
  "BAR": {
    "name": "Walt",
    "location": "Stockholm"

Using the with_entries shorthand, this becomes:

jq15 < json 'with_entries(select(.value.location=="Stockholm"))'
  "FOO": {
    "name": "Donald",
    "location": "Stockholm"
  "BAR": {
    "name": "Walt",
    "location": "Stockholm"

Shell script - remove first and last quote (") from a variable

You can do it with only one call to sed:

$ echo "\"html\\test\\\"" | sed 's/^"\(.*\)"$/\1/'

How to redirect stderr and stdout to different files in the same line in script?

Try this:

your_command 2>stderr.log 1>stdout.log

More information

The numerals 0 through 9 are file descriptors in bash. 0 stands for standard input, 1 stands for standard output, 2 stands for standard error. 3 through 9 are spare for any other temporary usage.

Any file descriptor can be redirected to a file or to another file descriptor using the operator >. You can instead use the operator >> to appends to a file instead of creating an empty one.


file_descriptor > filename

file_descriptor > &file_descriptor

Please refer to Advanced Bash-Scripting Guide: Chapter 20. I/O Redirection.

How to exit a function in bash

Use return operator:

function FUNCT {
  if [ blah is false ]; then
    return 1 # or return 0, or even you can omit the argument.
    keep running the function

Stop on first error

Maybe you want set -e:

This tells bash that it should exit the script if any statement returns a non-true return value. The benefit of using -e is that it prevents errors snowballing into serious issues when they could have been caught earlier. Again, for readability you may want to use set -o errexit.

How do I write a for loop in bash

The bash for consists on a variable (the iterator) and a list of words where the iterator will, well, iterate.

So, if you have a limited list of words, just put them in the following syntax:

for w in word1 word2 word3

Probably you want to iterate along some numbers, so you can use the seq command to generate a list of numbers for you: (from 1 to 100 for example)

seq 1 100

and use it in the FOR loop:

for n in $(seq 1 100)

Note the $(...) syntax. It's a bash behaviour, it allows you to pass the output from one command (in our case from seq) to another (the for)

This is really useful when you have to iterate over all directories in some path, for example:

for d in $(find $somepath -type d)

The possibilities are infinite to generate the lists.

How to generate a core dump in Linux on a segmentation fault?

It's worth mentioning that if you have a systemd set up, then things are a little bit different. The set up typically would have the core files be piped, by means of core_pattern sysctl value, through systemd-coredump(8). The core file size rlimit would typically be configured as "unlimited" already.

It is then possible to retrieve the core dumps using coredumpctl(1).

The storage of core dumps, etc. is configured by coredump.conf(5). There are examples of how to get the core files in the coredumpctl man page, but in short, it would look like this:

Find the core file:

[vps@phoenix]~$ coredumpctl list test_me | tail -1
Sun 2019-01-20 11:17:33 CET   16163  1224  1224  11 present /home/vps/test_me

Get the core file:

[vps@phoenix]~$ coredumpctl -o test_me.core dump 16163

Delete all lines beginning with a # from a file

This answer builds upon the earlier answer by Keith.

egrep -v "^[[:blank:]]*#" should filter out comment lines.

egrep -v "^[[:blank:]]*(#|$)" should filter out both comments and empty lines, as is frequently useful.

For information about [:blank:] and other character classes, refer to

How can I find out a file's MIME type (Content-Type)?

Try the file command with -i option.

-i option Causes the file command to output mime type strings rather than the more traditional human readable ones. Thus it may say text/plain; charset=us-ascii rather than ASCII text.

Check if string is neither empty nor space in shell script

In case you need to check against any amount of whitespace, not just single space, you can do this:

To strip string of extra white space (also condences whitespace in the middle to one space):

trimmed=`echo -- $original`

The -- ensures that if $original contains switches understood by echo, they'll still be considered as normal arguments to be echoed. Also it's important to not put "" around $original, or the spaces will not get removed.

After that you can just check if $trimmed is empty.

[ -z "$trimmed" ] && echo "empty!"

Command not found error in Bash variable assignment

I know this has been answered with a very high-quality answer. But, in short, you cant have spaces.

STR = "Hello World"
echo $STR

Didn't work because of the spaces around the equal sign. If you were to run...

STR="Hello World"
echo $STR

It would work

How do I tell if a regular file does not exist in Bash?


if [ ! -f "$envfile" ]
    echo "$envfile does not exist"
    exit 1

Get exit code for command in bash/ksh

It should be $cmd instead of $($cmd). Works fine with that on my box.

Edit: Your script works only for one-word commands, like ls. It will not work for "ls cpp". For this to work, replace cmd="$1"; $cmd with "$@". And, do not run your script as command="some cmd"; safeRun command, run it as safeRun some cmd.

Also, when you have to debug your bash scripts, execute with '-x' flag. [bash -x].

Create timestamp variable in bash script

And for my fellow Europeans, try using this:

timestamp=$(date +%d-%m-%Y_%H-%M-%S)

will give a format of the format: "15-02-2020_19-21-58"

You call the variable and get the string representation like this


Timeout a command in bash without unnecessary delay

If you already know the name of the program (let's assume program) to terminate after the timeout (as an example 3 seconds), I can contribute a simple and somewhat dirty alternative solution:

(sleep 3 && killall program) & ./program

This works perfectly if I call benchmark processes with system calls.

Run parallel multiple commands at once in the same terminal

This bash script is for N parallel threads. Each argument is a command.

trap will kill all subprocesses when SIGINT is catched.
wait $PID_LIST is waiting each process to complete. When all processes have completed, the program exits.


for cmd in "$@"; do {
  echo "Process \"$cmd\" started";
  $cmd & pid=$!
  PID_LIST+=" $pid";
} done

trap "kill $PID_LIST" SIGINT

echo "Parallel processes have started";

wait $PID_LIST

echo "All processes have completed";

Save this script as parallel_commands and make it executable.
This is how to use this script:

parallel_commands "cmd arg0 arg1 arg2" "other_cmd arg0 arg2 arg3"


parallel_commands "sleep 1" "sleep 2" "sleep 3" "sleep 4"

Start 4 parallel sleep and waits until "sleep 4" finishes.

How do I iterate over a range of numbers defined by variables in Bash?


Using seq is fine, as Jiaaro suggested. Pax Diablo suggested a Bash loop to avoid calling a subprocess, with the additional advantage of being more memory friendly if $END is too large. Zathrus spotted a typical bug in the loop implementation, and also hinted that since i is a text variable, continuous conversions to-and-fro numbers are performed with an associated slow-down.

integer arithmetic

This is an improved version of the Bash loop:

typeset -i i END
let END=5 i=1
while ((i<=END)); do
    echo $i
    let i++

If the only thing that we want is the echo, then we could write echo $((i++)).

ephemient taught me something: Bash allows for ((expr;expr;expr)) constructs. Since I've never read the whole man page for Bash (like I've done with the Korn shell (ksh) man page, and that was a long time ago), I missed that.


typeset -i i END # Let's be explicit
for ((i=1;i<=END;++i)); do echo $i; done

seems to be the most memory-efficient way (it won't be necessary to allocate memory to consume seq's output, which could be a problem if END is very large), although probably not the “fastest”.

the initial question

eschercycle noted that the {a..b} Bash notation works only with literals; true, accordingly to the Bash manual. One can overcome this obstacle with a single (internal) fork() without an exec() (as is the case with calling seq, which being another image requires a fork+exec):

for i in $(eval echo "{1..$END}"); do

Both eval and echo are Bash builtins, but a fork() is required for the command substitution (the $(…) construct).

Convert line endings

Doing this with POSIX is tricky:

  • POSIX Sed does not support \r or \15. Even if it did, the in place option -i is not POSIX

  • POSIX Awk does support \r and \15, however the -i inplace option is not POSIX

  • d2u and dos2unix are not POSIX utilities, but ex is

  • POSIX ex does not support \r, \15, \n or \12

To remove carriage returns:

awk 'BEGIN{RS="^$";ORS="";getline;gsub("\r","");print>ARGV[1]}' file

To add carriage returns:

awk 'BEGIN{RS="^$";ORS="";getline;gsub("\n","\r&");print>ARGV[1]}' file

How to concatenate string variables in Bash

I wanted to build a string from a list. Couldn't find an answer for that so I post it here. Here is what I did:

list=(1 2 3 4 5)

for elm in "${list[@]}"; do
    string="${string} ${elm}"

echo ${string}

and then I get the following output:

1 2 3 4 5

How do I use su to execute the rest of the bash script as that user?

Inspired by the idea from @MarSoft but I changed the lines like the following:

COMMANDARGS="$(printf " %q" "${@}")"
if [ $(whoami) != "$USERNAME" ]; then
  exec sudo -E su $USERNAME -c "/usr/bin/bash -l $COMMAND $COMMANDARGS"

I have used sudo to allow a password less execution of the script. If you want to enter a password for the user, remove the sudo. If you do not need the environment variables, remove -E from sudo.

The /usr/bin/bash -l ensures, that the profile.d scripts are executed for an initialized environment.

How to cd into a directory with space in the name?

$ cd "$DOCS"

You need to quote "$DOCS" to prevent spaces from being parsed as word separators. More often than not, variable references should be quoted.

Note that $HOME would have the same problem. The issue is coming from when the shell evaluates variable references; it's nothing to do with what variables you use or how you assign to them. It's the expansion that needs to be quoted.

$ echo $HOME
/home/my dir

This is deceptive. echo is actually echoing the two strings /home/my and dir. If you use cd or ls you'll see how it's actually working.

$ ls $HOME
ls: cannot access /home/my: No such file or directory
ls: cannot access dir: No such file or directory
$ cd $HOME
bash: cd: /home/my: No such file or directory
$ cd "$HOME"

Can I ask why it works when I manually type it in but not in a variable?

Great question! Let's examine the commands you typed:

$ DOCS="\"/cygdrive/c/Users/my dir/Documents\""
$ echo $DOCS
"/cygdrive/c/Users/my dir/Documents"
$ cd $DOCS
-bash: cd: "/cygdrive/c/Users/my: No such file or directory

The reason this doesn't work is because Bash doesn't parse quotes inside variable expansions. It does perform word splitting, so whitespace in unquoted variable expansions is taken as word separators. It doesn't parse quotes in any way, meaning you can't put double quotes inside a variable to override word splitting.

$ cd $DOCS

Because of this, cd is passed two parameters. As far as cd knows it looks like you wrote:

$ cd '"/cygdrive/c/Users/my' 'dir/Documents"'

Two parameters, with double quotes intact.

How does "cat << EOF" work in bash?


kennytm quoted man bash, but most of that is also POSIX 7: :

The redirection operators "<<" and "<<-" both allow redirection of lines contained in a shell input file, known as a "here-document", to the input of a command.

The here-document shall be treated as a single word that begins after the next and continues until there is a line containing only the delimiter and a , with no characters in between. Then the next here-document starts, if there is one. The format is as follows:


where the optional n represents the file descriptor number. If the number is omitted, the here-document refers to standard input (file descriptor 0).

If any character in word is quoted, the delimiter shall be formed by performing quote removal on word, and the here-document lines shall not be expanded. Otherwise, the delimiter shall be the word itself.

If no characters in word are quoted, all lines of the here-document shall be expanded for parameter expansion, command substitution, and arithmetic expansion. In this case, the in the input behaves as the inside double-quotes (see Double-Quotes). However, the double-quote character ( '"' ) shall not be treated specially within a here-document, except when the double-quote appears within "$()", "``", or "${}".

If the redirection symbol is "<<-", all leading <tab> characters shall be stripped from input lines and the line containing the trailing delimiter. If more than one "<<" or "<<-" operator is specified on a line, the here-document associated with the first operator shall be supplied first by the application and shall be read first by the shell.

When a here-document is read from a terminal device and the shell is interactive, it shall write the contents of the variable PS2, processed as described in Shell Variables, to standard error before reading each line of input until the delimiter has been recognized.


Some examples not yet given.

Quotes prevent parameter expansion

Without quotes:

cat <<EOF



With quotes:

cat <<'EOF'

or (ugly but valid):

cat <<E"O"F



Hyphen removes leading tabs

Without hyphen:

cat <<EOF

where <tab> is a literal tab, and can be inserted with Ctrl + V <tab>



With hyphen:

cat <<-EOF



This exists of course so that you can indent your cat like the surrounding code, which is easier to read and maintain. E.g.:

if true; then
    cat <<-EOF

Unfortunately, this does not work for space characters: POSIX favored tab indentation here. Yikes.

Adding timestamp to a filename with mv in BASH

A single line method within bash works like this.

[some out put] >$(date "+%Y.%m.%d-%H.%M.%S").ver

will create a file with a timestamp name with ver extension. A working file listing snap shot to a date stamp file name as follows can show it working.

find . -type f -exec ls -la {} \; | cut -d ' ' -f 6- >$(date "+%Y.%m.%d-%H.%M.%S").ver

Of course

cat somefile.log > $(date "+%Y.%m.%d-%H.%M.%S").ver

or even simpler

ls > $(date "+%Y.%m.%d-%H.%M.%S").ver

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

Every distribution has a default shell. Bash is the default on the majority of the systems. If you happen to work on a system that has a different default shell, then the scripts might not work as intended if they are written specific for Bash.

Bash has evolved over the years taking code from ksh and sh.

Adding #!/bin/bash as the first line of your script, tells the OS to invoke the specified shell to execute the commands that follow in the script.

#! is often referred to as a "hash-bang", "she-bang" or "sha-bang".

How can I pass a file argument to my bash script using a Terminal command in Linux?

Assuming you do as David Zaslavsky suggests, so that the first argument simply is the program to run (no option-parsing required), you're dealing with the question of how to pass arguments 2 and on to your external program. Here's a convenient way:

"$ext_program" "$@"

The shift will remove the first argument, renaming the rest ($2 becomes $1, and so on).$@` refers to the arguments, as an array of words (it must be quoted!).

If you must have your --file syntax (for example, if there's a default program to run, so the user doesn't necessarily have to supply one), just replace ext_program="$1" with whatever parsing of $1 you need to do, perhaps using getopt or getopts.

If you want to roll your own, for just the one specific case, you could do something like this:

if [ "$#" -gt 0 -a "${1:0:6}" == "--file" ]; then
    ext_program="default program"

ssh script returns 255 error

This is usually happens when the remote is down/unavailable; or the remote machine doesn't have ssh installed; or a firewall doesn't allow a connection to be established to the remote host.

ssh returns 255 when an error occurred or 255 is returned by the remote script:


     ssh exits with the exit status of the remote command or
     with 255 if an error occurred.

Usually you would an error message something similar to:

ssh: connect to host port 22: No route to host


ssh: connect to host HOSTNAME port 22: Connection refused


  • What happens if you run the ssh command directly from the command line?

  • Are you able to ping that machine?

  • Does the remote has ssh installed?

  • If installed, then is the ssh service running?

Bash Shell Script - Check for a flag and grab its value

You should read this getopts tutorial.

Example with -a switch that requires an argument :


while getopts ":a:" opt; do
  case $opt in
      echo "-a was triggered, Parameter: $OPTARG" >&2
      echo "Invalid option: -$OPTARG" >&2
      exit 1
      echo "Option -$OPTARG requires an argument." >&2
      exit 1

Like greybot said(getopt != getopts) :

The external command getopt(1) is never safe to use, unless you know it is GNU getopt, you call it in a GNU-specific way, and you ensure that GETOPT_COMPATIBLE is not in the environment. Use getopts (shell builtin) instead, or simply loop over the positional parameters.

Execute a shell script in current shell with sudo permission

Easiest method is to type:

sudo /bin/sh

Waiting for background processes to finish before exiting script

Even if you do not have the pid, you can trigger 'wait;' after triggering all background processes. For. eg. in

bteq < input_file1.sql > output_file1.sql &
bteq < input_file2.sql > output_file2.sql &
bteq < input_file3.sql > output_file3.sql &

Then when this is triggered, as -['sh', ''])
print('all background processes done.')

This will be printed only after all the background processes are done.

Add line break to 'git commit -m' from the command line

IMO the initial commit message line is supposed to be to short, to the point instead of paragraph. So using git commit -m "<short_message>" will suffice

After that in order to expand upon the initial commit message we can use

git commit --amend

which will open the vim and then we can enter the explanation for the commit message which in my opinion easier than command line.

How can I write a heredoc to a file in Bash script?

If you want to keep the heredoc indented for readability:

$ perl -pe 's/^\s*//' << EOF
     line 1
     line 2

The built-in method for supporting indented heredoc in Bash only supports leading tabs, not spaces.

Perl can be replaced with awk to save a few characters, but the Perl one is probably easier to remember if you know basic regular expressions.

How to tell if a string is not defined in a Bash shell script

Here is what I think is a much clearer way to check if a variable is defined:

var_defined() {
    local var_name=$1
    set | grep "^${var_name}=" 1>/dev/null
    return $?

Use it as follows:

if var_defined foo; then
    echo "foo is defined"
    echo "foo is not defined"

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

I was executing a get request an also want to see just the response and nothing else, seems like magic is done with -silent,-s option.

From the curl man page:

-s, --silent Silent or quiet mode. Don't show progress meter or error messages. Makes Curl mute. It will still output the data you ask for, potentially even to the terminal/stdout unless you redirect it.

Below the examples:

curl -s "http://host:8080/some/resource"
curl -silent "http://host:8080/some/resource"

Using custom headers

curl -s -H "Accept: application/json" "http://host:8080/some/resource")

Using POST method with a header

curl -s -X POST -H "Content-Type: application/json" "http://host:8080/some/resource") -d '{ "myBean": {"property": "value"}}'

You can also customize the output for specific values with -w, below the options I use to get just response codes of the curl:

curl -s -o /dev/null -w "%{http_code}" "http://host:8080/some/resource"

eval command in Bash and its typical uses

I've recently had to use eval to force multiple brace expansions to be evaluated in the order I needed. Bash does multiple brace expansions from left to right, so

xargs -I_ cat _/{11..15}/{8..5}.jpg

expands to

xargs -I_ cat _/11/8.jpg _/11/7.jpg _/11/6.jpg _/11/5.jpg _/12/8.jpg _/12/7.jpg _/12/6.jpg _/12/5.jpg _/13/8.jpg _/13/7.jpg _/13/6.jpg _/13/5.jpg _/14/8.jpg _/14/7.jpg _/14/6.jpg _/14/5.jpg _/15/8.jpg _/15/7.jpg _/15/6.jpg _/15/5.jpg

but I needed the second brace expansion done first, yielding

xargs -I_ cat _/11/8.jpg _/12/8.jpg _/13/8.jpg _/14/8.jpg _/15/8.jpg _/11/7.jpg _/12/7.jpg _/13/7.jpg _/14/7.jpg _/15/7.jpg _/11/6.jpg _/12/6.jpg _/13/6.jpg _/14/6.jpg _/15/6.jpg _/11/5.jpg _/12/5.jpg _/13/5.jpg _/14/5.jpg _/15/5.jpg

The best I could come up with to do that was

xargs -I_ cat $(eval echo _/'{11..15}'/{8..5}.jpg)

This works because the single quotes protect the first set of braces from expansion during the parsing of the eval command line, leaving them to be expanded by the subshell invoked by eval.

There may be some cunning scheme involving nested brace expansions that allows this to happen in one step, but if there is I'm too old and stupid to see it.

How do I fetch lines before/after the grep result in bash?

This prints 10 lines of trailing context after matching lines

grep -i "my_regex" -A 10

If you need to print 10 lines of leading context before matching lines,

grep -i "my_regex" -B 10

And if you need to print 10 lines of leading and trailing output context.

grep -i "my_regex" -C 10


user@box:~$ cat out 
line 1
line 2
line 3
line 4
line 5 my_regex
line 6
line 7
line 8
line 9

Normal grep

user@box:~$ grep my_regex out 
line 5 my_regex

Grep exact matching lines and 2 lines after

user@box:~$ grep -A 2 my_regex out   
line 5 my_regex
line 6
line 7

Grep exact matching lines and 2 lines before

user@box:~$ grep -B 2 my_regex out  
line 3
line 4
line 5 my_regex

Grep exact matching lines and 2 lines before and after

user@box:~$ grep -C 2 my_regex out  
line 3
line 4
line 5 my_regex
line 6
line 7

Reference: manpage grep

-A num

    Print num lines of trailing context after matching lines.
-B num

    Print num lines of leading context before matching lines.
-C num

    Print num lines of leading and trailing output context.

How to replace spaces in file names using a bash script

I use:

for f in *\ *; do mv "$f" "${f// /_}"; done

Though it's not recursive, it's quite fast and simple. I'm sure someone here could update it to be recursive.

The ${f// /_} part utilizes bash's parameter expansion mechanism to replace a pattern within a parameter with supplied string. The relevant syntax is ${parameter/pattern/string}. See: or .

Bash script plugin for Eclipse?

I tried ShellEd, but it wouldn't recognize any of my shell scripts, even when I restarted eclipse. I added the ksh interpreter and made it the default, but it made no diffence.

Finally, I closed the tab that was open and displaying a ksh file, then re-opened it. That made it work correctly. After having used it for a while, I can also recommend it.

Get current time in hours and minutes

you can use command

date | awk '{print $4}'| cut -d ':' -f3

as you mentioned using only the date|awk '{print $4}' pipeline gives you something like this


so as we can see if we want to extract some part of this string then we need a delimiter , for our case it is :, so we decide to chop on the basis of :. Now this delimiter will chop the string into three parts i.e. 20 ,18 and 19 , as we want the second one we use -f2 in our command. to sum up ,

cut : chops some string based on delimeter.

-d : delimeter (here :)

-f2 : the chopped off token that we want.

Relative paths based on file location instead of current working directory

@Martin Konecny's answer provides the correct answer, but - as he mentions - it only works if the actual script is not invoked through a symlink residing in a different directory.

This answer covers that case: a solution that also works when the script is invoked through a symlink or even a chain of symlinks:

Linux / GNU readlink solution:

If your script needs to run on Linux only or you know that GNU readlink is in the $PATH, use readlink -f, which conveniently resolves a symlink to its ultimate target:

 scriptDir=$(dirname -- "$(readlink -f -- "$BASH_SOURCE")")

Note that GNU readlink has 3 related options for resolving a symlink to its ultimate target's full path: -f (--canonicalize), -e (--canonicalize-existing), and -m (--canonicalize-missing) - see man readlink.
Since the target by definition exists in this scenario, any of the 3 options can be used; I've chosen -f here, because it is the most well-known one.

Multi-(Unix-like-)platform solution (including platforms with a POSIX-only set of utilities):

If your script must run on any platform that:

  • has a readlink utility, but lacks the -f option (in the GNU sense of resolving a symlink to its ultimate target) - e.g., macOS.

    • macOS uses an older version of the BSD implementation of readlink; note that recent versions of FreeBSD/PC-BSD do support -f.
  • does not even have readlink, but has POSIX-compatible utilities - e.g., HP-UX (thanks, @Charles Duffy).

The following solution, inspired by, defines helper shell function, rreadlink(), which resolves a given symlink to its ultimate target in a loop - this function is in effect a POSIX-compliant implementation of GNU readlink's -e option, which is similar to the -f option, except that the ultimate target must exist.

Note: The function is a bash function, and is POSIX-compliant only in the sense that only POSIX utilities with POSIX-compliant options are used. For a version of this function that is itself written in POSIX-compliant shell code (for /bin/sh), see here.

  • If readlink is available, it is used (without options) - true on most modern platforms.

  • Otherwise, the output from ls -l is parsed, which is the only POSIX-compliant way to determine a symlink's target.
    Caveat: this will break if a filename or path contains the literal substring -> - which is unlikely, however.
    (Note that platforms that lack readlink may still provide other, non-POSIX methods for resolving a symlink; e.g., @Charles Duffy mentions HP-UX's find utility supporting the %l format char. with its -printf primary; in the interest of brevity the function does NOT try to detect such cases.)

  • An installable utility (script) form of the function below (with additional functionality) can be found as rreadlink in the npm registry; on Linux and macOS, install it with [sudo] npm install -g rreadlink; on other platforms (assuming they have bash), follow the manual installation instructions.

If the argument is a symlink, the ultimate target's canonical path is returned; otherwise, the argument's own canonical path is returned.

#!/usr/bin/env bash

# Helper function.
rreadlink() ( # execute function in a *subshell* to localize the effect of `cd`, ...

  local target=$1 fname targetDir readlinkexe=$(command -v readlink) CDPATH= 

  # Since we'll be using `command` below for a predictable execution
  # environment, we make sure that it has its original meaning.
  { \unalias command; \unset -f command; } &>/dev/null

  while :; do # Resolve potential symlinks until the ultimate target is found.
      [[ -L $target || -e $target ]] || { command printf '%s\n' "$FUNCNAME: ERROR: '$target' does not exist." >&2; return 1; }
      command cd "$(command dirname -- "$target")" # Change to target dir; necessary for correct resolution of target path.
      fname=$(command basename -- "$target") # Extract filename.
      [[ $fname == '/' ]] && fname='' # !! curiously, `basename /` returns '/'
      if [[ -L $fname ]]; then
        # Extract [next] target path, which is defined
        # relative to the symlink's own directory.
        if [[ -n $readlinkexe ]]; then # Use `readlink`.
          target=$("$readlinkexe" -- "$fname")
        else # `readlink` utility not available.
          # Parse `ls -l` output, which, unfortunately, is the only POSIX-compliant 
          # way to determine a symlink's target. Hypothetically, this can break with
          # filenames containig literal ' -> ' and embedded newlines.
          target=$(command ls -l -- "$fname")
          target=${target#* -> }
        continue # Resolve [next] symlink target.
      break # Ultimate target reached.
  targetDir=$(command pwd -P) # Get canonical dir. path
  # Output the ultimate target's canonical path.
  # Note that we manually resolve paths ending in /. and /.. to make sure we
  # have a normalized path.
  if [[ $fname == '.' ]]; then
    command printf '%s\n' "${targetDir%/}"
  elif  [[ $fname == '..' ]]; then
    # Caveat: something like /var/.. will resolve to /private (assuming
    # /var@ -> /private/var), i.e. the '..' is applied AFTER canonicalization.
    command printf '%s\n' "$(command dirname -- "${targetDir}")"
    command printf '%s\n' "${targetDir%/}/$fname"

# Determine ultimate script dir. using the helper function.
# Note that the helper function returns a canonical path.
scriptDir=$(dirname -- "$(rreadlink "$BASH_SOURCE")")

How to have the cp command create any necessary folders for copying a file to a destination

rsync is work!

rsync -aqz _vimrc ~/.vimrc

rsync -aqz _vim/ ~/.vim

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

The extglob shell option gives you more powerful pattern matching in the command line.

You turn it on with shopt -s extglob, and turn it off with shopt -u extglob.

In your example, you would initially do:

$ shopt -s extglob
$ cp !(*Music*) /target_directory

The full available extended globbing operators are (excerpt from man bash):

If the extglob shell option is enabled using the shopt builtin, several extended pattern matching operators are recognized.A pattern-list is a list of one or more patterns separated by a |. Composite patterns may be formed using one or more of the following sub-patterns:

  • ?(pattern-list)
    Matches zero or one occurrence of the given patterns
  • *(pattern-list)
    Matches zero or more occurrences of the given patterns
  • +(pattern-list)
    Matches one or more occurrences of the given patterns
  • @(pattern-list)
    Matches one of the given patterns
  • !(pattern-list)
    Matches anything except one of the given patterns

So, for example, if you wanted to list all the files in the current directory that are not .c or .h files, you would do:

$ ls -d !(*@(.c|.h))

Of course, normal shell globing works, so the last example could also be written as:

$ ls -d !(*.[ch])

check if file exists on remote host with ssh

I wanted also to check if a remote file exist but with RSH. I have tried the previous solutions but they didn't work with RSH.

Finally, I did I short function which works fine:

function existRemoteFile ()
RESULT=$(rsh -l user $REMOTE  "test -e $FILE && echo \"0\" || echo \"1\"")
if [ $RESULT -eq 0 ]
    return 0
    return 1

Bash function to find newest file matching pattern

Unusual filenames (such as a file containing the valid \n character can wreak havoc with this kind of parsing. Here's a way to do it in Perl:

perl -le '@sorted = map {$_->[0]} 
                    sort {$a->[1] <=> $b->[1]} 
                    map {[$_, -M $_]} 
          print $sorted[0]
' b2*

That's a Schwartzian transform used there.

How do I escape double and single quotes in sed?

Regarding the single quote, see the code below used to replace the string let's with let us:


echo "hello, let's go"|sed 's/let'"'"'s/let us/g'


hello, let us go

How to split one text file into multiple *.txt files?

Regardless to what is said above, on my ubuntu 16 i had to do :

> split -b 10M -d  system.log system_split.log 

Please note the space between -b and the value

Replace one substring for another string in shell script

echo [string] | sed "s/[original]/[target]/g"
  • "s" means "substitute"
  • "g" means "global, all matching occurrences"

What are the differences among grep, awk & sed?

I just want to mention a thing, there are many tools can do text processing, e.g. sort, cut, split, join, paste, comm, uniq, column, rev, tac, tr, nl, pr, head, tail.....

they are very handy but you have to learn their options etc.

A lazy way (not the best way) to learn text processing might be: only learn grep , sed and awk. with this three tools, you can solve almost 99% of text processing problems and don't need to memorize above different cmds and options. :)

AND, if you 've learned and used the three, you knew the difference. Actually, the difference here means which tool is good at solving what kind of problem.

a more lazy way might be learning a script language (python, perl or ruby) and do every text processing with it.

Getting the count of unique values in a column in bash

Here is a way to do it in the shell:

cut -f $FIELD * | sort| uniq -c |sort -nr

This is the sort of thing bash is great at.

Copy folder recursively, excluding some folders

Use rsync:

rsync -av --exclude='path1/to/exclude' --exclude='path2/to/exclude' source destination

Note that using source and source/ are different. A trailing slash means to copy the contents of the folder source into destination. Without the trailing slash, it means copy the folder source into destination.

Alternatively, if you have lots of directories (or files) to exclude, you can use --exclude-from=FILE, where FILE is the name of a file containing files or directories to exclude.

--exclude may also contain wildcards, such as --exclude=*/.svn*

An efficient way to transpose a file in Bash

I've used below two scripts to do similar operations before. The first is in awk which is a lot faster than the second which is in "pure" bash. You might be able to adapt it to your own application.

awk '
    for (i = 1; i <= NF; i++) {
        s[i] = s[i]?s[i] FS $i:$i
    for (i in s) {
        print s[i]
}' file.txt
declare -a arr

while IFS= read -r line
    for word in $line
        [[ ${arr[$i]} ]] && arr[$i]="${arr[$i]} $word" || arr[$i]=$word
done < file.txt

for ((i=0; i < ${#arr[@]}; i++))
    echo ${arr[i]}

Checking from shell script if a directory contains files

Try with command find. Specify the directory hardcoded or as argument. Then initiate find to search all files inside the directory. Check if return of find is null. Echo the data of find


_FIND=$(find $_DIR -type f )
if [ -n "$_FIND" ]
   echo -e "$_DIR contains files or subdirs with files \n\n "
   echo "$_FIND"
echo "empty (or does not exist)"

echo that outputs to stderr

My suggestion:

echo "my errz" >> /proc/self/fd/2


echo "my errz" >> /dev/stderr

echo "my errz" > /proc/self/fd/2 will effectively output to stderr because /proc/self is a link to the current process, and /proc/self/fd holds the process opened file descriptors, and then, 0, 1, and 2 stand for stdin, stdout and stderr respectively.

The /proc/self link doesn't work on MacOS, however, /proc/self/fd/* is available on Termux on Android, but not /dev/stderr. How to detect the OS from a Bash script? can help if you need to make your script more portable by determining which variant to use.

How to set aliases in the Git Bash for Windows?

I had the same problem, I can't figured out how to find the aliases used by Git Bash on Windows. After searching for a while, I found the file under C:\Program Files\Git\etc\profile.d\

This is the path under windows 7, maybe can be different in other installation.

Just open it with your preferred editor in admin mode. After save it, reload your command prompt.

I hope this can help!

shell init issue when click tab, what's wrong with getcwd?

Just change the directory to another one and come back. Probably that one has been deleted or moved.

How to get the process ID to kill a nohup process?

This works for mi fine on mac

kill -9 `ps -ef | awk '/nohup/{ print \$2 }'`

Round a divided number in Bash

If you have integer division of positive numbers which rounds toward zero, then you can add one less than the divisor to the dividend to make it round up.

That is to say, replace X / Y with (X + Y - 1) / Y.


  • Case 1: X = k * Y (X is integer multiple of Y): In this case, we have (k * Y + Y - 1) / Y, which splits into (k * Y) / Y + (Y - 1) / Y. The (Y - 1)/Y part rounds to zero, and we are left with a quotient of k. This is exactly what we want: when the inputs are divisible, we want the adjusted calculation to still produce the correct exact quotient.

  • Case 2: X = k * Y + m where 0 < m < Y (X is not a multiple of Y). In this case we have a numerator of k * Y + m + Y - 1, or k * Y + Y + m - 1, and we can write the division out as (k * Y)/Y + Y/Y + (m - 1)/Y. Since 0 < m < Y, 0 <= m - 1 < Y - 1, and so the last term (m - 1)/Y goes to zero. We are left with (k * Y)/Y + Y/Y which work out to k + 1. This shows that the behavior rounds up. If we have an X which is a k multiple of Y, if we add just 1 to it, the division rounds up to k + 1.

But this rounding is extremely opposite; all inexact divisions go away from zero. How about something in between?

That can be achieved by "priming" the numerator with Y/2. Instead of X/Y, calculate (X+Y/2)/Y. Instead of proof, let's go empirical on this one:

$ round()
> {
>   echo $((($1 + $2/2) / $2))
> }
$ round 4 10
$ round 5 10
$ round 6 10
$ round 9 10
$ round 10 10
$ round 14 10
$ round 15 10

Whenever the divisor is an even, positive number, if the numerator is congruent to half that number, it rounds up, and rounds down if it is one less than that.

For instance, round 6 12 goes to 1, as do all values which are equal to 6, modulo 12, like 18 (which goes to 2) and so on. round 5 12 goes down to 0.

For odd numbers, the behavior is correct. None of the exact rational numbers are midway between two consecutive multiples. For instance, with a denominator of 11 we have 5/11 < 5.5/11 (exact middle) < 6/11; and round 5 11 rounds down, whereas round 6 11 rounds up.

How to extract one column of a csv file

I needed proper CSV parsing, not cut / awk and prayer. I'm trying this on a mac without csvtool, but macs do come with ruby, so you can do:

echo "require 'csv';'new.csv').each {|data| puts data[34]}" | ruby

How to use regex in file find

Just little elaboration of regex for search a directory and file

Find a directroy with name like book

find . -name "*book*" -type d

Find a file with name like book word

find . -name "*book*" -type f

How to generate random number in Bash?

A bash function that uses perl to generate a random number of n digits. Specify either the number of digits or a template of n 0s.

rand() {
  perl -E '$ARGV[0]||=""; $ARGV[0]=int($ARGV[0])||length($ARGV[0]); say join "", int(rand(9)+1)*($ARGV[0]?1:0), map { int(rand(10)) } (0..($ARGV[0]||0)-2)' $1


$ rand 3
$ rand 000

Demonstration of calling rand n, for n between 0 and 15:

$ for n in {0..15}; do printf "%02d: %s\n" $n $(rand $n); done
00: 0
01: 3
02: 98
03: 139
04: 1712
05: 49296
06: 426697
07: 2431421
08: 82727795
09: 445682186
10: 6368501779
11: 51029574113
12: 602518591108
13: 5839716875073
14: 87572173490132
15: 546889624135868

Demonstration of calling rand n, for n a template of 0s between length 0 and 15

$ for n in {0..15}; do printf "%15s :%02d: %s\n" $(printf "%0${n}d" 0) $n $(rand $(printf "%0${n}d" 0)); done
              0 :00: 0
              0 :01: 0
             00 :02: 70
            000 :03: 201
           0000 :04: 9751
          00000 :05: 62237
         000000 :06: 262860
        0000000 :07: 1365194
       00000000 :08: 83953419
      000000000 :09: 838521776
     0000000000 :10: 2355011586
    00000000000 :11: 95040136057
   000000000000 :12: 511889225898
  0000000000000 :13: 7441263049018
 00000000000000 :14: 11895209107156
000000000000000 :15: 863219624761093

Extract filename and extension in Bash

I use the following script

$ echo "foo.tar.gz"|rev|cut -d"." -f3-|rev

How do I disable Git Credential Manager for Windows?


C:\Program Files\Git\mingw64\libexec\git-core                                                                       
git credential-manager uninstall --force    

This works on Windows systems. I tested it, and it worked for me.

Convert absolute path into relative path given a current directory using Bash

I would just use Perl for this not-so-trivial task:


# Perl is magic
relative=$(perl -MFile::Spec -e 'print File::Spec->abs2rel("'$absolute'","'$current'")')

redirect COPY of stdout to log file from within bash script itself

Inside your script file, put all of the commands within parentheses, like this:

echo start
ls -l
echo end
) | tee foo.log

How to remove last n characters from a string in Bash?

What worked for me was:

echo "hello world" | rev | cut -c5- | rev
# hello w

But I used it to trim lines in a file so that's why it looks awkward. The real use was:

cat somefile | rev | cut -c5- | rev

cut only gets you as far as trimming from some starting position, which is bad if you need variable length rows. So this solution reverses (rev) the string and now we relate to its ending position, then uses cut as mentioned, and reverses (again, rev) it back to its original order.

Getting a 'source: not found' error when using source in a bash script

If you're writing a bash script, call it by name:


/bin/sh is not guaranteed to be bash. This caused a ton of broken scripts in Ubuntu some years ago (IIRC).

The source builtin works just fine in bash; but you might as well just use dot like Norman suggested.

Find multiple files and rename them in Linux

small script i wrote to replace all files with .txt extension to .cpp extension under /tmp and sub directories recursively


for file in $(find /tmp -name '*.txt')
  mv $file $(echo "$file" | sed -r 's|.txt|.cpp|g')

Open and write data to text file using Bash?



/bin/cat <<EOM >$FILE
text2 # This comment will be inside of the file.
The keyword EOM can be any text, but it must start the line and be alone.
 EOM # This will be also inside of the file, see the space in front of EOM.
EOM # No comments and spaces around here, or it will not work.

How to delete multiple files at once in Bash on Linux?

if you want to delete all files that belong to a directory at once. For example: your Directory name is "log" and "log" directory include abc.log.2012-03-14, abc.log.2012-03-15,... etc files. You have to be above the log directory and:

rm -rf /log/*

How do I remove newlines from a text file?

To also remove the trailing newline at the end of the file

python -c "s=open('filename','r').read();open('filename', 'w').write(s.replace('\n',''))"

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

If the shell scripts start with #!/bin/bash, they will always run with bash from /bin. If they however start with #!/usr/bin/env bash, they will search for bash in $PATH and then start with the first one they can find.

Why would this be useful? Assume you want to run bash scripts, that require bash 4.x or newer, yet your system only has bash 3.x installed and currently your distribution doesn't offer a newer version or you are no administrator and cannot change what is installed on that system.

Of course, you can download bash source code and build your own bash from scratch, placing it to ~/bin for example. And you can also modify your $PATH variable in your .bash_profile file to include ~/bin as the first entry (PATH=$HOME/bin:$PATH as ~ will not expand in $PATH). If you now call bash, the shell will first look for it in $PATH in order, so it starts with ~/bin, where it will find your bash. Same thing happens if scripts search for bash using #!/usr/bin/env bash, so these scripts would now be working on your system using your custom bash build.

One downside is, that this can lead to unexpected behavior, e.g. same script on the same machine may run with different interpreters for different environments or users with different search paths, causing all kind of headaches.

The biggest downside with env is that some systems will only allow one argument, so you cannot do this #!/usr/bin/env <interpreter> <arg>, as the systems will see <interpreter> <arg> as one argument (they will treat it as if the expression was quoted) and thus env will search for an interpreter named <interpreter> <arg>. Note that this is not a problem of the env command itself, which always allowed multiple parameters to be passed through but with the shebang parser of the system that parses this line before even calling env. Meanwhile this has been fixed on most systems but if your script wants to be ultra portable, you cannot rely that this has been fixed on the system you will be running.

It can even have security implications, e.g. if sudo was not configured to clean environment or $PATH was excluded from clean up. Let me demonstrate this:

Usually /bin is a well protected place, only root is able to change anything there. Your home directory is not, though, any program you run is able to make changes to it. That means malicious code could place a fake bash into some hidden directory, modify your .bash_profile to include that directory in your $PATH, so all scripts using #!/usr/bin/env bash will end up running with that fake bash. If sudo keeps $PATH, you are in big trouble.

E.g. consider a tool creates a file ~/.evil/bash with the following content:


if [ $EUID -eq 0 ]; then
  echo "All your base are belong to us..."
  # We are root - do whatever you want to do

/bin/bash "$@"

Let's make a simple script

#!/usr/bin/env bash

echo "Hello World"

Proof of concept (on a system where sudo keeps $PATH):

$ ./
Hello World

$ sudo ./
Hello World

$ export PATH="$HOME/.evil:$PATH"

$ ./
Hello World

$ sudo ./
All your base are belong to us...
Hello World

Usually the classic shells should all be located in /bin and if you don't want to place them there for whatever reason, it's really not an issue to place a symlink in /bin that points to their real locations (or maybe /bin itself is a symlink), so I would always go with #!/bin/sh and #!/bin/bash. There's just too much that would break if these wouldn't work anymore. It's not that POSIX would require these position (POSIX does not standardize path names and thus it doesn't even standardize the shebang feature at all) but they are so common, that even if a system would not offer a /bin/sh, it would probably still understand #!/bin/sh and know what to do with it and may it only be for compatibility with existing code.

But for more modern, non standard, optional interpreters like Perl, PHP, Python, or Ruby, it's not really specified anywhere where they should be located. They may be in /usr/bin but they may as well be in /usr/local/bin or in a completely different hierarchy branch (/opt/..., /Applications/..., etc.). That's why these often use the #!/usr/bin/env xxx shebang syntax.

linux script to kill java process

pkill -f for whatever reason does not work for me. Whatever that does, it seems very finicky about actually grepping through what ps aux shows me clearly is there.

After an afternoon of swearing I went for putting the following in my start script:

(ps aux | grep -v -e 'grep ' | grep MainApp | tr -s " " | cut -d " " -f 2 | xargs kill -9 ) || true

Automatically capture output of last command into a variable using Bash?

The shell doesn't have perl-like special symbols that store the echo result of the last command.

Learn to use the pipe symbol with awk.

find . | awk '{ print "FILE:" $0 }'

In the example above you could do:

find . -name "foo.txt" | awk '{ print "mv "$0" ~/bar/" | "sh" }'

How to define hash tables in Bash?

Just use the file system

The file system is a tree structure that can be used as a hash map. Your hash table will be a temporary directory, your keys will be filenames, and your values will be file contents. The advantage is that it can handle huge hashmaps, and doesn't require a specific shell.

Hashtable creation

hashtable=$(mktemp -d)

Add an element

echo $value > $hashtable/$key

Read an element

value=$(< $hashtable/$key)


Of course, its slow, but not that slow. I tested it on my machine, with an SSD and btrfs, and it does around 3000 element read/write per second.

Variables as commands in bash scripts

eval is not an acceptable practice if your directory names can be generated by untrusted sources. See BashFAQ #48 for more on why eval should not be used, and BashFAQ #50 for more on the root cause of this problem and its proper solutions, some of which are touched on below:

If you need to build up your commands over time, use arrays:

tar_cmd=( tar cv "$directory" )
split_cmd=( split -b 1024m - "$backup_file" )
encrypt_cmd=( openssl des3 -salt )
"${tar_cmd[@]}" | "${encrypt_cmd[@]}" | "${split_cmd[@]}"

Alternately, if this is just about defining your commands in one central place, use functions:

tar_cmd() { tar cv "$directory"; }
split_cmd() { split -b 1024m - "$backup_file"; }
encrypt_cmd() { openssl des3 -salt; }
tar_cmd | split_cmd | encrypt_cmd

Shell script to copy files from one location to another location and rename add the current date to every file

You could use a script like the below. You would just need to change the date options to match the format you wanted.


for i in `ls -l /directroy`
cp $i /newDirectory/$i.`date +%m%d%Y`

Ubuntu says "bash: ./program Permission denied"

chmod u+x program_name. Then execute it.

If that does not work, copy the program from the USB device to a native volume on the system. Then chmod u+x program_name on the local copy and execute that.

Unix and Unix-like systems generally will not execute a program unless it is marked with permission to execute. The way you copied the file from one system to another (or mounted an external volume) may have turned off execute permission (as a safety feature). The command chmod u+x name adds permission for the user that owns the file to execute it.

That command only changes the permissions associated with the file; it does not change the security controls associated with the entire volume. If it is security controls on the volume that are interfering with execution (for example, a noexec option may be specified for a volume in the Unix fstab file, which says not to allow execute permission for files on the volume), then you can remount the volume with options to allow execution. However, copying the file to a local volume may be a quicker and easier solution.

How to declare 2D array in bash

A way to simulate arrays in bash (it can be adapted for any number of dimensions of an array):


## The following functions implement vectors (arrays) operations in bash:
## Definition of a vector <v>:
##      v_0 - variable that stores the number of elements of the vector
##      v_1..v_n, where n=v_0 - variables that store the values of the vector elements

VectorAddElementNext () {
# Vector Add Element Next
# Adds the string contained in variable $2 in the next element position (vector length + 1) in vector $1

    local elem_value
    local vector_length
    local elem_name

    eval elem_value=\"\$$2\"
    eval vector_length=\$$1\_0
    if [ -z "$vector_length" ]; then

    vector_length=$(( vector_length + 1 ))

    eval $elem_name=\"\$elem_value\"
    eval $1_0=$vector_length

VectorAddElementDVNext () {
# Vector Add Element Direct Value Next
# Adds the string $2 in the next element position (vector length + 1) in vector $1

    local elem_value
    local vector_length
    local elem_name

    eval elem_value="$2"
    eval vector_length=\$$1\_0
    if [ -z "$vector_length" ]; then

    vector_length=$(( vector_length + 1 ))

    eval $elem_name=\"\$elem_value\"
    eval $1_0=$vector_length

VectorAddElement () {
# Vector Add Element
# Adds the string contained in the variable $3 in the position contained in $2 (variable or direct value) in the vector $1

    local elem_value
    local elem_position
    local vector_length
    local elem_name

    eval elem_value=\"\$$3\"
    eval vector_length=\$$1\_0
    if [ -z "$vector_length" ]; then

    if [ $elem_position -ge $vector_length ]; then


    eval $elem_name=\"\$elem_value\"
    if [ ! $elem_position -eq 0 ]; then
        eval $1_0=$vector_length

VectorAddElementDV () {
# Vector Add Element
# Adds the string $3 in the position $2 (variable or direct value) in the vector $1

    local elem_value
    local elem_position
    local vector_length
    local elem_name

    eval elem_value="$3"
    eval vector_length=\$$1\_0
    if [ -z "$vector_length" ]; then

    if [ $elem_position -ge $vector_length ]; then


    eval $elem_name=\"\$elem_value\"
    if [ ! $elem_position -eq 0 ]; then
        eval $1_0=$vector_length

VectorPrint () {
# Vector Print
# Prints all the elements names and values of the vector $1 on sepparate lines

    local vector_length

    if [ "$vector_length" = "0" ]; then
        echo "Vector \"$1\" is empty!"
        echo "Vector \"$1\":"
        for ((i=1; i<=$vector_length; i++)); do
            eval echo \"[$i]: \\\"\$$1\_$i\\\"\"
            ###OR: eval printf \'\%s\\\n\' \"[\$i]: \\\"\$$1\_$i\\\"\"

VectorDestroy () {
# Vector Destroy
# Empties all the elements values of the vector $1

    local vector_length

    if [ ! "$vector_length" = "0" ]; then
        for ((i=1; i<=$vector_length; i++)); do
            unset $1_$i
        unset $1_0

### MAIN START ###

## Setting vector 'params' with all the parameters received by the script:
for ((i=1; i<=$#; i++)); do
    eval param="\${$i}"
    VectorAddElementNext params param

# Printing the vector 'params':
VectorPrint params

read temp

## Setting vector 'params2' with the elements of the vector 'params' in reversed order:
if [ -n "$params_0" ]; then
    for ((i=1; i<=$params_0; i++)); do
        VectorAddElement params2 count params_$i

# Printing the vector 'params2':
VectorPrint params2

read temp

## Getting the values of 'params2'`s elements and printing them:
if [ -n "$params2_0" ]; then
    echo "Printing the elements of the vector 'params2':"
    for ((i=1; i<=$params2_0; i++)); do
        eval current_elem_value=\"\$params2\_$i\"
        echo "params2_$i=\"$current_elem_value\""
    echo "Vector 'params2' is empty!"

read temp

## Creating a two dimensional array ('a'):
for ((i=1; i<=10; i++)); do
    VectorAddElement a 0 i
    for ((j=1; j<=8; j++)); do
        value=$(( 8 * ( i - 1 ) + j ))
        VectorAddElementDV a_$i $j $value

## Manually printing the two dimensional array ('a'):
echo "Printing the two-dimensional array 'a':"
if [ -n "$a_0" ]; then
    for ((i=1; i<=$a_0; i++)); do
        eval current_vector_lenght=\$a\_$i\_0
        if [ -n "$current_vector_lenght" ]; then
            for ((j=1; j<=$current_vector_lenght; j++)); do
                eval value=\"\$a\_$i\_$j\"
                printf "$value "
        printf "\n"

### MAIN END ###

Delete files older than 10 days using shell script in Unix

find is the common tool for this kind of task :

find ./my_dir -mtime +10 -type f -delete


  • ./my_dir your directory (replace with your own)
  • -mtime +10 older than 10 days
  • -type f only files
  • -delete no surprise. Remove it to test your find filter before executing the whole command

And take care that ./my_dir exists to avoid bad surprises !

How to update one file in a zip archive

From zip(1):

When given the name of an existing zip archive, zip will replace identically named entries in the zip archive or add entries for new names.

So just use the zip command as you normally would to create a new .zip file containing only that one file, except the .zip filename you specify will be the existing archive.

if, elif, else statement issues in Bash

I would recommend you having a look at the basics of conditioning in bash.

The symbol "[" is a command and must have a whitespace prior to it. If you don't give whitespace after your elif, the system interprets elif[ as a a particular command which is definitely not what you'd want at this time.



In short, edit your code segment to:

elif [ "$seconds" -gt 0 ]

You'd be fine with no compilation errors. Your final code segment should look like this:

if [ "$seconds" -eq 0 ];then
    elif [ "$seconds" -gt 0 ]
       $timezone_string=`printf "%02d:%02d" $seconds/3600 ($seconds/60)%60`
       echo "Unknown parameter"

How to get the start time of a long-running Linux process?

ls -ltrh /proc | grep YOUR-PID-HERE

For example, my Google Chrome's PID is 11583:

ls -l /proc | grep 11583
dr-xr-xr-x  7 adam       adam                     0 2011-04-20 16:34 11583

How to split strings over multiple lines in Bash?

However, if you have indented code, it doesn't work out so well:

    echo "continuation \
>continuation     lines

Try with single quotes and concatenating the strings:

    echo 'continuation' \
>continuation lines

Note: the concatenation includes a whitespace.

vbscript output to console

I came across this post and went back to an approach that I used some time ago which is similar to @MadAntrax's.

The main difference is that it uses a VBScript user-defined class to wrap all the logic for switching to CScript and outputting text to the console, so it makes the main script a bit cleaner.

This assumes that your objective is to stream output to the console, rather than having output go to message boxes.

The cCONSOLE class is below. To use it, include the complete class at the end of your script, and then instantiate it right at the beginning of the script. Here is an example:

    Option Explicit

'// Instantiate the console object, this automatically switches to CSCript if required

'// Now we can use the Consol object to write to and read from the console

    '// Simply write a line
     .print "CSCRIPT Console demo script"

     '// Arguments are passed through correctly, if present
     .Print "Arg count=" & wscript.arguments.count

     '// List all the arguments on the console log
     dim ix
     for ix = 0 to wscript.arguments.count -1
        .print "Arg(" & ix & ")=" & wscript.arguments(ix)

     '// Prompt for some text from the user
     dim sMsg : sMsg = .prompt( "Enter any text:" )

     '// Write out the text in a box
     .Box sMsg

     '// Pause with the message "Hit enter to continue"

End With     

'= =========== End of script - the cCONSOLE class code follows here

Here is the code for the cCONSOLE class

 '= =================================================================
 '=    This class provides automatic switch to CScript and has methods
 '=    to write to and read from the CSCript console. It transparently
 '=    switches to CScript if the script has been started in WScript.
 '= =================================================================

    Private oOUT
    Private oIN

    Private Sub Class_Initialize()
    '= Run on creation of the cCONSOLE object, checks for cScript operation

        '= Check to make sure we are running under CScript, if not restart
        '= then run using CScript and terminate this instance.
        dim oShell
        set oShell = CreateObject("WScript.Shell")

        If InStr( LCase( WScript.FullName ), "cscript.exe" ) = 0 Then
            '= Not running under CSCRIPT

            '= Get the arguments on the command line and build an argument list
            dim ArgList, IX
            ArgList = ""

            For IX = 0 to wscript.arguments.count - 1
                '= Add the argument to the list, enclosing it in quotes
                argList = argList & " """ & wscript.arguments.item(IX) & """"

            '= Now restart with CScript and terminate this instance
            oShell.Run "cscript.exe //NoLogo """ & WScript.ScriptName & """ " & arglist

        End If

        '= Running under CScript so OK to continue
        set oShell = Nothing

        '= Save references to stdout and stdin for use with Print, Read and Prompt
        set oOUT = WScript.StdOut
        set oIN = WScript.StdIn

        '= Print out the startup box 
            BoxLine Wscript.ScriptName
            BoxLine "Started at " & Now()

    End Sub

    '= Utility methods for writing a box to the console with text in it

            Public Sub StartBox()

                Print "  " & String(73, "_") 
                Print " |" & Space(73) & "|"
            End Sub

            Public Sub BoxLine(sText)

                Print Left(" |" & Centre( sText, 74) , 75) & "|"
            End Sub

            Public Sub EndBox()
                Print " |" & String(73, "_") & "|"
                Print ""
            End Sub

            Public Sub Box(sMsg)
                BoxLine sMsg
            End Sub

    '= END OF Box utility methods

            '= Utility to center given text padded out to a certain width of text
            '= assuming font is monospaced
            Public Function Centre(sText, nWidth)
                dim iLen
                iLen = len(sText)

                '= Check for overflow
                if ilen > nwidth then Centre = sText : exit Function

                '= Calculate padding either side
                iLen = ( nWidth - iLen ) / 2

                '= Generate text with padding
                Centre = left( space(iLen) & sText & space(ilen), nWidth )
            End Function

    '= Method to write a line of text to the console
    Public Sub Print( sText )

        oOUT.WriteLine sText
    End Sub

    '= Method to prompt user input from the console with a message
    Public Function Prompt( sText )
        oOUT.Write sText
        Prompt = Read()
    End Function

    '= Method to read input from the console with no prompting
    Public Function Read()
        Read = oIN.ReadLine
    End Function

    '= Method to provide wait for n seconds
    Public Sub Wait(nSeconds)
        WScript.Sleep  nSeconds * 1000 
    End Sub

    '= Method to pause for user to continue
    Public Sub Pause
        Prompt "Hit enter to continue..."
    End Sub


Mockito: Mock private field initialization

Mockito comes with a helper class to save you some reflection boiler plate code:

import org.mockito.internal.util.reflection.Whitebox;


private Person mockedPerson;
private Test underTest;

// ...

public void testMethod() {
    Whitebox.setInternalState(underTest, "person", mockedPerson);
    // ...

Update: Unfortunately the mockito team decided to remove the class in Mockito 2. So you are back to writing your own reflection boilerplate code, use another library (e.g. Apache Commons Lang), or simply pilfer the Whitebox class (it is MIT licensed).

Update 2: JUnit 5 comes with its own ReflectionSupport and AnnotationSupport classes that might be useful and save you from pulling in yet another library.

How to style icon color, size, and shadow of Font Awesome Icons

text-shadow: 1px 1px 3px rgba(0,0,0,0.5);

How to suppress Pandas Future warning ?

@bdiamante's answer may only partially help you. If you still get a message after you've suppressed warnings, it's because the pandas library itself is printing the message. There's not much you can do about it unless you edit the Pandas source code yourself. Maybe there's an option internally to suppress them, or a way to override things, but I couldn't find one.

For those who need to know why...

Suppose that you want to ensure a clean working environment. At the top of your script, you put pd.reset_option('all'). With Pandas 0.23.4, you get the following:

>>> import pandas as pd
>>> pd.reset_option('all')
html.border has been deprecated, use display.html.border instead
(currently both are identical)

C:\projects\stackoverflow\venv\lib\site-packages\pandas\core\ FutureWarning: html.bord
er has been deprecated, use display.html.border instead
(currently both are identical)

  warnings.warn(d.msg, FutureWarning)

: boolean
    use_inf_as_null had been deprecated and will be removed in a future
    version. Use `use_inf_as_na` instead.

C:\projects\stackoverflow\venv\lib\site-packages\pandas\core\ FutureWarning:
: boolean
    use_inf_as_null had been deprecated and will be removed in a future
    version. Use `use_inf_as_na` instead.

  warnings.warn(d.msg, FutureWarning)


Following the @bdiamante's advice, you use the warnings library. Now, true to it's word, the warnings have been removed. However, several pesky messages remain:

>>> import warnings
>>> warnings.simplefilter(action='ignore', category=FutureWarning)
>>> import pandas as pd
>>> pd.reset_option('all')
html.border has been deprecated, use display.html.border instead
(currently both are identical)

: boolean
    use_inf_as_null had been deprecated and will be removed in a future
    version. Use `use_inf_as_na` instead.


In fact, disabling all warnings produces the same output:

>>> import warnings
>>> warnings.simplefilter(action='ignore', category=Warning)
>>> import pandas as pd
>>> pd.reset_option('all')
html.border has been deprecated, use display.html.border instead
(currently both are identical)

: boolean
    use_inf_as_null had been deprecated and will be removed in a future
    version. Use `use_inf_as_na` instead.


In the standard library sense, these aren't true warnings. Pandas implements its own warnings system. Running grep -rn on the warning messages shows that the pandas warning system is implemented in core/

$ grep -rn "html.border has been deprecated"
core/ has been deprecated, use display.html.border instead

Further chasing shows that I don't have time for this. And you probably don't either. Hopefully this saves you from falling down the rabbit hole or perhaps inspires someone to figure out how to truly suppress these messages!

How can I programmatically check whether a keyboard is present in iOS app?

Add an extension

extension UIApplication {
    /// Checks if view hierarchy of application contains `UIRemoteKeyboardWindow` if it does, keyboard is presented
    var isKeyboardPresented: Bool {
        if let keyboardWindowClass = NSClassFromString("UIRemoteKeyboardWindow"),
   { $0.isKind(of: keyboardWindowClass) }) {
            return true
        } else {
            return false

Then check if keyboard is present,

if UIApplication.shared.isKeyboardPresented {
     print("Keyboard presented")
} else { 
     print("Keyboard is not presented")

How do I display a text file content in CMD?

There is no built in option available with Windows. To constantly monitor logs you can use this free application BareTailPro.

Javascript regular expression password validation having special characters

it,s work perfect for me and i am sure will work for you guys checkout it easy and accurate

var regix = new RegExp("^(?=.*[a-z])(?=.*[A-Z])(?=.*[0-9])(?=.*[!@#\$%\^&\*])(?=. 

if(regix.test(password) == false ) {
     $('.messageBox').html(`<div class="messageStackError">
       password must be a minimum of 8 characters including number, Upper, Lower And 
       one special character

How to use SQL Order By statement to sort results case insensitive?

You can just convert everything to lowercase for the purposes of sorting:


If you want to make sure that the uppercase ones still end up ahead of the lowercase ones, just add that as a secondary sort:


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

There's a simple way (a trick, I guess) to remember which notation means what.

All of the Big-O notations can be considered to have a bar.

When looking at a O, the bar is at the bottom, so it is an (asymptotic) lower bound.

When looking at a T, the bar is obviously in the middle. So it is an (asymptotic) tight bound.

When handwriting O, you usually finish at the top, and draw a squiggle. Therefore O(n) is the upper bound of the function. To be fair, this one doesn't work with most fonts, but it is the original justification of the names.

Converting Secret Key into a String and Vice Versa

try this, it's work without Base64 ( that is included only in JDK 1.8 ), this code run also in the previous java version :)

private static String SK = "Secret Key in HEX";

//  To Encrupt

public static String encrypt( String Message ) throws Exception{

    byte[] KeyByte = hexStringToByteArray( SK);
    SecretKey k = new SecretKeySpec(KeyByte, 0, KeyByte.length, "DES");

    Cipher c = Cipher.getInstance("DES","SunJCE");
    c.init(1, k);
    byte mes_encrypted[] = cipher.doFinal(Message.getBytes());

    String MessageEncrypted = byteArrayToHexString(mes_encrypted);
    return MessageEncrypted;

//  To Decrypt

public static String decrypt( String MessageEncrypted )throws Exception{

    byte[] KeyByte = hexStringToByteArray( SK );
    SecretKey k = new SecretKeySpec(KeyByte, 0, KeyByte.length, "DES");

    Cipher dcr =  Cipher.getInstance("DES","SunJCE");
    dc.init(Cipher.DECRYPT_MODE, k);
    byte[] MesByte  = hexStringToByteArray( MessageEncrypted );
    byte mes_decrypted[] = dcipher.doFinal( MesByte );
    String MessageDecrypeted = new String(mes_decrypted);

    return MessageDecrypeted;

public static String byteArrayToHexString(byte bytes[]){

    StringBuffer hexDump = new StringBuffer();
    for(int i = 0; i < bytes.length; i++){
    if(bytes[i] < 0)
        hexDump.append(getDoubleHexValue(Integer.toHexString(256 - Math.abs(bytes[i]))).toUpperCase());
    return hexDump.toString();


public static byte[] hexStringToByteArray(String s) {

    int len = s.length();
    byte[] data = new byte[len / 2];
    for (int i = 0; i < len; i += 2)
        data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4) + Character.digit(s.charAt(i+1), 16));
    return data;


Log4j, configuring a Web App to use a relative path

If you use Spring you can:

1) create a log4j configuration file, e.g. "/WEB-INF/classes/" DO NOT name it ""


log4j.rootLogger=ERROR, stdout, rollingFile

log4j.appender.stdout.layout.ConversionPattern=%d %p [%c] - <%m>%n

log4j.appender.rollingFile.layout.ConversionPattern=%d %p [%c] - %m%n

We'll define "myWebapp-instance-root" later on point (3)

2) Specify config location in web.xml:


3) Specify a unique variable name for your webapp's root, e.g. "myWebapp-instance-root"


4) Add a Log4jConfigListener:


If you choose a different name, remember to change it in, too.

See my article (Italian only... but it should be understandable):

UPDATE (2009/08/01) I've translated my article to English:

excel - if cell is not blank, then do IF statement

You need to use AND statement in your formula


And if both conditions are met, return 1.

You could also add more conditions in your AND statement.

HttpServletRequest - Get query string parameters, no form data

Contrary to what cularis said there can be both in the parameter map.

The best way I see is to proxy the parameterMap and for each parameter retrieval check if queryString contains "&?<parameterName>=".

Note that parameterName needs to be URL encoded before this check can be made, as Qerub pointed out.

That saves you the parsing and still gives you only URL parameters.

SFTP in Python? (platform independent)

Here is a sample using pysftp and a private key.

import pysftp

def upload_file(file_path):

    private_key = "~/.ssh/your-key.pem"  # can use password keyword in Connection instead
    srv = pysftp.Connection(host="your-host", username="user-name", private_key=private_key)
    srv.chdir('/var/web/public_files/media/uploads')  # change directory on remote server
    srv.put(file_path)  # To download a file, replace put with get
    srv.close()  # Close connection

pysftp is an easy to use sftp module that utilizes paramiko and pycrypto. It provides a simple interface to sftp.. Other things that you can do with pysftp which are quite useful:

data = srv.listdir()  # Get the directory and file listing in a list
srv.get(file_path)  # Download a file from remote server
srv.execute('pwd') # Execute a command on the server

More commands and about PySFTP here.

What is ViewModel in MVC?

If you have properties specific to the view, and not related to the DB/Service/Data store, it is a good practice to use ViewModels. Say, you want to leave a checkbox selected based on a DB field (or two) but the DB field itself isn't a boolean. While it is possible to create these properties in the Model itself and keep it hidden from the binding to data, you may not want to clutter the Model depending on the amount of such fields and transactions.

If there are too few view-specific data and/or transformations, you can use the Model itself

How would you implement an LRU cache in Java?

Another thought and even a simple implementation using LinkedHashMap collection of Java.

LinkedHashMap provided method removeEldestEntry and which can be overridden in the way mentioned in example. By default implementation of this collection structure is false. If its true and size of this structure goes beyond the initial capacity than eldest or older elements will be removed.

We can have a pageno and page content in my case pageno is integer and pagecontent i have kept page number values string.

import java.util.LinkedHashMap;
import java.util.Map;

 * @author Deepak Singhvi
public class LRUCacheUsingLinkedHashMap {

     private static int CACHE_SIZE = 3;
     public static void main(String[] args) {
        System.out.println(" Pages for consideration : 2, 1, 0, 2, 8, 2, 4,99");

// accessOrder is true, so whenever any page gets changed or accessed,    // its order will change in the map, 
              LinkedHashMap<Integer,String> lruCache = new              
                 LinkedHashMap<Integer,String>(CACHE_SIZE, .75F, true) {

           private static final long serialVersionUID = 1L;

           protected boolean removeEldestEntry(Map.Entry<Integer,String>                           

                     eldest) {
                          return size() > CACHE_SIZE;


  lruCache.put(2, "2");
  lruCache.put(1, "1");
  lruCache.put(0, "0");
  System.out.println(lruCache + "  , After first 3 pages in cache");
  lruCache.put(2, "2");
  System.out.println(lruCache + "  , Page 2 became the latest page in the cache");
  lruCache.put(8, "8");
  System.out.println(lruCache + "  , Adding page 8, which removes eldest element 2 ");
  lruCache.put(2, "2");
  System.out.println(lruCache+ "  , Page 2 became the latest page in the cache");
  lruCache.put(4, "4");
  System.out.println(lruCache+ "  , Adding page 4, which removes eldest element 1 ");
  lruCache.put(99, "99");
  System.out.println(lruCache + " , Adding page 99, which removes eldest element 8 ");



Result of above code execution is as follows:

 Pages for consideration : 2, 1, 0, 2, 8, 2, 4,99
    {2=2, 1=1, 0=0}  , After first 3 pages in cache
    {2=2, 1=1, 0=0}  , Page 2 became the latest page in the cache
    {1=1, 0=0, 8=8}  , Adding page 8, which removes eldest element 2 
    {0=0, 8=8, 2=2}  , Page 2 became the latest page in the cache
    {8=8, 2=2, 4=4}  , Adding page 4, which removes eldest element 1 
    {2=2, 4=4, 99=99} , Adding page 99, which removes eldest element 8 

How to view query error in PDO PHP

I'm guessing that your complaint is that the exception is not firing. PDO is most likely configured to not throw exceptions. Enable them with this:


What are all the common ways to read a file in Ruby?

An even more efficient way is streaming by asking the operating system’s kernel to open a file, then read bytes from it bit by bit. When reading a file per line in Ruby, data is taken from the file 512 bytes at a time and split up in “lines” after that.

By buffering the file’s content, the number of I/O calls is reduced while dividing the file in logical chunks.


Add this class to your app as a service object:

class MyIO
  def initialize(filename)
    fd = IO.sysopen(filename)
    @io =
    @buffer = ""

  def each(&block)
    @buffer << @io.sysread(512) until @buffer.include?($/)

    line, @buffer = @buffer.split($/, 2)
  rescue EOFError

Call it and pass the :each method a block:

filename = './somewhere/large-file-4gb.txt'{|x| puts x }

Read about it here in this detailed post:

Ruby Magic Slurping & Streaming Files By AppSignal

Coding Conventions - Naming Enums

As already stated, enum instances should be uppercase according to the docs on the Oracle website (

However, while looking through a JavaEE7 tutorial on the Oracle website (, I stumbled across the "Duke's bookstore" tutorial and in a class (tutorial\examples\case-studies\dukes-bookstore\src\main\java\javaeetutorial\dukesbookstore\components\, I found the following enum definition:

private enum PropertyKeys {
    alt, coords, shape, targetImage;

According to the conventions, it should have looked like:

public enum PropertyKeys {
    ALT("alt"), COORDS("coords"), SHAPE("shape"), TARGET_IMAGE("targetImage");

    private final String val;

    private PropertyKeys(String val) {
        this.val = val;

    public String toString() {
        return val;

So it seems even the guys at Oracle sometimes trade convention with convenience.

Model backing a DB Context has changed; Consider Code First Migrations

Easiest and Safest Method If you know that you really want to change/update your data structure so that the database can sync with your DBContext, The safest way is to:

  1. Open up your Package Manager Console
  2. Type: update-database -verbose -force

This tells EF to make changes to your database so that it matches your DBContext data structure

What is copy-on-write?

I shall not repeat the same answer on Copy-on-Write. I think Andrew's answer and Charlie's answer have already made it very clear. I will give you an example from OS world, just to mention how widely this concept is used.

We can use fork() or vfork() to create a new process. vfork follows the concept of copy-on-write. For example, the child process created by vfork will share the data and code segment with the parent process. This speeds up the forking time. It is expected to use vfork if you are performing exec followed by vfork. So vfork will create the child process which will share data and code segment with its parent but when we call exec, it will load up the image of a new executable in the address space of the child process.

When to use RabbitMQ over Kafka?

I hear this question every week... While RabbitMQ (like IBM MQ or JMS or other messaging solutions in general) is used for traditional messaging, Apache Kafka is used as streaming platform (messaging + distributed storage + processing of data). Both are built for different use cases.

You can use Kafka for "traditional messaging", but not use MQ for Kafka-specific scenarios.

The article “Apache Kafka vs. Enterprise Service Bus (ESB)—Friends, Enemies, or Frenemies? (” discusses why Kafka is not competitive but complementary to integration and messaging solutions (including RabbitMQ) and how to integrate both.


First you most get record count from

 Declare @TableRowsCount Int
 select @TableRowsCount= COUNT(*) from <Your_Table>

And then :

In SQL Server 2012

FROM  <Your_Table> As L
ORDER BY L.<your Field>
OFFSET <@TableRowsCount-@N> ROWS

In SQL Server 2008

FROM  <Your_Table>
    Order By <your Field>
) AS TempTable
WHERE sequencenumber > @TableRowsCount-@N 

Writing MemoryStream to Response Object

First We Need To Write into our Memory Stream and then with the help of Memory Stream method "WriteTo" we can write to the Response of the Page as shown in the below code.

   MemoryStream filecontent = null;
   filecontent =//CommonUtility.ExportToPdf(inputXMLtoXSLT);(This will be your MemeoryStream Content)
   Response.ContentType = "image/pdf";
   string headerValue = string.Format("attachment; filename={0}", formName.ToUpper() + ".pdf");
   Response.AppendHeader("Content-Disposition", headerValue);



FormName is the fileName given,This code will make the generated PDF file downloadable by invoking a PopUp.

Converting JSON to XLS/CSV in Java

A JSON document basically consists of lists and dictionaries. There is no obvious way to map such a datastructure on a two-dimensional table.

How would I access variables from one class to another?

Can you explain why you want to do this?

You're playing around with instance variables/attributes which won't migrate from one class to another (they're bound not even to ClassA, but to a particular instance of ClassA that you created when you wrote ClassA()). If you want to have changes in one class show up in another, you can use class variables:

class ClassA(object):
   var1 = 1
   var2 = 2
   def method(cls):
       cls.var1 = cls.var1 + cls.var2
       return cls.var1

In this scenario, ClassB will pick up the values on ClassA from inheritance. You can then access the class variables via ClassA.var1, ClassB.var1 or even from an instance ClassA().var1 (provided that you haven't added an instance method var1 which will be resolved before the class variable in attribute lookup.

I'd have to know a little bit more about your particular use case before I know if this is a course of action that I would actually recommend though...

Handling Enter Key in Vue.js

You forget a '}' before the last line (to close the "methods {...").

This code works :

Vue.config.keyCodes.atsign = 50;_x000D_
new Vue({_x000D_
  el: '#myApp',_x000D_
  data: {_x000D_
    emailAddress: '',_x000D_
    log: ''_x000D_
  methods: {_x000D_
    onEnterClick: function() {_x000D_
     alert('Enter was pressed');_x000D_
    onAtSignClick: function() {_x000D_
     alert('@ was pressed');_x000D_
    postEmailAddress: function() {_x000D_
   this.log += '\n\nPosting';_x000D_
html, body, #editor {_x000D_
  margin: 0;_x000D_
  height: 100%;_x000D_
  color: #333;_x000D_
<script src=""></script>_x000D_
<div id="myApp" style="padding:2rem; background-color:#fff;">_x000D_
  <input type="text" v-model="emailAddress" v-on:keyup.enter="onEnterClick" v-on:keyup.atsign="onAtSignClick" />_x000D_
  <button type="button" v-on:click="postEmailAddress" >Subscribe</button> _x000D_
  <br /><br />_x000D_
  <textarea v-model="log" rows="4"></textarea>_x000D_

How to integrate sourcetree for gitlab

I ended up using GitKraken . I've installed, auth and connected to my repo in 30 seconds.

C# - Simplest way to remove first occurrence of a substring from another string

string myString = sourceString.Remove(sourceString.IndexOf(removeString),removeString.Length);

EDIT: @OregonGhost is right. I myself would break the script up with conditionals to check for such an occurence, but I was operating under the assumption that the strings were given to belong to each other by some requirement. It is possible that business-required exception handling rules are expected to catch this possibility. I myself would use a couple of extra lines to perform conditional checks and also to make it a little more readable for junior developers who may not take the time to read it thoroughly enough.

User Get-ADUser to list all properties and export to .csv

@AnsgarWiechers - it's not my experience that querying everything and then pruning the result is more efficient when you're doing a targeted search of known accounts. Although, yes, it is also more efficient to select just the properties you need to return.

The below examples are based on a domain in the range of 20,000 account objects.

measure-command {Get-ADUser -Filter '*' -Properties DisplayName,st }
Seconds           : 16
Milliseconds      : 208

measure-command {$userlist | get-aduser -Properties DisplayName,st}
Seconds           : 3
Milliseconds      : 496

In the second example, $userlist contains 368 account names (just strings, not pre-fetched account objects).

Note that if I include the where clause per your suggestion to prune to the actually desired results, it's even more expensive.

measure-command {Get-ADUser -Filter '*' -Properties DisplayName,st |where {$userlist -Contains $_.samaccountname } }
Seconds           : 17
Milliseconds      : 876

Indexed attributes seem to have similar performance (I tried just returning displayName).

Even if I return all user account properties in my set, it's more efficient. (Adding a select statement to the below brings it down by a half-second).

measure-command {$userlist | get-aduser -Properties *}
Seconds           : 12
Milliseconds      : 75

I can't find a good document that was written in ye olde days about AD queries to link to, but you're hitting every account in your search scope to return the properties. This discusses the basics of doing effective AD queries - scoping and filtering:

When your search scope is "*", you're still building a (big) list of the objects and iterating through each one. An LDAP search filter is always more efficient to build the list first (or a narrow search base, which is again building a smaller list to query).

CertPathValidatorException : Trust anchor for certificate path not found - Retrofit Android

After a long reserch and digging too deep i found the solution of certificate pinning in android and yes its different from iOS where we need a certificate itself but in android we just need a hash pin and that's it.

How to get hash pin for certificate?

Initially just use a wrong hash pin and your java class will throw an error with correct hash pins or pin chain, just copy and paste into your code thats it.

This solution fixed my problem :

Postman Chrome: What is the difference between form-data, x-www-form-urlencoded and raw

This explains better: Postman docs

Request body

While constructing requests, you would be dealing with the request body editor a lot. Postman lets you send almost any kind of HTTP request (If you can't send something, let us know!). The body editor is divided into 4 areas and has different controls depending on the body type.


multipart/form-data is the default encoding a web form uses to transfer data. This simulates filling a form on a website, and submitting it. The form-data editor lets you set key/value pairs (using the key-value editor) for your data. You can attach files to a key as well. Do note that due to restrictions of the HTML5 spec, files are not stored in history or collections. You would have to select the file again at the time of sending a request.


This encoding is the same as the one used in URL parameters. You just need to enter key/value pairs and Postman will encode the keys and values properly. Note that you can not upload files through this encoding mode. There might be some confusion between form-data and urlencoded so make sure to check with your API first.


A raw request can contain anything. Postman doesn't touch the string entered in the raw editor except replacing environment variables. Whatever you put in the text area gets sent with the request. The raw editor lets you set the formatting type along with the correct header that you should send with the raw body. You can set the Content-Type header manually as well. Normally, you would be sending XML or JSON data here.


binary data allows you to send things which you can not enter in Postman. For example, image, audio or video files. You can send text files as well. As mentioned earlier in the form-data section, you would have to reattach a file if you are loading a request through the history or the collection.


As pointed out by VKK, the WHATWG spec say urlencoded is the default encoding type for forms.

The invalid value default for these attributes is the application/x-www-form-urlencoded state. The missing value default for the enctype attribute is also the application/x-www-form-urlencoded state.

Can't perform a React state update on an unmounted component

I had a similar problem and solved it :

I was automatically making the user logged-in by dispatching an action on redux ( placing authentication token on redux state )

and then I was trying to show a message with this.setState({succ_message: "...") in my component.

Component was looking empty with the same error on console : "unmounted component".."memory leak" etc.

After I read Walter's answer up in this thread

I've noticed that in the Routing table of my application , my component's route wasn't valid if user is logged-in :

{!this.props.user.token &&
            <Route path="/register/:type" exact component={MyComp} />                                             

I made the Route visible whether the token exists or not.

Android - Package Name convention

Com = commercial application (just like .com, most people register their app as a com app)
First level = always the publishing entity's' name
Second level (optional) = sub-devison, group, or project name
Final level = product name

For example he android launcher (home screen) is

What is the simplest way to convert a Java string from all caps (words separated by underscores) to CamelCase (no word separators)?

You can Try this also :

 public static String convertToNameCase(String s)
        if (s != null)
            StringBuilder b = new StringBuilder();
            String[] split = s.split(" ");
            for (String srt : split)
                if (srt.length() > 0)
                    b.append(srt.substring(0, 1).toUpperCase()).append(srt.substring(1).toLowerCase()).append(" ");
            return b.toString().trim();
        return s;

Provisioning Profiles menu item missing from Xcode 5

Xcode 5 lost my Mac Provisioning Profile while the one for iOS was present. The tips elsewhere helped solve the problem; this is what I did, because I noticed the lists were too short and did not include *Mac Team Provisioning Profile: **

  1. Xcode menu => Preferences => Accounts
  2. Select the Apple ID in the left panel.
  3. Click the View Details button on the right.
  4. In the pop-over that follows click the round refresh arrow. The lists will refresh after the download from the Member Center finishes. This can take a few minutes.
  5. The provisioning profiles can then be selected in a Mac project under Build Settings => Code Signing => Provisioning Profile.

How to get time (hour, minute, second) in Swift 3 using NSDate?

For best useful I create this function:

func dateFormatting() -> String {
    let date = Date()
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "EEEE dd MMMM yyyy - HH:mm:ss"//"EE" to get short style
    let mydt = dateFormatter.string(from: date).capitalized

    return "\(mydt)"

You simply call it wherever you want like this:

print("Date = \(self.dateFormatting())")

this is the Output:

Date = Monday 15 October 2018 - 17:26:29

if want only the time simply change :

dateFormatter.dateFormat  = "HH:mm:ss"

and this is the output:

Date = 17:27:30

and that's it...

What does a circled plus mean?

It is XOR. Another name for the XOR function is addition without carry. I suppose that's how the symbol might make sense.

Why is Node.js single threaded?

Long story short, node draws from V8, which is internally single-threaded. There are ways to work around the constraints for CPU-intensive tasks.

At one point (0.7) the authors tried to introduce isolates as a way of implementing multiple threads of computation, but were ultimately removed:!msg/nodejs/zLzuo292hX0/F7gqfUiKi2sJ

Loop through columns and add string lengths as new columns

For the sake of completeness, there is also a data.table solution:

result <- setDT(df)[, paste0(names(df), "_length") := lapply(.SD, stringr::str_length)]
#      col1     col2 col1_length col2_length
#1:     abc adf qqwe           3           8
#2:    abcd        d           4           1
#3:       a        e           1           1
#4: abcdefg        f           7           1

How to increase Neo4j's maximum file open limit (ulimit) in Ubuntu?

You could alter the init script for neo4j to do a ulimit -n 40000 before running neo4j.

However, I can't help but feel you are barking up the wrong tree. Does neo4j legitimately need more than 10,000 open file descriptors? This sounds very much like a bug in neo4j or the way you are using it. I would try to address that.

How to update Identity Column in SQL Server?

INSERT INTO dbo.TableName 
    TableId, ColumnName1, ColumnName2, ColumnName3
    TableId_Value, ColumnName1_Value, ColumnName2_Value, ColumnName3_Value


When using Identity_Insert don't forget to include the column names because sql will not allow you to insert without specifying them

How to clear or stop timeInterval in angularjs?

var interval = $interval(function() {
  console.log('say hello');
}, 1000);


How to encrypt/decrypt data in php?

It took me quite a while to figure out, how to not get a false when using openssl_decrypt() and get encrypt and decrypt working.

    // cryptographic key of a binary string 16 bytes long (because AES-128 has a key size of 16 bytes)
    $encryption_key = '58adf8c78efef9570c447295008e2e6e'; // example
    $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length('aes-256-cbc'));
    $encrypted = openssl_encrypt($plaintext, 'aes-256-cbc', $encryption_key, OPENSSL_RAW_DATA, $iv);
    $encrypted = $encrypted . ':' . base64_encode($iv);

    // decrypt to get again $plaintext
    $parts = explode(':', $encrypted);
    $decrypted = openssl_decrypt($parts[0], 'aes-256-cbc', $encryption_key, OPENSSL_RAW_DATA, base64_decode($parts[1])); 

If you want to pass the encrypted string via a URL, you need to urlencode the string:

    $encrypted = urlencode($encrypted);

To better understand what is going on, read:

To generate 16 bytes long keys you can use:

    $bytes = openssl_random_pseudo_bytes(16);
    $hex = bin2hex($bytes);

To see error messages of openssl you can use: echo openssl_error_string();

Hope that helps.

How do I create a comma delimited string from an ArrayList?

Yes, I'm answering my own question, but I haven't found it here yet and thought this was a rather slick thing: VB.NET:

String.Join(",", CType(TargetArrayList.ToArray(Type.GetType("System.String")), String())) C#

string.Join(",", (string[])TargetArrayList.ToArray(Type.GetType("System.String")))

The only "gotcha" to these is that the ArrayList must have the items stored as Strings if you're using Option Strict to make sure the conversion takes place properly.

EDIT: If you're using .net 2.0 or above, simply create a List(Of String) type object and you can get what you need with. Many thanks to Joel for bringing this up!

String.Join(",", TargetList.ToArray())

Extract a subset of a dataframe based on a condition involving a field

Here are the two main approaches. I prefer this one for its readability:

bar <- subset(foo, location == "there")

Note that you can string together many conditionals with & and | to create complex subsets.

The second is the indexing approach. You can index rows in R with either numeric, or boolean slices. foo$location == "there" returns a vector of T and F values that is the same length as the rows of foo. You can do this to return only rows where the condition returns true.

foo[foo$location == "there", ]

How to uninstall mini conda? python

your have to comment that line in ~/.bashrc:

#export PATH=/home/jolth/miniconda3/bin:$PATH

and run:

source ~/.bashrc

PDF Editing in PHP?

Zend Framework can load and edit existing PDF files. I think it supports revisions too.

I use it to create docs in a project, and it works great. Never edited one though.

Check out the doc here

Update or Insert (multiple rows and columns) from subquery in PostgreSQL

OMG Ponies's answer works perfectly, but just in case you need something more complex, here is an example of a slightly more advanced update query:

UPDATE table1 
SET col1 = subquery.col2,
    col2 = subquery.col3 
    SELECT as col1, as col2, t3.foobar as col3 
    FROM table2 t2 INNER JOIN table3 t3 ON = t3.t2_id
    WHERE t2.created_at > '2016-01-01'
) AS subquery
WHERE = subquery.col1;

MySQL ORDER BY multiple column ASC and DESC

@DRapp is a genius. I never understood how he coded his SQL,so I tried coding it in my own understanding.

        JOIN users
        ON scores.user_id =
        ORDER BY scores.point DESC
        ) userscores
      ORDER BY
        point DESC,
      ) f
    GROUP BY f.username
    ORDER BY point DESC

It yields the same result by using GROUP BY instead of the user @variables.

ES6 Class Multiple inheritance

Justin Fagnani describes a very clean (imho) way to compose multiple classes into one using the fact that in ES2015, classes can be created with class expressions.

Expressions vs declarations

Basically, just like you can create a function with an expression:

function myFunction() {}      // function declaration
var myFunction = function(){} // function expression

you can do the same with classes:

class MyClass {}             // class declaration
var MyClass = class {}       // class expression

The expression is evaluated at runtime, when the code executes, whereas a declaration is executed beforehand.

Using class expressions to create mixins

You can use this to create a function that dynamically creates a class only when the function is called:

function createClassExtending(superclass) {
  return class AwesomeClass extends superclass {
    // you class body here as usual

The cool thing about it is that you can define the whole class beforehand and only decide on which class it should extend by the time you call the function:

class A {}
class B {}
var ExtendingA = createClassExtending(A)
var ExtendingB = createClassExtending(B)

If you want to mix multiple classes together, because ES6 classes only support single inheritance, you need to create a chain of classes that contains all the classes you want to mix together. So let's say you want to create a class C that extends both A and B, you could do this:

class A {}
class B extends A {}
class C extends B {}  // C extends both A and B

The problem with this is that it's very static. If you later decide you want to make a class D that extends B but not A, you have a problem.

But with some smart trickery using the fact that classes can be expressions, you can solve this by creating A and B not directly as classes, but as class factories (using arrow functions for brevity):

class Base {} // some base class to keep the arrow functions simple
var A = (superclass) => class A extends superclass
var B = (superclass) => class B extends superclass
var C = B(A(Base))
var D = B(Base)

Notice how we only decide at the last moment which classes to include in the hierarchy.

Listview Scroll to the end of the list after updating the list

A combination of TRANSCRIPT_MODE_ALWAYS_SCROLL and setSelection made it work for me

ChatAdapter adapter = new ChatAdapter(this);

ListView lv = (ListView) findViewById(;

adapter.registerDataSetObserver(new DataSetObserver() {
    public void onChanged() {
        lv.setSelection(adapter.getCount() - 1);    

nullable object must have a value

I got this message when trying to access values of a null valued object.

sName = myObj.Name;

this will produce error. First you should check if object not null

if(myObj != null)
  sName = myObj.Name;

This works.

Soft Edges using CSS?

Another option is to use one of my personal favorite CSS tools: box-shadow.

A box shadow is really a drop-shadow on the node. It looks like this:

-moz-box-shadow: 1px 2px 3px rgba(0,0,0,.5);
-webkit-box-shadow: 1px 2px 3px rgba(0,0,0,.5);
box-shadow: 1px 2px 3px rgba(0,0,0,.5);

The arguments are:

1px: Horizontal offset of the effect. Positive numbers shift it right, negative left.
2px: Vertical offset of the effect. Positive numbers shift it down, negative up.
3px: The blur effect.  0 means no blur.
color: The color of the shadow.

So, you could leave your current design, and add a box-shadow like:

box-shadow: 0px -2px 2px rgba(34,34,34,0.6);

This should give you a 'blurry' top-edge.

This website will help with more information:

What are some ways of accessing Microsoft SQL Server from Linux?

pymssql is a DB-API Python module, based on FreeTDS. It worked for me. Create some helper functions, if you need, and use it from Python shell.

CRC32 C or C++ implementation

I am the author of the source code at the specified link. While the intention of the source code license is not clear (it will be later today), the code is in fact open and free for use in your free or commercial applications with no strings attached.

How to search all loaded scripts in Chrome Developer Tools?

In addition to Ctrl+Shift+F (Cmd+Option+F on Mac) as suggested in this answer, you can right click on the top tree node in the sources tab and select "Search in All Files":

enter image description here

Convert String to System.IO.Stream

Try this:

// convert string to stream
byte[] byteArray = Encoding.UTF8.GetBytes(contents);
//byte[] byteArray = Encoding.ASCII.GetBytes(contents);
MemoryStream stream = new MemoryStream(byteArray);


// convert stream to string
StreamReader reader = new StreamReader(stream);
string text = reader.ReadToEnd();

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

To use cache-control in HTML, you use the meta tag, e.g.

<meta http-equiv="Cache-control" content="public">

The value in the content field is defined as one of the four values below.

Some information on the Cache-Control header is as follows

HTTP 1.1. Allowed values = PUBLIC | PRIVATE | NO-CACHE | NO-STORE.

Public - may be cached in public shared caches.
Private - may only be cached in private cache.
No-Cache - may not be cached.
No-Store - may be cached but not archived.

The directive CACHE-CONTROL:NO-CACHE indicates cached information should not be used and instead requests should be forwarded to the origin server. This directive has the same semantics as the PRAGMA:NO-CACHE.

Clients SHOULD include both PRAGMA: NO-CACHE and CACHE-CONTROL: NO-CACHE when a no-cache request is sent to a server not known to be HTTP/1.1 compliant. Also see EXPIRES.

Note: It may be better to specify cache commands in HTTP than in META statements, where they can influence more than the browser, but proxies and other intermediaries that may cache information.

Illegal Escape Character "\"

The character '\' is a special character and needs to be escaped when used as part of a String, e.g., "\". Here is an example of a string comparison using the '\' character:

if (invName.substring(j,k).equals("\\")) {...}

You can also perform direct character comparisons using logic similar to the following:

if (invName.charAt(j) == '\\') {...}

How can a file be copied?

Python provides in-built functions for easily copying files using the Operating System Shell utilities.

Following command is used to Copy File


Following command is used to Copy File with MetaData Information


How do I determine the current operating system with Node.js

I was facing the same issue running my node js code on Windows VM on mac machine. The following code did the trick.


process.platform == 'win32'


const os = require('os');

os.platform() == 'win32';

Android: how to get the current day of the week (Monday, etc...) in the user's language?


String output = ZoneId.of( "America/Montreal" ) )
             .getDisplayName( TextStyle.FULL , Locale.CANADA_FRENCH ) ;


The java.time classes built into Java 8 and later and back-ported to Java 6 & 7 and to Android include the handy DayOfWeek enum.

The days are numbered according to the standard ISO 8601 definition, 1-7 for Monday-Sunday.

DayOfWeek dow = DayOfWeek.of( 1 );

This enum includes the getDisplayName method to generate a String of the localized translated name of the day.

The Locale object specifies a human language to be used in translation, and specifies cultural norms to decide issues such as capitalization and punctuation.

String output = DayOfWeek.MONDAY.getDisplayName( TextStyle.FULL , Locale.CANADA_FRENCH ) ;

To get today’s date, use the LocalDate class. Note that a time zone is crucial as for any given moment the date varies around the globe.

ZoneId z = ZoneId.of( "America/Montreal" );
LocalDate today = z );
DayOfWeek dow = today.getDayOfWeek();
String output = dow.getDisplayName( TextStyle.FULL , Locale.CANADA_FRENCH ) ;

Keep in mind that the locale has nothing to do with the time zone.two separate distinct orthogonal issues. You might want a French presentation of a date-time zoned in India (Asia/Kolkata).


UPDATE: The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

The Joda-Time library provides Locale-driven localization of date-time values.

DateTimeZone zone = DateTimeZone.forID( "America/Montreal" );
DateTime now = zone );

Locale locale = Locale.CANADA_FRENCH;
DateTimeFormatter formatterUnJourQuébécois = DateTimeFormat.forPattern( "EEEE" ).withLocale( locale );

String output = formatterUnJourQuébécois.print( now );

System.out.println("output: " + output );

output: samedi

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

Where to obtain the java.time classes?

How to crop a CvMat in OpenCV?

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

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

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

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

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

Bootstrap's JavaScript requires jQuery version 1.9.1 or higher

meteor add thelohoadmin:bootstrap@=3.3.7 solves the issue. You get the latest bootstrap and no warning messages.

Logical operator in a handlebars.js {{#if}} conditional

You can use the following code:

{{#if selection1}}
   {{#if selection2}}

Check if value exists in column in VBA

Just to modify scott's answer to make it a function:

Function FindFirstInRange(FindString As String, RngIn As Range, Optional UseCase As Boolean = True, Optional UseWhole As Boolean = True) As Variant

    Dim LookAtWhat As Integer

    If UseWhole Then LookAtWhat = xlWhole Else LookAtWhat = xlPart

    With RngIn
        Set FindFirstInRange = .Find(What:=FindString, _
                                     After:=.Cells(.Cells.Count), _
                                     LookIn:=xlValues, _
                                     LookAt:=LookAtWhat, _
                                     SearchOrder:=xlByRows, _
                                     SearchDirection:=xlNext, _

        If FindFirstInRange Is Nothing Then FindFirstInRange = False

    End With

End Function

This returns FALSE if the value isn't found, and if it's found, it returns the range.

You can optionally tell it to be case-sensitive, and/or to allow partial-word matches.

I took out the TRIM because you can add that beforehand if you want to.

An example:

MsgBox FindFirstInRange(StringToFind, Range("2:2"), TRUE, FALSE).Address

That does a case-sensitive, partial-word search on the 2nd row and displays a box with the address. The following is the same search, but a whole-word search that is not case-sensitive:

MsgBox FindFirstInRange(StringToFind, Range("2:2")).Address

You can easily tweak this function to your liking or change it from a Variant to to a boolean, or whatever, to speed it up a little.

Do note that VBA's Find is sometimes slower than other methods like brute-force looping or Match, so don't assume that it's the fastest just because it's native to VBA. It's more complicated and flexible, which also can make it not always as efficient. And it has some funny quirks to look out for, like the "Object variable or with block variable not set" error.

How to put a List<class> into a JSONObject and then read that object?

Just to update this thread, here is how to add a list (as a json array) into JSONObject. Plz substitute YourClass with your class name;

List<YourClass> list = new ArrayList<>();
JSONObject jsonObject = new JSONObject(); objectMapper = new;
org.codehaus.jackson.JsonNode listNode = objectMapper.valueToTree(list);
org.json.JSONArray request = new org.json.JSONArray(listNode.toString());
jsonObject.put("list", request);

Find all files with name containing string

If the string is at the beginning of the name, you can do this

$ compgen -f .bash

how to loop through json array in jquery?

You are iterating through an undefined value, ie, com property of the Array's object, you should iterate through the array itself:

$.each(obj, function(key,value) {
   // here `value` refers to the objects 

Also note that jQuery intelligently tries to parse the sent JSON, probably you don't need to parse the response. If you are using $.ajax(), you can set the dataType to json which tells jQuery parse the JSON for you.

If it still doesn't work, check the browser's console for troubleshooting.

On Windows, running "import tensorflow" generates No module named "_pywrap_tensorflow" error

I have Win7 Pro 64-bit on AMD cpu, no gpu. I was following the instructions under "Installing with native pip" at The installation step went ok but the attempt to import tensorflow produced the infamous:

ImportError: No module named '_pywrap_tensorflow_internal'

This seems to be one of those situations where a lot of unrelated things can go wrong, depending on configuration, which all cascade through to the same error.

In my case, installing MSVCP140.DLL was the answer.

You have MSVCP140.DLL already if

  1. you have a file C:\Windows\System32\MSVCP140.DLL, AND
  2. if you have a 64 bit system, then you additionally have C:\Windows\SysWOW64\MSVCP140.DLL.

I installed it manually, which was unnecessary (the redistributable is not the whole Visual C++ development mess and isn't large). Use the link posted earlier in this thread to install it: Visual C++ 2015 redistributable.

Also, I recommend that you override the default install directory for Python and put it anywhere not under C:\Program Files, because Windows tries to write-protect files there, which causes problems later.

How to handle onchange event on input type=file in jQuery?

It should work fine, are you wrapping the code in a $(document).ready() call? If not use that or use live i.e.

$('#fileupload1').live('change', function(){ 

Here is a jsFiddle of this working against jQuery 1.4.4

How to split a string by spaces in a Windows batch file?

you can use vbscript instead of batch(cmd.exe)

Set objFS = CreateObject("Scripting.FileSystemObject")
Set objArgs = WScript.Arguments
str1 = objArgs(0)
s=Split(str1," ")
For i=LBound(s) To UBound(s)
    WScript.Echo s(i)
    WScript.Echo s(9) ' get the 10th element


c:\test> cscript /nologo test.vbs "AAA BBB CCC"

Get attribute name value of <input>

using value get input name


using id get input name


using class get input name

   $('.classname').attr('name');  //if classname have unique value

IPhone/IPad: How to get screen width programmatically?

Here is a Swift way to get screen sizes, this also takes current interface orientation into account:

var screenWidth: CGFloat {
    if UIInterfaceOrientationIsPortrait(screenOrientation) {
        return UIScreen.mainScreen().bounds.size.width
    } else {
        return UIScreen.mainScreen().bounds.size.height
var screenHeight: CGFloat {
    if UIInterfaceOrientationIsPortrait(screenOrientation) {
        return UIScreen.mainScreen().bounds.size.height
    } else {
        return UIScreen.mainScreen().bounds.size.width
var screenOrientation: UIInterfaceOrientation {
    return UIApplication.sharedApplication().statusBarOrientation

These are included as a standard function in:

Embedding VLC plugin on HTML page

test.html is will be helpful for how to use VLC WebAPI.

test.html is located in the directory where VLC was installed.

e.g. C:\Program Files (x86)\VideoLAN\VLC\sdk\activex\test.html

The following code is a quote from the test.html.


<object classid="clsid:9BE31822-FDAD-461B-AD51-BE1D1C159921" width="640" height="360" id="vlc" events="True">
  <param name="MRL" value="" />
  <param name="ShowDisplay" value="True" />
  <param name="AutoLoop" value="False" />
  <param name="AutoPlay" value="False" />
  <param name="Volume" value="50" />
  <param name="toolbar" value="true" />
  <param name="StartTime" value="0" />
  <EMBED pluginspage=""
    text="Waiting for video"


You can get vlc object from getVLC().
It works on IE 10 and Chrome.

function getVLC(name)
    if (window.document[name])
        return window.document[name];
    if (navigator.appName.indexOf("Microsoft Internet")==-1)
        if (document.embeds && document.embeds[name])
            return document.embeds[name];
    else // if (navigator.appName.indexOf("Microsoft Internet")!=-1)
        return document.getElementById(name);

var vlc = getVLC("vlc");

// do something.
// e.g.;

Multi-character constant warnings

This warning is useful for programmers that would mistakenly write 'test' where they should have written "test".

This happen much more often than programmers that do actually want multi-char int constants.

Best approach to converting Boolean object to string in java

If this is for the purpose of getting a constant "true" value, rather than "True" or "TRUE", you can use this:


How to rename JSON key

Try this:

let jsonArr = [
        "email":"[email protected]",
        "name":"Name 1"
        "email":"[email protected]",
        "name":"Name 2"

let idModified =
    obj => {
        return {
            "id" : obj._id,

How to close the current fragment by using Button like the back button?

This is a Kotlin way of doing this, I have created button in fragment layout and then set onClickListner in onViewCreated.

according to @Viswanath-Lekshmanan comment

override fun onViewCreated(view: View?, savedInstanceState: Bundle?) 
     super.onViewCreated(view, savedInstanceState)

     btn_FragSP_back.setOnClickListener {

ssh-copy-id no identities found error

You need to use the -i flag:

ssh-copy-id -i

From the man page:

If the -i option is given then the identity file (defaults to ~/.ssh/ is used, regardless of whether there are any keys in your ssh-agent. Otherwise, if this: ssh-add -L provides any output, it uses that in preference to the identity file

How to specify a port to run a create-react-app based project?

Just update a bit in webpack.config.js:

devServer: {
    historyApiFallback: true,
    contentBase: './',
    port: 3000 // <--- Add this line and choose your own port number

then run npm start again.

IntelliJ does not show project folders

For me, it happens when i set Project SDK as JAVA SDK 14 in a react-native project. Upon unset, all the folders show up again.

Why are only a few video games written in Java?

It was talked about it a lot already, u can find even on Wiki the reasons...

  • C/C++ for the game engine and all intensive stuff.
  • Lua or Python for scripting in the game.
  • Java - very-very bad performance, big memory usage + it's not available on Game Consoles(It is used for some very simple games(Yes, Runescape counts in here, it's not Battlefield or Crysis or what else is there) just because there are a lot of programmers that know this programming language).
  • C# - big memory usage(It is used for some very simple games just because there are pretty much programmers that know this programming language).

And I hear more and more Java programmers that try to convince people that Java is not slow, it is not slow for drawing a widget on the screen and drawing some ASCII characters on the widget, to receive and send data through network(And it is recommended to use it in this cases(network data manipulation) instead of C/C++)... But it is damn slow when it comes to serious stuff like math calculations, memory allocation/manipulation and a lot of this good stuff.

I remember an article on MIT site where they show what C/C++ can do if u use the language and compiler features: A matrix multiplier(2 matrices), 1 implementation in Java and 1 implementation in C/C++, with C/C++ features and appropriate compiler optimisations activated, the C/C++ implementation was ~296 260 times faster than the Java implementation.

I hope you understand now why people use C/C++ instead of Java in games, imagine Crysis in Java, there would not be any computer in this world which could handle that... + Garbage collection works ok for Widgets which just destroyed an image but it's still cached in there and needs to be cleaned but not for games, for sure, u will have even more lags on every garbage collection activation.

Edit: Because somebody asked for the article, here, I searched in the web archive to get that, I hope you are satisfied...MIT Case Study

And to add, no, Java for gaming is still an awful idea. Just a few days ago a big company that I will not name started rewriting their game client from Java to C++ because a very simple game(In terms of Graphics) was lagging and heating i7 Laptops with powerful nVidia GT 5xx and 6xx generation video cards(not only nVidia, the point here is that this powerful cards that can handle on Max settings most of the new games and can't handle this game) and the memory consumption was ~2.5 - 2.6 GB Ram. For such simple graphics it needs a beast of a machine.

How do you monitor network traffic on the iPhone?

A man-in-the-middle proxy, like suggested by other answers, is a good solution if you only want to see HTTP/HTTPS traffic.

The best solution for packet sniffing (though it only works for actual iOS devices, not the simulator) I've found is to use rvictl. This blog post has a nice writeup. Basically you do:

rvictl -s <iphone-uid-from-xcode-organizer>

Then you sniff the interface it creates with with Wireshark (or your favorite tool), and when you're done shut down the interface with:

rvictl -x <iphone-uid-from-xcode-organizer>

This is nice because if you want to packet sniff the simulator, you're having to wade through traffic to your local Mac as well, but rvictl creates a virtual interface that just shows you the traffic from the iOS device you've plugged into your USB port.

Note: this only works on a Mac.

The differences between initialize, define, declare a variable


Declaration, generally, refers to the introduction of a new name in the program. For example, you can declare a new function by describing it's "signature":

void xyz();

or declare an incomplete type:

class klass;
struct ztruct;

and last but not least, to declare an object:

int x;

It is described, in the C++ standard, at §3.1/1 as:

A declaration (Clause 7) may introduce one or more names into a translation unit or redeclare names introduced by previous declarations.


A definition is a definition of a previously declared name (or it can be both definition and declaration). For example:

int x;
void xyz() {...}
class klass {...};
struct ztruct {...};
enum { x, y, z };

Specifically the C++ standard defines it, at §3.1/1, as:

A declaration is a definition unless it declares a function without specifying the function’s body (8.4), it contains the extern specifier (7.1.1) or a linkage-specification25 (7.5) and neither an initializer nor a function- body, it declares a static data member in a class definition (9.2, 9.4), it is a class name declaration (9.1), it is an opaque-enum-declaration (7.2), it is a template-parameter (14.1), it is a parameter-declaration (8.3.5) in a function declarator that is not the declarator of a function-definition, or it is a typedef declaration (7.1.3), an alias-declaration (7.1.3), a using-declaration (7.3.3), a static_assert-declaration (Clause 7), an attribute- declaration (Clause 7), an empty-declaration (Clause 7), or a using-directive (7.3.4).


Initialization refers to the "assignment" of a value, at construction time. For a generic object of type T, it's often in the form:

T x = i;

but in C++ it can be:

T x(i);

or even:

T x {i};

with C++11.


So does it mean definition equals declaration plus initialization?

It depends. On what you are talking about. If you are talking about an object, for example:

int x;

This is a definition without initialization. The following, instead, is a definition with initialization:

int x = 0;

In certain context, it doesn't make sense to talk about "initialization", "definition" and "declaration". If you are talking about a function, for example, initialization does not mean much.

So, the answer is no: definition does not automatically mean declaration plus initialization.

Is there a way to automatically build the package.json file for Node.js projects

Command line:

npm init

will create package.json file

To install , update and uninstall packages under dependencies into package.json file:

Command line :

npm install <pkg>@* --save 

will automatically add the latest version for the package under dependencies into package.json file


npm install node-markdown@* --save

Command line:

npm install <pkg> --save

also will automatically add the latest version for the package under dependencies into package.json file

if you need specific version for a package use this Command line:

npm install <pkg>@<version> --save

will automatically add specific version of package under dependencies into package.json file


npm install [email protected] --save

if you need specific range of version for a package use this Command line:

npm install <pkg>@<version range>

will automatically add the latest version for the package between range of version under dependencies into package.json file


npm install koa-views@">1.0.0 <1.2.0" --save

For more details about how to write version for package npm Doc

Command line:

npm update --save

will update packages into package.json file and will automatically add updated version for all packages under dependencies into package.json file

Command line:

npm uninstall <pkg> --save

will automatically remove package from dependencies into package.json file and remove package from node_module folder

Function passed as template argument

Yes, it is valid.

As for making it work with functors as well, the usual solution is something like this instead:

template <typename F>
void doOperation(F f)
  int temp=0;
  std::cout << "Result is " << temp << std::endl;

which can now be called as either:


See it live

The problem with this is that if it makes it tricky for the compiler to inline the call to add2, since all the compiler knows is that a function pointer type void (*)(int &) is being passed to doOperation. (But add3, being a functor, can be inlined easily. Here, the compiler knows that an object of type add3 is passed to the function, which means that the function to call is add3::operator(), and not just some unknown function pointer.)

How to quickly test some javascript code?

Install firebug: . You can use its console to test Javascript code. Google Chrome comes with Web Inspector in which you can do the same. IE and Safari also have Web Developer tools in which you can test Javascript.

Xcode 10.2.1 Command PhaseScriptExecution failed with a nonzero exit code

I had a similar error

/{path to project root}/Pods/Target Support Files/Pods-{project name}/Pods-{project name} Permission denied
Command PhaseScriptExecution failed with a nonzero exit code

In my case I had received a zip of a repo that included the Pods folder. It turns out that at some point between it being originally created and sent to me, the *.sh files in Pods/Target Support Files/Pods-{PROJECT}/ had all lost their execute permissions. Giving those files +x was the solution

Detect If Browser Tab Has Focus

Important Edit: This answer is outdated. Since writing it, the Visibility API (mdn, example, spec) has been introduced. It is the better way to solve this problem.

var focused = true;

window.onfocus = function() {
    focused = true;
window.onblur = function() {
    focused = false;

AFAIK, focus and blur are all supported on...everything. (see )

How to return multiple values in one column (T-SQL)?

You can use a function with COALESCE.

CREATE FUNCTION [dbo].[GetAliasesById]
    @userID int
RETURNS varchar(max)
    declare @output varchar(max)
    select @output = COALESCE(@output + ', ', '') + alias
    from UserAliases
    where userid = @userID

    return @output


SELECT UserID, dbo.GetAliasesByID(UserID)
FROM UserAliases


Show/hide image with JavaScript


<img id="theImage" src="yourImage.png">
<a id="showImage">Show image</a>


document.getElementById("showImage").onclick = function() {
    document.getElementById("theImage").style.display = "block";


#theImage { display:none; }

How do I run .sh or .bat files from Terminal?


Easiest way for a lazy Mac user like me: Drag-and-drop the file from the Finder to the Terminal window and press Return.

To shutdown Tomcat, do the same with

You can delete all the .bat files as they are only for a Windows PC, of no use on a Mac to other Unix computer. I delete them as it makes it easier to read that folder's listing.

File Permissions

I find that a fresh Tomcat download will not run on my Mac because of file permission restrictions throwing errors during startup. I use the BatChmod app which wraps a GUI around the equivelant Unix commands to reset file permissions.


Unix systems protect access to ports numbered under 1024. So if you want to use port 80 with Tomcat you will need to learn how to do "port-forwarding" to forward incoming requests to port 8080 where Tomcat listens by default. To do port-forwarding, you issue commands to the packet-filtering (firewall) app built into Mac OS X (and BSD). In the old days we used ipfw. In Mac OS X 10.7 (Lion) and later Apple is moving to a newer tool, pf.

How to create a service running a .exe file on Windows 2012 Server?

You can just do that too, it seems to work well too. sc create "Servicename" binPath= "Path\To\your\App.exe" DisplayName= "My Custom Service"

You can open the registry and add a string named Description in your service's registry key to add a little more descriptive information about it. It will be shown in services.msc.

Can I run Keras model on gpu?

See if your script is running GPU in Task manager. If not, suspect your CUDA version is right one for the tensorflow version you are using, as the other answers suggested already.

Additionally, a proper CUDA DNN library for the CUDA version is required to run GPU with tensorflow. Download/extract it from here and put the DLL (e.g., cudnn64_7.dll) into CUDA bin folder (e.g., C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v10.1\bin).

PHP Change Array Keys

I think that he want:

$a = array(1=>'first_name', 2=>'last_name');
$a = array_flip($a);

$a['first_name'] = 3;
$a = array_flip($a);


Is there a standard function to check for null, undefined, or blank variables in JavaScript?

  1. you can use the arguments
  2. become arguments to array
  3. filter

function validateAttrs(arg1, arg2, arg3,arg4){
    var args = Object.values(arguments);
    return (args.filter(x=> x===null || !x)).length<=0
console.log(validateAttrs('1',2, 3, 4));
console.log(validateAttrs('1',2, 3, null));
console.log(validateAttrs('1',undefined, 3, 4));
console.log(validateAttrs('1',2, '', 4));
console.log(validateAttrs('1',2, 3, null));

How do I connect to my existing Git repository using Visual Studio Code?

Another option is to use the built-in Command Palette, which will walk you right through cloning a Git repository to a new directory.

From Using Version Control in VS Code:

You can clone a Git repository with the Git: Clone command in the Command Palette (Windows/Linux: Ctrl + Shift + P, Mac: Command + Shift + P). You will be asked for the URL of the remote repository and the parent directory under which to put the local repository.

At the bottom of Visual Studio Code you'll get status updates to the cloning. Once that's complete an information message will display near the top, allowing you to open the folder that was created.

Note that Visual Studio Code uses your machine's Git installation, and requires 2.0.0 or higher.

How I can get web page's content and save it into the string variable

I recommend not using WebClient.DownloadString. This is because (at least in .NET 3.5) DownloadString is not smart enough to use/remove the BOM, should it be present. This can result in the BOM () incorrectly appearing as part of the string when UTF-8 data is returned (at least without a charset) - ick!

Instead, this slight variation will work correctly with BOMs:

string ReadTextFromUrl(string url) {
    // WebClient is still convenient
    // Assume UTF8, but detect BOM - could also honor response charset I suppose
    using (var client = new WebClient())
    using (var stream = client.OpenRead(url))
    using (var textReader = new StreamReader(stream, Encoding.UTF8, true)) {
        return textReader.ReadToEnd();

Setting up a JavaScript variable from Spring model by using Thymeleaf

According to the documentation there are several ways to do the inlining.
The right way you must choose based on the situation.

1) Simply put the variable from server to javascript :

<script th:inline="javascript">

var message = [[${message}]];


2) Combine javascript variables with server side variables, e.g. you need to create link for requesting inside the javascript:

<script th:inline="javascript">
        function sampleGetByJquery(v) {
            var url = [[@{/my/get/url(var1=${#httpServletRequest.getParameter('var1')})}]] 
                      + "&var2="+v;
            $("#myPanel").load(url, function() {});

The one situation I can't resolve - then I need to pass javascript variable inside the Java method calling inside the template (it's impossible I guess).

How do you clone a Git repository into a specific folder?

Go into the folder.. If the folder is empty, then:

git clone [email protected]:whatever .


git init
git remote add origin PATH/TO/REPO
git fetch
git checkout -t origin/master

Pass multiple parameters to rest API - Spring

Multiple parameters can be given like below,

    @RequestMapping(value = "/mno/{objectKey}", method = RequestMethod.GET, produces = "application/json")
    public List<String> getBook(HttpServletRequest httpServletRequest, @PathVariable(name = "objectKey") String objectKey
      , @RequestParam(value = "id", defaultValue = "false")String id,@RequestParam(value = "name", defaultValue = "false") String name) throws Exception {

How can a LEFT OUTER JOIN return more records than exist in the left table?

LEFT OUTER JOIN just like INNER JOIN (normal join) will return as many results for each row in left table as many matches it finds in the right table. Hence you can have a lot of results - up to N x M, where N is number of rows in left table and M is number of rows in right table.

It's the minimum number of results is always guaranteed in LEFT OUTER JOIN to be at least N.

How to host material icons offline?

I solved it using this package (@mdi/font) and importing it on main.js:

import '@mdi/font/css/materialdesignicons.css'

Extracting substrings in Go

To get substring

  1. find position of "sp"

  2. cut string with array-logical

I need to know how to get my program to output the word i typed in and also the new rearranged word using a 2D array

  1. What exactly doesn't work?
  2. Why are you using a 2d array?
  3. If you must use a 2d array:

    int numOfPairs = 10;  String[][] array = new String[numOfPairs][2]; for(int i = 0; i < array.length; i++){     for(int j = 0; j < array[i].length; j++){         array[i] = new String[2];         array[i][0] = "original word";         array[i][1] = "rearranged word";     }    } 

Does this give you a hint?

Eclipse CDT: Symbol 'cout' could not be resolved

I had a similar problem with *std::shared_ptr* with Eclipse using MinGW and gcc 4.8.1. No matter what, Eclipse would not resolve *shared_ptr*. To fix this, I manually added the __cplusplus macro to the C++ symbols and - viola! - Eclipse can find it. Since I specified -std=c++11 as a compile option, I (ahem) assumed that the Eclipse code analyzer would use that option as well. So, to fix this:

  1. Project Context -> C/C++ General -> Paths and Symbols -> Symbols Tab
  2. Select C++ in the Languages panel.
  3. Add symbol __cplusplus with a value of 201103.

The only problem with this is that gcc will complain that the symbol is already defined(!) but the compile will complete as before.

Why does JSON.parse fail with the empty string?

Use try-catch to avoid it:

var result = null;
try {
  // if jQuery
  result = $.parseJSON(JSONstring);
  // if plain js
  result = JSON.parse(JSONstring);
catch(e) {
  // forget about it :)

How to get random value out of an array?

A simple way to getting Randdom value form Array.

$color_array =["red","green","blue","light_orange"];

now every time you will get different colors from Array.

PHP - print all properties of an object

<?php var_dump(obj) ?>


<?php print_r(obj) ?>

These are the same things you use for arrays too.

These will show protected and private properties of objects with PHP 5. Static class members will not be shown according to the manual.

If you want to know the member methods you can use get_class_methods():

$class_methods = get_class_methods('myclass');
// or
$class_methods = get_class_methods(new myclass());
foreach ($class_methods as $method_name) 
    echo "$method_name<br/>";

Related stuff:



get_class() <-- for the name of the instance

Checking if a list is empty with LINQ

@Konrad what surprises me is that in my tests, I'm passing the list into a method that accepts IEnumerable<T>, so the runtime can't optimize it by calling the Count() extension method for IList<T>.

I can only assume that the Count() extension method for IEnumerable is doing something like this:

public static int Count<T>(this IEnumerable<T> list)
    if (list is IList<T>) return ((IList<T>)list).Count;

    int i = 0;
    foreach (var t in list) i++;
    return i;

... in other words, a bit of runtime optimization for the special case of IList<T>.

/EDIT @Konrad +1 mate - you're right about it more likely being on ICollection<T>.

How to change the color of a button?

Through Programming:


and your colors.xml must contain...

<?xml version="1.0" encoding="utf-8"?>
 <color name="colorOffWhite">#80ffffff</color>

Concatenating strings in C, which method is more efficient?

I don't know that in case two there's any real concatenation done. Printing them back to back doesn't constitute concatenation.

Tell me though, which would be faster:

1) a) copy string A to new buffer b) copy string B to buffer c) copy buffer to output buffer


1)copy string A to output buffer b) copy string b to output buffer

Exception : mockito wanted but not invoked, Actually there were zero interactions with this mock

Your class MyClass creates a new MyClassToBeTested, instead of using your mock. My article on the Mockito wiki describes two ways of dealing with this.

Is it better to use "is" or "==" for number comparison in Python?

>>> a = 255556
>>> a == 255556
>>> a is 255556

I think that should answer it ;-)

The reason is that some often-used objects, such as the booleans True and False, all 1-letter strings and short numbers are allocated once by the interpreter, and each variable containing that object refers to it. Other numbers and larger strings are allocated on demand. The 255556 for instance is allocated three times, every time a different object is created. And therefore, according to is, they are not the same.

Java Spring - How to use classpath to specify a file location?

From an answer of @NimChimpsky in similar question:

Resource resource = new ClassPathResource("storedProcedures.sql");
InputStream resourceInputStream = resource.getInputStream();

Using ClassPathResource and interface Resource. And make sure you are adding the resources directory correctly (adding /src/main/resources/ into the classpath).

Note that Resource have a method to get a so you can also use:

Resource resource = new ClassPathResource("storedProcedures.sql");
FileReader fr = new FileReader(resource.getFile());

How to force NSLocalizedString to use a specific language

I like best Mauro Delrio's method. I also have added the following in my Project_Prefix.pch

#import "Language.h"    
#define MyLocalizedString(key, alt) [Language get:key alter:alt]

So if you ever want to use the standard method (that uses NSLocalizedString) you can make a quick syntax substitution in all files.

Output to the same line overwriting previous output?

I am using spyder 3.3.1 - windows 7 - python 3.6 although flush may not be needed. based on this posting -

   #works in spyder ipython console - \r at start of string , end=""
import time
import sys
    for i in range(20):

How to delete all files from a specific folder?

Add the following namespace,

using System.IO;

and use the Directory class to reach on the specific folder:

string[] fileNames = Directory.GetFiles(@"your directory path");
foreach (string fileName in fileNames)

How do I split a string with multiple separators in JavaScript?

I will provide a classic implementation for a such function. The code works in almost all versions of JavaScript and is somehow optimum.

  • It doesn't uses regex, which is hard to maintain
  • It doesn't uses new features of JavaScript
  • It doesn't uses multiple .split() .join() invocation which require more computer memory

Just pure code:

var text = "Create a function, that will return an array (of string), with the words inside the text";


function getWords(text)
    let startWord = -1;
    let ar = [];

    for(let i = 0; i <= text.length; i++)
        let c = i < text.length ? text[i] : " ";

        if (!isSeparator(c) && startWord < 0)
            startWord = i;

        if (isSeparator(c) && startWord >= 0)
            let word = text.substring(startWord, i);

            startWord = -1;

    return ar;

function isSeparator(c)
    var separators = [" ", "\t", "\n", "\r", ",", ";", ".", "!", "?", "(", ")"];
    return separators.includes(c);

You can see the code running in playground:

When should you use a class vs a struct in C++?

I never use "struct" in C++.

I can't ever imagine a scenario where you would use a struct when you want private members, unless you're willfully trying to be confusing.

It seems that using structs is more of a syntactic indication of how the data will be used, but I'd rather just make a class and try to make that explicit in the name of the class, or through comments.


class PublicInputData {
    //data members

What is the best way to implement constants in Java?

I use static final to declare constants and go with the ALL_CAPS naming notation. I have seen quite a few real life instances where all constants are bunched together into an interface. A few posts have rightly called that a bad practice, primarily because that's not what an interface is for. An interface should enforce a contract and should not be a place to put unrelated constants in. Putting it together into a class that cannot be instantiated (through a private constructor) too is fine if the constant semantics don't belong to a specific class(es). I always put a constant in the class that it's most related to, because that makes sense and is also easily maintainable.

Enums are a good choice to represent a range of values, but if you are storing standalone constants with an emphasis on the absolute value (eg. TIMEOUT = 100 ms) you can just go for the static final approach.

How to get old Value with onchange() event in text box

I am not sure, but maybe this logic would work.

var d = 10;
var prevDate = "";
var x = 0;
var oldVal = "";
var func = function (d) {
    if (x == 0 && d != prevDate && prevDate == "") {
        oldVal = d;
        prevDate = d;
    else if (x == 1 && prevDate != d) {
        oldVal = prevDate;
        prevDate = d;
    x = 1;

How to stop a vb script running in windows

in your code, just after 'do while' statement, add this line..

`Wscript.sleep 10000`

This will let your script sleep for 10 secs and let your system take rest. Else your processor will be running this script million times a second and this will definitely load your processor.

To kill it, just goto taskmanager and kill wscript.exe or if it is not found, you will find cscript.exe, kill it pressing delete button. These would be present in process tab of your taskmanager.

Once you add that line in code, I dont think you need to kill this process. It will not load your CPU.

Have a great day.

Read CSV with Scanner()

Split nextLine() by this delimiter: (?=([^\"]*\"[^\"]*\")*[^\"]*$)").

Change value in a cell based on value in another cell

If you want to do something like the following example, you'd have to use nested ifs.

If percentage is greater than or equal to 93%, then corresponding value in B should be 4 and if the percentage is greater than or equal to 90% and less than 92%, then corresponding value in B to be 3.7, etc.

Here's how you'd do it:

=IF(A2>=93%, 4, IF(A2>=90%, 3.7,IF(A2>=87%,3.3,0)))

Put search icon near textbox using bootstrap

I liked @KyleMit's answer on how to make an unstyled input group, but in my case, I only wanted the right side unstyled - I still wanted to use an input-group-addon on the left side and have it look like normal bootstrap. So, I did this:


.input-group.input-group-unstyled-right input.form-control {
    border-top-right-radius: 4px;
    border-bottom-right-radius: 4px;
.input-group-unstyled-right .input-group-addon.input-group-addon-unstyled {
    border-radius: 4px;
    border: 0px;
    background-color: transparent;


<div class="input-group input-group-unstyled-right">
    <span class="input-group-addon">
        <i class="fa fa-envelope-o"></i>
    <input type="text" class="form-control">
    <span class="input-group-addon input-group-addon-unstyled">
        <i class="fa fa-check"></i>

How to run a stored procedure in oracle sql developer?

-- If no parameters need to be passed to a procedure, simply:


How do I correct the character encoding of a file?

If you see question marks in the file or if the accents are already lost, going back to utf8 will not help your cause. e.g. if café became cafe - changing encoding alone will not help (and you'll need original data).

Can you paste some text here, that'll help us answer for sure.

Regarding Java switch statements - using return and omitting breaks in each case

Nope, what you have is fine. You could also do this as a formula (sliderVal < 5 ? (1.0 - 0.1 * sliderVal) : 1.0) or use a Map<Integer,Double>, but what you have is fine.


If you just need to output the date in ISO8601 format including the trailing Z and you are on at least SQL Server 2012, then you may use FORMAT:

SELECT FORMAT(GetUtcDate(),'yyyy-MM-ddTHH:mm:ssZ')

This will give you something like:


Just as @Pxtl points out in a comment FORMAT may have performance implications, a cost that has to be considered compared to any flexibility it brings.

NameError: global name 'unicode' is not defined - in Python 3

Hope you are using Python 3 , Str are unicode by default, so please Replace Unicode function with String Str function.

if isinstance(unicode_or_str, str):    ##Replaces with str
    text = unicode_or_str
    decoded = False

Could not load file or assembly 'Microsoft.ReportViewer.Common, Version=

Add Microsot.ReportViewer 2010 or 2012 in prerequisite of setup project then it first install Report Viewer if it's not present in "C:\Windows\assembly\GAC_MSIL..." and after installing, it installs set up project

Get parent of current directory from Python script

This worked for me (I am on Ubuntu):

import os

Why is printing "B" dramatically slower than printing "#"?

I performed tests on Eclipse vs Netbeans 8.0.2, both with Java version 1.8; I used System.nanoTime() for measurements.


I got the same time on both cases - around 1.564 seconds.


  • Using "#": 1.536 seconds
  • Using "B": 44.164 seconds

So, it looks like Netbeans has bad performance on print to console.

After more research I realized that the problem is line-wrapping of the max buffer of Netbeans (it's not restricted to System.out.println command), demonstrated by this code:

for (int i = 0; i < 1000; i++) {
    long t1 = System.nanoTime();
    System.out.print("BBB......BBB"); \\<-contain 1000 "B"
    long t2 = System.nanoTime();

The time results are less then 1 millisecond every iteration except every fifth iteration, when the time result is around 225 millisecond. Something like (in nanoseconds):


And so on..


  1. Eclipse works perfectly with "B"
  2. Netbeans has a line-wrapping problem that can be solved (because the problem does not occur in eclipse)(without adding space after B ("B ")).

Convert HTML Character Back to Text Using Java Standard Library

The URL decoder should only be used for decoding strings from the urls generated by html forms which are in the "application/x-www-form-urlencoded" mime type. This does not support html characters.

After a search I found a Translate class within the HTML Parser library.

Deleting records before a certain date

DELETE FROM table WHERE date < '2011-09-21 08:21:22';

Creating custom function in React component

You can try this.

// Author: Hannad Rehman Sat Jun 03 2017 12:59:09 GMT+0530 (India Standard Time)

import React from 'react';
import RippleButton from '../../Components/RippleButton/rippleButton.jsx';

class HtmlComponents extends React.Component {


        //do stuff. 
        // foo==bar

    render() {
      return (
             <h1>React Components</h1>
             <RippleButton onClick={this.rippleClickFunction}/>

export default HtmlComponents;

Yhe only concern is you have to bind the context to the function

What does "<html xmlns="">" do?

Its an XML namespace. It is required when you use XHTML 1.0 or 1.1 doctypes or application/xhtml+xml mimetypes.

You should be using HTML5 doctype, then you don't need it for text/html. Better start from template like this :

<!DOCTYPE html>
        <meta charset=utf-8 />
        <title>domcument title</title>
        <link rel="stylesheet" href="/stylesheet.css" type="text/css" />
            <!-- your html content -->
            <script src="/script.js"></script>

When you have put your Doctype straight - do and validate you html and your css .
That usually will sove you layout issues.

Python Create unix timestamp five minutes in the future

Here's a less broken datetime-based solution to convert from datetime object to posix timestamp:

future = datetime.datetime.utcnow() + datetime.timedelta(minutes=5)
return (future - datetime.datetime(1970, 1, 1)).total_seconds()

See more details at Converting to UTC timestamp in Python.

Requested registry access is not allowed

You Could Do The same as abatishchev but without the UAC

<assembly manifestVersion="1.0" xmlns="urn:schemas-microsoft-com:asm.v1">
<assemblyIdentity version="" name=""/>
 <trustInfo xmlns="urn:schemas-microsoft-com:asm.v2">
    <requestedPrivileges xmlns="urn:schemas-microsoft-com:asm.v3">

How to get first record in each group using Linq

var res = (from element in list)
      .OrderBy(x => x.F2).AsEnumerable()
      .GroupBy(x => x.F1)

Use .AsEnumerable() after OrderBy()

Insert 2 million rows into SQL Server quickly

I use the bcp utility. (Bulk Copy Program) I load about 1.5 million text records each month. Each text record is 800 characters wide. On my server, it takes about 30 seconds to add the 1.5 million text records into a SQL Server table.

The instructions for bcp are at

launch sms application with an intent

If android version is Kitkat or above, users can change default sms application. This method will get default sms app and start default sms app.

private void sendSMS() {    
      if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) // At least KitKat
         String defaultSmsPackageName = Telephony.Sms.getDefaultSmsPackage(this); // Need to change the build to API 19

         Intent sendIntent = new Intent(Intent.ACTION_SEND);
         sendIntent.putExtra(Intent.EXTRA_TEXT, "text");

         if (defaultSmsPackageName != null)// Can be null in case that there is no default, then the user would be able to choose
         // any app that support this intent.

      else // For early versions, do what worked for you before.
         Intent smsIntent = new Intent(android.content.Intent.ACTION_VIEW);

Check if a file is executable

Testing files, directories and symlinks

The solutions given here fail on either directories or symlinks (or both). On Linux, you can test files, directories and symlinks with:

if [[ -f "$file" && -x $(realpath "$file") ]]; then .... fi

On OS X, you should be able to install coreutils with homebrew and use grealpath.

Defining an isexec function

You can define a function for convenience:

isexec() {
    if [[ -f "$1" && -x $(realpath "$1") ]]; then

Or simply

isexec() { [[ -f "$1" && -x $(realpath "$1") ]]; }

Then you can test using:

if `isexec "$file"`; then ... fi

How can I get the current stack trace in Java?


is available since JDK1.5.

For an older version, you can redirect exception.printStackTrace() to a StringWriter() :

StringWriter sw = new StringWriter();
new Throwable("").printStackTrace(new PrintWriter(sw));
String stackTrace = sw.toString();

VB.NET - Remove a characters from a String

The String class has a Replace method that will do that.

Dim clean as String
clean = myString.Replace(",", "")

Pandas DataFrame to List of Lists

You could access the underlying array and call its tolist method:

>>> df = pd.DataFrame([[1,2,3],[3,4,5]])
>>> lol = df.values.tolist()
>>> lol
[[1L, 2L, 3L], [3L, 4L, 5L]]

adb shell su works but adb root does not

I use for enter su mode in abd shell

adb shell "su"

How to run 'sudo' command in windows

I am glad to help you.

To make a sudo command follow the steps :-

  1. Make a folder env in C:\ Drive.
  2. Make a folder inside the env folder named as bin.
  3. Now add C:\env\bin to your PATH.
  4. Create a file sudo.bat in C:\env\bin.
  5. Edit it with notepad and write this code :-

Hope this will help you

What do "branch", "tag" and "trunk" mean in Subversion repositories?

In general (tool agnostic view), a branch is the mechanism used for parallel development. An SCM can have from 0 to n branches. Subversion has 0.

  • Trunk is a main branch recommended by Subversion, but you are in no way forced to create it. You could call it 'main' or 'releases', or not have one at all!

  • Branch represents a development effort. It should never be named after a resource (like 'vonc_branch') but after:

    • a purpose 'myProject_dev' or 'myProject_Merge'
    • a release perimeter 'myProjetc1.0_dev'or myProject2.3_Merge' or 'myProject6..2_Patch1'...
  • Tag is a snapshot of files in order to easily get back to that state. The problem is that tag and branch is the same in Subversion. And I would definitely recommend the paranoid approach:

    you can use one of the access control scripts provided with Subversion to prevent anyone from doing anything but creating new copies in the tags area.

A tag is final. Its content should never change. NEVER. Ever. You forgot a line in the release note? Create a new tag. Obsolete or remove the old one.

Now, I read a lot about "merging back such and such in such and such branches, then finally in the trunk branch". That is called merge workflow and there is nothing mandatory here. It is not because you have a trunk branch that you have to merge back anything.

By convention, the trunk branch can represent the current state of your development, but that is for a simple sequential project, that is a project which has:

  • no 'in advance' development (for the preparing the next-next version implying such changes that they are not compatible with the current 'trunk' development)
  • no massive refactoring (for testing a new technical choice)
  • no long-term maintenance of a previous release

Because with one (or all) of those scenario, you get yourself four 'trunks', four 'current developments', and not all you do in those parallel development will necessarily have to be merged back in 'trunk'.

Laravel 5 – Clear Cache in Shared Hosting Server

Config caching The laravel config spreads across dozens of files, and including every one of them for each request is a costly process. To combine all of your config files into one, use:

php artisan config:cache

Keep in mind that any changes to the config will not have any effect once you cache it. To refresh the config cache, run the above command again. In case you want to completely get rid of the config cache, run

php artisan config:clear

Routes caching Routing is also an expensive task in laravel. To cache the routes.php file run the below command:

php artisan route:cache

Mind that it doesn't work with closures. In case you're using closures this is a great chance to move them into a controller, as the artisan command will throw an exception when trying to compile routes that are bound to closures instead of proper controller methods. In the same as the config cache, any changes to routes.php will not have any effect anymore. To refresh the cache, run the above command everytime you do a change to the routes file. To completely get rid of the route cache, run the below command:

php artisan route:clear

Classmap optimization

It's not uncommon for a medium-sized project to be spread across hundreds of PHP files. As good coding behaviours dictate us, everything has its own file. This, of course, does not come without drawbacks. Laravel has to include dozens of different files for each request, which is a costly thing to do.

Hence, a good optimization method is declaring which files are used for every request (this is, for example, all your service providers, middlewares and a few more) and combining them in only one file, which will be afterwards loaded for each request. This not different from combining all your javascript files into one, so the browser will have to make fewer requests to the server.

The additional compiles files (again: service providers, middlewares and so on) should be declared by you in config/compile.php, in the files key. Once you put there everything essential for every request made to your app, concatenate them in one file with:

php artisan optimize --force

Optimizing the composer autoload

This one is not only for laravel, but for any application that's making use of composer.

I'll explain first how the PSR-4 autoload works, and then I'll show you what command you should run to optimize it. If you're not interested in knowing how composer works, I recommend you jumping directly to the console command.

When you ask composer for the App\Controllers\AuthController class, it first searches for a direct association in the classmap. The classmap is an array with 1-to-1 associations of classes and files. Since, of course, you did not manually add the Login class and its associated file to the classmap, composer will move on and search in the namespaces. Because App is a PSR-4 namespace, which comes by default with Laravel and it's associated to the app/ folder, composer will try converting the PSR-4 class name to a filename with basic string manipulation procedures. In the end, it guesses that App\Controllers\AuthController must be located in an AuthController.php file, which is in a Controllers/ folder that should luckily be in the namespace folder, which is app/.

All this hard work only to get that the App\Controllers\AuthController class exists in the app/Controllers/AuthController.php file. In order to have composer scanning your entire application and create direct 1-to-1 associations of classes and files, run the following command:

composer dumpautoload -o

Keep in mind that if you already ran php artisan optimize --force, you don't have to run this one anymore. Since the optimize command already tells composer to create an optimized autoload.

LinkButton Send Value to Code Behind OnClick

Try and retrieve the text property of the link button in the code behind:

protected void ENameLinkBtn_Click (object sender, EventArgs e)
   string val = ((LinkButton)sender).Text

Python string prints as [u'String']

encode("latin-1") helped me in my case:


Error: class X is public should be declared in a file named

In my case (using IntelliJ) I copy and pasted and renamed the workspace, and I am still using the old path to compile the new project.

In this case this particular error will happen too, if you have the same error you can check if you have done the similar things.

Does HTML5 <video> playback support the .avi format?

The HTML specification never specifies any content formats. That's not its job. There's plenty of standards organizations that are more qualified than the W3C to specify video formats.

That's what content negotiation is for.

  • The HTML specification doesn't specify any image formats for the <img> element.
  • The HTML specification doesn't specify any style sheet languages for the <style> element.
  • The HTML specification doesn't specify any scripting languages for the <script> element.
  • The HTML specification doesn't specify any object formats for the <object> and embed elements.
  • The HTML specification doesn't specify any audio formats for the <audio> element.

Why should it specify one for the <video> element?

python ValueError: invalid literal for float()

I had a similar issue reading the serial output from a digital scale. I was reading [3:12] out of a 18 characters long output string.

In my case sometimes there is a null character "\x00" (NUL) which magically appears in the scale's reply string and is not printed.

I was getting the error:

> '     0.00'
> 3 0 fast loop, delta =  10.0 weight =  0.0 
> '     0.00'
> 1 800 fast loop, delta = 10.0 weight =  0.0 
> '     0.00'
> 6 0 fast loop, delta =  10.0 weight =  0.0
> '     0\x00.0' 
> Traceback (most recent call last):
>   File "", line 172, in start
>     valueScale = float(answer_string) 
>     ValueError: invalid literal for float(): 0

After some research I wrote few lines of code that work in my case.

replyScale =
answer = replyScale[3:12]
answer_decode = answer.replace("\x00", "")
answer_strip = str(answer_decode.strip())
valueScale = float(answer_strip)

The answers in these posts helped:

  1. How to get rid of \x00 in my array of bytes?
  2. Invalid literal for float(): 0.000001, how to fix error?

How do I uninstall a package installed using npm link?

"npm install" replaces all dependencies in your node_modules installed with "npm link" with versions from npmjs (specified in your package.json)

How to set <Text> text to upper case in react native

React Native .toUpperCase() function works fine in a string but if you used the numbers or other non-string data types, it doesn't work. The error will have occurred.

Below Two are string properties:



What is an MDF file?

SQL Server databases use two files - an MDF file, known as the primary database file, which contains the schema and data, and a LDF file, which contains the logs. See wikipedia. A database may also use secondary database file, which normally uses a .ndf extension.

As John S. indicates, these file extensions are purely convention - you can use whatever you want, although I can't think of a good reason to do that.

More info on MSDN here and in Beginning SQL Server 2005 Administation (Google Books) here.

How to start a Process as administrator mode in C#

Use this method:

public static int RunProcessAsAdmin(string exeName, string parameters)
        try {
            System.Diagnostics.ProcessStartInfo startInfo = new System.Diagnostics.ProcessStartInfo();
            startInfo.UseShellExecute = true;
            startInfo.WorkingDirectory = CurrentDirectory;
            startInfo.FileName = Path.Combine(CurrentDirectory, exeName);
            startInfo.Verb = "runas";
            startInfo.Arguments = parameters;
            startInfo.ErrorDialog = true;

            Process process = System.Diagnostics.Process.Start(startInfo);
            return process.ExitCode;
        } catch (Win32Exception ex) {
            switch (ex.NativeErrorCode) {
                case 1223:
                    return ex.NativeErrorCode;
                    return ErrorReturnInteger;

        } catch (Exception ex) {
            return ErrorReturnInteger;

Hope it helps.

How do I test for an empty JavaScript object?

How about using JSON.stringify? It is almost available in all modern browsers.

function isEmptyObject(obj){
    return JSON.stringify(obj) === '{}';

Initialize a Map containing arrays

Per Mozilla's Map documentation, you can initialize as follows:

private _gridOptions:Map<string, Array<string>> = 
    new Map([
        ["1", ["test"]],
        ["2", ["test2"]]

How to change legend title in ggplot

This should work:

p <- ggplot(df, aes(x=rating, fill=cond)) + 
           geom_density(alpha=.3) + 
           xlab("NEW RATING TITLE") + 
           ylab("NEW DENSITY TITLE")
p <- p + guides(fill=guide_legend(title="New Legend Title"))

(or alternatively)

p + scale_fill_discrete(name = "New Legend Title")

How to align an indented line in a span that wraps into multiple lines?

try to add display: block; (or replace the <span> by a <div>) (note that this could cause other problems becuase a <span> is inline by default - but you havn't posted the rest of your html)

Git push rejected "non-fast-forward"

I had this problem! I tried: git fetch + git merge, but dont resolved! I tried: git pull, and also dont resolved

Then I tried this and resolved my problem (is similar of answer of Engineer):

git fetch origin master:tmp
git rebase tmp
git push origin HEAD:master
git branch -D tmp

Convert list or numpy array of single element to float in python

I would simply use,

np.asarray(input, dtype=np.float)[0]
  • If input is an ndarray of the right dtype, there is no overhead, since np.asarray does nothing in this case.
  • if input is a list, np.asarray makes sure the output is of the right type.

How to delete a folder in C++?

The C++ Standard defines the remove() function, which may or may not delete a folder, depending on implementation. If it doesn't you need to use an implementation specific function such as rmdir().

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

How to send value attribute from radio button in PHP

When you select a radio button and click on a submit button, you need to handle the submission of any selected values in your php code using $_POST[] For example: if your radio button is:

<input type="radio" name="rdb" value="male"/>

then in your php code you need to use:

$rdb_value = $_POST['rdb'];

Ruby on Rails form_for select field with class

You can also add prompt option like this.

<%=, ['Item 1', 'Item 2'], {include_blank: "Select something"}, { :class => 'my_style_class' }) %>

Printing all properties in a Javascript Object

What about this:

var txt="";
var nyc = {
    fullName: "New York City",
    mayor: "Michael Bloomberg",
    population: 8000000,
    boroughs: 5

for (var x in nyc){
    txt += nyc[x];

Name [jdbc/mydb] is not bound in this Context

For those who use Tomcat with Bitronix, this will fix the problem:

The error indicates that no handler could be found for your datasource 'jdbc/mydb', so you'll need to make sure your tomcat server refers to your bitronix configuration files as needed.

In case you're using and files to configure the datasource, specify these two JVM arguments in tomcat:

(if you already used them, make sure your references are correct):

  • btm.root


-Dbtm.root="C:\Program Files\Apache Software Foundation\Tomcat 7.0.59""C:\Program Files\Apache Software Foundation\Tomcat 7.0.59\conf\" 

Now, restart your server and check the log.

What is the difference between the operating system and the kernel?

The difference between an operating system and a kernel:

The kernel is a part of an operating system. The operating system is the software package that communicates directly to the hardware and our application. The kernel is the lowest level of the operating system. The kernel is the main part of the operating system and is responsible for translating the command into something that can be understood by the computer. The main functions of the kernel are:

  1. memory management
  2. network management
  3. device driver
  4. file management
  5. process management

Read each line of txt file to new array element

$lines = array();
while (($line = fgets($file)) !== false)
    array_push($lines, $line);

Obviously, you'll need to create a file handle first and store it in $file.

Pass variable to function in jquery AJAX success callback

Just to share a similar problem I had in case it might help some one, I was using:

var NextSlidePage = $("bottomcontent" + Slide + ".html");

to make the variable for the load function, But I should have used:

var NextSlidePage = "bottomcontent" + Slide + ".html";

without the $( )

Don't know why but now it works! Thanks, finally i saw what was going wrong from this post!

How to run a Command Prompt command with Visual Basic code?

Yes. You can use Process.Start to launch an executable, including a console application.

If you need to read the output from the application, you may need to read from it's StandardOutput stream in order to get anything printed from the application you launch.

Remove all whitespace from C# string with regex

Why use Regex when you can simply use the Trim() method

Text='<%# Eval("FieldDescription").ToString().Trim() %>'


string test = "Testing    ";

Change first commit of project with Git?

If you want to modify only the first commit, you may try git rebase and amend the commit, which is similar to this post: How to modify a specified commit in git?

And if you want to modify all the commits which contain the raw email, filter-branch is the best choice. There is an example of how to change email address globally on the book Pro Git, and you may find this link useful

Find everything between two XML tags with RegEx

this can capture most outermost layer pair of tags, even with attribute in side or without end tags


edit: as mentioned in comment above, regex is always not enough to parse xml, trying to modify the regex to fit more situation only makes it longer but still useless

How to get a list of column names

$db = sqlite_open('mysqlitedb');
$cols = sqlite_fetch_column_types('form name'$db, SQLITE_ASSOC);
foreach ($cols as $column => $type) {
  echo "Column: $column  Type: $type\n";

How to create a temporary table in SSIS control flow task and then use it in data flow task?

I'm late to this party but I'd like to add one bit to user756519's thorough, excellent answer. I don't believe the "RetainSameConnection on the Connection Manager" property is relevant in this instance based on my recent experience. In my case, the relevant point was their advice to set "ValidateExternalMetadata" to False.

I'm using a temp table to facilitate copying data from one database (and server) to another, hence the reason "RetainSameConnection" was not relevant in my particular case. And I don't believe it is important to accomplish what is happening in this example either, as thorough as it is.

TypeError: p.easing[this.easing] is not a function

You need to include jQueryUI for the extended easing options.

I think there may be an option to only include the easing in the download, or at least just the base library plus easing.

Adding attribute in jQuery

$('#someid').attr('disabled', 'true');

How to stretch in width a WPF user control to its window?

The Canvas in WPF doesn't provide much automatic layout support. I try to steer clear of them for this reason (HorizontalAlignment and VerticalAlignment don't work as expected), but I got your code to work with these minor modifications (binding the Width and Height of the control to the canvas's ActualWidth/ActualHeight).

<Window x:Class="TCI.Indexer.UI.Operacao"
Title=" " MinHeight="550" MinWidth="675" Loaded="Load" 
ResizeMode="NoResize" WindowStyle="None" WindowStartupLocation="CenterScreen" 
WindowState="Maximized" Focusable="True" x:Name="windowOperacao">

<Canvas x:Name="canv">
        <tci:Status x:Name="ucStatus" Width="{Binding ElementName=canv
                                                    , Path=ActualWidth}" 
                                      Height="{Binding ElementName=canv
                                                    , Path=ActualHeight}"/> 
        <!-- the control which I want to stretch in width -->

The Canvas is the problem here. If you're not actually utilizing the features the canvas offers in terms of layout or Z-Order "squashing" (think of the flatten command in PhotoShop), I would consider using a control like a Grid instead so you don't end up having to learn the quirks of a control that works differently than you have come to expect with WPF.

Regex doesn't work in String.matches()

[a-z] matches a single char between a and z. So, if your string was just "d", for example, then it would have matched and been printed out.

You need to change your regex to [a-z]+ to match one or more chars.

What is the difference between ng-if and ng-show/ng-hide

The ng-if directive removes the content from the page and ng-show/ng-hide uses the CSS display property to hide content.

This is useful in case you want to use :first-child and :last-child pseudo selectors to style.

val() vs. text() for textarea

The best way to set/get the value of a textarea is the .val(), .value method.

.text() internally uses the .textContent (or .innerText for IE) method to get the contents of a <textarea>. The following test cases illustrate how text() and .val() relate to each other:

var t = '<textarea>';
console.log($(t).text('test').val());             // Prints test
console.log($(t).val('too').text('test').val());  // Prints too
console.log($(t).val('too').text());              // Prints nothing
console.log($(t).text('test').val('too').val());  // Prints too

console.log($(t).text('test').val('too').text()); // Prints test

The value property, used by .val() always shows the current visible value, whereas text()'s return value can be wrong.

Missing Push Notification Entitlement

FIX IDEA Hey guys so i have made an app and did not used any push notification functions but i still got an email. After checking the certificates, ids and profiles of the bundle identifier i used to create my app in apple store connect in the apple developer portal i realized that push notificiations were turned on.

What you have to do is:

go to apple developer login site where you can manage your certificates a.s.o 2. select "Certificates, IDs and Profiles" Tab on the right side 3. now select "Identifiers" 4. and the bundle id from the list to the right 5. now scroll down till you see push notification 6. turn it off 7. archive your build and reupload it to Apple Store Connect

Hope it helps!

"fatal: Not a git repository (or any of the parent directories)" from git status

This error got resolved when I tried initialising the git using git init . It worked

How to check if input file is empty in jQuery

Here is the jQuery version of it:

if ($('#videoUploadFile').get(0).files.length === 0) {
    console.log("No files selected.");

Making an image act like a button

You could use an image submit button:

<input type="image"  id="saveform" src="logg.png " alt="Submit Form" />

Where does the slf4j log file get saved?

slf4j is only an API. You should have a concrete implementation (for example log4j). This concrete implementation has a config file which tells you where to store the logs.

enter image description here

When slf4j catches a log messages with a logger, it is given to an appender which decides what to do with the message. By default, the ConsoleAppender displays the message in the console.

The default configuration file is :

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">

    <!-- By default => console -->
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>

    <Root level="error">
      <AppenderRef ref="Console"/>

If you put a configuration file available in the classpath, then your concrete implementation (in your case, log4j) will find and use it. See Log4J documentation.

Example of file appender :

<File name="File" fileName="${filename}">
    <pattern>%d %p %C{1.} [%t] %m%n</pattern>


Complete example with a file appender :

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">

    <File name="File" fileName="${filename}">
        <pattern>%d %p %C{1.} [%t] %m%n</pattern>

    <Root level="error">
      <AppenderRef ref="File"/>


How to get child element by class name?

In my opinion, each time you can, you should use Array and its methods. They are much, much faster then looping over the whole DOM / wrapper, or pushing stuff into empty array. Majority of solutions presented here you can call Naive as described here (great article btw):

My solution: (live preview on Codepen:

const wrapper = document.getElementById('test') // take a wrapper by ID -> fastest
const itemsArray = Array.from(wrapper.children) // make Array from his children

const pickOne = => { // loop over his children using .map() --> see MDN for more
   if(item.classList.contains('four')) // we place a test where we determine our choice
     item.classList.add('the-chosen-one') // your code here

How do I use regular expressions in bash scripts?

You need spaces around the operator =~

if [[ $i =~ "200[78]" ]];
  echo "OK"
  echo "not OK"

How to check if two words are anagrams

Lots of people have presented solutions, but I just want to talk about the algorithmic complexity of some of the common approaches:

  • The simple "sort the characters using Arrays.sort()" approach is going to be O(N log N).

  • If you use radix sorting, that reduces to O(N) with O(M) space, where M is the number of distinct characters in the alphabet. (That is 26 in English ... but in theory we ought to consider multi-lingual anagrams.)

  • The "count the characters" using an array of counts is also O(N) ... and faster than radix sort because you don't need to reconstruct the sorted string. Space usage will be O(M).

  • A "count the characters" using a dictionary, hashmap, treemap, or equivalent will be slower that the array approach, unless the alphabet is huge.

  • The elegant "product-of-primes" approach is unfortunately O(N^2) in the worst case This is because for long-enough words or phrases, the product of the primes won't fit into a long. That means that you'd need to use BigInteger, and N times multiplying a BigInteger by a small constant is O(N^2).

    For a hypothetical large alphabet, the scaling factor is going to be large. The worst-case space usage to hold the product of the primes as a BigInteger is (I think) O(N*logM).

  • A hashcode based approach is usually O(N) if the words are not anagrams. If the hashcodes are equal, then you still need to do a proper anagram test. So this is not a complete solution.

How to fix the datetime2 out-of-range conversion error using DbContext and SetInitializer?

Based on user @andygjp's answer, its better if you override the base Db.SaveChanges() method and add a function to override any date which does not fall between SqlDateTime.MinValue and SqlDateTime.MaxValue.

Here is the sample code

public class MyDb : DbContext
    public override int SaveChanges()
        return base.SaveChanges();

    private void UpdateDates()
        foreach (var change in ChangeTracker.Entries().Where(x => (x.State == EntityState.Added || x.State == EntityState.Modified)))
            var values = change.CurrentValues;
            foreach (var name in values.PropertyNames)
                var value = values[name];
                if (value is DateTime)
                    var date = (DateTime)value;
                    if (date < SqlDateTime.MinValue.Value)
                        values[name] = SqlDateTime.MinValue.Value;
                    else if (date > SqlDateTime.MaxValue.Value)
                        values[name] = SqlDateTime.MaxValue.Value;

Taken from the user @sky-dev's comment on

How do I "decompile" Java class files?

I tried several, and Procyon seemed to work the best for me. It's under active development and supports many features of the latest versions of Java.

These are the others I tried:

  • CFR
    • Promising, but often failed method decompilation. I'll be keeping my eye on this one. Also actively developed with support for the latest Java features.
  • Krakatau
    • Takes a different approach in that it tries to output equivalent Java code instead of trying to reconstruct the original source, which has the potential of making it better for obfuscated code. From my testing it was roughly on par with Procyon, but still nice to have something different. I did have to use the -skip command-line flag so it wouldn't stop on errors. Actively developed, and interestingly enough it's written in Python.
  • JD-GUI
  • JAD
    • Worked, but only supports Java 1.4 and below. Also available as an Eclipse plugin. No longer under development.