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Commands tagged while from sorted by
Terminal - Commands tagged while - 32 results
find . -type f -name "*.txt" | while read; do (($(cat $THISFILE | wc -l) < 10)) && rm -vf "$THISFILE"; done
/usr/bin/tail -fn0 /path/to/apache_error.log | while read line; do /usr/local/bin/growlnotify --title "Apache Notice" --message "$line"; done &
2013-01-22 05:25:41
User: jhyland87
Functions: read
0

Simply add this to whatever apache startup script you have, or if you are on a MAC, create a new automator application. This will show a pretty growl notification whenever theres a new Apache error log entry. Useful for local development

while sleep 1; do foo; done
2012-09-14 20:21:04
User: lowbatteries
Functions: sleep
0

For use when you can't use "watch" (user-defined functions, aliases). This isn't mine - its an alternate posted in the comments by flatcap, and is the shortest and easiest to remember.

hourglass(){ trap 'tput cnorm' 0 1 2 15 RETURN;local s=$(($SECONDS +$1));(tput civis;while (($SECONDS<$s));do for f in '|' '\' '-' '/';do echo -n "$f";sleep .2s;echo -n $'\b';done;done;);}
2012-06-21 05:40:22
User: AskApache
Functions: echo sleep tput trap
13

Displays an animated hourglass for x amount of seconds

while read ; do python <script> ; done
2012-02-23 22:29:09
User: Zulu
Functions: python read
-2

Very useful for test a script. After launch this command, you only have to press ENTER for launch your script again. I work with screen and tape ENTER instead of '!!'+ENTER

If you break your script with CTRL-C, it will wait for press ENTER and will re-launch

You can write like it : while read -p "Press ENTER" ; do python ; done

while ( nc -l 80 < /file.htm > : ) ; do : ; done &
2012-01-02 02:17:25
User: Zulu
Tags: while nc daemon
11

Allow to launch nc like a daemon, in background until you still stop it.

You can stop it with kill %1 (jobs method) or kill PID.

The -k option can force nc to listen another connection, but if you use redirection, it will work only one time.

The loop's inside doesn't do anything, but we can imagine to send a message to screen when a connection is established

(set -e; while true; do TEST_COMMAND; done) | tee log
2011-09-06 12:29:11
User: wipu
Functions: set tee
Tags: tee while set
-3

If you need to fix a randomly failing test (race condition), you need to run it until you get that hard-to-reproduce failure.

ping -a IP-ADDRESS
2011-04-28 13:51:12
User: markussesser
Functions: ping
0

pcspkr have to be enabled!

modprobe pcspkr

xset b on

continuar=true; while $continuar; do if ping -c 3 [target_IP_address] 2>&1> /dev/null ; then mplayer [sound_file]; continuar=false; break; fi; done
2011-04-25 21:44:05
User: mack
Functions: ping
0

If you're very busy and don't want to wait for a ping response, use it.

This command will be waiting for a successful ping response, to play a sound file to warn you that the target host is available.

for p in `ps L|cut -d' ' -f1`;do echo -e "`tput clear;read -p$p -n1 p`";ps wwo pid:6,user:8,comm:10,$p kpid -A;done
2

While going through the source code for the well known ps command, I read about some interesting things.. Namely, that there are a bunch of different fields that ps can try and enumerate for you. These are fields I was not able to find in the man pages, documentation, only in the source.

Here is a longer function that goes through each of the formats recognized by the ps on your machine, executes it, and then prompts you whether you would like to add it or not. Adding it simply adds it to an array that is then printed when you ctrl-c or at the end of the function run. This lets you save your favorite ones and then see the command to put in your .bash_profile like mine at : http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html

Note that I had to do the exec method below in order to pause with read.

t ()

{

local r l a P f=/tmp/ps c='command ps wwo pid:6,user:8,vsize:8,comm:20' IFS=' ';

trap 'exec 66

exec 66 $f && command ps L | tr -s ' ' >&$f;

while read -u66 l >&/dev/null; do

a=${l/% */};

$c,$a k -${a//%/} -A;

yn "Add $a" && P[$SECONDS]=$a;

done

}

cowsay -l | sed '1d;s/ /\n/g' | while read f; do cowsay -f $f $f;done
while [[ COUNTER -le 10 && IFS=':' ]]; do for LINE in $(cat /tmp/list); do some_command(s) $LINE; done; COUNTER=$((COUNTER+1)); done
2010-09-01 15:09:59
User: slashdot
Functions: cat
0

At times I find that I need to loop through a file where each value that I need to do something with is not on a separate line, but rather separated with a ":" or a ";". In this instance, I create a loop within which I define 'IFS' to be something other than a whitespace character. In this example, I iterate through a file which only has one line, and several fields separated with ":". The counter helps me define how many times I want to repeat the loop.

ls | while read -r FILE; do mv -v "$FILE" `echo $FILE | tr -d ' '`; done
2010-08-14 14:10:48
User: IgnitionWeb
Functions: ls mv read tr
Tags: space echo while tr
-3

all files in the directory get moved, in doing so the new name of the file is the original name with out spaces (using translate command)

find <dir> -name "<pattern>" | while read file; do echo -n .; output=$(<command>) || (echo ; echo $file:; echo "$output"; ); done
2010-08-10 11:45:31
User: Marco
Functions: echo find read
2

This is a command template for achiving the following:

* loop over files --> find -name "" | while read file; do ...; done

* output progress --> echo -n .

* execute some command on each file and save output for later usage --> output=$()

* if command failed, open subshell and echo newline --> || (echo;...;...;)

* echo output of command --> echo "$output"

cut -f 1 three-column.txt > first-column.txt
2010-07-11 10:13:45
User: postrational
Functions: cut
4

There is a common command for outputting a field or list of fields from each line in a file. Why wouldn't you just use cut?

awk '{print $1}' < three-column.txt > first-column.txt
while read col1 col23; do echo $col1; done < three-column.txt > first-column.txt
while read l; do echo ${l%% *}; done < three-column-list.txt > only-first-column.txt
2010-07-09 03:42:56
User: zed
Functions: echo read
1

The above is an example of grabbing only the first column. You can define the start and end points specifically by chacater position using the following command:

while read l; do echo ${l:10:40}; done < three-column-list.txt > column-c10-c40.txt

Of course, it doesn't have to be a column, or extraction, it can be replacement

while read l; do echo ${l/foo/bar}; done < list-with-foo.txt > list-with-bar.txt

Read more about parameter expansion here:

http://wiki.bash-hackers.org/syntax/pe

Think of this as an alternative to awk or sed for file operations

statt(){ C=c;stat --h|sed '/Th/,/NO/!d;/%/!d'|while read l;do p=${l/% */};[ $p == %Z ]&&C=fc&&echo ^FS:^;echo "`stat -$C $p \"$1\"` ^$p^${l#%* }";done|column -ts^; }
2010-06-11 23:31:03
User: AskApache
Functions: column read sed
3

This shows every bit of information that stat can get for any file, dir, fifo, etc. It's great because it also shows the format and explains it for each format option.

If you just want stat help, create this handy alias 'stath' to display all format options with explanations.

alias stath="stat --h|sed '/Th/,/NO/!d;/%/!d'"

To display on 2 lines:

( F=/etc/screenrc N=c IFS=$'\n'; for L in $(sed 's/%Z./%Z\n/'<<<`stat --h|sed -n '/^ *%/s/^ *%\(.\).*$/\1:%\1/p'`); do G=$(echo "stat -$N '$L' \"$F\""); eval $G; N=fc;done; )

For a similarly powerful stat-like function optimized for pretty output (and can sort by any field), check out the "lll" function

http://www.commandlinefu.com/commands/view/5815/advanced-ls-output-using-find-for-formattedsortable-file-stat-info

From my .bash_profile ->

http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html

wait $!
2010-06-07 21:56:36
User: noahspurrier
Functions: wait
2

Referring to the original post, if you are using $! then that means the process is a child of the current shell, so you can just use `wait $!`. If you are trying to wait for a process created outside of the current shell, then the loop on `kill -0 $PID` is good; although, you can't get the exit status of the process.

sortwc () { local L;while read -r L;do builtin printf "${#L}@%s\n" "$L";done|sort -n|sed -u 's/^[^@]*@//'; }
2010-05-20 20:13:52
User: AskApache
Functions: printf read sed sort
2

This provides a way to sort output based on the length of the line, so that shorter lines appear before longer lines. It's an addon to the sort that I've wanted for years, sometimes it's very useful. Taken from my http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html

alias dateh='date --help|sed -n "/^ *%%/,/^ *%Z/p"|while read l;do F=${l/% */}; date +%$F:"|'"'"'${F//%n/ }'"'"'|${l#* }";done|sed "s/\ *|\ */|/g" |column -s "|" -t'
21

If you have used bash for any scripting, you've used the date command alot. It's perfect for using as a way to create filename's dynamically within aliases,functions, and commands like below.. This is actually an update to my first alias, since a few commenters (below) had good observations on what was wrong with my first command.

# creating a date-based ssh-key for askapache.github.com

ssh-keygen -f ~/.ssh/`date +git-$USER@$HOSTNAME-%m-%d-%g` -C 'webmaster@askapache.com' # /home/gpl/.ssh/git-gplnet@askapache.github.com-04-22-10

# create a tar+gzip backup of the current directory

tar -czf $(date +$HOME/.backups/%m-%d-%g-%R-`sed -u 's/\//#/g' <<< $PWD`.tgz) . # tar -czf /home/gpl/.backups/04-22-10-01:13-#home#gpl#.rr#src.tgz .

I personally find myself having to reference

date --help

quite a bit as a result. So this nice alias saves me a lot of time. This is one bdash mofo. Works in sh and bash (posix), but will likely need to be changed for other shells due to the parameter substitution going on.. Just extend the sed command, I prefer sed to pretty much everything anyways.. but it's always preferable to put in the extra effort to go for as much builtin use as you can. Otherwise it's not a top one-liner, it's a lazyboy recliner.

Here's the old version:

alias dateh='date --help|sed "/^ *%%/,/^ *%Z/!d;s/ \+/ /g"|while read l;do date "+ %${l/% */}_${l/% */}_${l#* }";done|column -s_ -t'

This trick from my [ http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html bash_profile ]

wait
2010-01-15 04:03:11
User: bhepple
Functions: wait
0

If you really _must_ use a loop, this is better than parsing the output of 'ps':

PID=$! ;while kill -0 $PID &>/dev/null; do sleep 1; done

kill -0 $PID returns 0 if the process still exists; otherwise 1

while (ps -ef | grep [r]unning_program_name); do sleep 10; done; command_to_execute
2010-01-14 16:26:34
User: m_a_xim
Functions: grep ps sleep
-2

The '[r]' is to avoid grep from grepping itself. (interchange 'r' by the appropriate letter)

Here is an example that I use a lot (as root or halt will not work):

while (ps -ef | grep [w]get); do sleep 10; done; sleep 60; halt

I add the 'sleep 60' command just in case something went wrong; so that I have time to cancel.

Very useful if you are going to bed while downloading something and do not want your computer running all night.

dd if=fromfile of=tofile & DDPID=$! ; sleep 1 ; while kill -USR1 $DDPID ; do sleep 5; done
2010-01-12 15:01:44
User: deltaray
Functions: dd kill sleep
Tags: dd kill while sleep
4

This is a more accurate way to watch the progress of a dd process. The $DDPID=$! is needed so that you don't get the PID of the sleep. The sleep 1 is needed because in my testing at least, if you run kill -USR1 against dd too quickly, it will kill it off instead of display the status. So you need to wait a second, probably so that it can configure itself to trap the USR1 signal.