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2011-03-12 - Confoo 2011 presentation
Slides are available from the commandlinefu presentation at Confoo 2011: http://presentations.codeinthehole.com/confoo2011/
2011-01-04 - Moderation now required for new commands
To try and put and end to the spamming, new commands require moderation before they will appear on the site.
2010-12-27 - Apologies for not banning the trolls sooner
Have been away from the interwebs over Christmas. Will be more vigilant henceforth.
2010-09-24 - OAuth and pagination problems fixed
Apologies for the delay in getting Twitter's OAuth supported. Annoying pagination gremlin also fixed.




Commands using perl from sorted by
Terminal - Commands using perl - 326 results
perl -e 'printf qq{%d\n}, time/86400;'
2011-01-14 21:56:19
User: gwchamb
Functions: perl

There are some environments that use this value for password and account expiration. It's helpful to be able to quickly determine the number of days since the Unix epoch (dse) when working directly with the configuration files as an administrator.

perl -le 'print time()'
perl -e 'print for(map{chr(hex)}("4861707079204E6577205965617221"=~/(.{2})/g)),"\n";'
cat /dev/urandom | hexdump -C | highlight ca fe 3d 42 e1 b3 ae f8 | perl -MTime::HiRes -pne "Time::HiRes::usleep(rand()*1000000)"
2010-12-29 21:26:18
User: doherty
Functions: cat hexdump perl

Nobody wants the boss to notice when you're slacking off. This will fill your shell with random data, parts of it highlighted. Note that 'highlight' is the Perl module App::highlight, not "a universal sourcecode to formatted text converter." You'll also need Term::ANSIColor.

perl -wlne'/title>([^<]+)/i&&rename$ARGV,"$1.html"' *.html
2010-12-29 05:39:41
User: mhs
Functions: perl
Tags: rename

The above one-liner could be run against all HTML files in a directory. It renames the HTML files based on the text contained in their title tag. This helped me in a situation where I had a directory containing thousands of HTML documents with meaningless filenames.

perl -ane 'print unless $x{$F[0]}++' infile > outfile
netstat -atn | perl -ane 'if ( $F[3] =~ /(\d+)$/ ) { $x{$1}=1 } END{ print( (grep {!$x{$_}} 32768..61000)[0] . "\n" )}'
netstat -atn | perl -0777 -ne '@ports = /tcp.*?\:(\d+)\s+/imsg ; for $port (32768..61000) {if(!grep(/^$port$/, @ports)) { print $port; last } }'
2010-12-14 20:44:37
User: bashrc
Functions: last netstat perl

Not really better - just different ;)

There's probably a really simple solution out there somewhere...

perl -MMIME::Base64 -ne 'print decode_base64($_)' < file.txt > out
2010-12-13 23:35:20
User: dmmst19
Functions: perl

If you are in an environment where you don't have the base64 executable or MIME tools available, this can be very handy for salvaging email attachments when the headers are mangled but the encoded document itself is intact.

perl -e 'for(;;){@d=split("",`date +%H%M%S`);print"\r";for(0..5){printf"%.4b ",$d[$_]}sleep 1}'
2010-12-04 00:05:54
User: putnamhill
Functions: perl

Fun idea! This one adds seconds and keeps running on the same line. Perl's probably cheating though. :)

perl -pe 'eof()||s/\n/<SOMETEXT>/g' file.txt
2010-12-02 01:19:27
User: eightmillion
Functions: perl

This command turns a multi-line file into a single line joined with <SOMETEXT>. To skip blank lines, use:

perl -pe '(eof()||s/^\s*$//)||s/\n/<SOMETEXT>/g' file.txt
apt-cache search perl | grep module | awk '{print $1;}' | xargs sudo apt-get install -y

I used this to mass install a lot of perl stuff. Threw it together because I was feeling *especially* lazy. The 'perl' and the 'module' can be replaced with whatever you like.

find . -type f -print0 | xargs -0 perl -pi.save -e 'tr/A-Z/a-z/'
2010-11-25 13:55:34
User: depesz
Functions: find perl xargs
Tags: perl find regex

In this way it doesn't have problems with filenames with spaces.

perl -e "tr/[A-Z]/[a-z]/;" -pi.save $(find . -type f)
pcharc(){ perl -e 'for (0..255) {$_ = chr($_); print if /['$1']/}' | cat -v; echo;}
2010-11-13 00:32:41
User: putnamhill
Functions: cat perl
Tags: perl

Today I needed a way to print various character classes to use as input for a program I was writing. Also a nice way to visualize character classes.

dpkg -L iptables | perl -lne 'print if -f && -x'
git status | perl -F'\s' -nale 'BEGIN { $a = 0 }; $a = 1 if $_ =~ /changed but not updated/i; print $F[-1] if ( $a && -f $F[-1] )'
2010-10-15 07:58:14
Functions: perl
Tags: status git perl

Parse the output of git status.

Once the line '# Changed but not updated:' has passed print every last part of the line if it exists on disk.

diff <(perl -wpl -e '$_ =~ s/^\s+|\s+$//g ;' file1) <(perl -wpl -e '$_ =~ s/^\s+|\s+$//g ;' file2)
2010-10-06 19:14:42
User: jemptymethod
Functions: diff perl
Tags: bash diff perl

**NOTE** Tekhne's alternative is much more succinct and its output conforms to the files actual contents rather than with white space removed

My command on the other hand uses bash process substitution (and "Minimal" Perl), instead of files, to first remove leading and trailing white space from lines, before diff'ing the streams. Very useful when differences in indentation, such as in programming source code files, may be irrelevant

perl -e 'print crypt("PASSWORD",int(rand(128))).$/;'
find . -iname '*.jpg' -type f -print0 |perl -0 -ne '$a+=-s $_;END{print "$a\n"}'
2010-09-12 13:14:12
Functions: find perl

This deals nicely with filenames containing special characters and can deal with more files than can fit on a commandline. It also avoids spawning du.

perl -e 'print "\n"x100'
2010-09-07 10:11:10
User: SunX
Functions: perl

Perl variant of echo several blank lines command

useradd -m -p $(perl -e'print crypt("pass", "mb")') user
2010-09-03 19:00:56
User: mariusbutuc
Functions: perl useradd

Function: char * crypt (const char *key, const char *salt)

The crypt function takes a password, key, as a string, and a salt character array which is described below, and returns a printable ASCII string which starts with another salt. It is believed that, given the output of the function, the best way to find a key that will produce that output is to guess values of key until the original value of key is found.

The salt parameter does two things. Firstly, it selects which algorithm is used, the MD5-based one or the DES-based one. Secondly, it makes life harder for someone trying to guess passwords against a file containing many passwords; without a salt, an intruder can make a guess, run crypt on it once, and compare the result with all the passwords. With a salt, the intruder must run crypt once for each different salt.

For the MD5-based algorithm, the salt should consist of the string $1$, followed by up to 8 characters, terminated by either another $ or the end of the string. The result of crypt will be the salt, followed by a $ if the salt didn't end with one, followed by 22 characters from the alphabet ./0-9A-Za-z, up to 34 characters total. Every character in the key is significant.

For the DES-based algorithm, the salt should consist of two characters from the alphabet ./0-9A-Za-z, and the result of crypt will be those two characters followed by 11 more from the same alphabet, 13 in total. Only the first 8 characters in the key are significant.

perl -MURI::Escape -e 'print uri_escape("String encoded to a url");'
ls | perl -lne '++$x{lc $1} if /[.](.+)$/ }{ print for keys %x'
2010-08-13 20:05:15
User: recursiverse
Functions: ls perl

All with only one pipe. Should be much faster as well (sort is slow). Use find instead of ls for recursion or reliability.

Edit: case insensitive

perl -e 'print 1+1 ."\n";'