We collect practical, well-explained Bash one-liners, and promote best practices in Bash shell scripting. To get the latest Bash one-liners, follow @bashoneliners on Twitter. If you find any problems, report a bug on GitHub.



Extensive "cleanup" operations following "sudo yum upgrade"

 $ sudo yum upgrade && for pkg in $(package-cleanup --orphans -q); do repoquery $(rpm -q $pkg --queryformat="%{NAME}") | grep -q ".*" && echo $pkg; done | xargs sudo yum -y remove && for pkg in $(package-cleanup --leaves --all -q); do repoquery --groupmember $pkg | grep -q "@" || echo $pkg; done

— by openiduser143 on April 16, 2014, 9:58 p.m.


"sudo yum upgrade" does clean up outdated packages that the current upgrade replaces, but not other outdated packages or the ones that it willfully skips. Yes, that's what "package-cleanup --orphans" will finish, but "orphaned packages" also include packages that are at their latest version but just aren't updated by the repositories (usually a discrete .rpm installation). This one-liner uses "package-cleanup --orphans" but wraps around it to skip packages that aren't in the repositories anyway and just removes outdated packages that have a newer version in the repositories.

No, it's not at the end yet. It has a final command to display all packages that don't belong to any group. Choose any of the "manual extension" packages which aren't really necessary and only clog the system.


  • Specific to only rpm and yum
  • No, not just yum, it requires the yum-utils package (or whatever else provides package-cleanup and repoquery, if anything)


Get average CPU temperature from all cores.

 $ __=`sensors | grep Core` && echo \(`echo $__ | sed 's/.*+\(.*\).C\(\s\)\+(.*/\1/g' | tr "\n" "+" | head -c-1`\)\/`echo $__ | wc -l` | bc && unset __

— by openiduser139 on April 2, 2014, 10:04 p.m.


Uses the "sensors" command and bc along with sed, grep, head, and tr to fetch and calculate the average CPU temperature.


Concatenate multiple SSL certificate files to make one PEM file

 $ files=("yourcert.crt" "provider.ca.pem") && for i in ${files[@]} ; do $(cat $i >> yourcert.pem && echo "" >> yourcert.pem) ; done

— by renoirb on April 2, 2014, 5:41 p.m.


If you want to concat multiple files, you might end up with cat {a,b,c} >> yourcert.pem in a loop. But the problem is that it doesnt create new line after each cat.

This script is for that matter.

To use, e.g.:

cd /etc/ssl/certs
files=("yourcert.crt" "provider.ca.pem") && for i in ${files[@]} ; do $(cat $i >> yourcert.pem && echo "" >> yourcert.pem) ; done


List all non Git comited files and make a gzip archive with them

 $ GITFOLDER="/srv/some/folder"   ls-files --others --exclude-standard | tar czf ${GITFOLDER}-archives/uploads-$(date '+%Y%m%d%H%M').tar.gz -T -

— by renoirb on April 2, 2014, 5:18 p.m.


Assuming your web app has a git checkout is in /srv/some/folder (i.e. there is a /srv/some/folder/.git), archive the user uploads to /srv/some/folder-archives with that one liner.


cd /srv/some/folder
# this one-liner


A fully complete script would:

  • Check if $GITFOLDER exists
  • Check if $GITFOLDER has a .git directory
  • Create a temporary (e.g. tmp=$(mktemp)) file to log anything; if [ "$?" -ne 0 ] ; exit with status exit 1, otherwise delete the $tmp file and exit 0.


Have script run itself in a virtual terminal

 $ tty >/dev/null || { urxvt -hold -e "$0" "$@" & exit; }

— by openiduser111 on March 6, 2014, 3:18 a.m.


This can be the first line of a script that will be clicked from a graphical user interface in X to make it open up a virtual terminal to display output. If a terminal is already open it will run in the current terminal. It assumes urxvt and uses the hold option to keep from closing, both of which could be substituted for such as rxvt or add read at the end of the script.

  • It's a single line if statement that checks the exit code of tty which prints the current terminal name usually nothing under X.
  • The curly braces are needed for grouping.
  • A space is required after the opening brace { and a semicolon is required before the closing brace }.
  • Replacing what would be a semicolon, the ampersand & forks the terminal command to a second process and the launching script exits right away.
  • -e feeds to the terminal application the expression of $0which holds the path of the script itself and $@, the entire set of quoted arguments.


If the script is large, say several gigabytes and the system tries to make two copies of the script, twice the size of RAM or memory will be needed for loading it.


Converts DD/MM/YYYY date format to ISO-8601 (YYYY-MM-DD)

 $ sed 's_\([0-9]\{1,2\}\)/\([0-9]\{1,2\}\)/\([0-9]\{4\}\)_\3-\2-\1_g'

— by laurip on Dec. 30, 2013, 10:30 a.m.


Works on dates such as 01/02/1993, 01/10/1991, etc converting them to the superior ISO-8601 date format giving us 1993-02-01 and 1991-10-01 respectively. Test: echo '27/05/1994' | pattern given above Outputs 1994-05-27


Currently does not fully convert D/M/YYYY dates such as 1/2/1993 to 1993-02-01, but 1993-2-1


Convert text from decimal to little endian hexadecimal

 $ echo $(printf %08X 256 | grep -o .. | tac | tr -d '\n')

— by openiduser111 on Aug. 21, 2013, 8:44 p.m.


example of 256
printf %08X produces the 8 characters 00000100
grep breaks string by two characters
tac reverses
tr 00010000


could be put in a loop like this
for A in $(printf %08X'\n' 256 255); do echo $A | grep -o .. | tac | tr -d '\n'; done


Md5sum the last 5 files in a folder

 $ find /directory1/directory2/ -maxdepth 1 -type f | sort | tail -n 5 | xargs md5sum

— by openiduser113 on Aug. 21, 2013, 3:26 p.m.


  • find lists the files, no recursion, no directories, with full path
  • sort list files alphabetically
  • tail keep only the last 5 files
  • xargs send the list as arguments to md5sum
  • md5sum calculate the md5sum for each file


Probably can't handle spaces in file or directory names.


Get mac address from default interface OS X

 $ netstat -rn | awk '/default/ { print $NF }' | head -1 | xargs -I {}  ifconfig {} | awk '/ether/ {print $2}'

— by spotmac on Aug. 21, 2013, 10:28 a.m.


netstat -rn -> get routing table awk '/default/ { print $NF }' -> grep the default routes head -1 -> limit to the first result (is also the interface with the highest priority xargs -I {} ifconfig {} -> use the result to get data from ifconfig awk '/ether/ {print $2}' ->grep the mac address.


Tested on OSX.


Print a random cat

 $ wget -O - http://placekitten.com/$[500 + RANDOM % 500] | lp

— by openiduser104 on July 26, 2013, 11:43 p.m.


$RANDOM gives a random number.

http://placekitten.com is your cat place

wget -O - sends the output to stdout

lp prints


Tested on OSX

Cat rules


Convert a music file (mp3) to a mp4 video with a static image

 $ ffmpeg -loop_input -i cover.jpg -i soundtrack.mp3 -shortest -acodec copy output_video.mp4

— by kowalcj0 on May 17, 2013, 8:09 p.m.


Can come handy when you'd like to post a song to YT or somethin' :)

Can be easily wrapped up in a function:

function mp3tovidwithimg() {
  ffmpeg -loop_input -i $1 -i $2 -shortest -acodec copy $3

and used like that:

mp3tovidwithimg cover.jpeg music_track.mp3 output_vid.mp4


Find all of the distinct file extensions in a folder

 $ find . -type f | perl -ne 'print $1 if m/\.([^.\/]+)$/' | sort -u

— by kowalcj0 on May 17, 2013, 8:05 p.m.


Will find all of the distinct file extensions in a folder hierarchy.

Originally posted at: http://stackoverflow.com/questions/1842254/how-can-i-find-all-of-the-distinct-file-extensions-in-a-folder-hierarchy


Remove files and directories whose name is a timestamp older than a certain time

 $ ls | grep '....-..-..-......' | xargs -I {} bash -c "[[ x{} < x$(date -d '3 days ago' +%Y-%m-%d-%H%M%S) ]] && rm -rfv {}"

— by openiduser95 on May 7, 2013, 8:54 a.m.


Suppose you have a backup directory with backup snapshots named by timestamp:

$ ls

You want to remove snapshots older than 3 days. The one-liner does it:

$ date
Tue May  7 13:50:57 KST 2013
$ ls | grep '....-..-..-......' | sort | xargs -I {} bash -c "[[ x{} < x$(date -d '3 days ago' +%Y-%m-%d-%H%M%S) ]] && rm -rfv {}"
removed directory: `2013-05-03-103022'
removed directory: `2013-05-04-103033'


It doesn't work on OS X due to the differences between GNU date and BSD date).


Unhide all hidden files in the current directory.

 $ find . -maxdepth 1 -type f -name '\.*' | sed -e 's,^\./\.,,' | sort | xargs -iname mv .name name

— by openiduser93 on April 25, 2013, 7:46 a.m.


This will remove the leading dot from all files in the current directory using mv, effectively "unhiding" them.

It will not affect subdirectories.


Probably only works on GNU Linux, due to the specific usage of xargs.


Get only the latest version of a file from across mutiple directories.

 $ find . -name 'filename' | xargs -r ls -tc | head -n1

— by Anntoin on March 7, 2013, 11:39 p.m.


Shows latest file (by last modification of file status information) for the given pattern. So in this example filename = custlist*.xls.

We use ls to do the sorting (-t) and head to pick the top one. xargs is given the -r option so that ls isn't run if there is no match.


The filesystem needs to support ctime. Does not depend on a consistent naming scheme.


Get load average in a more parse-able format

 $ python -c 'import os; print os.getloadavg()[0]'

— by FoxWilson on Jan. 5, 2013, 3:32 a.m.


In short, it runs a Python one-line script which imports the 'os' module and uses it to get the load average. It then indexes into a tuple, using the index of zero. The tuple is like this: (one-minute-average, five-minute-average, fifteen-minute-average), so you could substitute 0 for 1 to get the five minute load average, or 2 to get the fifteen minute load average. I find this really useful when writing larger bash one-liners which require this information, as I don't have to parse the output of uptime.


Requires Python.


Function to extract columns from an input stream

 $ col() { awk '{print $('$(echo $* | sed -e s/-/NF-/g -e 's/ /),$(/g')')}'; }

— by Janos on Dec. 7, 2012, 4:14 p.m.


A slightly improved version of the original one-liner to allow negative indexes to extract columns relative to the end of the line, for example:

$ echo a b c | col 1 -0 -1
a c b

In this example the function expands to:

awk '{print $(1), $(NF-0), $(NF-1)}'


Define an own watch(1)-like function

 $ watch () { interrupted=false; trap "interrupted=true" INT; while ! $interrupted; do $*; sleep 1 || interrupted=true; done; }

— by ulidtko on Nov. 14, 2012, 10 p.m.


Once I needed a classical watch(1) command, but all I got on Mac OS X was -bash: watch: command not found.

So this is a simple interruptable while loop which can poll anything you like, e.g. watch grep alert /var/log/syslog.


Remove offending key from known_hosts file with one swift move

 $ vi +18d +wq ~/.ssh/known_hosts

— by Janos on Oct. 30, 2012, 9:28 p.m.


When you try to ssh to a server where the host key has changed then you probably get an error message like this:

Offending key in /home/jack/.ssh/known_hosts:18

If you know for sure that it was the server's admins who changed the host key, then your next move is to remove line 18 from the file so that ssh lets you connect after accepting the new key.

The one-liner does this in one swift move by passing simple commands to vi:

  • +18d -- delete line 18
  • +wq -- save the file and exit


Replace the header of all files found.

 $ find . -type f -name '*.html' -exec sed -i -e '1r common_header' -e '1,/STRING/d' {} \;

— by jam on Oct. 25, 2012, 9:29 a.m.


Replaces the lines from 1 to the first occurrence of a line starting with STRING of every file found with find.

  • find . -type f -name '*.html' returns a list of all files (not including directories) ending with .html. The ' ' in name is used to pass the literal wildcard * to the find command, instead of the * interpretation of bash, that is, repeat the command for every file in the current folder.
  • -exec execute the following command in each of the files found, using {} as the filename. the ; termination must be escaped with \;
  • sed -i replaces in file (output is the same file)
  • -e '1r common_header' -e '1,/STRING/d' {} reads common_header file, then finds the first occurrence of STRING and replaces it, deleting all the previous lines and putting the contents of common_header.


The -i flag of sed requires a parameter in BSD sed, used as the suffix of a backup file. To not use a backup file, you can pass an empty value with -i''.


Redirect stdout to a file you don't have write permission on

 $ echo hello | sudo tee -a /path/to/file

— by Janos on Sept. 11, 2012, 9:24 a.m.


  • The tee command copies standard input to standard output, making a copy in zero or more files.
  • If the -a flag is specified it appends instead of overwriting.
  • Calling tee with sudo makes it possible to write to files the current user has no permission to but root does.


`tail -f` a file until text is seen

 $ tail -f /path/to/file.log | sed '/^Finished: SUCCESS$/ q'

— by Janos on Aug. 22, 2012, 8:29 a.m.


tail -f until this exact line is seen:

Finished: SUCCESS

The exit condition does not have to be an exact line, it could just well be a simple pattern:

... | sed '/Finished/ q'


Recording SSH sessions

 $ ssh -l USER HOST | tee -a /path/to/file

— by LeandroToledo on Aug. 15, 2012, 5:04 p.m.


tee is a command which displays or pipes the output of a command and copies it into a file or a variable.

The -a option appends the output to the end of file instead of writing over it.

You can also create an alias in ~/.bashrc to record your session when using ssh:

function sshlog () { \ssh $@ 2>&1 | tee -a $(date +%Y%m%d).log; }
alias ssh=sshlog


Record audio from microphone or sound input from the console

 $ sox -t ossdsp -w -s -r 44100 -c 2 /dev/dsp -t raw - | lame -x -m s - File.mp3

— by Kleper on July 28, 2012, 8:55 p.m.


sox is a software that lets you connect directly to the sound card and send what passes for it in raw format and the system memory through the concatenation of the linux command we can make real-time audio processing is generated by licks and be converted to mp3.


Requires a plugin for alsa oss to run on modern distributions.


Use vim to pretty-print code with syntax highlighting

 $ vim +'hardcopy > output.ps' +q style.css 

— by Janos on July 21, 2012, 12:13 a.m.


If you have syntax highlighting properly setup in vim, this command will pretty-print the specified file with syntax highlighting to output.ps.

If you prefer PDF, you can convert using ps2pdf output.ps.