Hide

What's this?

commandlinefu.com is the place to record those command-line gems that you return to again and again.

Delete that bloated snippets file you've been using and share your personal repository with the world. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.


If you have a new feature suggestion or find a bug, please get in touch via http://commandlinefu.uservoice.com/

Get involved!

You can sign-in using OpenID credentials, or register a traditional username and password.

First-time OpenID users will be automatically assigned a username which can be changed after signing in.

Universal configuration monitoring and system of record for IT.
Hide

Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.

» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10

Subscribe to the feeds.

Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):

Subscribe to the feed for:

Hide

News

May 19, 2015 - A Look At The New Commandlinefu
I've put together a short writeup on what kind of newness you can expect from the next iteration of clfu. Check it out here.
March 2, 2015 - New Management
I'm Jon, I'll be maintaining and improving clfu. Thanks to David for building such a great resource!
Hide

Top Tags

Hide

Functions

Commands using cat from sorted by
Terminal - Commands using cat - 441 results
sudo mount -o remount,rw / && sudo cp /etc/hosts /etc/hosts.old && wget http://winhelp2002.mvps.org/hosts.txt && cp /etc/hosts ~/ && cat hosts.txt >> hosts && sudo cp hosts /etc/hosts
2016-06-06 15:01:19
User: bugmenot
Functions: cat cp mount sudo wget
1

Will append lines to the hosts file to do some basic ad blocking.

dir=/rom; a=$(find $dir -name \*.sh -exec cat '{}' \; | egrep -cv '^[[:space:]]*#'); b=$(find $dir -name \*.sh -exec cat '{}' \; | egrep -c '^[[:space:]]*#'); echo $((a+b)) lines = ${a} sloc [$((a*100/(a+b)))%] + ${b} comments [$((b*100/(a+b)))%]
cat user_public_key.pub | ssh root@<host> "cat | su -c 'mkdir -m 700 -p ~/.ssh && cat >> ~/.ssh/authorized_keys && chmod 600 ~/.ssh/authorized_keys' <user>"
scriptName="reorder_files.sh"; echo -e '#!/bin/sh\n' > "${scriptName}"; cat files.txt | while read file; do echo "touch ${file}; sleep 0.5;" >> "${scriptName}"; done; chmod +x "${scriptName}";
2016-04-19 11:52:00
User: programmer
Functions: cat chmod echo read
1

Create a bash script to change the modification time for each file in 'files.txt' such that they are in the same order as in 'files.txt'

File name for bash script specified by variable, 'scriptName'. It is made an executable once writing into it has been completed.

touch files.txt; cat reorder_files.sh | while read line; do x=`echo $line | sed 's/touch \([a-z0-9\.]\+.*.pdf\);.*/\1/'`; echo $x >> files.txt ; done;
echo /etc/*_ver* /etc/*-rel*; cat /etc/*_ver* /etc/*-rel*
2016-02-19 12:12:38
User: sxiii
Functions: cat echo
2

Just run this command and it will printout all the info available about your current distribution and package management system.

cat < /dev/tcp/74.125.224.40/80
cat *.jpg | ffmpeg -f image2pipe -r 1 -vcodec mjpeg -i - -vcodec libx264 out.mp4
while cat energy_now; do sleep 1; done |awk -v F=$(cat energy_full) -v C=60 'NR==1{P=B=$1;p=100/F} {d=$1-P; if(d!=0&&d*D<=0){D=d;n=1;A[0]=B=P}; if(n>0){r=g=($1-B)/n;if(n>C){r=($1-A[n%C])/C}}; A[n++%C]=P=$1; printf "%3d %+09.5f %+09.5f\n", p*$1, p*g, p*r}'
2015-09-19 15:45:40
User: sqweek
Functions: awk cat printf sleep
-1

Needs to be run in a battery sysfs dir, eg. /sys/class/power_supply/BAT0 on my system.

Displays the battery's current charge and the rate per-second at which energy is {dis,}charging. All values are displayed as percentages of "full" charge.

The first column is the current charge. The second is the rate of change averaged over the entire lifetime of the command (or since the AC cable was {un,}plugged), and the third column is the rate of change averaged over the last minute (controlled by the C=60 variable passed to awk).

The sample output captures a scenario where I ran 'yes' in another terminal to max out a CPU. My battery was at 76% charge and you can see the energy drain starts to rise above 0.01% per-second as the cpu starts working and the fan kicks in etc. While idle it was more like 0.005% per-second.

I tried to use this to estimate the remaining battery life/time until fully charged, but found it to be pretty useless... As my battery gets more charged it starts to charge slower, which meant the estimate was always wrong. Not sure if that's common for batteries or not.

exec 5<>/dev/tcp/time.nist.gov/13; cat <&5 & cat >&5; exec 5>&-
2015-07-30 21:12:38
User: tyzbit
Functions: cat exec
Tags: bash Linux unix
14

Ever needed to test firewalls but didn't have netcat, telnet or even FTP?

Enter /dev/tcp, your new best friend. /dev/tcp/(hostname)/(port) is a bash builtin that bash can use to open connections to TCP and UDP ports.

This one-liner opens a connection on a port to a server and lets you read and write to it from the terminal.

How it works:

First, exec sets up a redirect for /dev/tcp/$server/$port to file descriptor 5.

Then, as per some excellent feedback from @flatcap, we launch a redirect from file descriptor 5 to STDOUT and send that to the background (which is what causes the PID to be printed when the commands are run), and then redirect STDIN to file descriptor 5 with the second cat.

Finally, when the second cat dies (the connection is closed), we clean up the file descriptor with 'exec 5>&-'.

It can be used to test FTP, HTTP, NTP, or can connect to netcat listening on a port (makes for a simple chat client!)

Replace /tcp/ with /udp/ to use UDP instead.

echo "text to prepend" | cat - file
cat <file>|column -t
for p in $(pgrep -t $(cat /sys/class/tty/tty0/active)); do d=$(awk -v RS='\0' -F= '$1=="DISPLAY" {print $2}' /proc/$p/environ 2>/dev/null); [[ -n $d ]] && break; done; echo $d
2015-05-18 20:01:20
User: geyslan
Functions: awk cat echo
Tags: display xorg
1

It's useful when you cannot access your env (systemd) or the process DISPLAY variable is not set. Perhaps also when you have a multi-head/user configuration.

diff <(ssh $remote_site cat $file) $file
2015-05-09 11:11:56
User: hal8
Functions: cat diff ssh
0

opens the output of some command as a file so this also works with graphical editors like meld, kdiff3 etc

meld <(ssh $remote_site cat .zshrc) .zshrc
a=$(b=$(($LINES/2));f() { for c in $(seq $b); do for i in $(seq $c);do echo x;done|xargs echo;done };paste <(f) <(f|tac|tr 'x' '-') <(f|tac|tr 'x' '-') <(f)|tr '\t' ' ');(cat <<<"$a"|tac;cat <<<"$a")|tr '-' ' '
for USER in /var/spool/cron/*; do echo "--- crontab for $USER ---"; cat "$USER"; done
2014-12-11 19:48:46
User: tyzbit
Functions: cat echo
0

This is not exhaustive but after checking /etc/cron* is a good way to see if there are any other jobs any users may have set.

Note: this is a repost from a comment "flatcap" made on http://www.commandlinefu.com/commands/view/3726/print-crontab-entries-for-all-the-users-that-actually-have-a-crontab#comment, for which I am grateful and I take no credit.

while sleep 1; do if [ $(echo "$(cat /proc/loadavg | cut -d' ' -f1) > .8 " | bc) -gt 0 ]; then echo -e "\n\a"$(date)" \e[5m"$(cat /proc/loadavg)"\e[0m"; ps aux --sort=-%cpu|head -n 5; fi; done
2014-12-08 15:44:40
User: tyzbit
Functions: cat echo head ps sleep
0

This checks the system load every second and if it's over a certain threshold (.8 in this example), it spits out the date, system loads and top 4 processes sorted by CPU.

Additionally, the \a in the first echo creates an audible bell.

cat File.txt | grep -io 'http://www.acme.com/a/files/.*.pdf'| uniq
cat /etc/named.conf | grep -Po '(?<=(named/)).*(?=\.db)'
2014-10-25 20:16:17
User: KonKar
Functions: cat grep
0

Allows you to have a list of the domains on the server.

cat /etc/httpd/logs/access.log | awk '{ print $6}' | sed -e 's/\[//' | awk -F'/' '{print $1}' | sort | uniq -c
2014-10-13 13:39:53
User: suyashjain
Functions: awk cat sed sort uniq
1

The command will read the apache log file and fetch the virtual host requested and the number of requests.

cat /usr/share/dict/words | egrep '^\w{13,}$' | egrep -iv '(\w).*\1'
2014-09-29 12:52:09
User: hackerb9
Functions: cat egrep
6

This is the most straightforward approach: first regexp limits dictionary file to words with thirteen or more characters, second regexp discards any words that have a letter repeated. (Bonus challenge: Try doing it in a single regexp!)

echo "DISK:";df -Pl | grep -v "Filesystem" | awk '{print $5,$6}' ; echo "MEM:" ; free -mto | awk '{ print $1,$2,$3,$4 }'; echo "CPU:"; top -b -d1 -n1 | grep Cpu | awk '{print $2,$3,$4,$5,$6,$7,$8,$9}';echo "LOAD:"; cat /proc/loadavg
2014-09-29 12:43:52
User: injez
Functions: awk cat df echo free grep top
0

Monitoring system in one line :

DISK : disk space

MEM: memory ( mem , swap, Total)

CPU : all information about cpu activity

LOAD : load average

cat /var/log/syslog | grep score= | awk '{print $15}' | more
w !sudo cat >%
cat h.txt| while read line; do curl -s -X POST 'https://www.virustotal.com/vtapi/v2/file/report' --form apikey="APIKEY" --form resource="$line"|awk -F'positives\":' '{print "VTHits"$2}'|awk -F' ' '{print $1" "$2$5$6}'|sed 's/["}]//g' && sleep 15; done