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.


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

Psst. Open beta.

Wow, didn't really expect you to read this far down. The latest iteration of the site is in open beta. It's a gentle open beta-- not in prime-time just yet. It's being hosted over at UpGuard (link) and you are more than welcome to give it a shot. Couple things:

  • » The open beta is running a copy of the database that will not carry over to the final version. Don't post anything you don't mind losing.
  • » If you wish to use your user account, you will probably need to reset your password.
Your feedback is appreciated via the form on the beta page. Thanks! -Jon & CLFU Team

All commands from sorted by
Terminal - All commands - 12,372 results
eject /dev/sdb; sleep 1; eject -t /dev/sdb
2009-10-11 23:16:49
User: Escher
Functions: eject sleep
7

Remounts a usb disk /dev/sdb, without having to physically remove and reinsert. (Gnome desktop)

b="http://2010.utosc.com"; for p in $( curl -s $b/presentation/schedule/ | grep /presentation/[0-9]*/ | cut -d"\"" -f2 ); do f=$(curl -s $b$p | grep "/static/slides/" | cut -d"\"" -f4); if [ -n "$f" ]; then echo $b$f; curl -O $b$f; fi done
2009-10-11 17:28:46
User: danlangford
Functions: cut echo grep
Tags: curl cut for UTOSC
2

miss a class at UTOSC2010? need a refresher? use this to curl down all the presentations from the UTOSC website. (http://2010.utosc.com) NOTE/WARNING this will dump them in the current directory and there are around 37 and some are big - tested on OSX10.6.1

rename 'y/A-Z/a-z/' *
ssh -R 2001:localhost:22 [username]@[remote server ip]
2009-10-11 09:51:04
User: felix001
Functions: ssh
7

Allows you to establish a tunnel (encapsulate packets) to your (Server B) remote server IP from your local host (Server A).

On Server B you can then connect to port 2001 which will forward all packets (encapsulated) to port 22 on Server A.

-- www.fir3net.com --

find my_root_dir -depth -exec rename 's/(.*)\/([^\/]*)/$1\/\L$2/' {} \;
AUTOSSH_POLL=1 autossh -M 21010 hostname -t 'screen -Dr'
2009-10-11 06:04:29
Functions: hostname
11

Only useful for really flakey connections (but im stuck with one for now). Though if youre in this situation ive found this to be a good way to run autossh and it does a pretty good job of detecting when the session is down and restarting. Combined with the -t and screen commands this pops you back into your working session lickety split w/ as few headaches as possible.

And if autossh is a bit slow at detecting the downed ssh connection, just run this in another tab/terminal window to notify autossh that it should drop it and start over. Basically for when polling is too slow.

kill -SIGUSR1 `pgrep autossh`

ps aux --sort=%mem,%cpu
2009-10-10 22:48:51
User: mrwill
Functions: ps
13

you can also pipe it to "tail" command to show 10 most memory using processes.

ifs () { echo -n "${IFS}"|hexdump -e '"" 10/1 "'\''%_c'\''\t" "\n"' -e '"" 10/1 "0x%02x\t" "\n\n"'|sed "s/''\|\t0x[^0-9]//g; $,/^$/d"
2009-10-10 22:41:35
User: dennisw
Functions: echo hexdump sed
2

You can display, save and restore the value of $IFS using conventional Bash commands, but these functions, which you can add to your ~/.bashrc file make it really easy.

To display $IFS use the function ifs shown above. In the sample output, you can see that it displays the characters and their hexadecimal equivalent.

This function saves it in a variable called $saveIFS:

sifs () { saveIFS=$IFS; }

Use this function to restore it

rifs () { IFS=$saveIFS; }

Add this line in your ~/.bashrc file to save a readonly copy of $IFS:

declare -r roIFS=$IFS

Use this function to restore that one to $IFS

rrifs () { IFS=$roIFS; }
tree -d
2009-10-10 21:40:56
User: bsussman
2

tree has lots of parms - man is your friend

find / -name FILENAME
find . -type d -print | sed -e 's;[^/]*/;..........;g'|awk '{print $0"-("NR-1")"}'
:set scroll=0
2009-10-10 07:38:27
User: tmsh
1

Resets the scroll parameter to the default (half the rows in the current window). The scroll parameter can be inadvertently set to 1, e..g., if you type '1 Ctrl-D' or '1 Ctrl-U' in normal mode.

( trap '' 1; ( nice -n 19 sleep 2h && command rm -v -rf /garbage/ &>/dev/null && trap 1 ) & )
2

Check out the usage of 'trap', you may not have seen this one much. This command provides a way to schedule commands at certain times by running them after sleep finishes sleeping. In the example 'sleep 2h' sleeps for 2 hours. What is cool about this command is that it uses the 'trap' builtin bash command to remove the SIGHUP trap that normally exits all processes started by the shell upon logout. The 'trap 1' command then restores the normal SIGHUP behaviour.

It also uses the 'nice -n 19' command which causes the sleep process to be run with minimal CPU.

Further, it runs all the commands within the 2nd parentheses in the background. This is sweet cuz you can fire off as many of these as you want. Very helpful for shell scripts.

ps -ef | grep pmon
find . -type f -printf "%h\n" | cut -d/ -f-2 | sort | uniq -c | sort -rn
2009-10-09 23:49:53
User: ivancho
Functions: cut find sort uniq
Tags: file count
6

counts the total (recursive) number of files in the immediate (depth 1) subdirectories as well as the current one and displays them sorted.

Fixed, as per ashawley's comment

arping 192.168.1.2
2009-10-09 21:39:35
5

arping sends ARP requests to a neighboring host. This won't work if there is an ARP subnet gateway in the middle. If there is, you'll just get the gateway's MAC address not the host's address you are really trying to get to.

watch -n60 du /var/log/messages
2009-10-09 18:37:45
User: matrixguy
Functions: du watch
8

use "watch" instead of while-loops in these simple cases

while [ 1 ]; do du /var/log/messages;sleep 60; done
2009-10-09 17:22:19
User: savanik
Functions: du
0

Got a file you're generating and you want the size without typing in 'ls -l file' all the time? Use this instead.

head -c10 <(echo $RANDOM$RANDOM$RANDOM)
2009-10-09 15:09:02
User: jgc
Functions: echo head
Tags: HEAD random
0

Makes use of $RANDOM environment variable.

if [ "$testnum" -eq "$testnum" 2>/dev/null ]; then echo It is numeric; fi
2009-10-09 14:57:27
User: jgc
Functions: echo
0

Using the standard numeric comparison but suppressing the STDERR output acts as the simplest way to check a value is numeric. See sample output for some examples.

echo $X | egrep "^[0-9]+$"
tr -c -d 0-9 < /dev/urandom | head -c 10
netstat -an|grep -ci "tcp.*established"
2009-10-09 01:08:18
User: romulusnr
Functions: grep netstat
3

If you want prepend/append text just wrap in echo:

echo Connected: `netstat -an|grep -ci "tcp.*established"`
for USER in `ls /var/spool/cron`; do echo "=== crontab for $USER ==="; echo $USER; done
grep $'\t' file.txt