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

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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
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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:

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All commands from sorted by
Terminal - All commands - 12,362 results
: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
getenforce
2009-10-08 23:06:00
User: felix001
-5

Shows the status of SElinux.

-- fir3net.com --

ls -d */
2009-10-08 22:07:22
User: brianmuckian
Functions: ls
37

-d: list directory entries instead of contents, and do not dereference symbolic links

rm ~/.bash_history; ln -s /dev/null ~/.bash_history
2009-10-08 17:40:48
Functions: ln rm
-5

Remove your BASH history and then link it to /dev/null

tput smcup; echo "Doing some things..."; sleep 2; tput rmcup
2009-10-08 16:48:04
User: jgc
Functions: echo sleep tput
8

Very useful for interactive scripts where you would like to return the terminal contents to its original state before the script was run. This would be similar to how vi exits and returns you to your original terminal screen.

Save and clear the terminal contents with:

tput smcup

Execute some commands, then restore the saved terminal contents with:

tput rmcup
ls -F|grep /
2009-10-08 16:35:15
User: romulusnr
Functions: grep ls
-1

No need for -l and the output can be sent directly into another function expecting directory names.

perl -pi -e 's/([[:lower:]]+)/uc $1/gsex' file
2009-10-08 14:18:50
Functions: perl
Tags: perl
-2

same, except it works on any OS with Perl installed. DOS, Windose, whatever

export HISTFILE=/dev/null && kill -9 $$
rm ~/.bash_history && kill -9 $$
2009-10-08 12:25:47
User: Velenux
Functions: kill rm
-5

Best way I know to get rid of .bash_history and don't allow bash to save the current one on exit

Edit: added ~/ before .bash_history, just in case... ;)

(printf "PERMISSIONS LINKS OWNER GROUP SIZE MONTH DAY HH:MM PROG-NAME\n" \ ; ls -l | sed 1d) | column -t
tr '[:lower:]' '[:upper:]' <"$1"
2009-10-08 11:34:07
User: opexxx
Functions: tr
Tags: tr
6

Transforms a file to all uppercase.

head -c4 /dev/urandom | od -N4 -tu4 | sed -ne '1s/.* //p'