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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.




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Terminal - All commands - 12,018 results
cat /dev/mem > /dev/audio
unset files i; set -f; O=$IFS; while IFS= read -r -d $'\0' files[i++]; do :; done < <(find . -name '*.avi' -print0) && IFS=$O; set +f && echo "Running: mplayer \"${files[ $(( $RANDOM % ${#files[@]} )) ]}\""
2009-02-18 16:53:57
User: DEinspanjer
Functions: echo find read set unset

unsets variables used by the one-liner

sets up the IFS bash variable to not be affected by whitespace and disables extra glob expansion

uses read to slurp the results of the find command into an array

selects an element of the array at random to be passed as an argument to mplayer

last | grep -v "^$" | awk '{ print $1 }' | sort -nr | uniq -c
2009-02-18 16:38:59
User: hkyeakley
Functions: awk grep last sort uniq

This command takes the output of the 'last' command, removes empty lines, gets just the first field ($USERNAME), sort the $USERNAMES in reverse order and then gives a summary count of unique matches.

perl -pe '$_=reverse;s/\d{3}(?=\d)(?!.*?\.)/$&,/g;$_=reverse'
2009-02-18 16:34:18
User: sil
Functions: perl

Insert a comma where necessary when counting large numbers. I needed to separate huge amounts of packets and after 12+ hours of looking in a terminal, I wanted it in readable form.

blockdev --setra 1024 /dev/sdb
2009-02-18 16:27:01
User: starchox

(WARN) This will absolutely not work on all systems, unless you're running large, high speed, hardware RAID arrays. For example, systems using Dell PERC 5/i SAS/SATA arrays. If you have a hardware RAID array, try it. It certainly wont hurt.

You may be can test the speed disk with some large file in your system, before and after using this:

time dd if=/tmp/disk.iso of=/dev/null bs=256k

To know the value of block device parameter known as readahead.

blockdev --getra /dev/sdb

And set the a value 1024, 2048, 4096, 8192, and maybe 16384... it really depends on the number of hard disks, their speed, your RAID controller, etc. (see sample)

printf %d 0x`dd if=/dev/urandom bs=1 count=4 2>/dev/null | od -x | awk 'NR==1 {print $2$3}'`
2009-02-18 16:23:09
User: introp
Functions: awk od printf

Sometimes, in a shell script, you need a random number bigger than the range of $RANDOM. This will print a random number made of four hex values extracted from /dev/urandom.

svn diff $* | colordiff | less -r
2009-02-18 16:19:08
User: introp
Functions: diff less

I put this in a shell script called "svndiff", as it provides a handy decorated "svn diff" output that is colored (which you can't see here) and paged. The -r is required so less doesn't mangle the color codes.

wget -qO - http://infiltrated.net/blacklisted|awk '!/#|[a-z]/&&/./{print "iptables -A INPUT -s "$1" -j DROP"}'
2009-02-18 16:08:23
User: sil
Functions: wget

Blacklisted is a compiled list of all known dirty hosts (botnets, spammers, bruteforcers, etc.) which is updated on an hourly basis. This command will get the list and create the rules for you, if you want them automatically blocked, append |sh to the end of the command line. It's a more practical solution to block all and allow in specifics however, there are many who don't or can't do this which is where this script will come in handy. For those using ipfw, a quick fix would be {print "add deny ip from "$1" to any}. Posted in the sample output are the top two entries. Be advised the blacklisted file itself filters out RFC1918 addresses (10.x.x.x, 172.16-31.x.x, 192.168.x.x) however, it is advisable you check/parse the list before you implement the rules

grep -iR find_me ./
2009-02-18 15:38:59
User: lfamorim
Functions: grep

Searching for a String in Multiple Files With Grep

pg_dump -Ft -b -Uusername -hdb.host.com db_name > db.tar
find . -type l ! -exec test -e {} \; -print
2009-02-18 15:34:25
User: Shango1980
Functions: find test

Locate broken symlinks in the current directory. Also useful, to remove broken links:

find . -type l ! -exec test -e {} \; -print0 | xargs -0 rm
ffmpeg -i movie.avi -s 320x240 -b 1000k -vcodec wmv2 -ar 44100 -ab 56000 -ac 2 -y movie.wmv
2009-02-18 15:32:13
User: logik

I used this to cut down the file size of a 1gb .avi to about 200mb without sacrificing much quality.

dd if=10gb of=/dev/zero bs=1M count=10240
2009-02-18 15:30:29
User: logik
Functions: dd

Test your XFS filesystem and Raptor hard drives for write performance.

dd if=/dev/zero of=10gb bs=1M count=10240
2009-02-18 15:29:38
User: logik
Functions: dd

Test your XFS filesystem and Raptor hard drives for write performance.

ls -ad .*
2009-02-18 15:22:39
User: osantana
Functions: ls

List only hidden files (or directories). You also can use:

ls -lad .*
TF=`mktemp` && man -t YOUR_COMMAND >> $TF && gnome-open $TF
2009-02-18 15:18:35
User: furicle
Functions: man

Would be better if gnome-open would accept std in

Should be doable in KDE - anyone?

diff <(sort file1.txt) <(sort file2.txt)
2009-02-18 15:17:59
Functions: diff sort

Sees if two records differ in their entries, irrespective of order.

vim scp://username@host//path/to/somefile
wget -qO - snubster.com|sed -n '65p'|awk 'gsub(/<span><br>.*/,"")&&1'|perl -p -e 's:myScroller1.addItem\("<span class=atHeaderOrange>::g;s:</span> <span class=snubFontSmall>::g;s:&quot;:":g;s:^:\n:g;s:$:\n:'
2009-02-18 15:05:13
User: sil
Functions: wget

I've got this posted in one of my .bash_profiles for humor whenever I log in.

sudo dmidecode | grep Serial\ Number | head -n1
2009-02-18 14:54:28
User: nlinux
Functions: grep head sudo

This will give you the Dell Service tag number associated with your machine. Incredibly useful when you need that number for tech support or downloads.

tar zcf - user | pv /bin/gzip > /tmp/backup.tar.gz
2009-02-18 14:50:45
User: nlinux
Functions: tar

This command tar?s up a directory and sends the output to gzip, showing a rate of 223MB/s.

This may require you installing the pv command.

For debian based users out there:

sudo aptitude install pv
/usr/local/bin/OFPW -mode 1
2009-02-18 14:48:31
User: tomslick

Sets the Open Firmware to ask for password when selecting a boot volume other then the hd

watch -d "free -mt"
sed 's/\(..\)/\1:/g;s/:$//' mac_address_list
2009-02-18 14:38:37
User: sil
Functions: sed

I sometimes have large files of MAC addresses stored in a file, some databases need the information stored with the semicolon (makes for easier programming a device) others don't. I have a barcode to text file scanner which usually butchers MAC addresses so this was the fix> I initially did this in awk ;)

awk '{for(i=10;i>=2;i-=2)$0=substr($0,1,i)":"substr($0,i+1);print}' mac_address_list

find . -type d -exec chmod 0755 {} \;
2009-02-18 14:38:22
User: osantana
Functions: chmod find

WARNING! This command may set an invalid permission under your current directory.

This command will set the 0755 permissions to all directories under your current directory. An alternative version of this command is: find ~/.ssh -type d -exec chmod 0700 {} \;