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https://linuxcommandlibrary.com/basic/oneliners.html

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Show numerical values for each of the 256 colors in bash

$ for code in {0..255}; do echo -e "\e[38;05;${code}m $code: Test"; done
 

Remove security limitations from PDF documents using ghostscript

gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=OUTPUT.pdf -c .setpdfwrite -f INPUT.pdf
 

Check your unread Gmail from the command line

curl -u username:password --silent "https://mail.google.com/mail/feed/atom" | tr -d '
' | awk -F '<en try>' '{for (i=2; i<=NF; i++) {print $i}}' | sed -n "s/<title>\(.*\)<\/title.*name>\(.*\)<\/name>.*/\2 - \1/p"
 

Search commandlinefu.com from the command line using the API

$ cmdfu(){ curl"http://www.commandlinefu.com/commands/matching/$@/$(echo -n $@ | openssl base64)/plaintext"; }

Display a cool clock on your terminal

watch -t -n1 "date +%T|figlet"

(Debian/Ubuntu) Discover what package a file belongs to

dpkg -S /usr/bin/ls

Processor / memory bandwidthd? in GB/s

dd if=/dev/zero of=/dev/null bs=1M count=32768

Mount a .iso file in UNIX/Linux

mount /path/to/file.iso /mnt/cdrom -oloop

Get the 10 biggest files/folders for the current direcotry

du -s * | sort -n | tail

Create a persistent connection to a machine

ssh -MNf <user>@<host>

Remove a line in a text file. Useful to fix

ssh-keygen -R <the_offending_host>

Open Finder from the current Terminal location

$ open .

Makes the permissions of file2 the same as file1

chmod --reference file1 file2

Show a 4-way scrollable process tree with full details.

ps awwfux | less -S

Attach screen over ssh

ssh -t remote_host screen -r

Run a command only when load average is below a certain threshold

echo "rm -rf /unwanted-but-large/folder" | batch

List all bash shortcuts

$ bind -P

Start COMMAND, and kill it if still running after 5 seconds

timeout 5s COMMAND

Pretend to be busy in office to enjoy a cup of coffee

cat /dev/urandom | hexdump -C | grep "ca fe"

Recursively remove all empty directories

find . -type d -empty -delete

Create a quick back-up copy of a file

cp file.txt{,.bak}

To print a specific line from a file

sed -n 5p <file>

Directly ssh to host B that is only accessible through host A

$ ssh -t hostA ssh hostB

Remove all files previously extracted from a tar(.gz) file.

tar -tf <file. tar.gz> | xargs rm -r

Share a terminal screen with others

$ % screen -r someuser/

RTFM function

$ rtfm() { help $@ || man $@ || $BROWSER "http://www.google.com/search?q=$@"; }

Broadcast your shell thru ports 5000, 5001, 5002 ...

script -qf | tee >(nc -kl 5000) >(nc -kl 5001) >(nc -kl 5002)

Edit a google doc with vim

google docs edit --title "To-Do List" --editor vim

Eavesdrop on your system

diff <( lsof -p 1234) <(sleep 10; lsof -p 1234)

Run a file system check on your next boot.

touch /forcefsck

Nice weather forecast on your shell

curl wttr.in/seville

Retry the previous command until it exits successfully

$ until !!; do :; done

Synchronize date and time with a server over ssh

date --set="$(ssh user@server date)"

Google text-to-speech in mp3 format

wget -q -U Mozilla -O output.mp3 "http://translate.google.com/translate_tts?ie=UTF-8&tl=en&q=hello+world

List only the directories

ls -d */

What is my public IP-address?

curl ifconfig.me

Which program is this port belongs to ?

lsof -i tcp:80

Sort the size usage of a directory tree by gigabytes, kilobytes, megabytes, then bytes.

du -b --max-depth 1 | sort -nr | perl -pe 's{([0-9]+)}{sprintf "%.1f%s", $1>=2**30? ($1/2**30, "G"): $1>=2**20? ($1/2**20, "M"): $1>=2**10? ($1/2**10, "K"): ($1, "")}e'

Duplicate installed packages from one machine to the other (RPM-based systems)

ssh root@remote.host "rpm -qa" | xargs yum -y install

Draw kernel module dependancy graph.

lsmod | perl -e ' print "digraph \" lsmod\" {";<>;while(<>){@_=split/\s+/; print "\"$_[0]\" -> \"$_\"
" for split/,/,$_[3]} print "}"' | dot -Tpng | display -

Download Youtube video with wget!

$ wget http://www.youtube.com/watch?v=dQw4w9WgXcQ -qO- | sed -n "/fmt_url_map/{s/[\'\"\|]/
/g;p}" | sed -n '/^fmt_url_map/,/videoplayback/p' | sed -e :a -e '$q;N;5,$D;ba' | tr -d '
' | sed -e 's/\(.*\),\(.\)\{1,3\}/\1/' | wget -i - -O surprise.flv

Binary Clock

watch -n 1 'echo "obase=2;`date +%s`" | bc'

Remind yourself to leave in 15 minutes

$ leave +15

Download all images from a site

wget -r -l1 --no-parent -nH -nd -P/tmp -A".gif,.jpg" http://example.com/images

Find out how much data is waiting to be written to disk

grep ^Dirty /proc/meminfo

Backup all MySQL Databases to individual files

$ for I in $(mysql -e 'show databases' -s --skip-column-names); do mysqldump $I | gzip > "$I.sql.gz"; done

Bring the word under the cursor on the :ex line in Vim

$ :<C-R><C-W>

Make directory tree

mkdir -p work/{d1,d2}/{src,bin,bak}

Convert Youtube videos to MP3

$ youtube-dl -t --extract-audio --audio-format mp3 YOUTUBE_URL_HERE

Using `!#$' to referance backward-word

cp /work/host/phone/ui/main. cpp !#$:s/host/target

Use tee to process a pipe with two or more processes

echo "tee can split a pipe in two"|tee >(rev) >(tr ' ' '_')

Get your outgoing IP address

dig +short myip.opendns.com @resolver1.opendns.com

Port Knocking!

$ knock <host> 3000 4000 5000 && ssh -p <port> user@host && knock <host> 5000 4000 3000

Compare two directory trees.

diff <(cd dir1 && find | sort) <(cd dir2 && find | sort)

Add timestamp to history

export HISTTIMEFORMAT="%F %T "

Search recursively to find a word or phrase in certain file types, such as C code

find . -name "*.[ch]" -exec grep -i -H "search pharse" {} \;

Recursively change permissions on files, leave directories alone.

find ./ -type f -exec chmod 644 {} \;

Find files that have been modified on your system in the past 60 minutes

find / -mmin 60 -type f

Quick access to ASCII code of a key

showkey -a

Find files in a date range

find . -type f -newermt "2010-01-01" ! -newermt "2010-06-01"

Run complex remote shell cmds over ssh, without escaping quotes

ssh host -l user $(<cmd.txt)

A robust, modular log coloriser

$ ccze

Intercept, monitor and manipulate a TCP connection.

mkfifo /tmp/fifo; cat /tmp/fifo | nc -l -p 1234 | tee -a to.log | nc machine port | tee -a from.log > /tmp/fifo

Block known dirty hosts from reaching your machine

wget -qO - http://infiltrated.net/blacklisted|awk '!/#|[a-z]/&&/./{print "iptables -A INPUT -s "$1" -j DROP"}'

Check site ssl certificate dates

echo | openssl s_client -connect www.google.com:443 2>/dev/null |openssl x509 -dates -noout

Control ssh connection

$ [enter]~?

Python version 3: Serve current directory tree at http://$HOSTNAME:8000/

python -m http.server

Ls not pattern

ls !(*.gz)

Show apps that use internet connection at the moment.

lsof -P -i -n | cut -f 1 -d " "| uniq | tail -n +2

Colorized grep in less

grep --color=always | less -R

Given a file path, unplug the USB device on which the file is located (the file must be on an USB device !)

echo $( sudo lshw -businfo | grep -B 1 -m 1 $(df "/path/to/file" | tail -1 | awk '{print $1}' | cut -c 6-8) | head -n 1 | awk '{print $1}' | cut -c 5- | tr ":" "-") | sudo tee/sys/bus/usb/drivers/usb/unbind

Remove a line in a text file. Useful to fix "ssh host key change" warnings

sed -i 8d ~/.ssh/known_hosts

Save a file you edited in vim without the needed permissions (no echo)

$ :w !sudo tee > /dev/null %

Analyze traffic remotely over ssh w/ wireshark

ssh root@server.com 'tshark -f "port !22" -w -' | wireshark-k -i -

Create a directory and change into it at the same time

$ md () { mkdir -p "$@" && cd "$@"; }

Exclude multiple columns using AWK

awk '{$1=$3=""}1' file

Easily find megabyte eating files or directories

alias dush="du -sm *|sort -n|tail"

Exclude .svn, .git and other VCS junk for a pristine tarball

tar --exclude-vcs -cf src. tar src/

Remove blank lines from a file using grep and save output to new file

grep . filename > newfilename

Delete a line from your shell history

history -d

Exit without saving history

kill -9 $$

How to establish a remote Gnu screen session that you can re-connect to

ssh -t user@some.domain.com /usr/bin/screen -xRR

Copy a MySQL Database to a new Server via SSH with one command

$ mysqldump --add-drop-table --extended-insert --force --log-error=error.log -uUSER -pPASS OLD_DB_NAME |ssh -C user@newhost "mysql -uUSER -pPASS NEW_DB_NAME"

Get the IP of the host your coming from when logged in remotely

echo ${SSH_CLIENT%% *}

Random Number Between 1 And X

echo $[RANDOM%X+1]

Notify yourself when a long-running command which has ALREADY STARTED is finished

$ <ctrl+z> fg; notify_me

Create colorized html file from Vim or Vimdiff

$ :TOhtml

Output your microphone to a remote computer's speaker

$ arecord -f dat | ssh -C user@host aplay -f dat

Create a nifty overview of the hardware in your computer

lshw -html > hardware.html

Save your sessions in vim to resume later

$ :mksession! <filename>

Convert PDF to JPG

$ for file in `ls *.pdf`; do convert -verbose -colorspace RGB -resize 800 -interlace none -density 300 -quality 80 $ file`echo $ file | sed 's/\.pdf$/\.jpg/'`; done

Bind a key with a command

$ bind -x '"\C-l":ls -l'

Find all file larger than 500M

find / -type f -size +500M

GREP a PDF file.

pdftotext [file] - | grep 'YourPattern'

Live ssh network throughput test

yes | pv | ssh $host "cat > /dev/null"

Convert unixtime to human-readable

date -d @1234567890

A fun thing to do with ram is actually open it up and take a peek. This command will show you all the string (plain text) values in ram

strings /dev/mem

Prettify an XML file

$ tidy -xml -i -m [file]

Tell local Debian machine to install packages used by remote Debian machine

ssh remotehost ' dpkg --get-selections' | dpkg --set-selections && dselect install

Lists all listening ports together with the PID of the associated process

lsof -Pan -i tcp -i udp

Intersection between two files

grep -Fx -f file1 file2

Alias HEAD for automatic smart output

alias head='head -n $((${LINES:-`tput lines 2>/dev/null||echo -n 12`} - 2))'

Colorful man

apt-get install most && update-alternatives --set pager /usr/bin/most

Prints line numbers

nl

Diff on two variables

diff <(echo "$a") <(echo "$b")

Manually Pause/Unpause Firefox Process with POSIX-Signals

killall -STOP -m firefox

Use lynx to run repeating website actions

lynx -accept_all_cookies -cmd_script=/your/keystroke-file

Display a list of committers sorted by the frequency of commits

svn log -q|grep "|"|awk "{print \$3}"|sort|uniq -c|sort -nr

Check the status of 'dd' in progress (OS X)

$ CTRL + T

Convert seconds into minutes and seconds

bc <<< 'obase=60;299'

A child process which survives the parent's death (for sure)

$ ( command & )

Find usb device

diff <(lsusb) <(sleep 3s && lsusb)

Take screenshot through SSH

$ DISPLAY=:0.0 import -window root /tmp/shot.png

Opens vi/vim at pattern in file

vi +/pattern [file]

April Fools' Day Prank

$ PROMPT_COMMAND='if [ $RANDOM -le 3200 ]; thenprintf "\0337\033[%d;%dH\033[4%dm \033[m\0338" $((RANDOM%LINES+1)) $((RANDOM%COLUMNS+1)) $((RANDOM%8)); fi'

Copy working directory and compress it on-the-fly while showing progress

tar -cf - . | pv -s $(du -sb . | awk '{print $1}') | gzip > out.tgz

Pipe stdout and stderr, etc., to separate commands

$ some_command > >(/bin/cmd_for_stdout) 2> >(/bin/cmd_for_stderr)

Schedule a script or command in x num hours, silently run in the background even if logged out

$ ( ( sleep 2h; your-command your-args ) & )

Go to parent directory of filename edited in last command

cd !$:h

Draw a Sierpinski triangle

perl -e 'print "P1
256 256
", map {$_&($_>>8)?1:0} (0..0xffff)' | display

Make anything more awesome

$ command | figlet

List all files opened by a particular command

lsof -c dhcpd

Gets a random Futurama quote from /.

curl -Is slashdot.org | egrep '^X-(F|B|L)' | cut -d \- -f 2

Recursive search and replace old with new string, inside files

$ $ grep -rl oldstring . |xargs sed -i -e 's/oldstring/newstring/'

Shut of the screen.

xset dpms force standby

Runs a bash script in debugging mode

$ bash -x ./post_to_commandlinefu.sh

List the number and type of active network connections

netstat -ant | awk '{print $NF}' | grep -v '[a-z]' | sort | uniq -c

Encrypted archive with openssl and tar

tar --create --file - --posix --gzip -- <dir> | openssl enc -e -aes256 -out <file>

Create strong, but easy to remember password

$ read -s pass; echo $pass | md5sum | base64 | cut -c -16

Use file(1) to view device information

file -s /dev/sd*

Prevent accidents while using wildcards

rm *.txt <TAB> <TAB>

Insert the last argument of the previous command

$ <ESC> .

View the newest xkcd comic.

$ xkcd(){ wget -qO- http://xkcd.com/|tee >(feh $(grep -Po '(?<=")http://imgs[^/]+/comics/[^"]+\.\w{3}'))|grep -Po '(?<=(\w{3})" title=").*(?=" alt)';}

Press Any Key to Continue

$ read -sn 1 -p "Press any key to continue..."

Backup all your commandlinefu.com favourites to a plaintext file

$ clfavs(){ URL="http://www.commandlinefu.com"; wget -O - --save-cookies c --post-data "username=$1&password=$2&submit=Let+me+in" $URL/users/signin;for i in `seq 0 25 $3`;do wget -O - --load-cookies c $URL/commands/favourites/plaintext/$i >>$4;done;rm -f c;}

Remove color codes (special characters) with sed

sed -r "s/\x1B\[([0-9]{1,2}(;[0-9]{1,2})?)?[m|K]//g"

Throttle bandwidth with cstream

tar -cj /backup | cstream -t 777k | ssh host ' tar -xj -C /backup'

Run a long job and notify me when it's finished

$ ./my-really-long-job.sh && notify-send "Job finished"

When feeling down, this command helps

$ sl

Nicely display permissions in octal format with filename

stat -c '%A %a %n' *

Create a single-use TCP (or UDP) proxy

$ nc -l -p 2000 -c "nc example.org 3000"

Find geographical location of an ip address

lynx -dump http://www.ip-adress.com/ip_tracer/?QRY=$1|grep address|egrep 'city|state|country'|awk '{print $3,$4,$5,$6,$7,$8}'|sed 's\ip address flag \\'|sed 's\My\\'

Read manpage of a unix command as pdf in preview (Os X)

man -t UNIX_COMMAND | open -f -a preview

Instead of writing a multiline if/then/else/fi construct you can do that by one line

$ [[ test_condition ]] && if_true_do_this || otherwise_do_that

Switch 2 characters on a command line.

$ ctrl-t

Speed up launch of firefox

find ~ -name '*.sqlite' -exec sqlite3 '{}' 'VACUUM;' \;

Format txt as table not joining empty columns

column -tns: /etc/passwd

Shell recorder with replay

script -t /tmp/mylog.out 2>/tmp/mylog.time; <do your work>; <CTRL-D>; scriptreplay /tmp/mylog.time /tmp/mylog.out

Bind a key with a command

$ bind '"\C-l":"ls -l
"'

Exclude a column with cut

cut -f5 --complement

List files with quotes around each filename

ls -Q

Duplicate several drives concurrently

$ dd if=/dev/sda | tee >( dd of=/dev/sdb) | dd of=/dev/sdc

Create an audio test CD of sine waves from 1 to 99 Hz

$ ( echo CD_DA; for f in {01..99}; do echo "$f Hz">&2; sox -nt cdda -r44100 -c2 $f.cdda synth 30 sine $f; echo TRACK AUDIO; echo FILE \"$f.cdda\" 0; done) > cdrdao.toc && cdrdao write cdrdao.toc && rm ??.cdda cdrdao.toc

Listen to BBC Radio from the command line.

$ bbcradio() { local s PS3="Select a station: ";select s in 1 1x 2 3 4 5 6 7 "Asian Network an" "Nations & Local lcl";do break;done;s=($s);mplayer -playlist "http://www.bbc.co.uk/radio/listen/live/r"${s[@]: -1}".asx";}

Get your external IP address

curl ip.appspot.com

List installed deb packages by size

dpkg-query -Wf '${Installed-Size}\t${Package}
' | sort -n

Monitor bandwidth by pid

$ nethogs -p eth0

Execute a command with a timeout

timeout 10 sleep 11

Send echo to socket network

echo "foo" > /dev/tcp/192.168.1.2/25

Use vim to get colorful diff output

svn diff | view -

Find files containing text

grep -lir "some text" *

Perform a branching conditional

true && { echo success;} || { echo failed; }

Resume scp of a big file

rsync --partial --progress --rsh=ssh $file_source $user@$host:$destination_file

Brute force discover

sudo zcat /var/log/auth.log.*.gz | awk '/Failed password/&&!/for invalid user/{a[$9]++}/Failed password for invalid user/{a["*" $11]++}END{for (i in a) printf"%6s\t%s
", a[i], i|"sort -n"}'

Use tee + process substitution to split STDOUT to multiple commands

$ some_command | tee >(command1) >(command2) >(command3) ... | command4

Annotate tail -f with timestamps

tail -f file | while read; do echo "$(date +%T.%N) $REPLY"; done

Fast, built-in pipe-based data sink

$ <COMMAND> |:

Repoint an existing symlink to a new location

ln -nsf <TARGET> <LINK>

GRUB2: set Super Mario as startup tune

echo "GRUB_INIT_TUNE=\"1000 334 1 334 1 0 1 334 1 0 1 261 1 334 1 0 1 392 2 0 4 196 2\"" | sudo tee -a /etc/default/grub > /dev/null && sudo update-grub

Find Duplicate Files (based on size first, then MD5 hash)

$ fdupes -r .

Close a hanging ssh session

$ ~.

Recover a deleted file

grep -a -B 25 -A 100 'some string in the file' /dev/sda1 > results.txt

Makes you look busy

alias busy='my_file=$(find /usr/include -type f | sort -R |head -n 1); my_len=$(wc -l $my_file | awk "{print $1}"); let "r = $RANDOM % $my_len" 2>/dev/null; vim +$r $my_file'

Convert filenames in current directory to lowercase

$ rename 'y/A-Z/a-z/' *

Find files that were modified by a given command

touch /tmp/file ; $EXECUTECOMMAND ; find /path -newer /tmp/file

Quickly graph a list of numbers

$ gnuplot -persist <(echo "plot '<(sort -n listOfNumbers.txt)' with lines")

Cut out a piece of film from a file. Choose an arbitrary length and starting time.

ffmpeg -vcodec copy -acodec copy -i orginalfile -ss 00:01:30 -t 0:0:20 newfile

Analyse an Apache access log for the most common IP addresses

$ tail -10000 access_log | awk '{print $1}' | sort | uniq -c | sort -n | tail

Prevent large files from being cached in memory (backups!)

$ nocache <I/O-heavy-command>

Convert single digit to double digits

$ for i in ?.ogg; do mv $i 0$i; done

Limit the cpu usage of a process

sudo cpulimit -p pid -l 50

Generate an XKCD #936 style 4 word password

shuf -n4 /usr/share/dict/words | tr -d '
'

Single use vnc-over-ssh connection

ssh -f -L 5900:localhost:5900 your. ssh.server "x11vnc -safer -localhost -nopw -once -display :0"; vinagre localhost:5900

Diff remote webpages using wget

diff <(wget -q -O - URL1) <(wget -q -O - URL2)

List alive hosts in specific subnet

nmap -sP 192.168.1.0/24

Processes per user counter

ps hax -o user | sort | uniq -c

View all date formats, Quick Reference Help Alias

alias dateh=' date --help|sed -n "/^ *%%/,/^ *%Z/p"|while read l;do F=${l/% */}; date +%$F:"|'"'"'${F//%n/ }'"'"'|${l#* }";done|sed "s/\ *|\ */|/g" |column -s "|" -t'

Your terminal sings

echo {1..199}" bottles of beer on the wall, cold bottle of beer, take one down, pass it around, one less bottle of beer on the wall,, " | espeak -v english -s 140

Make sure a script is run in a terminal.

$ [ -t 0 ] || exit 1

Matrix Style

$ echo -e "\e[32m"; while :; do for i in {1..16}; do r="$(($RANDOM % 2))"; if [[ $(($RANDOM % 5)) == 1 ]]; then if [[ $(($RANDOM % 4)) == 1 ]]; then v+="\e[1m $r "; else v+="\e[2m $r "; fi; else v+=" "; fi; done; echo -e "$v"; v=""; done

Quickly (soft-)reboot skipping hardware checks

$ /sbin/kexec -l /boot/$KERNEL --append="$KERNELPARAMTERS" --initrd=/boot/$INITRD; sync; /sbin/kexec -e

Pipe output of a command to your clipboard

$ some command|xsel --clipboard

Ls -hog --> a more compact ls -l

ls -hog

Git remove files which have been deleted

git rm $( git ls-files --deleted)

Efficiently print a line deep in a huge log file

sed '1000000!d;q' < massive-log-file.log

Silently ensures that a FS is mounted on the given mount point (checks if it's OK, otherwise unmount, create dir and mount)

$ ( mountpoint -q "/media/mpdr1" && df /media/mpdr1/* > /dev/null 2>&1) || (( sudo u mount "/media/mpdr1" > /dev/null 2>&1 || true) && ( sudo mkdir "/media/mpdr1" > /dev/null 2>&1 || true) && sudo mount "/dev/sdd1" "/media/mpdr1")

Sniff network traffic on a given interface and displays the IP addresses of the machines communicating with the current host (one IP per line)

sudo tcpdump -i wlan0 -n ip | awk '{ printgensub(/(.*)\..*/,"\\1","g",$3), $4, gensub(/(.*)\..*/,"\\1","g",$5) }' | awk -F " > " '{ print $1"
"$2}'

Check if system is 32bit or 64bit

getconf LONG_BIT

Create a local compressed tarball from remote host directory

ssh user@host "tar -zcf - /path/to/dir" > dir.tar.gz

Rapidly invoke an editor to write a long, complex, or tricky command

$ <ESC> v or ctrl-x ctrl-e

Send a circular

wall <<< "Broadcast This"

The BOFH Excuse Server

telnet towel.blinkenlights.nl 666

I finally found out how to use notify-send with at or cron

echo " export DISPLAY=:0; exportXAUTHORITY=~/.Xauthority; notify-send test" | at now+1minute

See udev at work

udevadm monitor

Bash: hotkey to put current commandline to text-editor

$ bash-hotkey: <CTRL+x+e>

Show current working directory of a process

pwdx pid

Base conversions with bc

echo "obase=2; 27" | bc -l

Put readline into vi mode

$ set -o vi

Transfer SSH public key to another machine in one step

ssh-keygen; ssh-copy-id user@host; ssh user@host

Start a command on only one CPU core

taskset -c 0 your_command

Convert uppercase files to lowercase files

$ rename 'y/A-Z/a-z/' *

List of commands you use most often

history | awk '{print $2}' | sort | uniq -c | sort -rn | head

Notepad in a browser (type this in the URL bar)

$ data:text/html, <html contenteditable>

Display current time in requested time zones.

zdump Japan America/New_York

Dmesg with colored human-readable dates

dmesg -T|sed -e 's|\(^.*'`date +%Y`']\)\(.*\)|\x1b[0;34m\1\x1b[0m - \2|g'

Stamp a text line on top of the pdf pages.

echo "This text gets stamped on the top of the pdf pages." | enscript -B -f Courier-Bold16 -o- | ps2pdf - | pdftk input.pdf stamp - output output.pdf

Print diagram of user/groups

awk 'BEGIN{FS=":"; print "digraph{"}{split($4, a, ","); for (i in a) printf "\"%s\" [shape=box]
\"%s\" -> \"%s\"
", $1, a[i], $1}END{ print "}"}' /etc/group|display

Create a file server, listening in port 7000

$ while true; do nc -l 7000 | tar -xvf -; done

Bypass any aliases and functions for the command

$ \foo

Share your terminal session real-time

mkfifo foo; script -f foo

Df without line wrap on long FS name

df -P | column -t

Stderr in color

$ mycommand 2> >(while read line; do echo -e "\e[01;31m$line\e[0m"; done)

VI config to save files with +x when a shebang is found on line 1

$ au BufWritePost * if getline(1) =~ "^#!" | if getline(1) =~ "/bin/" | silent !chmod +x <afile> | endif | endif

Create a single PDF from multiple images with ImageMagick

convert *.jpg output.pdf

Dd with progress bar and statistics

$ sudo dd if=/dev/sdc bs=4096 | pv -s 2G | sudo dd bs=4096 of=~/USB_BLACK_BACKUP.IMG

Delete all empty lines from a file with vim

$ :g/^$/d

Perl one-liner to get the current week number

date +%V

Backup all MySQL Databases to individual files

$ for db in $(mysql -e 'show databases' -s --skip-column-names); do mysqldump $db | gzip > "/backups/mysqldump-$(hostname)-$db-$(date +%Y-%m-%d-%H.%M.%S).gz"; done

Ultimate current directory usage command

$ ncdu

Terminal - Show directories in the PATH, one per line with sed and bash3.X `here string'

tr : '
' <<<$PATH

Have an ssh session open forever

$ autossh -M50000 -t server.example.com 'screen -raAd mysession'

Recursively compare two directories and output their differences on a readable format

diff -urp /originaldirectory /modifieddirectory

DELETE all those duplicate files but one based on md5 hash comparision in the current directory tree

find . -type f -print0|xargs -0 md5sum|sort|perl -ne 'chomp;$ph=$h;($h,$f)=split(/\s+/,$_,2);print "$f"."\x00" if ($h eq $ph)'|xargs -0 rm -v --

Find broken symlinks and delete them

find -L /path/to/check -type l -delete

List recorded formular fields of Firefox

$ cd ~/.mozilla/firefox/ && sqlite3 `cat profiles.ini | grepPath | awk -F= '{print $2}'`/formhistory.sqlite "select * from moz_formhistory" && cd - > /dev/null

Using awk to sum/count a column of numbers.

cat count.txt | awk '{ sum+=$1} END {print sum}'

Get all the keyboard shortcuts in screen

$ ^A ?

Get list of servers with a specific port open

nmap -sT -p 80 -oG - 192.168.1.* | grep open

Return external ip

curl ipinfo.io

Simple multi-user encrypted chat server for 5 users

$ ncat -vlm 5 --ssl --chat 9876

Check if your ISP is intercepting DNS queries

dig +short which.opendns.com txt @208.67.220.220

Remove a range of lines from a file

sed -i <file> -re '<start>,<end>d'

Extract audio from Flash video (*.flv) as mp3 file

ffmpeg -i video.flv -vn -ar 44100 -ac 2 -ab 192k -f mp3 audio.mp3

Cat a bunch of small files with file indication

grep . *

Stop Flash from tracking everything you do.

$ for i in ~/.adobe ~/.macromedia ; do ( rm $i/ -rf ; ln -s /dev/null $i ) ; done

List all open ports and their owning executables

lsof -i -P | grep -i "listen"

Purge configuration files of removed packages on debian based systems

$ aptitude purge '~c'

Monitor open connections for httpd including listen, count and sort it per IP

watch "netstat -plan|grep :80|awk {'print \$5'} | cut -d: -f 1 | sort | uniq -c | sort -nk 1"

Convert text to picture

echo -e "Some Text Line1
Some Text Line 2" | convert -background none -density 196 -resample 72 -unsharp 0x.5 -font "Courier" text:- -trim +repage -bordercolor white -border 3 text.gif

Remote screenshot

$ DISPLAY=":0.0" import -window root screenshot.png

Define words and phrases with google.

$ define(){ local y="$@";curl -sA"Opera" "http://www.google.com/search?q=define:${y// /+}"|grep -Po '(?<=<li>)[^<]+'|nl|perl -MHTML::Entities -pe 'decode_entities($_)' 2>/dev/null;}

List all authors of a particular git project

git log --format='%aN' | sort -u

Track flights from the command line

$ flight_status() { if [[ $# -eq 3 ]];then offset=$3; else offset=0; fi; curl"http://mobile.flightview.com/TrackByRoute.aspx?view=detail&al="$1"&fn="$2"&dpdat=$(date +%Y%m%d -d ${offset}day)" 2>/dev/null |html2text |grep ":"; }

Harder, Faster, Stronger SSH clients

ssh -4 -C -c blowfish-cbc

Clean up poorly named TV shows.

$ rename -v 's/.*[s,S](\d{2}).*[e,E](\d{2}).*\.avi/SHOWNAME\ S$1E$2.avi/' poorly.named.file.s01e01.avi

Pretty Print a simple csv in the command line

column -s, -t <tmp.csv

Cleanup firefox's database.

find ~/.mozilla/firefox/ -type f -name "*.sqlite" -execsqlite3 {} VACUUM \;

Check open ports

lsof -Pni4 | grep LISTEN

Find Duplicate Files (based on MD5 hash)

find -type f -exec md5sum '{}' ';' | sort | uniq --all-repeated=separate -w 33 | cut -c 35-

Triple monitoring in screen

$ tmpfile=$(mktemp) && echo -e 'startup_message off
screen -t top h top
split
focus
screen -t nethogs nethogs wlan0
split
focus
screen -t io top io top' > $tmpfile && sudo screen -c $tmpfile

Smiley Face Bash Prompt

$ PS1="\`if [ \$? = 0 ]; then echo \e[33\;40m\\\^\\\_\\\^\e[0m; else echo \e[36\;40m\\\-\e[0m\\\_\e[36\;40m\\\-\e[0m; fi\` \u \w:\h)"

Save an HTML page, and covert it to a .pdf file

wget $URL | htmldoc --webpage -f "$URL".pdf - ; xpdf "$URL".pdf &

Create an emergency swapfile when the existing swap space is getting tight

$ sudo dd if=/dev/zero of=/swapfile bs=1024 count=1024000; sudo mkswap /swapfile; sudo swapon/swapfile

Relocate a file or directory, but keep it accessible on the old location throug a simlink.

mv $1 $2 && ln -s $2/$(basename $1) $(dirname $1)

A short counter

yes '' | cat -n

Rsync remote data as root using sudo

rsync -- rsync-path 'sudo rsync' username@source:/folder/ /local/

Convert all MySQL tables and fields to UTF8

$ mysql --database=dbname -B -N -e "SHOW TABLES" |awk '{print "ALTER TABLE", $1, "CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;"}' | mysql --database=dbname &

Pipe STDOUT to vim

tail -1000 /some/file | vim -

Copy stdin to your X11 buffer

ssh user@host cat /path/to/some/file | xclip

Get info about remote host ports and OS detection

nmap -sS -P0 -sV -O <target>

Copy a file structure without files

find * -type d -exec mkdir /where/you/wantem/\{\} \;

Start a new command in a new screen window

alias s='screen -X screen'; s top; s vi; s man ls;

Convert from hexidecimal or octal to decimal

echo $((0x1fe)) $((033))

Save man-page as pdf

man -t awk | ps2pdf - awk.pdf

Convert seconds into minutes and seconds

echo 'obase=60;299' | bc

List files accessed by a command

strace -ff -e trace=file my_command 2>&1 | perl -ne 's/^[^"]+"(([^\\"]|\\[\\"nt])*)".*/$1/ && print'

Short and elegant way to backup a single file before you change it.

cp httpd.conf{,.bk}

Find all the links to a file

find -L / -samefile /path/to/file -exec ls -ld {} +

Recover tmp flash videos (deleted immediately by the browser plugin)

$ for h in `find /proc/*/fd -i lname "/tmp/Flash*" 2>/dev/null`; do ln -s "$h" `readlink "$h" | cut -d' ' -f1`; done

Rsync instead of scp

rsync --progress --partial --rsh="ssh -p 8322" --bwlimit=100 --ipv4 user@domain.com:~/file.tgz .

Send a circular

echo "dear admin, please ban eribsskog" | wall

Visit wikileaks.com

echo 213.251.145.96 wikileaks.com >>/etc/hosts

Make sudo forget password instantly

sudo -K

Print a row of characters across the terminal

printf "%`tput cols`s"|tr ' ' '#'

Download and unpack tarball without leaving it sitting on your hard drive

wget -qO - http://example.com/path/to/blah. tar.gz | tar xzf -

Colored diff ( via vim ) on 2 remotes files on your local computer.

vimdiff scp://root@server-foo.com//etc/snmp/snmpd.conf scp://root@server-bar.com//etc/snmp/snmpd.conf

Split a tarball into multiple parts

tar cf - <dir>|split -b<max_size>M - <name>. tar.

Remove executable bit from all files in the current directory recursively, excluding other directories

chmod -R -x+X *

More precise BASH debugging

env PS4=' ${BASH_SOURCE}:${LINENO}(${FUNCNAME[0]}) ' sh -x /etc/profile

Get all pdf and zips from a website using wget

wget --reject html,htm --accept pdf,zip -rl1 url

Mount the first NTFS partition inside a VDI file (VirtualBox Disk Image)

mount -t ntfs-3g -o ro,loop,uid=user,gid=group,umask=0007,fmask=0117,offset=0x$(hd -n 1000000 image.vdi | grep "eb 52 90 4e 54 46 53" | cut -c 1-8) image.vdi /mnt/vdi-ntfs

Show me a histogram of the busiest minutes in a log file:

cat /var/log/secure.log | awk '{print substr($0,0,12)}' | uniq-c | sort -nr | awk '{printf("
%s ",$0) ; for (i = 0; i<$1 ; i++) {printf("*")};}'

Print a great grey scale demo !

yes "$(seq 232 255;seq 254 -1 233)" | while read i; doprintf "\x1b[48;5;${i}m
"; sleep .01; done

Create a list of binary numbers

echo {0..1}{0..1}{0..1}{0..1}

Create a system overview dashboard on F12 key

$ bind '"\e[24~"':"\"ps -elF;df -h;free -mt;netstat -lnpt;who -a\C-m"""

Coloured tail

tail -f FILE | perl -pe 's/KEYWORD/\e[1;31;43m$&\e[0m/g'

Disable history for current shell session

$ unset HISTFILE

Search for commands from the command line

$ clfu-seach <search words>

How to run X without any graphics hardware

startx -- `which Xvfb` :1 -screen 0 800x600x24 && DISPLAY=:1 x11vnc

Install a Firefox add-on/theme to all users

sudo firefox -install-global-extension /path/to/add-on

Clear current line

$ CTRL+u

Quickly generate an MD5 hash for a text string using OpenSSL

echo -n 'text to be encrypted' | openssl md5

Terminate a frozen SSH-session

$ RETURN~.

Backup a remote database to your local filesystem

ssh user@host 'mysqldump dbname | gzip' > /path/to/backups/db-backup-`date +%Y-%m-%d`.sql.gz

Generat a Random MAC address

$ MAC=`(date; cat /proc/interrupts) | md5sum | sed -r 's/^(.{10}).*$/\1/; s/([0-9a-f]{2})/\1:/g; s/:$//;'`

Batch convert files to utf-8

find . -name "*.php" -exec iconv -f ISO-8859-1 -t UTF-8 {} -o ../newdir_utf8/{} \;

Get http headers for an url

curl -I www.commandlinefu.com

Random git-commit message

git commit -m "$(curl -s http://whatthecommit.com/index.txt)";

Generate QR code for a WiFi hotspot

$ qrencode -s 7 -o qr-wifi.png "WIFI:S:$(zenity --entry --text="Network name (SSID)" --title="Create WiFi QR");T:WPA;P:$(zenity --password --title="Wifi Password");;"

Check if system is 32bit or 64bit

arch

Vi a remote file

vi scp://username@host//path/to/somefile

Show permissions of current directory and all directories upwards to /

namei -m $(pwd)

Move you up one directory quickly

$ shopt -s autocd

Hide the name of a process listed in the `ps` output

$ exec -a "/sbin/getty 38400 tty7" your_cmd -erase_all_files

Remove a line from a file using sed (useful for updating known SSH server keys when they change)

ssh-keygen -R <thehost>

Show what PID is listening on port 80 on Linux

fuser -v 80/tcp

List by size all of the directories in a given tree.

du -h /path | sort -h

Find the most recently changed files (recursively)

find . -type f -printf '%TY-%Tm-%Td %TT %p
' | sort

All IP connected to my host

netstat -lantp | grep ESTABLISHED | awk '{print $5}' |awk -F: '{print $1}' | sort -u

Figure out what shell you're running

echo $0

Download a file and uncompress it while it downloads

wget http://URL/FILE. tar.gz -O - | tar xfz -

Rename all .jpeg and .JPG files to have .jpg extension

$ rename 's/\.jpe?g$/.jpg/i' *

Remove Thumbs.db files from folders

find ./ -name Thumbs.db -delete

List open files that have no links to them on the filesystem

lsof +L1

Display BIOS Information

$ # dd if=/dev/mem bs=1k skip=768 count=256 2>/dev/null | strings -n 8

Open path with your default program (on Linux/*BSD)

xdg-open [path]

Copy an element from the previous command

$ !:1-3

View user activity per directory.

sudo lsof -u someuser -a +D /etc

Use the previous commands params in the current command

$ !!:[position]

Mirror a directory structure from websites with an Apache-generated file indexes

$ lftp -e "mirror -c" http://example.com/foobar/

Quickly share code or text from vim to others.

$ :w !curl -F "sprunge=<-" http://sprunge.us | xclip

Copy from host1 to host2, through your host

$ ssh root@host1 "cd /somedir/tocopy/ && tar -cf - ." | ssh root@host2 "cd /samedir/tocopyto/ && tar -xf -"

Convert all Flac in a directory to Mp3 using maximum quality variable bitrate

$ for file in *.flac; do flac -cd "$ file" | lame -q 0 --vbr-new -V 0 - "${ file%.flac}.mp3"; done

Limit bandwidth usage by apt-get

sudo apt-get -o Acquire::http::Dl-Limit=30 upgrade

Tune your guitar from the command line.

$ for n in E2 A2 D3 G3 B3 E4;do play -n synth 4 pluck $n repeat 2;done

Grep -v with multiple patterns.

$ grep 'test' somefile | grep -vE '(error|critical|warning)'

Redirect stdout and stderr each to separate files and print both to the screen

$ (some_command 2>&1 1>&3 | tee /path/to/errorlog ) 3>&1 1>&2 | tee /path/to/stdoutlog

Identify long lines in a file

awk 'length>72' file

Use all the cores or CPUs when compiling

make -j 4

Prints total line count contribution per user for an SVN repository

$ svn ls -R | egrep -v -e "\/$" | xargs svn blame | awk '{print $2}' | sort | uniq -c | sort -r

Analyze awk fields

awk '{print NR": "$0; for(i=1;i<=NF;++i)print "\t"i": "$i}'

Colored SVN diff

svn diff <file> | vim -R -

Run a command, store the output in a pastebin on the internet and place the URL on the xclipboard

ls | curl -F 'sprunge=<-' http://sprunge.us | xclip

Show git branches by date - useful for showing active branches

$ for k in `git branch|perl -pe s/^..//`;do echo -e `git show --pretty=format:"%Cgreen%ci %Cblue%cr%Creset" $k|head -n 1`\\t$k;done|sort -r

Find if the command has an alias

$ type -all command

Find last reboot time

who -b

Show a config file without comments

egrep -v "^$|^[[:space:]]*#" /etc/some/file

Start screen in detached mode

$ screen -d -m [<command>]

Iso-8859-1 to utf-8 safe recursive rename

$ detox -r -s utf_8 /path/to/old/win/files/dir

Create dir tree

mkdir -p doc/{text/,img/{wallpaper/,photos/}}

Run any GUI program remotely

ssh -fX <user>@<host> <program>

Delete all empty lines from a file with vim

$ :g!/\S/d

List the files any process is using

lsof +p xxxx

Show biggest files/directories, biggest first with 'k,m,g' eyecandy

du --max-depth=1 | sort -r -n | awk '{split("k m g",v); s=1; while($1>1024){$1/=1024; s++} print int($1)" "v[s]"\t"$2}'

Change directory to actual path instead of symlink path

cd `pwd -P`

Download an entire static website to your local machine

wget --recursive --page-requisites --convert-links www.moyagraphix.co.za

Recursively remove .svn directories from the current location

find . -type d -name '.svn' -print0 | xargs -0 rm -rdf

Count files beneath current directory (including subfolders)

find . -type f | wc -l

Read and write to TCP or UDP sockets with common bash tools

$ exec 5<>/dev/tcp/time.nist.gov/13; cat <&5 & cat >&5; exec 5>&-

Use top to monitor only all processes with the same name fragment 'foo'

top -p $(pgrep -d , foo)

Delete command line last word

$ ctrl+w

Draw kernel module dependancy graph.

lsmod | awk 'BEGIN{ print "digraph{"}{split($4, a, ","); for (i in a) print $1, "->", a[i]}END{ print "}"}'|display

Color man pages

echo "export LESS_TERMCAP_mb=$'\E[01;31m'" >> ~/.bashrc

Print without executing the last command that starts with...

$ !ssh:p

What is the use of this switch ?

manswitch () { man $1 | less -p "^ +$2"; }

Save the list of all available commands in your box to a file

$ compgen -c | sort -u > commands

Protect directory from an overzealous rm -rf *

cd <directory>; touch ./-i

Watch RX/TX rate of an interface in kb/s

$ while [ /bin/ true ]; do OLD=$NEW; NEW=`cat /proc/net/dev | grep eth0 | tr -s ' ' | cut -d' ' -f "3 11"`; echo$NEW $OLD | awk '{printf("\rin: % 9.2g\t\tout: % 9.2g", ($1-$3)/1024, ($2-$4)/1024)}'; sleep 1; done

List 10 largest directories in current directory

du -hs */ | sort -hr | head

Reuse last parameter

$ !$

Blink LED Port of NIC Card

ethtool -p eth0

Pretend to be busy in office to enjoy a cup of coffee

$ j=0;while true; do let j=$j+1; for i in $(seq 0 20 100); doecho $i;sleep 1; done | dialog --gauge "Install part $j : `sed $(perl -e "print int rand(99999)")"q;d" /usr/share/dict/words`" 6 40;done

See where a shortened url takes you before click

$ check(){ curl -sI $1 | sed -n 's/Location: *//p';}

Stream YouTube URL directly to MPlayer

$ yt () mplayer -fs -quiet $(youtube-dl -g "$1")

Generate a Random MAC address

$ openssl rand -hex 6 | sed 's/\(..\)/\1:/g; s/.$//'

Running scripts after a reboot for non-root users .

$ @reboot <yourscript.sh>

Run command on a group of nodes in parallel

echo "uptime" | pee "ssh host1" "ssh host2" "ssh host3"

Make, or run a script, everytime a file in a directory is modified

$ while true; do inotifywait -r -e MODIFY dir/ && make; done;

Choose from a nice graphical menu which DI.FM radio station to play

zenity --list --width 500 --height 500 --column 'radio' --column 'url' --print-column 2 $(curl -s http://www.di.fm/ | awk -F '"' '/href="http:.*\.pls.*96k/ {print $2}' | sort | awk -F '/|\.' '{print $(NF-1) " " $0}') | xargs mplayer

Check the status of 'dd' in progress (OS X)

killall -INFO dd

Ping scanning without nmap

$ for i in {1..254}; do ping -c 1 -W 1 10.1.1.$i | grep 'from'; done

Convert a Nero Image File to ISO

dd bs=1k if=image.nrg of=image.iso skip=300

View network activity of any application or user in realtime

lsof -r 2 -p PID -i -a

Copy with progress

rsync --progress file1 file2

Print a list of standard error codes and descriptions.

perl -le 'print $!+0, "\t", $!++ for 0..127'

Recursive search and replace old with new string, inside files

find . -type f -exec sed -i s/oldstring/newstring/g {} +

Generate random password

$ pwgen -Bs 10 1

A function to output a man page as a pdf file

$ function man2pdf(){ man -t ${1:?Specify man as arg} |ps2pdf -dCompatibility=1.3 - - > ${1}.pdf; }

Unbelievable Shell Colors, Shading, Backgrounds, Effects for Non-X

$ for c in `seq 0 255`;do t=5;[[ $c -lt 108 ]]&&t=0;for i in `seq $t 5`;do echo -e "\e[0;48;$i;${c}m|| $i:$c `seq -s+0 $(($COLUMNS/2))|tr -d '[0-9]'`\e[0m";done;done

Show directories in the PATH, one per line

echo $PATH | tr \: \

Move all images in a directory into a directory hierarchy based on year, month and day based on exif information

$ exiftool '-Directory<DateTimeOriginal' -d %Y/%m/%d dir

Follow tail by name (fix for rolling logs with tail -f)

tail -F file

Convert "man page" to text file

man ls | col -b > ~/Desktop/ manls.txt

Get your public ip using dyndns

curl -s http://checkip.dyndns.org/ | grep -o "[[:digit:].]\+"

Display current bandwidth statistics

$ ifstat -nt

Given process ID print its environment variables

sed 's/\o0/
/g' /proc/INSERT_PID_HERE/environ

Restoring some data from a corrupted text file

$ ( cat badfile.log ; tac badfile.log | tac ) > goodfile.log

View the system console remotely

sudo cat /dev/vcs1 | fold -w 80

Look up the definition of a word

curl dict://dict.org/d:something

Diff files on two remote hosts.

diff <(ssh alice cat /etc/apt/sources.list) <(ssh bob cat /etc/apt/sources.list)

Ctrl+S Ctrl+Q terminal output lock and unlock

$ Ctrl+S Ctrl+Q

Redirect STDIN

$ < /path/to/file.txt grep foo

I hate `echo X | Y`

base64 -d <<< aHR0cDovL3d3dy50d2l0dGVyc2hlZXAuY29tL3Jlc3VsdHMucGhwP3U9Y29tbWFuZGxpbmVmdQo=

Send keypresses to an X application

$ xvkbd -xsendevent -text "Hello world"

Add calendar to desktop wallpaper

convert -font -misc-fixed-*-*-*-*-*-*-*-*-*-*-*-* -fill black -draw "text 270,260 \" `cal` \"" testpic.jpg newtestpic.jpg

Browse system RAM in a human readable form

sudo cat /proc/kcore | strings | awk 'length > 20' | less

Backup your hard drive with dd

sudo dd if=/dev/sda of=/media/disk/backup/sda.backup

Calculates the date 2 weeks ago from Saturday the specified format.

date -d '2 weeks ago Saturday' +%Y-%m-%d

Get Cisco network information

tcpdump -nn -v -i eth0 -s 1500 -c 1 'ether[20:2] == 0x2000'

Press ctrl+r in a bash shell and type a few letters of a previous command

$ ^r in bash begins a reverse-search-history with command completion

Extract audio from a video

ffmpeg -i video.avi -f mp3 audio.mp3

Quick glance at who's been using your system recently

last | grep -v "^$" | awk '{ print $1 }' | sort -nr | uniq -c

Ping a range of IP addresses

nmap -sP 192.168.1.100-254

Use last argument of last command

file !$

Show which programs are listening on TCP and UDP ports

netstat -plunt

Determine if a port is open with bash

$ : </dev/tcp/127.0.0.1/80

Search for a process by name

ps -fC PROCESSNAME

Download all mp3's listed in an html page

wget -r -l1 -H -t1 -nd -N -np -A.mp3 -erobots=off [url of website]

Run the built in PHP-server in current folder

$ php -S 127.0.0.1:8080

Press enter and take a WebCam picture.

$ read && ffmpeg -y -r 1 -t 3 -f video4linux2 -vframes 1 -s sxga -i /dev/video0 ~/webcam-$(date +%m_%d_%Y_%H_%M).jpeg

Commandline document conversion with Libreoffice

$ soffice --headless -convert-to odt:"writer8" somefile.docx

HourGlass

$ hourglass(){ trap 'tput cnorm' 0 1 2 15 RETURN;local s=$(($SECONDS +$1));(tput civis;while (($SECONDS<$s));do for f in '|' '\' '-' '/';do echo -n "$f";sleep .2s; echo -n $'\b';done;done;);}

Gets the english pronunciation of a phrase

$ say() { mplayer "http://translate.google.com/translate_tts?q=$1"; }

Check syntax for all PHP files in the current directory and all subdirectories

find . -name \*.php -exec php -l "{}" \;

Ask for a password, the passwd-style

$ read -s -p"Password: " USER_PASSWORD_VARIABLE; echo

Monitor memory usage

watch vmstat -sSM

Content search.

$ ff() { local IFS='|'; grep -rinE "$*" . ; }

Timer with sound alarm

sleep 3s && espeak "wake up, you bastard" 2>/dev/null

Rapidly invoke an editor to write a long, complex, or tricky command

$ <ESC> v

Run command on a group of nodes in parallel

echo "uptime" | tee >(ssh host1) >(ssh host2) >(ssh host3)

List of commands you use most often

history | awk '{a[$2]++}END{for(i in a){print a[i] " " i}}' | sort-rn | head > /tmp/cmds | gnuplot -persist <(echo 'plot "/tmp/cmds" using 1:xticlabels(2) with boxes')

Kill process by name

pkill -x firefox

Change prompt to MS-DOS one (joke)

export PS1="C:\$( pwd | sed 's:/:\\\\\\:g' )\\> "

Make ISO image of a folder

$ mkisofs -J -allow-lowercase -R -V "OpenCD8806" -iso-level 4 -o OpenCD.iso ~/OpenCD

A shell function to print a ruler the width of the terminal window.

$ ruler() { for s in '....^....|' '1234567890'; do w=${#s}; str=$( for (( i=1; $i<=$(( ($COLUMNS + $w) / $w )) ; i=$i+1 )); do echo -n $s; done ); str=$( echo $str | cut -c -$COLUMNS) ; echo $str; done; }

Typing the current date ( or any string ) via a shortcut as if the keys had been actually typed with the hardware keyboard in any application.

$ xvkbd -xsendevent -text $(date +%Y%m%d)

Update twitter via curl (and also set the "from" bit)

curl -u twitter-username -d status="Hello World, Twitter!" -d source="cURL" http://twitter.com/statuses/update.xml

Quickest (i blv) way to get the current program name minus the path (BASH)

$ path_stripped_programname="${0##*/}"

A trash function for bash

$ trash <file>

Clean your broken terminal

stty sane

Play music from youtube without download

wget -q -O - `youtube-dl -b -g $url`| ffmpeg -i - -f mp3 -vn -acodec libmp3lame -| mpg123 -

Generate a unique and secure password for every website that you login to

$ sitepass() { echo -n "$@" | md5sum | sha1sum |sha224sum | sha256sum | sha384sum | sha512sum | gzip- | s trings -n 1 | tr -d "[:space:]" | tr -s '[:print:]' | tr '!-~' 'P-~!-O' | rev | cut -b 2-11; history -d $(($HISTCMD-1)); }

Search back through previous commands

$ Ctrl-R <search-text>

Identify differences between directories (possibly on different servers)

diff <(ssh server01 'cd config; find . -type f -exec md5sum {} \;| sort -k 2') <(ssh server02 'cd config; find . -type f -exec md5sum {} \;| sort -k 2')

Replace spaces in filenames with underscores

$ rename -v 's/ /_/g' *

Show directories in the PATH, one per line

echo "${PATH//:/$'
'}"

Move a lot of files over ssh

rsync -az /home/user/test user@sshServer:/tmp/

Find and delete empty dirs, start in current working dir

find . -empty -type d -exec rmdir {} +

List your largest installed packages.

$ wajig large

Monitor TCP opened connections

watch -n 1 "netstat -tpanl | grep ESTABLISHED"

Fix Ubuntu's Broken Sound Server

sudo killall -9 pulseaudiopulseaudio >/dev/null 2>&1 &

Download all Delicious bookmarks

curl -u username -o bookmarks.xml https://api.del.icio.us/v1/posts/all

Beep when a server goes offline

$ while true; do [ "$(ping -c1W1w1 server-or-ip.com | awk'/received/ {print $4}')" != 1 ] && beep; sleep 1; done

Number of open connections per ip.

netstat -ntu | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -n

Fibonacci numbers with awk

seq 50| awk 'BEGIN {a=1; b=1} {print a; c=a+b; a=b; b=c}'

Create a favicon

convert -colors 256 -resize 16x16 face.jpg face.ppm && ppmtowinicon -output favicon.ico face.ppm

Check Ram Speed and Type in Linux

sudo dmidecode --type 17 | more

Run the Firefox Profile Manager

firefox -no-remote -P

Add forgotten changes to the last git commit

git commit --amend

Sort dotted quads

sort -nt . -k 1,1 -k 2,2 -k 3,3 -k 4,4

Get Dell Service Tag Number from a Dell Machine

sudo dmidecode | grep Serial\ Number | head -n1

Resume aborted scp file transfers

rsync --partial --progress --rsh=ssh SOURCE DESTINATION

Add your public SSH key to a server in one command

cat . ssh/id_rsa.pub | ssh hostname ' cat >> . ssh/authorized_keys'

Cycle through a 256 colour palette

yes "$(seq 232 255;seq 254 -1 233)" | while read i; doprintf "\x1b[48;5;${i}m
"; sleep .01; done

Google text-to-speech in mp3 format

$ t2s() { wget -q -U Mozilla -O $(tr ' ' _ <<< "$1"| cut -b 1-15).mp3 "http://translate.google.com/translate_tts?ie=UTF-8&tl=en&q=$(tr ' ' + <<< "$1")"; }

Google verbatim search on your terminal

$ function google { Q="$@"; GOOG_URL='https://www. google.de/search?tbs=li:1&q='; AGENT="Mozilla/4.0"; stream=$(curl -A "$AGENT" -skLm 10 "${GOOG_URL}${Q//\ /+}" | grep -oP '\/url\?q=.+?&amp' |sed 's|/url?q=||; s|&amp||'); echo -e "${stream//\%/\x}"; }

Grep processes list avoiding the grep itself

ps axu | grep [a]pache2

Swap the two last arguments of the current command line

$ <ctrl+e> <esc+t>

Transfer a file to multiple hosts over ssh

$ pscp -h hosts.txt -l username /etc/hosts /tmp/hosts

Tail a log over ssh

ssh -t remotebox "tail -f /var/log/remote.log"

Du with colored bar graph

$ t=$(df| awk 'NR!=1{sum+=$2}END{print sum}');sudo du / --max-depth=1|sed '$d'|sort -rn -k1 | awk -v t=$t 'OFMT="%d" {M=64; for (a=0;a<$1;a++){if (a>c){c=a}}br=a/c;b=M*br;for(x=0;x<b;x++){printf "\033[1;31m" "|" "\033[0m"}print " "$2" "(a/t*100)"% total"}'

Sort the output of the 'du' command by largest first, using human readable output.

du -h --max-depth=1 |sort -rh

Verify/edit bash history command before executing it

$ shopt -s histverify

Resize an image to at least a specific resolution

convert -resize '1024x600^' image.jpg small-image.jpg

Query well known ports list

getent services <<service>>

Create .pdf from .doc

$ oowriter -pt pdf your_word_file.doc

Diff XML files

diffxml() { diff -wb <(xmllint --format "$1") <(xmllint --format "$2"); }

Discovering all open files/dirs underneath a directory

lsof +D <dirname>

Clear screen, keep prompt at eye-level (faster than clear(1), tput cl, etc.)

$ cls(){ printf "\33[2J";} or, if no printf, cat >cls;<ctrl-v><ctrl+[>[2J<enter><ctrl+d> cls(){ cat cls;}

Down for everyone or just me?

$ down4me() { wget -qO - "http://www.downforeveryoneorjustme.com/$1" | sed '/just you/!d;s/<[^>]*>//g' ; }

A formatting test for David Winterbottom: improving commandlinefu for submitters

echo "?????, these are the umlauted vowels I sing to you. Oh, and sometimes ?, but I don't sing that one cause it doesn't rhyme."

Run a program transparently, but print a stack trace if it fails

gdb -batch -ex "run" -ex "bt" ${my_program} 2>&1 | grep-v ^"No stack."$

Compare copies of a file with md5

cmp file1 file2

Backup delicious bookmarks

curl --user login:password -o DeliciousBookmarks.xml -O 'https://api.del.icio.us/v1/posts/all'

Continue a current job in the background

$ <ctrl+z> bg

Get all links of a website

lynx -dump http://www.domain.com | awk '/http/{print $2}'

Find all active ip's in a subnet

sudo arp-scan -I eth0 192.168.1.0/24

Display BIOS Information

dmidecode -t bios

Disassemble some shell code

echo -ne "<shellcode>" | x86dis -e 0 -s intel

List bash functions defined in .bash_profile or .bashrc

$ compgen -A function

Ignore the .svn directory in filename completion

export FIGNORE=.svn

Working random fact generator

wget randomfunfacts.com -O - 2>/dev/null | grep \<strong\> | sed "s;^.*<i>\(.*\)</i>.*$;\1;"

Remote backups with tar over ssh

tar jcpf - [sourceDirs] |ssh user@host "cat > /path/to/backup/backupfile. tar.bz2"

Pronounce an English word using Dictionary.com

$ pronounce(){ wget -qO- $( wget -qO- "http://dictionary.reference.com/browse/$@" | grep'soundUrl' | head -n 1 | sed 's|.*soundUrl=\([^&]*\)&.*|\1|' | sed 's/%3A/:/g;s/%2F/\//g') | mpg123 -; }

Change pidgin status

$ purple-remote "setstatus?status=away&message=AFK"

Grep by paragraph instead of by line.

$ grepp() { [ $# -eq 1 ] && perl -00ne "print if /$1/i" || perl -00ne "print if /$1/i" < "$2";}

Vim: Switch from Horizontal split to Vertical split

$ ^W-L

Numbers guessing game

$ A=1;B=100;X=0;C=0;N=$[$RANDOM%$B+1];until [ $X -eq $N ];do read -p "N between $A and $B. Guess? " X;C=$(($C+1));A=$(($X<$N?$X:$A));B=$(($X>$N?$X:$B));done;echo "Took you $C tries, Einstein";

Sort all running processes by their memory & CPU usage

ps aux --sort=%mem,%cpu

Change user, assume environment, stay in current dir

su -- user

Save current layout of top

$ <Shift + W>

Function that outputs dots every second until command completes

sleeper(){ while `ps -p $1 &>/dev/null`; do echo -n "${2:-.}"; sleep ${3:-1}; done; }; export -f sleeper

Testing hard disk reading speed

hdparm -t /dev/sda

How fast is the connexion to a URL, some stats from curl

$ URL="http://www.google.com";curl -L --w "$URL
DNS %{ time_namelookup}s conn %{ time_connect}s time%{ time_total}s
Speed %{speed_download}bps Size %{size_download}bytes
" -o/dev/null -s $URL

An easter egg built into python to give you the Zen of Python

python -c 'import this'

Get all IPs via ifconfig

ifconfig -a | perl -nle'/(\d+\.\d+\.\d+\.\d+)/ && print $1'

Use Cygwin to talk to the Windows clipboard

cat /dev/clipboard; $(somecommand) > /dev/clipboard

List programs with open ports and connections

lsof -i

Find corrupted jpeg image files

find . -name "*jpg" -exec jpeginfo -c {} \; | grep -E "WARNING|ERROR"

'Fix' a typescript file created by the 'script' program to remove control characters

cat typescript | perl -pe 's/\e([^\[\]]|\[.*?[a-zA-Z]|\].*?\a)//g' |col -b > typescript-processed

Share a 'screen'-session

$ screen -x

Purge configuration files of removed packages on debian based systems

sudo aptitude purge `dpkg --get-selections | grepdeinstall | awk '{print $1}'`

Show all detected mountable Drives/Partitions/BlockDevices

$ hwinfo --block --short

Merge *.pdf files

gs -q -sPAPERSIZE=letter -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=out.pdf `ls *.pdf`

Append stdout and stderr to a file, and print stderr to the screen [bash]

$ somecommand 2>&1 >> logfile | tee -a logfile

Quickly change all .html extensions on files in folder to .htm

$ for i in *.html ; do mv $i ${i%.html}.htm ; done

Delete the specified line

sed -i 8d ~/.ssh/known_hosts

Read the output of a command into the buffer in vim

$ :r !command

Find broken symlinks

find . -type l ! -exec test -e {} \; -print

Ssh tunnel with auto reconnect ability

$ while [ ! -f /tmp/stop ]; do ssh -o ExitOnForwardFailure=yes -R 2222:localhost:22 target "while nc -zv localhost 2222; do sleep 5; done"; sleep 5;done

Find process associated with a port

fuser [portnumber]/[proto]

Scping files with streamlines compression (tar gzip)

$ tar czv file1 file2 folder1 | ssh user@server tar zxv -C /destination

Add all files not under version control to repository

$ svn status |grep '\?' |awk '{print $2}'| xargs svn add

Disco lights in the terminal

$ while true; do printf "\e[38;5;$(($(od -d -N 2 -A n /dev/urandom)%$(tput colors)))m.\e[0m"; done

Select rectangular screen area

$ Ctrl + Alt

Show how old your linux OS installtion is

sudo tune2fs -l $(df -h / |(read; awk '{print $1; exit}')) |grep -i created

Discover the process start time

ps -eo pid,lstart,cmd

Automatically find and re-attach to a detached screen session

$ screen -D -R

This is how you should push a string in a command's stdin.

$ command <<< word

Ping as traceroute

$ for i in {1..30}; do ping -t $i -c 1 google.com; done | grep"Time to live exceeded"

What model of computer I'm using?

sudo dmidecode | grep Product

Extract tar content without leading parent directory

tar -xaf archive. tar.gz --strip-components=1

Target a specific column for pattern substitution

awk '{gsub("foo","bar",$5)}1' file

Run a command when a file is changed

$ while inotifywait -e modify /tmp/myfile; do firefox; done

Substrings a variable

$ var='123456789'; echo ${var:<start_pos>:<offset>}

One command line web server on port 80 using nc (netcat)

$ while true ; do nc -l 80 < index.html ; done

RDP through SSH tunnel

ssh -f -L3389:<RDP_HOST>:3389 <SSH_PROXY> "sleep 10" && rdesktop -T'<WINDOW_TITLE>' -uAdministrator -g800x600 -a8 -rsound:off -rclipboard:PRIMARYCLIPBOARD -5 localhost

"Clone" a list of installed packages from one Debian/Ubuntu Server to another

apt-get install `ssh root@host_you_want_to_clone "dpkg -l | grep ii" | awk '{print $2}'`

Remote screenshot

ssh user@remote-host "DISPLAY=:0.0 import -window root -format png -"|display -format png -

Google text-to-speech in mp3 format

$ say(){ mplayer -user-agent Mozilla "http://translate.google.com/translate_tts?tl=en&q=$(echo $* | sed 's#\ #\+#g')" > /dev/null 2>&1 ; }

Add the result of a command into vi

$ !!command

Place the NUM-th argument of the most recent command on the shell

$ <ALT>+<.> or <ALT>+<NUM>+<.> or <ALT>+<NUM>,<ALT>+<.>

Find the package a command belongs to on Debian

dpkg -S $( which ls )

Look up a unicode character by name

egrep -i "^[0-9a-f]{4,} .*$*" $(locate CharName.pm) | while read h d; do /usr/bin/printf "\U$(printf "%08x" 0x$h)\tU+%s\t%s
" $h "$d"; done

Start dd and show progress every X seconds

$ dd if=/path/inputfile | pv | dd of=/path/outpufile

Ask user to confirm

$ Confirm() { read -sn 1 -p "$1 [Y/N]? "; [[ $REPLY = [Yy] ]]; }

Random unsigned integer

echo $(openssl rand 4 | od -DAn)

Kill all process that belongs to you

kill -9 -1

Make a file not writable / immutable by root

sudo chattr +i <file>

Analyze traffic remotely over ssh w/ wireshark

ssh root@HOST tcpdump -U -s0 -w - 'not port 22' |wireshark -k -i -

Send email with curl and gmail

curl -n --ssl-reqd --mail-from "<user@gmail.com>" --mail-rcpt "<user@server.tld>" --url smtps://smtp.gmail.com:465 -T file.txt

Translates acronyms for you

wtf is <acronym>

Delete DOS Characters via VIM (^M)

$ :set ff=unix

Create an animated gif from a Youtube video

$ url=http://www.youtube.com/watch?v=V5bYDhZBFLA; youtube-dl -b $url; mplayer $(ls ${url##*=}*| tail -n1) -ss 00:57 -endpos 10 -vo gif89a:fps=5:output=output.gif -vf scale=400:300 -nosound

Print just line 4 from a textfile

sed -n '4{p;q}'

Print just line 4 from a textfile

sed -n '4p'

Quick HTML image gallery from folder contents

find . -iname '*.jpg' -exec echo '<img src="{}">' \; > gallery.html

Get your external IP address without curl

wget -qO- icanhazip.com

Resume a detached screen session, resizing to fit the current terminal

$ screen -raAd

Start a HTTP server which serves Python docs

$ pydoc -p 8888 & gnome-open http://localhost:8888

Do some learning...

ls /usr/bin | xargs whatis | grep -v nothing | less

Insert the last argument of the previous command

$ <ALT> .

Carriage return for reprinting on the same line

$ while true; do echo -ne "$(date)\r"; sleep 1; done

Copy a folder tree through ssh using compression (no temporary files)

ssh <host> ' tar -cz /<folder>/<subfolder>' | tar -xvz

Command line calculator

$ calc(){ awk "BEGIN{ print $* }" ;}

Backup a local drive into a file on the remote host via ssh

dd if=/dev/sda | ssh user@server ' dd of=sda.img'

Kill processes that have been running for more than a week

find /proc -user myuser -maxdepth 1 -type d -mtime +7 -exec basename {} \; | xargs kill -9

List Network Tools in Linux

apropos network |more

Print text string vertically, one character per line.

echo "vertical text" | grep -o '.'

Add prefix onto filenames

$ rename 's/^/prefix/' *

Salvage a borked terminal

$ <ctrl+j>stty sane<ctrl+j>

Pick a random line from a file

shuf -n1 file.txt

Get all these commands in a text file with description.

$ for x in `jot - 0 2400 25`; do curl"http://www.commandlinefu.com/commands/browse/sort-by-votes/plaintext/$x" ; done > commandlinefu.txt

Stripping ^M at end of each line for files

dos2unix <filenames>

Backup files incremental with rsync to a NTFS-Partition

rsync -rtvu --modify-window=1 --progress /media/SOURCE/ /media/TARGET/

Find removed files still in use via /proc

find -L /proc/*/fd -links 0 2>/dev/null

Connect to google talk through ssh by setting your IM client to use the localhost 5432 port

ssh -f -N -L 5432:talk.google.com:5222 user@home.network.com

Urldecoding

sed -e's/%\([0-9A-F][0-9A-F]\)/\\\\\x\1/g' | xargs echo -e

For all flv files in a dir, grab the first frame and make a jpg.

$ for f in *.flv; do ffmpeg -y -i "$f" -f image2 -ss 10 -vframes 1 -an "${f%.flv}.jpg"; done

Wrap long lines of a text

fold -s -w 90 file.txt

Validate and pretty-print JSON expressions.

echo '{"json":"obj"}' | python -m simplejson.tool

Grep colorized

grep -i --color=auto

From within vi, pipe a chunk of lines to a command line and replace the chunk with the result

$ !}sort

Grep for word in directory (recursive)

grep --color=auto -iRnH "$search_word" $directory

Unix alias for date command that lets you create timestamps in ISO 8601 format

alias timestamp='date "+%Y%m%dT%H%M%S"'

Another Curl your IP command

curl -s http://checkip.dyndns.org | sed 's/[a-zA-Z<>/ :]//g'

Count IPv4 connections per IP

netstat -anp |grep 'tcp\|udp' | awk '{print $5}' | sed s/::ffff:// |cut -d: -f1 | sort | uniq -c | sort -n

Files extension change

$ rename .oldextension .newextension *.oldextension

Archive all files containing local changes (svn)

svn st | cut -c 8- | sed 's/^/\"/;s/$/\"/' | xargs tar -czvf ../backup.tgz

Just run it ;)

echo SSBMb3ZlIFlvdQo= | base64 -d

Pattern match in awk - no grep

awk '/pattern1/ && /pattern2/ && !/pattern3/ {print}'

Optimal way of deleting huge numbers of files

find /path/to/dir -type f -print0 | xargs -0 rm

Du with colored bar graph

du -x --max-depth=1|sort -rn|awk -F / -v c=$COLUMNS 'NR==1{t=$1} NR>1{r=int($1/t*c+.5); b="\033[1;31m"; for (i=0; i<r; i++) b=b"#"; printf " %5.2f%% %s\033[0m %s
", $1/t*100, b, $2}'|tac

Mount a VMware virtual disk (.vmdk) file on a Linux box

kpartx -av <image-flat.vmdk>; mount -o /dev/mapper/loop0p1 /mnt/vmdk

Quick copy

cp foo{,bak}

Sending a file over icmp with hping

hping3 10.0.2.254 --icmp --sign MSGID1 -d 50 -c 1 --file a_file

Fetch the current human population of Earth

curl -s http://www.census.gov/popclock/data/population/world |python -c 'import json,sys;obj=json.load(sys.stdin);print obj["world"]["population"]'

Kill a broken ssh connection

$ <Return>~.

Convert JSON to YAML

$ ruby -ryaml -rjson -e 'puts YAML.dump(JSON.parse(STDIN.read))' < file.json > file.yaml

Convert Shell Text to Upper/Lower Case

$ ALT-U / ALT-L

The fastest remote directory rsync over ssh archival I can muster (40MB/s over 1gb NICs)

rsync -aHAXxv --numeric-ids --delete --progress -e "ssh -T -c arcfour -o Compression=no -x" user@<source>:<source_dir> <dest_dir>

Binary digits Matrix effect

perl -e '$|++; while (1) { print " " x (rand(35) + 1), int(rand(2)) }'

Open two files side by side in vim (one window, two panes)

vim -O file1 file2

Repeat a command every one second

watch -n 1 "do foo"

Update all packages installed via homebrew

$ brew update && brew upgrade `brew outdated`

Daemonize nc - Transmit a file like a http server

$ while ( nc -l 80 < /file.htm > : ) ; do : ; done &

Find ulimit values of currently running process

cat /proc/PID/limits

Diff current vi buffer edits against original file

$ :w !diff -u % -

Redirect tar extract to another directory

tar xfz filename. tar.gz -C PathToDirectory

Print multiplication formulas

seq 9 | sed 'H;g' | awk -v RS='' '{for(i=1;i<=NF;i++)printf("%dx%d=%d%s", i, NR, i*NR, i==NR?"
":"\t")}'

Find Malware in the current and sub directories by MD5 hashes

$ IFS=$'
' && for f in `find . -type f -exec md5sum "{}" \;`; do echo $f |sed -r 's/^[^ ]+/Checking:/'; echo $f | cut -f1 -d' ' | netcathash.cymru.com 43 ; done

Watch several log files of different machines in a single multitail window on your own machine

$ multitail -l 'ssh machine1 "tail -f /var/log/apache2/error.log"' -l 'ssh machine2 "tail -f /var/log/apache2/error.log"'

Execute a command, convert output to .png file, upload file to imgur.com, then returning the address of the .png.

$ imgur(){ $*|convert label:@- png:-|curl -F "image=@-" -F "key=1913b4ac473c692372d108209958fd15" http://api.imgur.com/2/upload.xml| grep -Eo "<original>(.)*</original>" | grep -Eo "http://i.imgur.com/[^<]*";}

All out

pkill -KILL -u username

Numeric zero padding file rename

$ rename 's/\d+/sprintf("%04d",$&)/e' *.jpg

Find out the starting directory of a script

echo "${0%/*}"

Selecting a random file/folder of a folder

shuf -n1 -e *

List your MACs address

$ lsmac() { ifconfig -a | sed '/eth\|wl/!d;s/ Link.*HWaddr//' ; }

Ssh to machine behind shared NAT

ssh -NR 0.0.0.0:2222:127.0.0.1:22 user@jump.host.com

Countdown Clock

$ MIN=10;for ((i=MIN*60;i>=0;i--));do echo -ne "\r$(date -d"0+$i sec" +%H:%M:%S)";sleep 1;done

List all file extensions in a directory

find . -type f | awk -F'.' '{print $NF}' | sortuniq -c | sort -g

Send an http HEAD request w/curl

curl -I http://localhost

View hex mode in vim

$ :%!xxd

View ~/.ssh/known_hosts key information

ssh-keygen -l -f ~/.ssh/known_hosts

Kill all Zombie processes (Guaranteed!)

kill -9 `ps -xaw -o state -o ppid | grep Z | grep -v PID | awk'{print $2}'`

Prevent accidents and test your command with echo

echo rm *.txt

Exclude a column with awk

awk '{ $5=""; print }' file

Get My Public IP Address

curl ifconfig.me

Pretend to be busy in office to enjoy a cup of coffee

$ for i in `seq 0 100`;do timeout 6 dialog --gauge "Install..." 6 40 "$i";done

Empty a file

$ :> file

Better way to use notify-send with at or cron

$ DISPLAY=:0.0 XAUTHORITY=~/.Xauthority notify-sendtest

Emptying a text file in one shot

$ :%d

Computes the most frequent used words of a text file

$ cat WAR_AND_PEACE_By_LeoTolstoi.txt | tr -cs "[:alnum:]" "
"| tr "[:lower:]" "[:upper:]" | awk '{h[$1]++}END{for (i in h){print h[i]" "i}}'|sort -nr | cat -n | head -n 30

Countdown Clock

$ MIN=1 && for i in $(seq $(($MIN*60)) -1 1); do echo -n "$i, "; sleep 1; done; echo -e "

BOOOM! Time to start."

Print info about your real user.

who loves mum

Serve current directory tree at http://$HOSTNAME:8080/

twistd -n web --path .

JSON processing with Python

curl -s "http://feeds.delicious.com/v2/json?count=5" |python -m json.tool | less -R

Move items from subdirectories to current directory

find -type f -exec mv {} . \;

Restrict the bandwidth for the SCP command

scp -l10 pippo@serverciccio:/home/zutaniddu/* .

Optimize PDF documents

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/screen -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf

Live ssh network throughput test

pv /dev/zero|ssh $host 'cat > /dev/null'

Bash screensaver (scrolling ascii art with customizable message)

$ while [ 1 ]; do banner 'ze missiles, zey are coming! ' | while IFS="
" read l; do echo "$l"; sleep 0.01; done; done

Upgrade all perl modules via CPAN

cpan -r

Remove lines that contain a specific pattern($1) from file($2).

sed -i '/myexpression/d' /path/to/file.txt

List your largest installed packages (on Debian/Ubuntu)

$ dpigs

Rsync + find

find . -name "whatever.*" -print0 | rsync -av --files-from=- --from0 ./ ./destination/

Autossh + ssh + screen = super rad perma-sessions

$ AUTOSSH_POLL=1 autossh -M 21010 hostname -t 'screen -Dr'

Record microphone input and output to date stamped mp3 file

$ arecord -q -f cd -r 44100 -c2 -t raw | lame -S -x -h -b 128 - `date +%Y%m%d%H%M`.mp3

Find running binary executables that were not installed using dpkg

cat /var/lib/dpkg/info/*.list > /tmp/listin ; ls /proc/*/exe |xargs -l readlink | grep -xvFf /tmp/listin; rm /tmp/listin

Cycle through a 256 colour palette

yes "$(seq 1 255)" | while read i; do printf"\x1b[48;5;${i}m
"; sleep .01; done

Parallel file downloading with wget

$ wget -nv http://en.wikipedia.org/wiki/Linux -O- | egrep -o "http://[^[:space:]]*.jpg" | xargs -P 10 -r -n 1 wget -nv

Move a lot of files over ssh

$ tar -cf - /home/user/test | gzip -c | ssh user@ sshServer 'cd /tmp; tar xfz -'

Cleanup firefox's database.

pgrep -u `id -u` firefox-bin || find ~/.mozilla/firefox -name '*.sqlite'|(while read -e f; do echo 'vacuum;'|sqlite3 "$f" ; done)

Vim easter egg

$ $ vim ... :help 42

Find the process you are looking for minus the grepped one

pgrep command_name

Stream YouTube URL directly to mplayer

$ id="dMH0bHeiRNg";mplayer -fs http://youtube.com/get_video.php?video_id=$id\&t=$(curl -s http://www.youtube.com/watch?v=$id | sed -n 's/.*, "t": "\([^"]*\)", .*/\1/p')

Update twitter via curl

curl -u user -d status="Tweeting from the shell" http://twitter.com/statuses/update.xml

Ssh autocomplete

$ complete -W "$(echo $(grep '^ ssh ' .bash_history | sort -u | sed 's/^ ssh //'))" ssh

Get all IPs via ifconfig

ifconfig | perl -nle'/dr:(\S+)/ && print $1'

VIM: Replace a string with an incrementing number between marks 'a and 'b (eg, convert string ZZZZ to 1, 2, 3, ...)

$ :let i=0 | 'a,'bg/ZZZZ/s/ZZZZ/\=i/ | let i=i+1

Get the canonical, absolute path given a relative and/or noncanonical path

readlink -f ../super/symlink_bon/ahoy

Create a Multi-Part Archive Without Proprietary Junkware

tar czv Pictures | split -d -a 3 -b 16M - pics. tar.gz.

List and delete files older than one year

find <directory path> -mtime +365 -and -not -type d -delete

Display last exit status of a command

echo $?

Enable ** to expand files recursively (>=bash-4.0)

$ shopt -s globstar

Command Line to Get the Stock Quote via Yahoo

curl -s 'http://download.finance.yahoo.com/d/quotes.csv?s=csco&f=l1'

Plays Music from SomaFM

$ read -p "Which station? "; mplayer --reallyquiet -vo none -ao sdl http://somafm.com/startstream=${REPLY}.pls

Convert camelCase to underscores (camel_case)

sed -r 's/([a-z]+)([A-Z][a-z]+)/\1_\l\2/g' file.txt

Set your profile so that you resume or start a screen session on login

echo "screen -DR" >> ~/.bash_profile

Play high-res video files on a slow processor

$ mplayer -framedrop -vfm ffmpeg -lavdopts lowres=1:fast:skiploopfilter=all

Create directory named after current date

mkdir $(date +%Y%m%d)

Monitor dynamic changes in the dmesg log.

watch "dmesg |tail -15"

Generate a list of installed packages on Debian-based systems

dpkg --get-selections > LIST_FILE

Find the process that is using a certain port e.g. port 3000

lsof -P | grep ':3000'

Pause Current Thread

$ ctrl-z

Converts to PDF all the OpenOffice.org files in the directory

$ for i in $(ls *.od{tp}); do unoconv -f pdf $i; done

Create a bunch of dummy files for testing

touch {1..10}.txt

Convert .wma files to .ogg with ffmpeg

find -name '*wma' -exec ffmpeg -i {} -acodec vorbis -ab 128k {}.ogg \;

Find distro name and/or version/release

cat /etc/*-release

Generate Random Passwords

$ < /dev/urandom tr -dc _A-Z-a-z-0-9 | head -c6

Bash shortcut: !$ !^ !* !:3 !:h and !:t

$ echo foo bar foobar barfoo && echo !$ !^ !:3 !* && echo /usr/bin/foobar&& echo !$:h !$:t

Grep without having it show its own process in the results

ps aux | grep "[s]ome_text"

Find recursively, from current directory down, files and directories whose names contain single or multiple whitespaces and replace each such occurrence with a single underscore.

find ./ -name '*' -exec rename 's/\s+/_/g' {} \;

Tells which group you DON'T belong to (opposite of command "groups") --- uses sed

$ sed -e "/$USER/d;s/:.*//g" /etc/group | sed -e :a -e '/$/N;s/
/ /;ta'

Quickly get summary of sizes for files and folders

du -sh *

Echo the latest commands from commandlinefu on the console

wget -O - http://www.commandlinefu.com/commands/browse/rss 2>/dev/null | awk '/\s*<title/ {z=match($0, /CDATA\[([^\]]*)\]/, b);print b[1]} /\s*<description/ {c=match($0, /code>(.*)<\/code>/, d);print d[1]"
"} '

Optimal way of deleting huge numbers of files

rsync -a --delete empty-dir/ target-dir/

Drop first column of output by piping to this

awk '{ $1="";print}'

Create a bunch of dummy text files

base64 /dev/urandom | head -c 33554432 | split -b 8192 -da 4 - dummy.

Get the Nth argument of the last command (handling spaces correctly)

$ !:n

Temporarily ignore mismatched SSH host key

ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no username@host

Remove all zero size files from current directory (not recursive)

find . -maxdepth 1 -size 0c -delete

Watch the progress of 'dd'

pv -tpreb /dev/urandom | dd of=file.img

Get a stream feed from a Twitter user

$ step1 ; step2 ; step3 ; step4 ; curl -o- --get 'https://stream.twitter.com/1/statuses/filter.json' --header "$oauth_header" --data "follow=$id"

Create the authorization header required for a Twitter stream feed

$ step4() { oauth_header="Authorization: OAuth oauth_consumer_key=\"$k1\", oauth_nonce=\"$once\", oauth_signature=\"$signature\", oauth_signature_method=\"HMAC-SHA1\", oauth_timestamp=\"$ts\", oauth_token=\"$k3\", oauth_version=\"1.0\"" ; }

Create the signature base string required for a Twitter stream feed

$ step2(){ b="GET&https%3A%2F%2Fstream.twitter.com%2F1%2Fstatuses%2Ffilter.json&follow%3D${id}%26oauth_consumer_key%3D${k1}%26oauth_nonce%3D${once}%26oauth_signature_method%3DHMAC-SHA1%26oauth_timestamp%3D${ts}%26oauth_token%3D${k3}%26oauth_version%3D1.0";}

Create the oauth token required for a Twitter stream feed

$ step3() { s=$( echo -n $b | openssl dgst -sha1 -hmac $hmac -binary | openssl base64); signature=`for((i=0;i<${#s};i++)); do case ${s:i:1} in +) e %2B;; /) e %2F;; =) e %3D;; *) e ${s:i:1};; esac ; done` ; } ; e() { echo -n $1; }

Open a screenshot of a remote desktop via ssh

$ xloadimage <(ssh USER@HOSTNAME DISPLAY=:0.0import -window root png:-)

Check your spelling

aspell -a <<< '<WORDS>'

Find all files larger than 500M and less than 1GB

find / -type f -size +500M -size -1G

Show bandwidth use oneliner

$ while true; do cat /proc/net/dev; sleep 1; done | awk -v dc="date \"+%T\"" '/eth0/{i = $2 - oi; o = $10 - oo; oi = $2; oo = $10; dc|getline d; close(dc); if (a++) printf "%s %8.2f KiB/s in %8.2f KiB/s out
", d, i/1024, o/1024}'

Change/Modify timestamp interactively

touch -d $(zenity --calendar --date-format=%F) filename

Sort the contents of a text file in place.

sort -g -o list.txt{,}

Instantly load bash history of one shell into another running shell

$ $ history -a #in one shell , and $ history -r #in another running shell

Copy with progress bar - rsync

rsync -rv <src> <dst> --progress

Multiple variable assignments from command output in BASH

$ read day month year < <(date +'%d %m %y')

Generate a random password 30 characters long

$ gpg --gen-random --armor 1 30

Run a ext4 file system check and badblocks scan with progress info

$ fsck.ext4 -cDfty -C 0 /dev/sdxx

List your MACs address

cat /sys/class/net/eth0/address

Rename all files which contain the sub-string 'foo', replacing it with 'bar'

$ for i in ./*foo*;do mv -- "$i" "${i//foo/bar}";done

Create a 5 MB blank file via a seek hole

dd if=/dev/zero of=testfile.seek seek=5242879 bs=1 count=1

ROT13 using the tr command

alias rot13="tr a-zA-Z n-za-mN-ZA-M"

Make vim open in tabs by default (save to .profile)

alias vim="vim -p"

Secure copy from one server to another without rsync and preserve users, etc

$ tar -czvf - /src/dir | ssh remotehost "(cd /dst/dir ; tar -xzvf -)"

The same as [Esc] in vim

$ Ctrl + [

Binary clock

perl -e 'for(;;){@d=split("",`date +%H%M%S`);print"\r";for(0..5){printf"%.4b ",$d[$_]}sleep 1}'

Function to split a string into an array

$ read -a ARR <<<'world domination now!'; echo${ARR[2]};

Generate MD5 hash for a string

md5sum <<<"test"

Recompress all .gz files in current directory using bzip2 running 1 job per CPU core in parallel

$ parallel -j+0 "zcat {} | bzip2 >{.}.bz2 && rm {}" ::: *.gz

Phpinfo from the command line

$ php -i

Run a command whenever a file is touched

$ ontouchdo(){ while :; do a=$(stat -c%Y "$1"); [ "$b" != "$a" ] && b="$a" && sh -c "$2"; sleep 1; done }

Escape potential tarbombs

$ atb() { l=$( tar tf $1); if [ $(echo "$l" | wc -l) -eq $(echo "$l" | grep $(echo "$l" | head -n1) | wc -l) ]; then tar xf $1; elsemkdir ${1%. tar.gz} && tar xf $1 -C ${1%. tar.gz}; fi ;}

Pretend to be busy in office to enjoy a cup of coffee

$ for i in {0..600}; do echo $i; sleep 1; done | dialog --gauge "Install..." 6 40

Get notified when a job you run in a terminal is done, using NotifyOSD

alias alert='notify-send -i /usr/share/icons/gnome/32x32/apps/gnome-terminal.png "[$?] $(history|tail -n1|sed -e '\''s/^\s*[0-9]\+\s*//;s/;\s*alert$//'\'')"'

Runs a X session within your X session

ssh -C -Y -l$USER xserver.mynet.xx 'Xnest -geometry 1900x1150 -query localhost'

Use screen as a terminal emulator to connect to serial consoles

$ screen /dev/tty<device> 9600

Have a random "cow" say a random thing

fortune | cowsay -f $(ls /usr/share/ cowsay/cows/ | shuf -n1)

Sends a postscript file to a postscript printer using netcat

cat my.ps | nc -q 1 hp4550.mynet.xx 9100

Lines in file2 that are not in file1

grep -Fxv -f file1 file2

Display which distro is installed

cat /etc/*release

Fetch every font from dafont.com to current folder

$ d="www.dafont.com/alpha.php?";for c in {a..z}; do l=`curl -s "${d}lettre=${c}"|sed -n 's/.*ge=\([0-9]\{2\}\).*/\1/p'`;for((p=1;p<=l;p++));do for u in `curl -s "${d}page=${p}&lettre=${c}"|egrep -o "http\S*.com/dl/\?f=\w*"`;do aria2c "${u}";done;done;done

Intercept stdout/stderr of another process

strace -ff -e write=1,2 -s 1024 -p PID 2>&1 | grep "^ |" |cut -c11-60 | sed -e 's/ //g' | xxd -r -p

Send DD a signal to print its progress

$ while :;do killall -USR1 dd;sleep 1;done

Open Remote Desktop (RDP) from command line and connect local resources

$ rdesktop -a24 -uAdministrator -pPassword -r clipboard:CLIPBOARD -r disk:share=~/share -z -g 1280x900 -0 $@ &

See your current RAM frequency

dmidecode -t 17 | awk -F":" '/Speed/ { print $2 }'

Scp with compression.

scp -C 10.0.0.4:/tmp/backup.sql /path/to/backup.sql

Perl Command Line Interpreter

perl -e 'while(1){print"> ";eval<>}'

Find unused IPs on a given subnet

nmap -T4 -sP 192.168.2.0/24 && egrep"00:00:00:00:00:00" /proc/net/arp

Find and delete empty dirs, start in current working dir

find . -type d -empty -delete

Check which files are opened by Firefox then sort by largest size.

lsof -p $(pidof firefox) | awk '/.mozilla/ { s = int($7/(2^20)); if(s>0) print (s)" MB -- "$9 | "sort -rn" }'

Optimal way of deleting huge numbers of files

find /path/to/dir -type f -delete

Geoip information

curl -s "http://www.geody.com/geoip.php?ip=$( curl -s icanhazip.com)" | sed '/^IP:/!d;s/<[^>][^>]*>//g'

What is my ip?

curl http://www.whatismyip.org/

FAST Search and Replace for Strings in all Files in Directory

$ sh -c 'S=askapache R=htaccess; find . -mount -type f|xargs -P5 -iFF grep -l -m1 "$S" FF|xargs -P5 -iFF sed -i -e "s%${S}%${R}%g" FF'

Get the total length of all video / audio in the current dir (and below) in H:m:s

find -type f -name "*.avi" -print0 | xargs -0 mplayer -vo dummy -ao dummy -identify 2>/dev/null | perl -nle '/ID_LENGTH=([0-9\.]+)/ && ($t +=$1) && printf"%02d:%02d:%02d
",$t/3600,$t/60%60,$t%60' | tail -n 1

Send data securly over the net.

cat /etc/passwd | openssl aes-256-cbc -a -e -pass pass:password | net cat -l -p 8080

When was your OS installed?

ls -lct /etc | tail -1 | awk '{print $6, $7}'

How to run a command on a list of remote servers read from a file

$ while read server; do ssh -n user@$server "command"; done < servers.txt

Replace spaces in filenames with underscorees

ls | while read f; do mv "$f" "${f// /_}";done

Find the biggest files recursively, no matter how many

find . -type f -printf '%20s %p
' | sort -n | cut -b22- | tr '
' '\000' | xargs -0 ls -laSr

Grep certain file types recursively

grep -r --include="*.[ch]" pattern .

Change proccess affinity.

taskset -cp <core> <pid>

Back up your commandlinefu contributed commands

curl http://www.commandlinefu.com/commands/by/<your username>/rss|gzip ->commandlinefu-contribs-backup-$(date +%Y-%m-%d-%H.%M.%S).rss.gz

Currently mounted filesystems in nice layout

column -t /proc/mounts

Benchmark web server with apache benchmarking tool

ab -n 9000 -c 900 localhost:8080/index.php

Salvage a borked terminal

echo <ctrl-v><esc>c<enter>

Multiple SSH Tunnels

ssh -L :: -L :: @

LDAP search to query an ActiveDirectory server

$ ldapsearch -LLL -H ldap://activedirectory.example.com:389 -b 'dc=example,dc=com' -D 'DOMAIN\Joe.Bloggs' -w 'p@ssw0rd' '(sAMAccountName=joe.bloggs)'

Easily scp a file back to the host you're connecting from

$ mecp () { scp "$@" ${SSH_CLIENT%% *}:Desktop/; }

Super Speedy Hexadecimal or Octal Calculations and Conversions to Decimal.

echo "$(( 0x10 )) - $(( 010 )) = $(( 0x10 - 010 ))"

Find and replace tabs for spaces within files recursively

find ./ -type f -exec sed -i 's/\t/ /g' {} \;

Delete all files found in directory A from directory B

$ for file in <directory A>/*; do rm <directory B>/`basename $ file`; done

Synchronicity

$ cal 09 1752

Terminal redirection

script /dev/null | tee /dev/pts/3

Displays the attempted user name, ip address, and time of SSH failed logins on Debian machines

awk '/sshd/ && /Failed/ {gsub(/invalid user/,""); printf"%-12s %-16s %s-%s-%s
", $9, $11, $1, $2, $3}' /var/log/auth.log

Rot13 using the tr command

alias rot13="tr '[A-Za-z]' '[N-ZA-Mn-za-m]'"

Measures download speed on eth0

$ while true; do X=$Y; sleep 1; Y=$(ifconfig eth0|grep RX\ bytes|awk '{ print $2 }'|cut -d : -f 2); echo "$(( Y-X )) bps"; done

Clean swap area after using a memory hogging application

swapoff -a ; swapon -a

Loop over a set of items that contain spaces

ls | while read ITEM; do echo "$ITEM"; done

Traceroute w/TCP to get through firewalls.

$ tcptraceroute www.google.com

Launch a command from a manpage

$ !date

Split File in parts

split -b 19m file Nameforpart

Speak the top 6 lines of your twitter timeline every 5 minutes.....

$ while [ 1 ]; do curl -s -u username:password http://twitter.com/statuses/friends_timeline.rss|grep title|sed -ne 's/<\/*title>//gp' | head -n 6 |festival --tts; sleep 300;done

Create an SSH SOCKS proxy server on localhost:8000 that will re-start itself if something breaks the connection temporarily

$ autossh -f -M 20000 -D 8000 somehost -N

To get you started!

$ vimtutor

Exclude grep from your grepped output of ps (alias included in description)

ps aux | grep [h]ttpd

Renames multiple files that match the pattern

$ rename 's/foo/bar/g' *

Block an IP address from connecting to a server

iptables -A INPUT -s 222.35.138.25/32 -j DROP

Infile search and replace on N files (including backup of the files)

perl -pi.bk -e's/foo/bar/g' file1 file2 fileN

Show running services (using systemctl)

$ command systemctl --no-page --no-legend --plain -tservice --state=running

Binary clock

perl -e 'for(;;sleep 1){printf"\r"."%.4b "x6,split"",`date +%H%M%S`}'

Pulsed terminal clock

$ clear;while true;sleep 1;do for((a=1;a<=$( tput cols)/3;a++));do tput cup 0 $a;echo " " $(date);done;sleep 1;for((a;a>=1;a--));do tput cup 0 $a;echo $(date) " ";done;done

Removes characters from cursor to the end of line

$ Ctrl+k

All what exists in dir B and not in dir A will be copied from dir B to new or existing dir C

rsync -v -r --size-only --compare-dest=../A/ B/ C/

Find previously entered commands (requires configuring .inputrc)

$ <Meta-p> (aka <ALT+P>)

Add directory to $PATH if it's not already there

$ if [[ ":$PATH:" != *":$dir:"* ]]; then PATH=${PATH}:$dir; fi

Debug how files are being accessed by a process

$ inotifywait -m -r .

Retry the previous command until it exits successfully

$ !!; while [ $? -ne 0 ]; do !!; done

Convert JSON to YAML

python -c 'import sys, yaml, json; yaml.safe_dump(json.load(sys.stdin), sys.stdout, default_flow_style=False)' < file.json > file.yaml

Search google.com on your terminal

$ Q="YOURSEARCH"; GOOG_URL="http://www.google.com/search?q="; AGENT="Mozilla/4.0"; stream=$(curl -A "$AGENT" -skLm 10 "${GOOG_URL}\"${Q/\ /+}\"" | grep -oP '\/url\?q=.+?&amp' | sed 's/\/url?q=//;s/&amp//'); echo -e "${stream//\%/\x}"

Play awesome rythmic noise using aplay

echo "main(i){for(i=0;;i++)putchar(((i*(i>>8|i>>9)&46&i>>8))^(i&i>>13|i>>6));}" | gcc -x c - && ./a.out | aplay

Turns red the stderr output

$ color()(set -o pipefail;"$@" 2>&1>&3|sed $'s,.*,\e[31m&\e[m,'>&2)3>&1

Recursively unrar into dir containing archive

find . -name '*.rar' -execdir unrar e {} \;

True Random Dice Roll

tr -cd '1-6' < /dev/urandom | head -c 1; echo

Find biggest 10 files in current and subdirectories and sort by file size

find . -type f -print0 | xargs -0 du -h | sort -hr | head -10

Get your external IP and Network Info

curl ifconfig.me/all

List all commands present on system

ls ${PATH//:/ }

A line across the entire width of the terminal

printf "%$(tput cols)s
"|tr ' ' '='

Recursively find top 20 largest files (> 1MB) sort human readable format

find . -type f -print0 | xargs -0 du -h | sort -hr | head -20

Create the four oauth keys required for a Twitter stream feed

$ step1() { k1="Consumer key" ; k2="Consumer secret" ; k3="Access token" ; k4="Access token secret" ; once=$RANDOM ; ts=$(date +%s) ; hmac="$k2&$k4" ; id="19258798" ; }

Check if a machine is online

ping -c 1 -q MACHINE_IP_OR_NAME >/dev/null 2>&1 && echo ONLINE || echo OFFLINE

Extract element of xml

$ xmlstarlet sel -t -c "/path/to/element" file.xml

Generate a random password 30 characters long

cat /dev/urandom | tr -dc A-Za-z0-9 | head -c 32

Remove the first and the latest caracter of a string

$ var=:foobar:; echo ${var:1:-1}

Load file into RAM (cache) for faster accessing for repeated usage

cat <file> > /dev/null

Show IP Address in prompt --> PS1 var

export PS1="[\u@`hostname -I` \W]$ "

Log a command to console and to 2 files separately stdout and stderr

$ command > >(tee stdout.log) 2> >(tee stderr.log >&2)

Join lines split with backslash at the end

sed -e '/\\$/{:0;N;s/\\
//;t0}'

Convert text to lowercase

$ lower() { echo ${@,,}; }

Find builtin in bash v4+

ls -l /etc/**/*killall

Make image semi-transparent

convert input.png -alpha set -channel A -fx 0.5 output.png

Compare directories via diff

diff -rq dirA dirB

Execute a shell with netcat without -e

mknod backpipe p && nc remote_server 1337 0<backpipe | /bin/bash 1>backpipe

Save your terminal commands in bash history in real time

$ shopt -s histappend ; PROMPT_COMMAND="history -a;$PROMPT_COMMAND"

Connect via SSH to VirtualBox guest VM without knowing IP address

ssh vm-user@`VBoxManage guestproperty get "vm-name" "/VirtualBox/GuestInfo/Net/0/V4/IP" | awk '{ print $2 }'`

Make redirects to localhost via /etc/hosts more interesting

sudo socat TCP4-LISTEN:80,bind=127.0.0.1,fork EXEC:'echo "HTTP/1.1 503 Service Unavailable";'

Screensaver

alias screensaver='for ((;;)); do echo -ne "\033[$((1+RANDOM%LINES));$((1+RANDOM%COLUMNS))H\033[$((RANDOM%2));3$((RANDOM%8))m$((RANDOM%10))"; sleep 0.1 ; done'

Tricky implementation of two-dimensional array in Bash.

$ arr[i*100+j]="whatever"

Terrorist threat level text

echo "Terrorist threat level: `od -An -N1 -i /dev/random`"

Bash logger

script /tmp/log.txt

Use wget to download one page and all it's requisites for offline viewing

wget -e robots=off -E -H -k -K -p http://<page>

Convert a string to "Title Case"

echo "this is a test" | sed 's/.*/\L&/; s/[a-z]*/\u&/g'

RTFM function

$ rtfm() { help $@ || info $@ || man $@ || $BROWSER "http://www.google.com/search?q=$@"; }

Back ssh from firewalled hosts

ssh -R 5497:127.0.0.1:22 -p 62220 user@public.ip

Rename HTML files according to their title tag

perl -wlne'/title>([^<]+)/i&&rename$ARGV,"$1.html"' *.html

Rename files according to file with colums of corresponding names

xargs -n 2 mv < file_with_colums_of_names

Create a new file

$ > file

Monitor a file with tail with timestamps added

tail -f file | awk '{now=strftime("%F %T%z\t");sub(/^/, now);print}'

Check disk for bad sectors

badblocks -n -s -b 2048 /dev/sdX

Create a file of a given size in linux

truncate -s 1M file

Pretend to be busy in office to enjoy a cup of coffee

$ while [ true ]; do head -n 100 /dev/urandom; sleep .1; done | hexdump -C | grep "ca fe"

Extended man command

$ /usr/bin/man $* || w3m -dump http://google.com/search?q="$*"\&btnI | less

Show which process is blocking umount (Device or resource is busy)

lsof /folder

Show the UUID of a filesystem or partition

blkid /dev/sda7

Run command on a group of nodes

$ mussh -h host1 host2 host3 -c uptime

Setting global redirection of STDERR to STDOUT in a script

$ exec 2>&1

Outgoing IP of server

dig +short @resolver1.opendns.com myip.opendns.com

Isolate file name from full path/find output

echo ${fullpath##*/}

Show numerical values for each of the 256 colors in bash

$ for i in {0..255}; do echo -e "\e[38;05;${i}m${i}"; done |column -c 80 -s ' '; echo -e "\e[m"

Find all symlinks that link to directories

find -type l -xtype d

Use Kernighan & Ritchie coding style in C program

$ indent -kr hello.c

Delay execution until load average falls under 1.5

echo 'some command' | batch

Backup with mysqldump a really big mysql database to a remote machine over ssh

$ mysqldump -q --skip-opt --force --log-error=dbname_error.log -uroot -pmysqlpassword dbname |ssh -C user@ sshserver 'cd /path/to/backup/dir; cat > dbname.sql'

Tail -f at your own pace

tail -fs 1 somefile

Watch the progress of 'dd'

$ dd if=/dev/zero | pv | dd of=/dev/null

Realtime lines per second in a log file

tail -f access.log | pv -l -i10 -r >/dev/null

Smart `cd`.. cd to the file directory if you try to cd to a file

$ cd() { if [ -z "$1" ]; then command cd; else if [ -f "$1" ]; then command cd $(dirname "$1"); else command cd "$1"; fi; fi; }

Temporarily ignore known SSH hosts

ssh -o UserKnownHostsFile=/dev/null root@192.168.1.1

Dd with progress bar

dd if=/dev/nst0 |pv| dd of=restored_file.tar

Save the Top 2500 commands from commandlinefu to a single text file

curlhttp://www.commandlinefu.com/commands/browse/sort-by-votes/plaintext/[0-2500:25] | grep -v _ curl_ > comfu.txt

Print a row of 50 hyphens

python -c 'print "-"*50'

Display a wave pattern

$ ruby -e "i=0;loop{puts ' '*(29*(Math.sin(i)/2+1))+'|'*(29*(Math.cos(i)/2+1)); i+=0.1}"

Grep tab chars

grep "^V<TAB>" your_file

Send a message to a windows machine in a popup

echo "message" | smbclient -M NAME_OF_THE_COMPUTER

Using mplayer to play the audio only but suppress the video

$ mplayer -novideo something.mpg

Using mplayer to play the audio only but suppress the video

$ mplayer -vo null something.mpg

Create a temporary file in a command line call

$ any_script.sh < <(some command)

Shell function to make gnu info act like man.

$ my info() { info --subnodes -o - $1 | less; }

Replace spaces in filenames with underscores

$ for f in *;do mv "$f" "${f// /_}";done

Insert the last argument of the previous command

$ !$

Change the From: address on the fly for email sent from the command-line

$ mail -s "subject" user@todomain.com <emailbody.txt -- -f customfrom@fromdomain.com -F 'From Display Name'

Remote control for Rhythmbox on an Ubuntu Media PC

alias rc='ssh ${MEDIAPCHOSTNAME} envDISPLAY=:0.0 rhythmbox-client --no-start'

Use colordiff in side-by-side mode, and with automatic column widths.

$ colordiff -yW"`tput cols`" /path/to/file1 /path/to/file2

Extract email adresses from some file (or any other pattern)

grep -Eio '([[:alnum:]_.-]+@[[:alnum:]_.-]+?\.[[:alpha:].]{2,6})'

Amazing real time picture of the sun in your wallpaper

curlhttp://sohowww.nascom.nasa.gov/data/realtime/eit_195/512/latest.jpg | xli -onroot -fill stdin

Bash screensaver off

setterm -powersave off -blank 0

Convert vdi to vmdk (virtualbox hard disk conversion to vmware hard disk format)

$ VBoxManage internalcommands converttoraw winxp.vdi winxp.raw && qemu-img convert -O vmdk winxp.raw winxp.vmdk && rm winxp.raw

Smart renaming

$ mmv 'banana_*_*.asc' 'banana_#2_#1.asc'

Is today the end of the month?

$ [ `date --date='next day' +'%B'` == `date +'%B'` ] || echo'end of month'

Port scan a range of hosts with Netcat.

$ for i in {21..29}; do nc -v -n -z -w 1 192.168.0.$i 443; done

Log your internet download speed

$ echo $(date +%s) > start-time; URL=http://www.google.com; while true; do echo $(curl -L --w %{speed_download} -o/dev/null -s $URL) >> bps; sleep10; done &

Show Directories in the PATH Which does NOT Exist

$ (IFS=:;for p in $PATH; do test -d $p || echo $p; done)

Backup files older than 1 day on /home/dir, gzip them, moving old file to a dated file.

find /home/dir -mtime +1 -print -exec gzip -9 {} \; -exec mv{}.gz {}_`date +%F`.gz \;

Alias to close terminal with :q

alias ':q'='exit'

Display an embeded help message from bash script header

$ [ "$1" == "--help" ] && { sed -n -e '/^# Usage:/,/^$/ s/^# \?//p' < $0; exit; }

Sort file greater than a specified size in human readeable format including their path and typed by color, running from current directory

find ./ -size +10M -type f -print0 | xargs -0 ls -Ssh1 --color

Print file without duplicated lines using awk

awk '!a[$0]++' file

Get the 10 biggest files/folders for the current direcotry

du -sk * |sort -rn |head

Get your external IP address

curl -s 'http://checkip.dyndns.org' | sed 's/.*Current IP Address: \([0-9\.]*\).*/\1/g'

Send email with one or more binary attachments

echo "Body goes here" | mutt -s "A subject" -a /path/to/file.tar.gz recipient@example.com

Convert a web page into a png

touch $2;firefox -print $1 -printmode PNG -printfile $2

Uncomment the lines where the word DEBUG is found

sed '/^#.*DEBUG.*/ s/^#//' $FILE

This toggles mute on the Master channel of an alsa soundcard

amixer sset Master toggle

Submit data to a HTML form with POST method and save the response

curl -sd 'rid=value&submit=SUBMIT' <URL> > out.html

Count how many times a string appears in a (source code) tree

$ $ grep -or string path/ | wc -l

Search commandlinefu from the CLI

curl -sd q=Network http://www.commandlinefu.com/search/autocomplete |html2text -width 100

Compare a remote file with a local file

vimdiff <file> scp://[<user>@]<host>/<file>

Using netcat to copy files between servers

$ On target: "nc -l 4000 | tar xvf -" On source: " tar -cf - . | nctarget_ip 4000"

Search command history on bash

$ ctrl + r

Redirect incoming traffic to SSH, from a port of your choosing

iptables -t nat -A PREROUTING -p tcp --dport [port of your choosing] -j REDIRECT --to-ports 22

Using bash inline

$ <<<"k=1024; m=k*k; g=k*m; g" bc

Alt + 1 .

$ alt + 1 .

Create several copies of a file

$ for i in {1..5}; do cp test{,$i};done

Search for a single file and go to it

cd $(dirname $(find ~ -name emails.txt))

Nice info browser

$ pinfo

Sends your internal IP by email

ifconfig en1 | awk '/inet / {print $2}' | mail -s "hello world" email@email.com

Download schedule

echo 'wget url' | at 12:00

Use mtr to create a text file report

mtr --report --report-cycles 10 www.google.com > google_net_report.txt

Quick screenshot

import -pause 5 -window root desktop_screenshot.jpg

Edit the last or previous command line in an editor then execute

$ fc [history-number]

Quicker move to parent directory

alias ..='cd ..'

Show webcam output

$ mplayer tv:// -tv driver=v4l:width=352:height=288

Open the last file you edited in Vim.

alias lvim="vim -c \"normal '0\""

Keep from having to adjust your volume constantly

find . -iname \*.mp3 -print0 | xargs -0 mp3gain -krd 6 && vorbisgain -rfs .

[re]verify a disc with very friendly output

dd if=/dev/cdrom | pv -s 700m | md5sum | tee test.md5

Processes by CPU usage

ps -e -o pcpu,cpu, nice,state,cputime,args --sort pcpu |sed "/^ 0.0 /d"

Rotate a set of photos matching their EXIF data.

$ jhead -autorot *.jpg

Awk using multiple field separators

awk -F "=| "

Shows size of dirs and files, hidden or not, sorted.

du -cs * .[^\.]* | sort -n

Hard disk information - Model/serial no.

hdparm -i[I] /dev/sda

Use mplayer to save video streams to a file

$ mplayer -dumpstream -dumpfile "yourfile" -playlist "URL"

Wrap text files on the command-line for easy reading

fold -s <filename>

Re-read partition table on specified device without rebooting system (here /dev/sda).

blockdev --rereadpt /dev/sda

Get your mac to talk to you

$ say -v Vicki "Hi, I'm a mac"

Sort a one-per-line list of email address, weeding out duplicates

sed 's/[ \t]*$//' < emails.txt | tr 'A-Z' 'a-z' | sort | uniq > emails_ sorted.txt

Recursively change file name from uppercase to lowercase (or viceversa)

find . -type f|while read f; do mv $f `echo $f |tr '[:upper:]' '[ :lower:]'`; done

Check the age of the filesystem

df / | awk '{print $1}' | grep dev | xargs tune2fs -l | grep create

Backup all MySQL Databases to individual files

$ for I in `echo "show databases;" | mysql | grep -v Database`; do mysqldump $I > "$I.sql"; done

Remove all subversion files from a project recursively

rm -rf `find . -type d -name .svn`

Click on a GUI window and show its process ID and command used to run the process

xprop | awk '/PID/ {print $3}' | xargs ps h -o pid,cmd

Print indepth hardware info

sudo dmidecode | more

Concatenate (join) video files

mencoder -forceidx -ovc copy -oac copy -o output.avi video1.avi video2.avi

Convert the contents of a directory listing into a colon-separated environment variable

find . -name '*.jar' -printf '%f:'

Make a log of a terminal session

script

Remove invalid host keys from ~/.ssh/known_hosts

ssh-keygen -R \[localhost\]:8022

Remove all spaces from all files in current folder

$ rename 's/ //g' *

A function to find the fastest free DNS server

$ timeDNS() { parallel -j0 --tag dig @{} "$*" ::: 208.67.222.222 208.67.220.220 198.153.192.1 198.153.194.1 156.154.70.1 156.154.71.1 8.8.8.8 8.8.4.4 | grep Query | sort -nk5; }

New Maintainer for CommandLineFu

$ mail tech@commandlinefu.com

Bare Metal IRC Client

$ nik=clf$RANDOM;sr=irc.efnet.org;expect -c "set timeout-1;spawn nc $sr 6666;set send_human {.1 .2 1 .2 1};expect AUTH*
;send -h \"user $nik * * :$nik commandlinefu
nick $nik
\"; interact -o -re (PING.:)(.*\$) {send \"PONG :\$interact_out(2,string)\"}"

Get your Firefox history

sqlite3 ~/.mozilla/firefox/*.[dD]efault/places.sqlite "SELECT strftime('%d.%m.%Y %H:%M:%S', visit_date/1000000, 'unixepoch', 'localtime'),url FROM moz_places, moz_historyvisits WHERE moz_places.id = moz_historyvisits.place_id ORDER BY visit_date;"

Submit command & rewrite orginal command

$ <ctrl>+o

Check all bash scripts in current dir for syntax errors

find . -name '*.sh' -exec bash -n {} \;

Encrypted chat with netcat and openssl (one-liner)

$ server$ while true; do read -n30 ui; echo $ui |openssl enc -aes-256-ctr -a -k PaSSw; done | nc -l -p 8877 | while read so; do decoded_so=` echo "$so"| openssl enc -d -a -aes-256-ctr -k PaSSw`; echo -e "Incoming: $decoded_so"; done

Symlink all files from a base directory to a target directory

ln -s /BASE/* /TARGET/

List directories only

ls -d */