Commands tagged bash (821)

  • [Update! Thanks to a tip from ioggstream, I've fixed both of the bugs mentioned below.] You, yes, 𝙔𝙊𝙐, can be the terror of the Internet! Why use normal, boring bullet points in your text, when you could use a ROTATED HEAVY BLACK HEART BULLET (❥)!? (Which would also be an awesome band name, by the way).  This script makes it easy to find unusual characters from the command line. You can then cut and paste them or, if you're using a GTK application, type Control+Shift+U followed by the code point number (e.g., 2765) and then a SPACE.  USAGE: Put this script in a file (I called mine "ugrep") and make it executable. Run it from the command line like so,  ugrep heart  The output will look like this,  ☙ U+2619 REVERSED ROTATED FLORAL HEART BULLET ♡ U+2661 WHITE HEART SUIT ♥ U+2665 BLACK HEART SUIT ❣ U+2763 HEAVY HEART EXCLAMATION MARK ORNAMENT ❤ U+2764 HEAVY BLACK HEART ❥ U+2765 ROTATED HEAVY BLACK HEART BULLET ❦ U+2766 FLORAL HEART ❧ U+2767 ROTATED FLORAL HEART BULLET ⺖ U+2E96 CJK RADICAL HEART ONE ⺗ U+2E97 CJK RADICAL HEART TWO ⼼ U+2F3C KANGXI RADICAL HEART  You can, of course, use regular expressions. For example, if you are looking for the "pi" symbol, you could do this:  ugrep '\bpi\b'  REQUIREMENTS: Although this is written in Bash, it assumes you have Perl installed because it greps through the Perl Unicode character name module (/usr/lib/perl5/Unicode/CharName.pm). Note that it would not have made more sense to write this in Perl, since the CharName.pm module doesn't actually include a subroutine for looking up a character based on the description. (Weird.)  BUGS: In order to fit this script in the commandlinefu limits, a couple bugs were added. ① Astral characters beyond the BMP (basic multilingual plane) are not displayed correctly, but see below. ② Perl code from the perl module being grepped is sometimes extraneously matched.  MISFEATURES: Bash's printf cannot, given a Unicode codepoint, print the resulting character to the terminal. GNU's coreutils printf (usually "/usr/bin/printf") can do so, but it is brokenly pedantic about how many hexadecimal digits follow the escape sequence and will actually die with an error if you give the wrong number. This is especially annoying since Unicode code points are usually variable length with implied leading zeros. The CharNames.pm file represents BMP characters as 4 hexits, but astral characters as 5. In the actual version of this script that I use, I've kludged around this misfeature by zero-padding to 8 hexits like so,  /usr/bin/printf "\U$(printf "%08x" 0x$hex)"  TIP 1: The author recommends "xsel" for command line cut-and-paste. For example,  ugrep biohazard | xsel  TIP 2: In Emacs, instead of running this command in a subshell, you can type Unicode code points directly by pressing Control-Q first, but you'll likely want to change the default input from octal to hexadecimal. (setq read-quoted-char-radix 16).  TIP 3: Of course, if you're using X, and you want to type one of the more common unusual characters, it's easiest of all to do it with your Compose (aka Multi) key. For example, hitting [Compose] <3 types ♥. Show Sample Output


    12
    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\n" $h "$d"; done
    hackerb9 · 2010-12-31 16:47:59 15
  • Very simple web server listening on port 80 will serve index.html file or whatever file you like pointing your browser at http://your-IP-address/index.html for example. If your web server is down for maintenance and you'd like to inform your visitors about it, quickly and easily, you just have to put into the index.html file the right HTML code and you are done! Of course you need to be root to run the command using port 80.


    12
    while true ; do nc -l 80 < index.html ; done
    ztank1013 · 2011-08-31 15:17:33 10
  • This command uses ping to get the routers' IP addresses to the destination host as traceroute does. If you know what I mean..


    12
    for i in {1..30}; do ping -t $i -c 1 google.com; done | grep "Time to live exceeded"
    6bc98f7f · 2012-02-19 13:37:04 8
  • Don't do this: echo word | command Using a bash "here strings" and "here documents" look leeter than piping echo into the command. Also prevents subshell execution. Word is also expanded as usual.


    12
    command <<< word
    adeverteuil · 2012-02-29 03:14:54 10
  • Bash's here string


    12
    sudo -s <<< 'apt update -y && apt upgrade -y'
    metropolis · 2019-08-07 14:03:30 73
  • Hold ctrl and press z to pause the current thread. Run fg to resume it.


    11
    ctrl-z
    mallegonian · 2009-03-16 20:58:31 23
  • If you would like to edit a previous command, which might be long and complicated, you can use the fc (I think it stands for fix command). Invoke fc alone will edit the last command using the default editor (specified by $FCEDIT, $EDITOR, or emacs, in that order). After you make the changes in the editor, save and exit to execute that command. The fc command is more flexible than what I have described. Please 'man bash' for more information.


    11
    fc [history-number]
    haivu · 2009-03-20 15:09:43 47
  • This command looks for a single file named emails.txt which is located somewhere in my home directory and cd to that directory. This command is especially helpful when the file is burried deep in the directory structure. I tested it against the bash shells in Xubuntu 8.10 and Mac OS X Leopard 10.5.6


    11
    cd $(dirname $(find ~ -name emails.txt))
    haivu · 2009-05-01 21:26:58 14
  • This command asks for the station name and then connects to somafm, Great for those who have linux home entertainment boxes and ssh enabled on them, just for the CLI fiends out there ( I know I'm one of them ;) Also, don't forget to add this as alias(ie alias somafm="read -p 'Which Station? "; mplayer --reallyquite -vo none -ao sdl


    11
    read -p "Which station? "; mplayer --reallyquiet -vo none -ao sdl http://somafm.com/startstream=${REPLY}.pls
    denzuko · 2009-05-04 00:26:19 24
  • Since bash 4.0, you can use ** to recursively expand to all files in the current directory. This behaviour is disabled by default, this command enables it (you'd best put it in your .profile). See the sample output for clarification. In my opinion this is much better than creating hacks with find and xargs when you want to pass files to an application. Show Sample Output


    11
    shopt -s globstar
    Alanceil · 2009-05-05 16:02:44 8
  • The original doesn't work for me - but this does. I'm guessing that Youtube updated the video page so the original doesn't work.


    11
    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')
    matthewbauer · 2009-08-13 14:16:01 7
  • Barely worth posting because it is so simple, but I use it literally all the time. I was always frustrated by the limitations that a non-gui environment imposes on diff'ing files. This fixes some of those limitations by colourising the output (you'll have to install colordiff, but it is just a wrapper for diff itself), using side-by-side mode for clearer presentation, and of course, the -W parameter, using tput to automatically insert you terminal width. Note that the double quotes aren't necessary if typed into terminal as-is. I included them for safety sake,


    11
    colordiff -yW"`tput cols`" /path/to/file1 /path/to/file2
    dweomer21 · 2009-11-26 18:00:53 7
  • Displays a scrolling banner which loops until you hit Ctrl-C to terminate it. Make sure you finish your banner message with a space so it will loop nicely.


    11
    while [ 1 ]; do banner 'ze missiles, zey are coming! ' | while IFS="\n" read l; do echo "$l"; sleep 0.01; done; done
    craigds · 2009-12-14 07:40:07 10
  • I used only shuf command. Show Sample Output


    11
    shuf -n1 -e *
    seungwon · 2011-03-23 03:52:56 9
  • If you want to operate on a set of items in Bash, and at least one of them contains spaces, the `for` loop isn't going to work the way you might expect. For example, if the current dir has two files, named "file" and "file 2", this would loop 3 times (once each for "file", "file", and "2"): for ITEM in `ls`; do echo "$ITEM"; done Instead, use a while loop with `read`: ls | while read ITEM; do echo "$ITEM"; done Show Sample Output


    10
    ls | while read ITEM; do echo "$ITEM"; done
    fletch · 2009-03-22 23:33:13 9

  • 10
    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
    stuntdawg · 2009-03-27 08:26:39 10
  • This Anti-TarBomb function makes it easy to unpack a .tar.gz without worrying about the possibility that it will "explode" in your current directory. I've usually always created a temporary folder in which I extracted the tarball first, but I got tired of having to reorganize the files afterwards. Just add this function to your .zshrc / .bashrc and use it like this; atb arch1.tar.gz and it will create a folder for the extracted files, if they aren't already in a single folder. This only works for .tar.gz, but it's very easy to edit the function to suit your needs, if you want to extract .tgz, .tar.bz2 or just .tar. More info about tarbombs at http://www.linfo.org/tarbomb.html Tested in zsh and bash. UPDATE: This function works for .tar.gz, .tar.bz2, .tgz, .tbz and .tar in zsh (not working in bash): atb() { l=$(tar tf $1); if [ $(echo "$l" | wc -l) -eq $(echo "$l" | grep $(echo "$l" | head -n1) | wc -l) ]; then tar xf $1; else mkdir ${1%.t(ar.gz||ar.bz2||gz||bz||ar)} && tar xf $1 -C ${1%.t(ar.gz||ar.bz2||gz||bz||ar)}; fi ;} UPDATE2: From the comments; bepaald came with a variant that works for .tar.gz, .tar.bz2, .tgz, .tbz and .tar in bash: atb() {shopt -s extglob ; l=$(tar tf $1); if [ $(echo "$l" | wc -l) -eq $(echo "$l" | grep $(echo "$l" | head -n1) | wc -l) ]; then tar xf $1; else mkdir ${1%.t@(ar.gz|ar.bz2|gz|bz|ar)} && tar xf $1 -C ${1%.t@(ar.gz|ar.bz2|gz|bz|ar)}; fi ; shopt -u extglob} Show Sample Output


    10
    atb() { l=$(tar tf $1); if [ $(echo "$l" | wc -l) -eq $(echo "$l" | grep $(echo "$l" | head -n1) | wc -l) ]; then tar xf $1; else mkdir ${1%.tar.gz} && tar xf $1 -C ${1%.tar.gz}; fi ;}
    elfreak · 2010-10-16 05:50:32 8

  • 10
    md5sum <<<"test"
    unefunge · 2010-11-24 12:04:41 15

  • 10
    read -a ARR <<<'world domination now!'; echo ${ARR[2]};
    unefunge · 2010-12-03 16:27:03 5
  • Console screensaver.


    10
    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'
    lkj · 2011-03-24 16:58:14 14
  • No command substitution but subshell redirection


    10
    read day month year < <(date +'%d %m %y')
    frans · 2011-07-30 06:06:29 6
  • By default bash history of a shell is appended (appended on Ubuntu by default: Look for 'shopt -s histappend' in ~/.bashrc) to history file only after that shell exits. Although after having written to the history file, other running shells do *not* inherit that history - only newly launched shells do. This pair of commands alleviate that. Show Sample Output


    10
    $ history -a #in one shell , and $ history -r #in another running shell
    b_t · 2011-11-05 01:19:30 7

  • 10
    color()(set -o pipefail;"$@" 2>&1>&3|sed $'s,.*,\e[31m&\e[m,'>&2)3>&1
    bkmeneguello · 2013-01-30 13:42:03 7
  • Sometimes in a script you want to make sure that a directory is in the path, and add it in if it's not already there. In this example, $dir contains the new directory you want to add to the path if it's not already present. There are multiple ways to do this, but this one is a nice clean shell-internal approach. I based it on http://stackoverflow.com/a/1397020. You can also do it using tr to separate the path into lines and grep -x to look for exact matches, like this: if ! $(echo "$PATH" | tr ":" "\n" | grep -qx "$dir") ; then PATH=$PATH:$dir ; fi which I got from http://stackoverflow.com/a/5048977. Or replace the "echo | tr" part with a shell parameter expansion, like if ! $(echo "${PATH//:/$'\n'}" | grep -qx "$dir") ; then PATH=$PATH:$dir ; fi which I got from http://www.commandlinefu.com/commands/view/3209/. There are also other more regex-y ways to do it, but I find the ones listed here easiest to follow. Note some of this is specific to the bash shell.


    10
    if [[ ":$PATH:" != *":$dir:"* ]]; then PATH=${PATH}:$dir; fi
    dmmst19 · 2013-08-11 01:19:13 19
  • Bash's history expansion character, "!", has many features, including "!:" for choosing a specific argument (or range of arguments) from the history. The gist is any number after !: is the number of the argument you want, with !:1 being the first argument and !:0 being the command. See the sample output for a few examples. For full details search for "^HISTORY EXPANSION" in the bash(1) man page.    Note that this version improves on the previous function in that it handles arguments that include whitespace correctly. Show Sample Output


    10
    !:n
    hackerb9 · 2013-09-15 03:41:13 7
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Search for a line of text in a directory of files recursively (while limiting to certain file extensions)

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Set laptop display brightness
Run as root. Path may vary depending on laptop model and video card (this was tested on an Acer laptop with ATI HD3200 video). $ cat /proc/acpi/video/VGA/LCD/brightness to discover the possible values for your display.

Downsample mp3s to 128K
This will lower the quality of mp3 files, but is necessary to play them on some mobile devices.

Prefix every line with a timestamp


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