Commands tagged bash (734)

  • For example, if you are the type who type ls very often, then PROMPT_COMMAND=ls will ls after every command you issue.


    1
    PROMPT_COMMAND=command
    haivu · 2009-10-15 06:01:18 0
  • Place this in your .bash_profile and you can use it two different ways. If you issue 'h' on its own, then it acts like the history command. If you issue: h cd Then it will display all the history with the word 'cd'


    7
    h() { if [ -z "$1" ]; then history; else history | grep "$@"; fi; }
    haivu · 2009-10-13 21:49:37 4
  • Joker wants an email if the Brand X server is down. Set a cron job for every 5 mins with this line and he gets an email when/if a ping takes longer than 3 seconds. Show Sample Output


    7
    ping -q -c1 -w3 brandx.jp.sme 2&>1 /dev/null || echo brandx.jp.sme ping failed | mail -ne -s'Server unavailable' joker@jp.co.uk
    mccalni · 2009-10-13 14:13:04 6
  • 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 1
  • This will comment out a line, specified by line number, in a given file.


    5
    sed -i '19375 s/^/#/' file
    TuxOtaku · 2009-10-07 17:50:40 2

  • 17
    env PS4=' ${BASH_SOURCE}:${LINENO}(${FUNCNAME[0]}) ' sh -x /etc/profile
    oernii2 · 2009-10-07 14:44:59 4
  • I've used this a number of times troubleshooting user permissions. Instead of just 'su - user' you can throw another hyphen and stay in the original directory. Show Sample Output


    13
    su -- user
    matthewdavis · 2009-09-28 04:23:43 1
  • How often do you make a directory (or series of directories) and then change into it to do whatever? 99% of the time that is what I do. This BASH function 'md' will make the directory path then immediately change to the new directory. By using the 'mkdir -p' switch, the intermediate directories are created as well if they do not exist. Show Sample Output


    30
    md () { mkdir -p "$@" && cd "$@"; }
    drewk · 2009-09-24 16:09:19 5
  • This is how I typically grep. -R recurse into subdirectories, -n show line numbers of matches, -i ignore case, -s suppress "doesn't exist" and "can't read" messages, -I ignore binary files (technically, process them as having no matches, important for showing inverted results with -v) I have grep aliased to "grep --color=auto" as well, but that's a matter of formatting not function.


    48
    grep -RnisI <pattern> *
    birnam · 2009-09-22 15:09:43 3
  • The backtick operator, in general, will execute the text inside the backticks. On OS X, the pbpaste command will put the contents of the OS X clipboard to STDOUT. So if you put backticks around pbpaste, the text from the OS X clipboard is executed. If you add the pipeline | pbcopy, the output from executing the command on the clipboard is placed back on the clipboard. Note: make sure the clipboard is text only. Show Sample Output


    7
    `pbpaste` | pbcopy
    drewk · 2009-09-21 23:10:11 3
  • This pipeline will find, sort and display all files based on mtime. This could be done with find | xargs, but the find | xargs pipeline will not produce correct results if the results of find are greater than xargs command line buffer. If the xargs buffer fills, xargs processes the find results in more than one batch which is not compatible with sorting. Note the "-print0" on find and "-0" switch for perl. This is the equivalent of using xargs. Don't you love perl? Note that this pipeline can be easily modified to any data produced by perl's stat operator. eg, you could sort on size, hard links, creation time, etc. Look at stat and just change the '9' to what you want. Changing the '9' to a '7' for example will sort by file size. A '3' sorts by number of links.... Use head and tail at the end of the pipeline to get oldest files or most recent. Use awk or perl -wnla for further processing. Since there is a tab between the two fields, it is very easy to process. Show Sample Output


    3
    find $HOME -type f -print0 | perl -0 -wn -e '@f=<>; foreach $file (@f){ (@el)=(stat($file)); push @el, $file; push @files,[ @el ];} @o=sort{$a->[9]<=>$b->[9]} @files; for $i (0..$#o){print scalar localtime($o[$i][9]), "\t$o[$i][-1]\n";}'|tail
    drewk · 2009-09-21 22:11:16 4
  • I was looking for the fastest way to create a bunch of ansi escapes for use in echo -e commands throughout a lot of my shell scripts. This is what I came up with, and I actually stick that loop command in a function and then just call that at the beginning of my scripts to not clutter the environment with these escape codes, which can wreck havok on my terminal when I'm dumping the environment. More of a cool way to store escape ansi codes in an array. You can echo them like: echo -e "${CC[15]}This text is black on bright green background." I usually just use with a function: # setup_colors - Adds colors to array CC for global use # 30 - Black, 31 - Red, 32 - Green, 33 - Yellow, 34 - Blue, 35 - Magenta, 36 - Blue/Green, 37 - White, 30/42 - Black on Green '30\;42' function setup_colors(){ declare -ax CC; for i in `seq 0 7`;do ii=$(($i+7));CC[$i]="\033[1;3${i}m";CC[$ii]="\033[0;3${i}m";done;CC[15]="\033[30;42m"; export R='\033[0;00m';export X="\033[1;37m"; }; export -f setup_colors CC[15] has a background of bright green which is why it is separate. R resets everything, and X is my default font of bright white. CC[15]="\033[30;42m"; R=$'\033[0;00m'; X=$'\033[1;37m' Those are just my favorite colors that I often use in my scripts. You can test which colors by running for i in $(seq 0 $((${#CC[@]} - 1))); do echo -e "${CC[$i]}[$i]\n$R"; done See: http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html for more usage. Show Sample Output


    1
    declare -ax CC; for i in `seq 0 7`;do ii=$(($i+7)); CC[$i]="\033[1;3${i}m"; CC[$ii]="\033[0;3${i}m"; done
    AskApache · 2009-09-21 07:00:55 4
  • for one line per process: ss -p | cat for established sockets only: ss -p | grep STA for just process names: ss -p | cut -f2 -sd\" or ss -p | grep STA | cut -f2 -d\"


    51
    ss -p
    Escher · 2009-09-19 21:55:01 0

  • 5
    seq -s " " -w 3 20
    edo · 2009-09-19 21:26:57 2
  • show only the name of the apps that are using internet Show Sample Output


    31
    lsof -P -i -n | cut -f 1 -d " "| uniq | tail -n +2
    edo · 2009-09-19 21:23:54 2

  • 87
    lsof -P -i -n
    OJM · 2009-09-19 18:28:48 1
  • I often need to know of my directory in the PATH, which one DOES NOT exist. This command answers that question * This command uses only bash's built-in commands * The parentheses spawn a new sub shell to prevent the modification of the IFS (input field separator) variable in the current shell


    9
    (IFS=:;for p in $PATH; do test -d $p || echo $p; done)
    haivu · 2009-09-19 17:51:06 1
  • Show apps that use internet connection at the moment. Can be used to discover what programms create internet traffic. Skip the part after awk to get more details, though it will not work showing only unique processes. This version will work with other languages such as Spanish and Portuguese, if the word for "ESTABLISHED" still contain the fragment "STAB"(e.g. "ESTABELECIDO") Show Sample Output


    7
    netstat -lantp | grep -i stab | awk -F/ '{print $2}' | sort | uniq
    ProMole · 2009-09-19 14:54:31 0
  • This corrects duplicate output from the previous command. Show Sample Output


    4
    netstat -lantp | grep -i establ | awk -F/ '{print $2}' | sort | uniq
    HarimaKenji · 2009-09-19 14:42:31 1
  • Can be used to discover what programms create internet traffic. Skip the part after awk to get more details. Has anyone an idea why the uniq doesn't work propperly here (see sample output)? Show Sample Output


    -1
    netstat -lantp | grep -i establ | awk -F/ '{print $2}' | uniq | sort
    ktoso · 2009-09-19 13:54:36 3
  • I usually have 5 or more ssh connections to various servers, and putting this command in my .bash_profile file makes my putty window or x terminal window title change to this easily recognizable and descriptive text. Includes the username, group, server hostname, where I am connecting from (for SSH tunneling), which device pts, current server load, and how many processes are running. You can also use this for your PROMPT_COMMAND variable, which updates the window title to the current values each time you exec a command. I prefix running this in my .bash_profile with [[ ! -z "$SSH_TTY" ]] && which makes sure it only does this when connecting via SSH with a TTY. Here's some rougher examples from http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html # If set, the value is executed as a command prior to issuing each primary prompt. #H=$((hostname || uname -n) 2>/dev/null | sed 1q);W=$(whoami) #export PROMPT_COMMAND='echo -ne "\033]0;${W}@${H}:${PWD/#$HOME/~} ${SSH_TTY/\/dev\//} [`uptime|sed -e "s/.*: \([^,]*\).*/\1/" -e "s/ //g"`]\007"' #PROMPT_COMMAND='echo -ne "\033]0;`id -un`:`id -gn`@`hostname||uname -n 2>/dev/null|sed 1q` `command who -m|sed -e "s%^.* \(pts/[0-9]*\).*(\(.*\))%[\1] (\2)%g"` [`uptime|sed -e "s/.*: \([^,]*\).*/\1/" -e "s/ //g"` / `command ps aux|wc -l`]\007"' #[[ -z "$SSH_TTY" ]] || export PROMPT_COMMAND #[[ -z "$SSH_TTY" ]] && [[ -f /dev/stdout ]] && SSH_TTY=/dev/stdout And here's a simple function example for setting the title: function set_window_title(){ echo -e "\033]0; ${1:-$USER@$HOST - $SHLVL} \007"; } Show Sample Output


    4
    echo -ne "\033]0;`id -un`:`id -gn`@`hostname||uname -n|sed 1q` `who -m|sed -e "s%^.* \(pts/[0-9]*\).*(\(.*\))%[\1] (\2)%g"` [`uptime|sed -e "s/.*: \([^,]*\).*/\1/" -e "s/ //g"` / `ps aux|wc -l`]\007"
    AskApache · 2009-09-19 06:57:53 1
  • Finds executable and existing directories in your path that can be useful if migrating a profile script to another system. This is faster and smaller than any other method due to using only bash builtin commands. See also: + http://www.commandlinefu.com/commands/view/743/list-all-execs-in-path-usefull-for-grepping-the-resulting-list + http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html Show Sample Output


    1
    for p in ${PATH//:/ }; do [[ -d $p && -x $p ]] && echo $p; done
    AskApache · 2009-09-19 06:43:57 1
  • emulates bash4's "echo {03..20}" Uses bash3 builtin function printf Show Sample Output


    0
    printf "%02u " {3..20}; echo
    Escher · 2009-09-18 18:48:41 1
  • Uses 'seq' with formatting parameter to generate the necessary padded sequence. Change '%02.0f' to how many digits you need (for 3, use %03.0f, etc) and replace 5 & 15 with your desired min and max. Show Sample Output


    0
    for s in `seq -f %02.0f 5 15`; do echo $s; done
    Yeraze · 2009-09-18 13:21:38 3
  • Bash 4 will let you do {00..19} to get leading zeros, but Bash 3 doesn't have that feature. This technique gets you partway there (the sequences need be such that the last digit ranges from zero to nine - you can't use this for something like Bash 4's {03..27}, for example). When this limitation is not a problem, you can avoid some complicated string manipulation for concatenating leading zeros. You can add more digits like this: {0..1}{0..9}{0..9} (ranges from 0 to 99 with up to two leading zeros). To pad with additional zeros: for i in 000{0..1}{0..9}; do echo $i; done or for i in {0..1}{0..9}; do echo "000$i"; done This is useful for creating values to sort or for creating filenames with a fixed format. Note that this will also work: touch {0..1}{0..9} Show Sample Output


    -1
    for i in {0..1}{0..9}; do echo $i; done
    dennisw · 2009-09-18 02:51:12 2
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