What is your single most favorite command-line trick using Bash

Question

We all know how to use  lt ctrl gt -R to reverse search through history  but did you know you can use  lt ctrl gt -S to forward search if you set stty stop      Also  have you ever tried running bind -p to see all of your keyboard shortcuts listed   There are over 455 on Mac OS X by default     What is your single most favorite obscure trick  keyboard shortcut or shopt configuration using bash

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Apropos history -- using cryptic carets  etc  is not entirely intuitive   To print all history items containing a given string   function histgrep   fc -l -   HISTSIZE-1     egrep

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Ctrl   L will usually clear the screen  Works from the Bash prompt  obviously  and in GDB  and a lot of other prompts

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type -a PROG   in order to find all the places where PROG is available  usually somewhere in   bin rather than the one in  usr bin PROG that might have been expected

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The FIGNORE environment variable is nice when you want TAB completion to ignore files or folders with certain suffixes  e g    export FIGNORE  CVS  svn      Use the IFS environment variable when you want to define an item separator other than space  e g    export IFS       This will make you able to loop through files and folders with spaces in them without performing any magic  like this     touch  with spaces  withoutspaces   for i in  ls     do echo  i  done with spaces withoutspaces   IFS       for i in  ls     do echo  i  done with spaces withoutspaces

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dollar underscore   the last word from the previous command  Similar to    except it doesn t put its substitution in your history like    does

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bash can redirect to and from TCP IP sockets   dev tcp  and  dev udp   Some people think it s a security issue  but that s what OS level security like Solaris X s jail is for   As Will Robertson notes  change prompt to do stuff    print the command   for  nn  Set the Xterm terminal name  If it s an old Xterm that doesn t sniff traffic to set it s title

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One of my favorites tricks with bash is the  tar pipe   When you have a monstrous quantity of files to copy from one directory to another  doing  cp    an other dir  doesn t work if the number of files is too high and explode the bash globber  so  the tar pipe     cd  path to source dir    tar cf -        cd  path to destination    tar xf -       and if you have netcat  you can even do the  netcat tar pipe  through the network

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I like a splash of colour in my prompts   export PS1     033 07 31m    h    033 47 30m    W    033 00 31m         e m      I m afraid I don t have a screenshot for what that looks like  but it s supposed to be something like  all on one line     RED BACK WHITE TEXT  Computer name   BLACK BACK WHITE TEXT  Working Directory   WHITE BACK RED TEXT      Customise as per what you like to see

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I m new to programming on a mac  and I miss being able to launch gui programs from bash   so I have to create functions like this   function macvim    Applications MacVim app Contents MacOS Vim      -gp  amp

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Using  set -o vi  from the command line  or better  in  bashrc  puts you in vi editing mode on the command line  You start in  insert  mode so you can type and backspace as normal  but if you make a  large  mistake you can hit the esc key and then use  b  and  f  to move around as you do in vi  cw to change a word  Particularly useful after you ve brought up a history command that you want to change

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ESC   Inserts the last arguments from your last bash command   It comes in handy more than you think   cp file  to some long path   cd ESC

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Another favorite        Repeats your last command   Most useful in the form   sudo

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bash can redirect to and from TCP IP sockets   dev tcp  and  dev udp   Some people think it s a security issue  but that s what OS level security like Solaris X s jail is for   As Will Robertson notes  change prompt to do stuff    print the command   for  nn  Set the Xterm terminal name  If it s an old Xterm that doesn t sniff traffic to set it s title

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The FIGNORE environment variable is nice when you want TAB completion to ignore files or folders with certain suffixes  e g    export FIGNORE  CVS  svn      Use the IFS environment variable when you want to define an item separator other than space  e g    export IFS       This will make you able to loop through files and folders with spaces in them without performing any magic  like this     touch  with spaces  withoutspaces   for i in  ls     do echo  i  done with spaces withoutspaces   IFS       for i in  ls     do echo  i  done with spaces withoutspaces

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find -iregex      py       xml     xargs egrep -niH  a search pattern     vi -R -   Searches a pattern in all Python files and all XML files and pipes the result in a readonly Vim session

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Since I always need the for i in   ls  statement I made a shortcut   fea       if test -z   2 0 1   then action echo  else action  2  fi    for i in   ls  1         do  action  i      done      Another one is   echo    B     It will print a list of all defined variables that start with  B

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I have got a secret weapon   shell-fu   There are thousand of smart tips  cool tricks and efficient recipes that most of the time fit on a single line    One that I love  but I cheat a bit since I use the fact that Python is installed on most Unix system now     alias webshare  python -m SimpleHTTPServer    Now everytime you type  webshare   the current directory will be available through the port 8000  Really nice when you want to share files with friends on a local network without usb key or remote dir  Streaming video and music will work too   And of course the classic fork bomb that is completely useless but still a lot of fun               amp        Don t try that in a production server

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How to list only subdirectories in the current one    ls -d      It s a simple trick  but you wouldn t know how much time I needed to find that one

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When navigating between two separate directories and copying files back and forth  I do this   cd  some where long src  pwd  cd  other where long dest  pwd   cp  src foo  dest  command completion will work by expanding the variable  so you can use tab completion to specify a file you re working with

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Not really interactive shell tricks  but valid nonetheless as tricks for writing good scripts   getopts  shift   OPTIND   OPTARG   I love making customizable scripts   while getopts  vo   flag  do     case   flag  in          v           VERBOSE 1                     o           OUT   OPTARG                 esac done shift     OPTIND-1        xargs 1    I have a triple-core processor and like to run scripts that perform compression  or some other CPU-intensive serial operation on a set of files  I like to speed it up using xargs as a job queue   if        -gt 1    then       schedule using xargs      for file  do         echo -n   file          echo -ne   0      done   xargs -0 -n 1 -P   NUM JOBS  --   0  else       do the actual processing fi   This acts a lot like make -j  NUM JOBS

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To be able to quickly edit a shell script you know is in your  PATH  do not try with ls       function viscr   vi   which

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How to list only subdirectories in the current one    ls -d      It s a simple trick  but you wouldn t know how much time I needed to find that one

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Curly-Brace Expansion   Really comes in handy when running a   configure with a lot of options     configure -- prefix  usr mandir  usr man   sh libdir  usr lib64   enable- gpl pthreads bzlib lib faad  bin  mp3lame schroedinger speex theora vorbis xvid x264    pic shared postproc avfilter -lavf    disable-static    This is quite literally my configure settings for ffmpeg  Without the braces it s 409 characters   Or  even better   echo  I can count to a thousand       0 1 2 3 4 5 6 7 8 9  0 1 2 3 4 5 6 7 8 9  0 1 2 3 4 5 6 7 8 9

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cd -   It s the command-line equivalent of the back button  takes you to the previous directory you were in

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My favorite is   string string2  which takes the last command  replaces string with string2 and executes it    ehco foo bar baz bash  ehco  command not found    ehco echo foo bar baz   Bash command line history guide

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The easiest keystrokes for me for  last argument of the last command  is     echo what the heck   what the heck   echo     heck

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Ctrl   L will usually clear the screen  Works from the Bash prompt  obviously  and in GDB  and a lot of other prompts

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A simple thing to do when you realize you just typed the wrong line is hit Ctrl C  if you want to keep the line  but need to execute something else first  begin a new line with a back slash -    then Ctrl C  The line will remain in your history

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Not really obscure  but one of the features I absolutely love is tab completion  Really useful when you are navigating trough an entire subtree structure  or when you are using some obscure  or long command

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I ve always been partial to   ctrl-E   move cursor to end of line ctrl-A   move cursor to beginning of line   I also use shopt -s cdable vars  then you can create bash variables to common directories   So  for my company s source tree  I create a bunch of variables like   export Dcentmain   var localdata p4ws centaur main apps core    then I can change to that directory by cd Dcentmain

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I like to set a prompt which shows the current directory in the window title of an xterm   It also shows the time and current directory   In addition  if bash wants to report that a background job has finished  it is reported in a different colour using ANSI escape sequences   I use a black-on-light console so my colours may not be right for you if you favour light-on-black   PROMPT COMMAND  echo -e   033 0   USER    HOSTNAME        PWD   HOME    007 033 1 31m  PWD   HOME    033 1 34m   PS1     e 1 31m   t       e 0m      Make sure you understand how to use    and    correctly in your PS1 string so that bash knows how long your prompt-string actually renders on screen  This is so it can redraw your command-line correctly when you move beyond a single line command

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My favorite command is  ls -thor   It summons the power of the gods to list the most recently modified files in a conveniently readable format

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rename  Example     ls this has text to find 1 txt this has text to find 2 txt this has text to find 3 txt this has text to find 4 txt    rename  s text to find been renamed     txt   ls this has been renamed 1 txt this has been renamed 2 txt this has been renamed 3 txt this has been renamed 4 txt    So useful

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Top 10 commands again  like ctcherry s post  only shorter    history   awk    print  2      sort   uniq -c  sort -rn   head

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Some useful mencoder commands I found out about when looking for some audio and video editing tools   from  xxx to  avi  mencoder movie wmv -o movie avi -ovc lavc -oac lavc    Dump sound from a video   mplayer -ao pcm -vo null -vc dummy -dumpaudio -dumpfile fileout mp3 filein avi

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Good for making an exact recursive copy backup of a directory including symlinks  rather than following them or ignoring them like cp      mkdir new dir   cd old dir   tar cf -       cd    old dir  tar xf -

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Well  this may be a bit off topic  but if you are an Emacs user  I would say  emacs  is the most powerful trick     before you downvote this  try out  M-x shell  within an emacs instance    you get a shell inside emacs  and have all the power of emacs along with the power of a shell  there are some limitations  such as opening another emacs within it  but in most cases it is a lot more powerful than a vanilla bash prompt

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type -a PROG   in order to find all the places where PROG is available  usually somewhere in   bin rather than the one in  usr bin PROG that might have been expected

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One preferred way of navigating when I m using multiple directories in widely separate places in a tree hierarchy is to use acf func sh  listed below   Once defined  you can do  cd --   to see a list of recent directories  with a numerical menu  cd -2  to go to the second-most recent directory   Very easy to use  very handy   Here s the code     do    acd func sh    acd func 1 0 5  10-nov-2004   petar marinov  http  geocities com h2428  this is public domain  cd func        local x2 the new dir adir index   local -i cnt    if     1      --      then     dirs -v     return 0   fi    the new dir  1      -z  1     amp  amp  the new dir  HOME    if      the new dir 0 1      -      then             Extract dir N from dirs     index   the new dir 1         -z  index     amp  amp  index 1     adir   dirs   index         -z  adir     amp  amp  return 1     the new dir  adir   fi              has to be substituted by   HOME         the new dir 0 1             amp  amp  the new dir    HOME   the new dir 1            Now change to the new dir and add to the top of the stack   pushd    the new dir    gt   dev null         -ne 0     amp  amp  return 1   the new dir   pwd           Trim down everything beyond 11th entry   popd -n  11 2 gt  dev null 1 gt  dev null          Remove any other occurence of this dir  skipping the top of the stack   for   cnt 1  cnt  lt   10  cnt      do     x2   dirs    cnt  2 gt  dev null            -ne 0     amp  amp  return 0          x2 0 1             amp  amp  x2    HOME   x2 1       if       x2         the new dir       then       popd -n   cnt 2 gt  dev null 1 gt  dev null       cnt cnt-1     fi   done    return 0    alias cd cd func  if     BASH VERSION  gt   2 05a      then     ctrl w shows the menu   bind -x     C-w   cd func --    fi

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Some useful mencoder commands I found out about when looking for some audio and video editing tools   from  xxx to  avi  mencoder movie wmv -o movie avi -ovc lavc -oac lavc    Dump sound from a video   mplayer -ao pcm -vo null -vc dummy -dumpaudio -dumpfile fileout mp3 filein avi

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Batch extension renamer  usage  renamer txt mkd  renamer        local fn    for fn in     1   do      mv   fn     fn        2     done

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Since I always need the for i in   ls  statement I made a shortcut   fea       if test -z   2 0 1   then action echo  else action  2  fi    for i in   ls  1         do  action  i      done      Another one is   echo    B     It will print a list of all defined variables that start with  B

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I ve always been partial to   ctrl-E   move cursor to end of line ctrl-A   move cursor to beginning of line   I also use shopt -s cdable vars  then you can create bash variables to common directories   So  for my company s source tree  I create a bunch of variables like   export Dcentmain   var localdata p4ws centaur main apps core    then I can change to that directory by cd Dcentmain

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One of my favorites tricks with bash is the  tar pipe   When you have a monstrous quantity of files to copy from one directory to another  doing  cp    an other dir  doesn t work if the number of files is too high and explode the bash globber  so  the tar pipe     cd  path to source dir    tar cf -        cd  path to destination    tar xf -       and if you have netcat  you can even do the  netcat tar pipe  through the network

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I like a splash of colour in my prompts   export PS1     033 07 31m    h    033 47 30m    W    033 00 31m         e m      I m afraid I don t have a screenshot for what that looks like  but it s supposed to be something like  all on one line     RED BACK WHITE TEXT  Computer name   BLACK BACK WHITE TEXT  Working Directory   WHITE BACK RED TEXT      Customise as per what you like to see

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On Mac OS X   ESC     will cycle through recent arguments in place  That s  press and release ESC  then press and release    period key   On Ubuntu  I think it s ALT     You can do that more than once  to go back through all your recent arguments  It s kind of like CTRL   R  but for arguments only  It s also much safer than    or     since you see what you re going to get before you actually run the command

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Mac only  This is simple  but MAN do I wish I had known about this years ago   open      Opens the current directory in Finder  You can also use it to open any file with it s default application  Can also be used for URLs  but only if you prefix the URL with http     which limits it s utility for opening the occasional random site

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You changed to a new directory and want to move a file from the new directory to the old one  In one move  mv file  OLDPWD

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Two of my favorites are   1  Make tab-completion case insensitive  e g   cd  home User   converts your command line to   cd  home user  if the latter exists and the former doesn t  You can turn it on with  set completion-ignore-case on  at the prompt  or add it permanently by adding  set completion-ignore-case on  to your  inputrc file   2  The built-in  type  command is like  which  but aware of aliases also  For example    type cdhome cdhome is aliased to  cd      type bash bash is  bin bash

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Apropos history -- using cryptic carets  etc  is not entirely intuitive   To print all history items containing a given string   function histgrep   fc -l -   HISTSIZE-1     egrep

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Some Bash nuggets also here   http   codesnippets joyent com tag bash

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You should be able to paste the following into a bash terminal window   Display ANSI colour palette   e   033   for f in 0 7  seq 6   do   no    bo      for b in n 7 0  seq 6   do     co  3 f   p             b   n        co   co 4 b  p           no    no   e   co m     p   co    e 0m      bo    bo   e 1   co m   p 1   co    e 0m    done   echo -e   no n bo  done   256 colour demo   yes    seq 232 255 seq 254 -1 233     while read i  do printf   x1b 48 5   i m n   sleep  01  done

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R reverse search  Hit  R  type a fragment of a previous command you want to match  and hit  R until you find the one you want  Then I don t have to remember recently used commands that are still in my history  Not exclusively bash  but also   E for end of line   A for beginning of line   U and  K to delete before and after the cursor  respectively

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pbcopy and pbpaste aliases for GNU Linux  alias pbcopy  xclip -selection clipboard  alias pbpaste  xclip -selection clipboard -o

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Expand complicated lines before hitting the dreaded enter   Alt Ctrl e  mdash  shell-expand-line  may need to use Esc  Ctrl e on your keyboard  Ctrl    mdash   undo Ctrl x     mdash   glob-expand-word     echo     -2    Alt Ctrl e   echo aword someotherword   Ctrl     echo     -2    Ctrl x      echo     -2  LOG Makefile bar c foo h   amp c

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alias     cd      So when navigating back up a directory just use    lt Enter gt

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I have got a secret weapon   shell-fu   There are thousand of smart tips  cool tricks and efficient recipes that most of the time fit on a single line    One that I love  but I cheat a bit since I use the fact that Python is installed on most Unix system now     alias webshare  python -m SimpleHTTPServer    Now everytime you type  webshare   the current directory will be available through the port 8000  Really nice when you want to share files with friends on a local network without usb key or remote dir  Streaming video and music will work too   And of course the classic fork bomb that is completely useless but still a lot of fun               amp        Don t try that in a production server

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lt first few characters of the command  will execute the last command which matches   Example    b will run  build whatever -O -p -t -i -on     will run   a out  It works best with long and repetitive commands  like compile  build  execute  etc  It saved me sooo much time when coding and testing

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You can use the watch command in conjunction with another command to look for changes  An example of this was when I was testing my router  and I wanted to get up-to-date numbers on stuff like signal-to-noise ratio  etc   watch --interval 10 lynx -dump http   dslrouter stats html

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You changed to a new directory and want to move a file from the new directory to the old one  In one move  mv file  OLDPWD

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ctrl-u delete all written stuff

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CTRL D quits the shell

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find -iregex      py       xml     xargs egrep -niH  a search pattern     vi -R -   Searches a pattern in all Python files and all XML files and pipes the result in a readonly Vim session

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My favorite command is  ls -thor   It summons the power of the gods to list the most recently modified files in a conveniently readable format

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alias -- ddt  ls -trFld  dt      ddt --color        tail -n 30      Gives you the most recent files in the current directory  I use it all the time

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Apropos history -- using cryptic carets  etc  is not entirely intuitive   To print all history items containing a given string   function histgrep   fc -l -   HISTSIZE-1     egrep

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I like to construct commands with echo and pipe them to the shell     find dir -name       xargs echo rm       find dir -name       xargs echo rm   ksh -s   Why   Because it allows me to look at what s going to be done before I do it   That way if I have a horrible error  like removing my home directory   I can catch it before it happens   Obviously  this is most important for destructive or irrevocable actions

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Top 10 commands again  like ctcherry s post  only shorter    history   awk    print  2      sort   uniq -c  sort -rn   head

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Top 10 commands again  like ctcherry s post  only shorter    history   awk    print  2      sort   uniq -c  sort -rn   head

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pushd and popd almost always come in handy

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Using alias can be time-saving  alias myDir    cd  this is a long directory  pwd

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You changed to a new directory and want to move a file from the new directory to the old one  In one move  mv file  OLDPWD

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If I am searching for something in a directory  but I am not sure of the file  then I just grep the files in the directory by   find   -exec grep whatIWantToFind

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I like to construct commands with echo and pipe them to the shell     find dir -name       xargs echo rm       find dir -name       xargs echo rm   ksh -s   Why   Because it allows me to look at what s going to be done before I do it   That way if I have a horrible error  like removing my home directory   I can catch it before it happens   Obviously  this is most important for destructive or irrevocable actions

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pbcopy  This copies to the Mac system clipboard  You can pipe commands to it   try   pwd   pbcopy

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Two of my favorites are   1  Make tab-completion case insensitive  e g   cd  home User   converts your command line to   cd  home user  if the latter exists and the former doesn t  You can turn it on with  set completion-ignore-case on  at the prompt  or add it permanently by adding  set completion-ignore-case on  to your  inputrc file   2  The built-in  type  command is like  which  but aware of aliases also  For example    type cdhome cdhome is aliased to  cd      type bash bash is  bin bash

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Quick Text  I use these sequences of text all too often  so I put shortcuts to them in by  inputrc     redirection short cuts   ew               2 gt  amp 1    eq                amp  gt  dev null  amp     e C-q            2 gt  dev null    eg                amp  gt    garbage out  amp     e C-g            2 gt    garbage out    if term xterm   M-w              2 gt  amp 1    M-q               amp  gt  dev null  amp     M- C-q           2 gt  dev null    M-g               amp  gt    garbage out  amp     M- C-g           2 gt    garbage out   endif

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The easiest keystrokes for me for  last argument of the last command  is     echo what the heck   what the heck   echo     heck

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Two of my favorites are   1  Make tab-completion case insensitive  e g   cd  home User   converts your command line to   cd  home user  if the latter exists and the former doesn t  You can turn it on with  set completion-ignore-case on  at the prompt  or add it permanently by adding  set completion-ignore-case on  to your  inputrc file   2  The built-in  type  command is like  which  but aware of aliases also  For example    type cdhome cdhome is aliased to  cd      type bash bash is  bin bash

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Custom Tab Completion  compgen and complete bash builtins   Tab Completion is nice  but being able to apply it to more than just filenames is great   I have used it to create custom functions to expand arguments to commands I use all the time   For example  lets say you often need to add the FQDN as an argument to a command  e g  ping blah really long domain name foo com    You can use compgen and complete to create a bash function that reads your  etc hosts file for results so all you have to type then is   ping blah  lt tab gt    and it will display all your current match options   So basically anything that can return a word list can be used as a function

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If I am searching for something in a directory  but I am not sure of the file  then I just grep the files in the directory by   find   -exec grep whatIWantToFind

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Insert preceding lines final parameter  ALT-   the most useful key combination ever  try it and see  for some reason no one knows about this one   Press it again and again to select older last parameters    Great when you want to do something else to something you used just a moment ago

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I have a really stupid  but extremely helpful one when navigating deep tree structures   Put this in  bashrc  or similar    alias cd6  cd                    alias cd5  cd                 alias cd4  cd              alias cd3  cd           alias cd2  cd

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Not really interactive shell tricks  but valid nonetheless as tricks for writing good scripts   getopts  shift   OPTIND   OPTARG   I love making customizable scripts   while getopts  vo   flag  do     case   flag  in          v           VERBOSE 1                     o           OUT   OPTARG                 esac done shift     OPTIND-1        xargs 1    I have a triple-core processor and like to run scripts that perform compression  or some other CPU-intensive serial operation on a set of files  I like to speed it up using xargs as a job queue   if        -gt 1    then       schedule using xargs      for file  do         echo -n   file          echo -ne   0      done   xargs -0 -n 1 -P   NUM JOBS  --   0  else       do the actual processing fi   This acts a lot like make -j  NUM JOBS

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Eliminate duplicate lines from a file   sort -u filename  gt  filename new   List all lines that do not match a condition   grep -v ajsk filename   These are not necessarily Bash specific  but hey neither is ls -thor       Some other useful cmds   prtdiag  psrinfo  prtconf - more info here and here  posts on my blog

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sudo      Runs the last command with administrator privileges

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I ve always been partial to   ctrl-E   move cursor to end of line ctrl-A   move cursor to beginning of line   I also use shopt -s cdable vars  then you can create bash variables to common directories   So  for my company s source tree  I create a bunch of variables like   export Dcentmain   var localdata p4ws centaur main apps core    then I can change to that directory by cd Dcentmain

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I m a big fan of Bash job control  mainly the use of Control-Z and fg  especially if I m doing development in a terminal  If I ve got emacs open and need to compile  deploy  etc  I just Control-Z to suspend emacs  do what I need  and fg to bring it back  This keeps all of the emacs buffers intact and makes things much easier than re-launching whatever I m doing

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Another favorite        Repeats your last command   Most useful in the form   sudo

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Renaming moving files with suffixes quickly  cp  home foo realllylongname cpp  -old   This expands to  cp  home foo realllylongname cpp  home foo realllylongname cpp-old

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When downloading a large file I quite often do   while ls -la  lt filename gt   do sleep 5  done   And then just ctrl c when I m done  or if ls returns non-zero   It s similar to the watch program but it uses the shell instead  so it works on platforms without watch   Another useful tool is netcat  or nc  If you do   nc -l -p 9100  gt  printjob prn   Then you can set up a printer on another computer but instead use the IP address of the computer running netcat  When the print job is sent  it is received by the computer running netcat and dumped into printjob prn

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Expand complicated lines before hitting the dreaded enter   Alt Ctrl e  mdash  shell-expand-line  may need to use Esc  Ctrl e on your keyboard  Ctrl    mdash   undo Ctrl x     mdash   glob-expand-word     echo     -2    Alt Ctrl e   echo aword someotherword   Ctrl     echo     -2    Ctrl x      echo     -2  LOG Makefile bar c foo h   amp c

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I prefer reading man pages in vi  so I have the following in my  profile or  bashrc file  man          sought         usr bin man  sought   col -b   vim -R -c  set nonumber  -c  set syntax man   -

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You should be able to paste the following into a bash terminal window   Display ANSI colour palette   e   033   for f in 0 7  seq 6   do   no    bo      for b in n 7 0  seq 6   do     co  3 f   p             b   n        co   co 4 b  p           no    no   e   co m     p   co    e 0m      bo    bo   e 1   co m   p 1   co    e 0m    done   echo -e   no n bo  done   256 colour demo   yes    seq 232 255 seq 254 -1 233     while read i  do printf   x1b 48 5   i m n   sleep  01  done

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Some Bash nuggets also here   http   codesnippets joyent com tag bash

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I have various typographical error corrections in aliases  alias mkae make  alias mroe less

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Some useful mencoder commands I found out about when looking for some audio and video editing tools   from  xxx to  avi  mencoder movie wmv -o movie avi -ovc lavc -oac lavc    Dump sound from a video   mplayer -ao pcm -vo null -vc dummy -dumpaudio -dumpfile fileout mp3 filein avi

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To be able to quickly edit a shell script you know is in your  PATH  do not try with ls       function viscr   vi   which

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Signal trapping   You can trap signals sent to the shell process and have them silently run commands in their respective environment as if typed on the command line     TERM or QUIT probably means the system is shutting down  make sure history is   saved to  HISTFILE  does not do this by default  trap  logout                       TERM QUIT    save history when signalled by cron 1  script with USR1 trap  history -a  amp  amp  history -n     USR1

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alias mycommand    verylongcommand -with -a -lot -of -parameters  alias grep  grep --color    find more than one word with grep    netstat -c  grep  msn  skype  icq

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I ve always liked this one  Add this to your  etc inputrc or    inputrc    e A  history-search-backward   e B  history-search-forward  When you type ls  lt up-arrow gt  it will be replaced with the last command starting with  ls   or whatever else you put in

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The easiest keystrokes for me for  last argument of the last command  is     echo what the heck   what the heck   echo     heck

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Not really obscure  but one of the features I absolutely love is tab completion  Really useful when you are navigating trough an entire subtree structure  or when you are using some obscure  or long command

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bash can redirect to and from TCP IP sockets   dev tcp  and  dev udp   Some people think it s a security issue  but that s what OS level security like Solaris X s jail is for   As Will Robertson notes  change prompt to do stuff    print the command   for  nn  Set the Xterm terminal name  If it s an old Xterm that doesn t sniff traffic to set it s title

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Apropos history -- using cryptic carets  etc  is not entirely intuitive   To print all history items containing a given string   function histgrep   fc -l -   HISTSIZE-1     egrep

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I often have aliases for vi  ls  etc  but sometimes you want to escape the alias  Just add a back slash to the command in front   Eg     alias vi vim     To escape the alias for vi     vi   This doesn t open VIM   Cool  isn t it

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cd -   It s the command-line equivalent of the back button  takes you to the previous directory you were in

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A simple thing to do when you realize you just typed the wrong line is hit Ctrl C  if you want to keep the line  but need to execute something else first  begin a new line with a back slash -    then Ctrl C  The line will remain in your history

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When running commands  sometimes I ll want to run a command with the previous ones arguments   To do that  you can use this shortcut     mkdir  tmp new   cd        Occasionally  in lieu of using find  I ll break-out a one-line loop if I need to run a bunch of commands on a list of files     for file in   wav  do lame   file     basename   file   wav  mp3    done    Configuring the command-line history options in my  bash login  or  bashrc  is really useful   The following is a cadre of settings that I use on my Macbook Pro    Setting the following makes bash erase duplicate commands in your history   export HISTCONTROL  erasedups ignoreboth    I also jack my history size up pretty high too   Why not   It doesn t seem to slow anything down on today s microprocessors   export HISTFILESIZE 500000 export HISTSIZE 100000   Another thing that I do is ignore some commands from my history   No need to remember the exit command    export HISTIGNORE   amp       exit    You definitely want to set histappend   Otherwise  bash overwrites your history when you exit   shopt -s histappend   Another option that I use is cmdhist   This lets you save multi-line commands to the history as one command   shopt -s cmdhist   Finally  on Mac OS X  if you re not using vi mode   you ll want to reset  lt CTRL gt -S from being scroll stop   This prevents bash from being able to interpret it as forward search    stty stop

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A few years ago  I discovered the p  commands or get information about processes  ptree  pgrep  pkill  and pfiles   Of course  the mother of them all is ps  but you need to pipe the output into less  grep and or awk to make sense of the output under heavy load   top  and variants  help too

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Shell-fu is a place for storing  moderating and propagating command line tips and tricks  A bit like StackOverflow  but solely for shell  You ll find plenty of answers to this question there

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This prevents less  less is more  from clearing the screen at the end of a file   export LESS  -X

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One preferred way of navigating when I m using multiple directories in widely separate places in a tree hierarchy is to use acf func sh  listed below   Once defined  you can do  cd --   to see a list of recent directories  with a numerical menu  cd -2  to go to the second-most recent directory   Very easy to use  very handy   Here s the code     do    acd func sh    acd func 1 0 5  10-nov-2004   petar marinov  http  geocities com h2428  this is public domain  cd func        local x2 the new dir adir index   local -i cnt    if     1      --      then     dirs -v     return 0   fi    the new dir  1      -z  1     amp  amp  the new dir  HOME    if      the new dir 0 1      -      then             Extract dir N from dirs     index   the new dir 1         -z  index     amp  amp  index 1     adir   dirs   index         -z  adir     amp  amp  return 1     the new dir  adir   fi              has to be substituted by   HOME         the new dir 0 1             amp  amp  the new dir    HOME   the new dir 1            Now change to the new dir and add to the top of the stack   pushd    the new dir    gt   dev null         -ne 0     amp  amp  return 1   the new dir   pwd           Trim down everything beyond 11th entry   popd -n  11 2 gt  dev null 1 gt  dev null          Remove any other occurence of this dir  skipping the top of the stack   for   cnt 1  cnt  lt   10  cnt      do     x2   dirs    cnt  2 gt  dev null            -ne 0     amp  amp  return 0          x2 0 1             amp  amp  x2    HOME   x2 1       if       x2         the new dir       then       popd -n   cnt 2 gt  dev null 1 gt  dev null       cnt cnt-1     fi   done    return 0    alias cd cd func  if     BASH VERSION  gt   2 05a      then     ctrl w shows the menu   bind -x     C-w   cd func --    fi

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I ve always liked this one  Add this to your  etc inputrc or    inputrc    e A  history-search-backward   e B  history-search-forward  When you type ls  lt up-arrow gt  it will be replaced with the last command starting with  ls   or whatever else you put in

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alias     cd      So when navigating back up a directory just use    lt Enter gt

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Well  this may be a bit off topic  but if you are an Emacs user  I would say  emacs  is the most powerful trick     before you downvote this  try out  M-x shell  within an emacs instance    you get a shell inside emacs  and have all the power of emacs along with the power of a shell  there are some limitations  such as opening another emacs within it  but in most cases it is a lot more powerful than a vanilla bash prompt

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R reverse search  Hit  R  type a fragment of a previous command you want to match  and hit  R until you find the one you want  Then I don t have to remember recently used commands that are still in my history  Not exclusively bash  but also   E for end of line   A for beginning of line   U and  K to delete before and after the cursor  respectively

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Here s a couple of configuration tweaks      inputrc     C-  A   history-search-backward   C-  B   history-search-forward   This works the same as  R but using the arrow keys instead  This means I can type  e g   cd  media  then hit up-arrow to go to the last thing I cd d to inside the  media  folder    I use Gnome Terminal  you may need to change the escape codes for other terminal emulators    Bash completion is also incredibly useful  but it s a far more subtle addition  In    bashrc   if   -f  etc bash completion    then        etc bash completion fi   This will enable per-program tab-completion  e g  attempting tab completion when the command line starts with evince will only show files that evince can open  and it will also tab-complete command line options    Works nicely with this also in    inputrc   set completion-ignore-case on set show-all-if-ambiguous on set show-all-if-unmodified on

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Some useful mencoder commands I found out about when looking for some audio and video editing tools   from  xxx to  avi  mencoder movie wmv -o movie avi -ovc lavc -oac lavc    Dump sound from a video   mplayer -ao pcm -vo null -vc dummy -dumpaudio -dumpfile fileout mp3 filein avi

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When downloading a large file I quite often do   while ls -la  lt filename gt   do sleep 5  done   And then just ctrl c when I m done  or if ls returns non-zero   It s similar to the watch program but it uses the shell instead  so it works on platforms without watch   Another useful tool is netcat  or nc  If you do   nc -l -p 9100  gt  printjob prn   Then you can set up a printer on another computer but instead use the IP address of the computer running netcat  When the print job is sent  it is received by the computer running netcat and dumped into printjob prn

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I have various typographical error corrections in aliases  alias mkae make  alias mroe less

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extended globbing   rm   foo bar    expands like   without foo or bar     ls foo bar foobar FOO   echo   foo bar  foobar FOO

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When downloading a large file I quite often do   while ls -la  lt filename gt   do sleep 5  done   And then just ctrl c when I m done  or if ls returns non-zero   It s similar to the watch program but it uses the shell instead  so it works on platforms without watch   Another useful tool is netcat  or nc  If you do   nc -l -p 9100  gt  printjob prn   Then you can set up a printer on another computer but instead use the IP address of the computer running netcat  When the print job is sent  it is received by the computer running netcat and dumped into printjob prn

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http   www commandlinefu com is also a great site   I learned quite useful things there like   sudo      or  mount   column -t

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More of a novelty  but it s clever     Top 10 commands used     history   awk   print  2     awk  BEGIN  FS      print  1     sort   uniq -c   sort -nr   head   Sample output    242 git   83 rake   43 cd   33 ss   24 ls   15 rsg   11 cap   10 dig    9 ping    3 vi

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And this one is key for me actually   set -o vi   Allan

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Sure  you can  diff file1 txt file2 txt   but Bash supports process substitution  which allows you to diff the output of commands   For example  let s say I want to make sure my script gives me the output I expect   I can just wrap my script in  lt     and feed it to diff to get a quick and dirty unit test     cat myscript sh    bin sh echo -e  one nthree        myscript sh  one three     cat expected output txt one two three     diff  lt    myscript sh  expected output txt 1a2  gt  two     As another example  let s say I want to check if two servers have the same list of RPMs installed   Rather than sshing to each server  writing each list of RPMs to separate files  and doing a diff on those files  I can just do the diff from my workstation     diff  lt  ssh server1  rpm -qa   sort    lt  ssh server2  rpm -qa   sort   241c240  lt  kernel-2 6 18-92 1 6 el5 ---  gt  kernel-2 6 18-92 el5 317d315  lt  libsmi-0 4 5-2 el5 727 728d724  lt  wireshark-0 99 7-1 el5  lt  wireshark-gnome-0 99 7-1 el5     There are more examples in the  Advanced Bash-Scripting Guide at http   tldp org LDP abs html process-sub html

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rename  Example     ls this has text to find 1 txt this has text to find 2 txt this has text to find 3 txt this has text to find 4 txt    rename  s text to find been renamed     txt   ls this has been renamed 1 txt this has been renamed 2 txt this has been renamed 3 txt this has been renamed 4 txt    So useful

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ESC   Inserts the last arguments from your last bash command   It comes in handy more than you think   cp file  to some long path   cd ESC

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CTRL D quits the shell

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To be able to quickly edit a shell script you know is in your  PATH  do not try with ls       function viscr   vi   which

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My favorite command is  ls -thor   It summons the power of the gods to list the most recently modified files in a conveniently readable format

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I like to set a prompt which shows the current directory in the window title of an xterm   It also shows the time and current directory   In addition  if bash wants to report that a background job has finished  it is reported in a different colour using ANSI escape sequences   I use a black-on-light console so my colours may not be right for you if you favour light-on-black   PROMPT COMMAND  echo -e   033 0   USER    HOSTNAME        PWD   HOME    007 033 1 31m  PWD   HOME    033 1 34m   PS1     e 1 31m   t       e 0m      Make sure you understand how to use    and    correctly in your PS1 string so that bash knows how long your prompt-string actually renders on screen  This is so it can redraw your command-line correctly when you move beyond a single line command

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CTRL D quits the shell

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I have a really stupid  but extremely helpful one when navigating deep tree structures   Put this in  bashrc  or similar    alias cd6  cd                    alias cd5  cd                 alias cd4  cd              alias cd3  cd           alias cd2  cd

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On Mac OS X   ESC     will cycle through recent arguments in place  That s  press and release ESC  then press and release    period key   On Ubuntu  I think it s ALT     You can do that more than once  to go back through all your recent arguments  It s kind of like CTRL   R  but for arguments only  It s also much safer than    or     since you see what you re going to get before you actually run the command

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lt anything    sort   uniq -c   sort -n  will give you a count of all the different occurrences of  lt anything    Often  awk  sed  or cut help with the parsing of data in  lt anything

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My favorite is   string string2  which takes the last command  replaces string with string2 and executes it    ehco foo bar baz bash  ehco  command not found    ehco echo foo bar baz   Bash command line history guide

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When running a command with lots of output  like a big  make   I want to not only save the output  but also see it   make install 2  amp 1   tee E make

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SSH tunnel   ssh -fNR 1234 localhost 22 root 123 123 123 123

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I often have aliases for vi  ls  etc  but sometimes you want to escape the alias  Just add a back slash to the command in front   Eg     alias vi vim     To escape the alias for vi     vi   This doesn t open VIM   Cool  isn t it

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I m a fan of the        and    expandos  returning  from the most recent submitted command line  the last item  first non-command item  and all non-command items  To wit  Note that the shell prints out the command first      echo foo bar baz foo bar baz   echo bang-dollar     bang-hat     bang-star     echo bang-dollar  baz bang-hat  foo bang-star  foo bar baz bang-dollar  baz bang-hat  foo bang-star  foo bar baz   This comes in handy when you  say ls filea fileb  and want to edit one of them  vi    or both of them  vimdiff     It can also be generalized to  the nth argument  like so     echo foo bar baz   echo   2 echo bar bar   Finally  with pathnames  you can get at parts of the path by appending  h and  t to any of the above expandos     ls  usr bin id  usr bin id   echo Head     h  Tail     t echo Head   usr bin Tail  id Head   usr bin Tail  id

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Not my favorite  by very helpful if you re trying any of the other answers using copy and paste   function                  Now you can paste examples that include a   prompt at the start of each line

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A simple thing to do when you realize you just typed the wrong line is hit Ctrl C  if you want to keep the line  but need to execute something else first  begin a new line with a back slash -    then Ctrl C  The line will remain in your history

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ctrl-u delete all written stuff

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How to list only subdirectories in the current one    ls -d      It s a simple trick  but you wouldn t know how much time I needed to find that one

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Another favorite        Repeats your last command   Most useful in the form   sudo

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My favorite is   string string2  which takes the last command  replaces string with string2 and executes it    ehco foo bar baz bash  ehco  command not found    ehco echo foo bar baz   Bash command line history guide

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One preferred way of navigating when I m using multiple directories in widely separate places in a tree hierarchy is to use acf func sh  listed below   Once defined  you can do  cd --   to see a list of recent directories  with a numerical menu  cd -2  to go to the second-most recent directory   Very easy to use  very handy   Here s the code     do    acd func sh    acd func 1 0 5  10-nov-2004   petar marinov  http  geocities com h2428  this is public domain  cd func        local x2 the new dir adir index   local -i cnt    if     1      --      then     dirs -v     return 0   fi    the new dir  1      -z  1     amp  amp  the new dir  HOME    if      the new dir 0 1      -      then             Extract dir N from dirs     index   the new dir 1         -z  index     amp  amp  index 1     adir   dirs   index         -z  adir     amp  amp  return 1     the new dir  adir   fi              has to be substituted by   HOME         the new dir 0 1             amp  amp  the new dir    HOME   the new dir 1            Now change to the new dir and add to the top of the stack   pushd    the new dir    gt   dev null         -ne 0     amp  amp  return 1   the new dir   pwd           Trim down everything beyond 11th entry   popd -n  11 2 gt  dev null 1 gt  dev null          Remove any other occurence of this dir  skipping the top of the stack   for   cnt 1  cnt  lt   10  cnt      do     x2   dirs    cnt  2 gt  dev null            -ne 0     amp  amp  return 0          x2 0 1             amp  amp  x2    HOME   x2 1       if       x2         the new dir       then       popd -n   cnt 2 gt  dev null 1 gt  dev null       cnt cnt-1     fi   done    return 0    alias cd cd func  if     BASH VERSION  gt   2 05a      then     ctrl w shows the menu   bind -x     C-w   cd func --    fi

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As an extension to CTRL-r to search backwards  you can auto-complete your current input with your history if you bind  history-search-backward    I typically bind it to the same key that it is in tcsh   ESC-p   You can do this by putting the following line in your  inputrc file     M-p   history-search-backward  E g   if you have previously executed  make some really painfully long target  you can type    gt  make  lt ESC p gt   and it will give you   gt  make some really painfully long target

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Programmable Completion   Nothing fancy  I always disable it when I m using Knoppix because it gets in the way too often  Just some basic ones   shopt -s progcomp  complete -A stopped -P              bg complete -A job     -P              fg jobs disown wait complete -A variable                readonly export complete -A variable -A function    unset complete -A setopt                  set complete -A shopt                   shopt complete -A helptopic               help complete -A alias                   alias unalias complete -A binding                 bind complete -A command                 type which                                       killall pidof complete -A builtin                 builtin complete -A disabled                enable

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String multiple commands together using the  amp  amp  command     run sh  amp  amp  tail -f log txt   or  kill -9 1111  amp  amp    start sh

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alias -- ddt  ls -trFld  dt      ddt --color        tail -n 30      Gives you the most recent files in the current directory  I use it all the time

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Signal trapping   You can trap signals sent to the shell process and have them silently run commands in their respective environment as if typed on the command line     TERM or QUIT probably means the system is shutting down  make sure history is   saved to  HISTFILE  does not do this by default  trap  logout                       TERM QUIT    save history when signalled by cron 1  script with USR1 trap  history -a  amp  amp  history -n     USR1

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alias mycommand    verylongcommand -with -a -lot -of -parameters  alias grep  grep --color    find more than one word with grep    netstat -c  grep  msn  skype  icq

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I always set my default prompt to  username hostname  current path name in full     PS1   u  h  w gt    export PS1   Saves lots of confusion when you re dealing with lots of different machines

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pushd and popd almost always come in handy

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sudo      Runs the last command with administrator privileges

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Renaming moving files with suffixes quickly  cp  home foo realllylongname cpp  -old   This expands to  cp  home foo realllylongname cpp  home foo realllylongname cpp-old

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Renaming moving files with suffixes quickly  cp  home foo realllylongname cpp  -old   This expands to  cp  home foo realllylongname cpp  home foo realllylongname cpp-old

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You can use the watch command in conjunction with another command to look for changes  An example of this was when I was testing my router  and I wanted to get up-to-date numbers on stuff like signal-to-noise ratio  etc   watch --interval 10 lynx -dump http   dslrouter stats html

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My favorite command is  ls -thor   It summons the power of the gods to list the most recently modified files in a conveniently readable format

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String multiple commands together using the  amp  amp  command     run sh  amp  amp  tail -f log txt   or  kill -9 1111  amp  amp    start sh

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I often have aliases for vi  ls  etc  but sometimes you want to escape the alias  Just add a back slash to the command in front   Eg     alias vi vim     To escape the alias for vi     vi   This doesn t open VIM   Cool  isn t it

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Two of my favorites are   1  Make tab-completion case insensitive  e g   cd  home User   converts your command line to   cd  home user  if the latter exists and the former doesn t  You can turn it on with  set completion-ignore-case on  at the prompt  or add it permanently by adding  set completion-ignore-case on  to your  inputrc file   2  The built-in  type  command is like  which  but aware of aliases also  For example    type cdhome cdhome is aliased to  cd      type bash bash is  bin bash

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Using  set -o vi  from the command line  or better  in  bashrc  puts you in vi editing mode on the command line  You start in  insert  mode so you can type and backspace as normal  but if you make a  large  mistake you can hit the esc key and then use  b  and  f  to move around as you do in vi  cw to change a word  Particularly useful after you ve brought up a history command that you want to change

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touch  1 2  txt   ls  12  txt 1 txt  2 txt   rm   1 rm  12  txt   history   tail -10     10007  touch  1 2  txt        10007 touch  1 2  txt   for f in   txt  do mv  f   f txt doc   done

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When running a command with lots of output  like a big  make   I want to not only save the output  but also see it   make install 2  amp 1   tee E make

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lt anything    sort   uniq -c   sort -n  will give you a count of all the different occurrences of  lt anything    Often  awk  sed  or cut help with the parsing of data in  lt anything

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du -a   sort -n   tail -99  to find the big files  or directories of files  to clean up to free up disk space

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while IFS  read -r line  do echo   line  done  lt  somefile txt   This is a good way to process a file line by line  Clearing IFS is needed to get whitespace characters at the front or end of the line  The  -r  is needed to get all raw characters  including backslashes

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When navigating between two separate directories and copying files back and forth  I do this   cd  some where long src  pwd  cd  other where long dest  pwd   cp  src foo  dest  command completion will work by expanding the variable  so you can use tab completion to specify a file you re working with

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For the sheer humor factor  create an empty file  myself  and then    touch myself

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lt first few characters of the command  will execute the last command which matches   Example    b will run  build whatever -O -p -t -i -on     will run   a out  It works best with long and repetitive commands  like compile  build  execute  etc  It saved me sooo much time when coding and testing

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Shell-fu is a place for storing  moderating and propagating command line tips and tricks  A bit like StackOverflow  but solely for shell  You ll find plenty of answers to this question there

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This prevents less  less is more  from clearing the screen at the end of a file   export LESS  -X

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Renaming moving files with suffixes quickly  cp  home foo realllylongname cpp  -old   This expands to  cp  home foo realllylongname cpp  home foo realllylongname cpp-old

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When navigating between two separate directories and copying files back and forth  I do this   cd  some where long src  pwd  cd  other where long dest  pwd   cp  src foo  dest  command completion will work by expanding the variable  so you can use tab completion to specify a file you re working with

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As a quick calculator  say to compute a percentage     date Thu Sep 18 12 55 33 EDT 2008   answers 60   curl  http   stackoverflow com questions 68372 what-are-some-of-your-favorite-command-line-tricks-using-bash    gt  tmp html   words  awk   class  post-text    s   s  0     gt    lt   div gt     gsub   lt    gt    gt        s   print s  s          gt  length s   gt  0  s   s  0   tmp html    gt     awk   n   n   NF  END  print n      answers  awk     0-9    Answers   sub   lt h2 gt         1   print  1   tmp html    and finally     echo  words words   answers answers     words    answers   words per answer 4126 words  60 answers  68 words per answer     Not that division is truncated  not rounded   But often that s good enough for a quick calculation

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I want to mention how we can redirect top command output to file using its batch mode  -b     top -b -n 1   top out   date   s   By default  top is invoked using interactive mode in which top runs indefinitely and accepts keypress to redefine how top works   A post I wrote can be found here

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When running commands  sometimes I ll want to run a command with the previous ones arguments   To do that  you can use this shortcut     mkdir  tmp new   cd        Occasionally  in lieu of using find  I ll break-out a one-line loop if I need to run a bunch of commands on a list of files     for file in   wav  do lame   file     basename   file   wav  mp3    done    Configuring the command-line history options in my  bash login  or  bashrc  is really useful   The following is a cadre of settings that I use on my Macbook Pro    Setting the following makes bash erase duplicate commands in your history   export HISTCONTROL  erasedups ignoreboth    I also jack my history size up pretty high too   Why not   It doesn t seem to slow anything down on today s microprocessors   export HISTFILESIZE 500000 export HISTSIZE 100000   Another thing that I do is ignore some commands from my history   No need to remember the exit command    export HISTIGNORE   amp       exit    You definitely want to set histappend   Otherwise  bash overwrites your history when you exit   shopt -s histappend   Another option that I use is cmdhist   This lets you save multi-line commands to the history as one command   shopt -s cmdhist   Finally  on Mac OS X  if you re not using vi mode   you ll want to reset  lt CTRL gt -S from being scroll stop   This prevents bash from being able to interpret it as forward search    stty stop

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I like a splash of colour in my prompts   export PS1     033 07 31m    h    033 47 30m    W    033 00 31m         e m      I m afraid I don t have a screenshot for what that looks like  but it s supposed to be something like  all on one line     RED BACK WHITE TEXT  Computer name   BLACK BACK WHITE TEXT  Working Directory   WHITE BACK RED TEXT      Customise as per what you like to see

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Well  this may be a bit off topic  but if you are an Emacs user  I would say  emacs  is the most powerful trick     before you downvote this  try out  M-x shell  within an emacs instance    you get a shell inside emacs  and have all the power of emacs along with the power of a shell  there are some limitations  such as opening another emacs within it  but in most cases it is a lot more powerful than a vanilla bash prompt

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Custom Tab Completion  compgen and complete bash builtins   Tab Completion is nice  but being able to apply it to more than just filenames is great   I have used it to create custom functions to expand arguments to commands I use all the time   For example  lets say you often need to add the FQDN as an argument to a command  e g  ping blah really long domain name foo com    You can use compgen and complete to create a bash function that reads your  etc hosts file for results so all you have to type then is   ping blah  lt tab gt    and it will display all your current match options   So basically anything that can return a word list can be used as a function

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Quick Text  I use these sequences of text all too often  so I put shortcuts to them in by  inputrc     redirection short cuts   ew               2 gt  amp 1    eq                amp  gt  dev null  amp     e C-q            2 gt  dev null    eg                amp  gt    garbage out  amp     e C-g            2 gt    garbage out    if term xterm   M-w              2 gt  amp 1    M-q               amp  gt  dev null  amp     M- C-q           2 gt  dev null    M-g               amp  gt    garbage out  amp     M- C-g           2 gt    garbage out   endif

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Good for making an exact recursive copy backup of a directory including symlinks  rather than following them or ignoring them like cp      mkdir new dir   cd old dir   tar cf -       cd    old dir  tar xf -

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If I am searching for something in a directory  but I am not sure of the file  then I just grep the files in the directory by   find   -exec grep whatIWantToFind

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More of a novelty  but it s clever     Top 10 commands used     history   awk   print  2     awk  BEGIN  FS      print  1     sort   uniq -c   sort -nr   head   Sample output    242 git   83 rake   43 cd   33 ss   24 ls   15 rsg   11 cap   10 dig    9 ping    3 vi

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Well  this may be a bit off topic  but if you are an Emacs user  I would say  emacs  is the most powerful trick     before you downvote this  try out  M-x shell  within an emacs instance    you get a shell inside emacs  and have all the power of emacs along with the power of a shell  there are some limitations  such as opening another emacs within it  but in most cases it is a lot more powerful than a vanilla bash prompt

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http   www commandlinefu com is also a great site   I learned quite useful things there like   sudo      or  mount   column -t

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I m a big fan of Bash job control  mainly the use of Control-Z and fg  especially if I m doing development in a terminal  If I ve got emacs open and need to compile  deploy  etc  I just Control-Z to suspend emacs  do what I need  and fg to bring it back  This keeps all of the emacs buffers intact and makes things much easier than re-launching whatever I m doing

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bash can redirect to and from TCP IP sockets   dev tcp  and  dev udp   Some people think it s a security issue  but that s what OS level security like Solaris X s jail is for   As Will Robertson notes  change prompt to do stuff    print the command   for  nn  Set the Xterm terminal name  If it s an old Xterm that doesn t sniff traffic to set it s title

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pushd and popd almost always come in handy

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The FIGNORE environment variable is nice when you want TAB completion to ignore files or folders with certain suffixes  e g    export FIGNORE  CVS  svn      Use the IFS environment variable when you want to define an item separator other than space  e g    export IFS       This will make you able to loop through files and folders with spaces in them without performing any magic  like this     touch  with spaces  withoutspaces   for i in  ls     do echo  i  done with spaces withoutspaces   IFS       for i in  ls     do echo  i  done with spaces withoutspaces

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Delete everything except important-file     shopt -s extglob   rm -rf   important-file    The same in zsh     rm -rf   important-file   Bevore I knew that I had to move the important fiels to an other dictionary  delete everything and move the important back again

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Not really obscure  but one of the features I absolutely love is tab completion  Really useful when you are navigating trough an entire subtree structure  or when you are using some obscure  or long command

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I like a splash of colour in my prompts   export PS1     033 07 31m    h    033 47 30m    W    033 00 31m         e m      I m afraid I don t have a screenshot for what that looks like  but it s supposed to be something like  all on one line     RED BACK WHITE TEXT  Computer name   BLACK BACK WHITE TEXT  Working Directory   WHITE BACK RED TEXT      Customise as per what you like to see

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pbcopy  This copies to the Mac system clipboard  You can pipe commands to it   try   pwd   pbcopy

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rename  Example     ls this has text to find 1 txt this has text to find 2 txt this has text to find 3 txt this has text to find 4 txt    rename  s text to find been renamed     txt   ls this has been renamed 1 txt this has been renamed 2 txt this has been renamed 3 txt this has been renamed 4 txt    So useful

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Ctrl   L will usually clear the screen  Works from the Bash prompt  obviously  and in GDB  and a lot of other prompts

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I have plenty of directories which I want to access quickly  CDPATH variable is solution  that speed up my work-flow enormously    export CDPATH    home gadolin sth  home gadolin dir1 importantDir   now with cd I can jump to any of sub directories of  home gadolin sth or  home gadolin dir1 importantDir without providing the full path  And also  lt tab gt  works here just like I would be there  So if there are directories  home gadolin sth 1  home gadolin sth 2  I type cd 1 wherever  and I am there

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I like to set a prompt which shows the current directory in the window title of an xterm   It also shows the time and current directory   In addition  if bash wants to report that a background job has finished  it is reported in a different colour using ANSI escape sequences   I use a black-on-light console so my colours may not be right for you if you favour light-on-black   PROMPT COMMAND  echo -e   033 0   USER    HOSTNAME        PWD   HOME    007 033 1 31m  PWD   HOME    033 1 34m   PS1     e 1 31m   t       e 0m      Make sure you understand how to use    and    correctly in your PS1 string so that bash knows how long your prompt-string actually renders on screen  This is so it can redraw your command-line correctly when you move beyond a single line command

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Delete everything except important-file     shopt -s extglob   rm -rf   important-file    The same in zsh     rm -rf   important-file   Bevore I knew that I had to move the important fiels to an other dictionary  delete everything and move the important back again

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When running a command with lots of output  like a big  make   I want to not only save the output  but also see it   make install 2  amp 1   tee E make

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Another favorite        Repeats your last command   Most useful in the form   sudo

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ESC   Inserts the last arguments from your last bash command   It comes in handy more than you think   cp file  to some long path   cd ESC

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extended globbing   rm   foo bar    expands like   without foo or bar     ls foo bar foobar FOO   echo   foo bar  foobar FOO

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Custom Tab Completion  compgen and complete bash builtins   Tab Completion is nice  but being able to apply it to more than just filenames is great   I have used it to create custom functions to expand arguments to commands I use all the time   For example  lets say you often need to add the FQDN as an argument to a command  e g  ping blah really long domain name foo com    You can use compgen and complete to create a bash function that reads your  etc hosts file for results so all you have to type then is   ping blah  lt tab gt    and it will display all your current match options   So basically anything that can return a word list can be used as a function

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More of a novelty  but it s clever     Top 10 commands used     history   awk   print  2     awk  BEGIN  FS      print  1     sort   uniq -c   sort -nr   head   Sample output    242 git   83 rake   43 cd   33 ss   24 ls   15 rsg   11 cap   10 dig    9 ping    3 vi

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Custom Tab Completion  compgen and complete bash builtins   Tab Completion is nice  but being able to apply it to more than just filenames is great   I have used it to create custom functions to expand arguments to commands I use all the time   For example  lets say you often need to add the FQDN as an argument to a command  e g  ping blah really long domain name foo com    You can use compgen and complete to create a bash function that reads your  etc hosts file for results so all you have to type then is   ping blah  lt tab gt    and it will display all your current match options   So basically anything that can return a word list can be used as a function

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I prefer reading man pages in vi  so I have the following in my  profile or  bashrc file  man          sought         usr bin man  sought   col -b   vim -R -c  set nonumber  -c  set syntax man   -

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R reverse search  Hit  R  type a fragment of a previous command you want to match  and hit  R until you find the one you want  Then I don t have to remember recently used commands that are still in my history  Not exclusively bash  but also   E for end of line   A for beginning of line   U and  K to delete before and after the cursor  respectively

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I m a fan of the        and    expandos  returning  from the most recent submitted command line  the last item  first non-command item  and all non-command items  To wit  Note that the shell prints out the command first      echo foo bar baz foo bar baz   echo bang-dollar     bang-hat     bang-star     echo bang-dollar  baz bang-hat  foo bang-star  foo bar baz bang-dollar  baz bang-hat  foo bang-star  foo bar baz   This comes in handy when you  say ls filea fileb  and want to edit one of them  vi    or both of them  vimdiff     It can also be generalized to  the nth argument  like so     echo foo bar baz   echo   2 echo bar bar   Finally  with pathnames  you can get at parts of the path by appending  h and  t to any of the above expandos     ls  usr bin id  usr bin id   echo Head     h  Tail     t echo Head   usr bin Tail  id Head   usr bin Tail  id

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Sure  you can  diff file1 txt file2 txt   but Bash supports process substitution  which allows you to diff the output of commands   For example  let s say I want to make sure my script gives me the output I expect   I can just wrap my script in  lt     and feed it to diff to get a quick and dirty unit test     cat myscript sh    bin sh echo -e  one nthree        myscript sh  one three     cat expected output txt one two three     diff  lt    myscript sh  expected output txt 1a2  gt  two     As another example  let s say I want to check if two servers have the same list of RPMs installed   Rather than sshing to each server  writing each list of RPMs to separate files  and doing a diff on those files  I can just do the diff from my workstation     diff  lt  ssh server1  rpm -qa   sort    lt  ssh server2  rpm -qa   sort   241c240  lt  kernel-2 6 18-92 1 6 el5 ---  gt  kernel-2 6 18-92 el5 317d315  lt  libsmi-0 4 5-2 el5 727 728d724  lt  wireshark-0 99 7-1 el5  lt  wireshark-gnome-0 99 7-1 el5     There are more examples in the  Advanced Bash-Scripting Guide at http   tldp org LDP abs html process-sub html

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I use the following a lot   The  p modifier to print a history result  E g      p   Will print the last command so you can check that it s correct before running it again  Just enter    to execute it   In a similar vein     foo  p   Will search your history for the most recent command that contained the string  foo  and print it   If you don t need to print     foo   does the search and executes it straight away

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I often have aliases for vi  ls  etc  but sometimes you want to escape the alias  Just add a back slash to the command in front   Eg     alias vi vim     To escape the alias for vi     vi   This doesn t open VIM   Cool  isn t it

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Duplicate file finder  This will run checksums recursively from the current directory  and give back the filenames of all identical checksum results   find    -type f -print0   xargs -0 -n1 md5sum   sort -k 1 32   uniq -w 32 -d --all-repeated separate   sed -e  s   0-9a-f            You can  of course  change the path around  Maybe put it into a function or alias  and pass in the target path as a parameter

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I m a fan of the        and    expandos  returning  from the most recent submitted command line  the last item  first non-command item  and all non-command items  To wit  Note that the shell prints out the command first      echo foo bar baz foo bar baz   echo bang-dollar     bang-hat     bang-star     echo bang-dollar  baz bang-hat  foo bang-star  foo bar baz bang-dollar  baz bang-hat  foo bang-star  foo bar baz   This comes in handy when you  say ls filea fileb  and want to edit one of them  vi    or both of them  vimdiff     It can also be generalized to  the nth argument  like so     echo foo bar baz   echo   2 echo bar bar   Finally  with pathnames  you can get at parts of the path by appending  h and  t to any of the above expandos     ls  usr bin id  usr bin id   echo Head     h  Tail     t echo Head   usr bin Tail  id Head   usr bin Tail  id

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dollar underscore   the last word from the previous command  Similar to    except it doesn t put its substitution in your history like    does

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I have various typographical error corrections in aliases  alias mkae make  alias mroe less

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As a quick calculator  say to compute a percentage     date Thu Sep 18 12 55 33 EDT 2008   answers 60   curl  http   stackoverflow com questions 68372 what-are-some-of-your-favorite-command-line-tricks-using-bash    gt  tmp html   words  awk   class  post-text    s   s  0     gt    lt   div gt     gsub   lt    gt    gt        s   print s  s          gt  length s   gt  0  s   s  0   tmp html    gt     awk   n   n   NF  END  print n      answers  awk     0-9    Answers   sub   lt h2 gt         1   print  1   tmp html    and finally     echo  words words   answers answers     words    answers   words per answer 4126 words  60 answers  68 words per answer     Not that division is truncated  not rounded   But often that s good enough for a quick calculation

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Using history substiution characters    to access the current command line  in combination with       etc   E g  move a file out of the way with an  old-  prefix   mv file-with-long-name-typed-with-tab-completion txt old-

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Not my favorite  by very helpful if you re trying any of the other answers using copy and paste   function                  Now you can paste examples that include a   prompt at the start of each line

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I like to construct commands with echo and pipe them to the shell     find dir -name       xargs echo rm       find dir -name       xargs echo rm   ksh -s   Why   Because it allows me to look at what s going to be done before I do it   That way if I have a horrible error  like removing my home directory   I can catch it before it happens   Obviously  this is most important for destructive or irrevocable actions

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Mac only  This is simple  but MAN do I wish I had known about this years ago   open      Opens the current directory in Finder  You can also use it to open any file with it s default application  Can also be used for URLs  but only if you prefix the URL with http     which limits it s utility for opening the occasional random site

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A simple thing to do when you realize you just typed the wrong line is hit Ctrl C  if you want to keep the line  but need to execute something else first  begin a new line with a back slash -    then Ctrl C  The line will remain in your history

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As an extension to CTRL-r to search backwards  you can auto-complete your current input with your history if you bind  history-search-backward    I typically bind it to the same key that it is in tcsh   ESC-p   You can do this by putting the following line in your  inputrc file     M-p   history-search-backward  E g   if you have previously executed  make some really painfully long target  you can type    gt  make  lt ESC p gt   and it will give you   gt  make some really painfully long target

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Here s a couple of configuration tweaks      inputrc     C-  A   history-search-backward   C-  B   history-search-forward   This works the same as  R but using the arrow keys instead  This means I can type  e g   cd  media  then hit up-arrow to go to the last thing I cd d to inside the  media  folder    I use Gnome Terminal  you may need to change the escape codes for other terminal emulators    Bash completion is also incredibly useful  but it s a far more subtle addition  In    bashrc   if   -f  etc bash completion    then        etc bash completion fi   This will enable per-program tab-completion  e g  attempting tab completion when the command line starts with evince will only show files that evince can open  and it will also tab-complete command line options    Works nicely with this also in    inputrc   set completion-ignore-case on set show-all-if-ambiguous on set show-all-if-unmodified on

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Similar to many above  my current favorite is the keystroke  alt    Alt and     keys together  this is the same as     Inserts the last argument from the previous command  except that it s immediate and for me easier to type   Just can t be used in scripts   eg   mkdir -p  tmp test blah oops something cd  alt

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I m new to programming on a mac  and I miss being able to launch gui programs from bash   so I have to create functions like this   function macvim    Applications MacVim app Contents MacOS Vim      -gp  amp

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How to find which files match text  using find   grep -H In this example  which ruby file contains the jump string -  find   -name    rb  -exec grep -H jump

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And this one is key for me actually   set -o vi   Allan

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dollar underscore   the last word from the previous command  Similar to    except it doesn t put its substitution in your history like    does

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I want to mention how we can redirect top command output to file using its batch mode  -b     top -b -n 1   top out   date   s   By default  top is invoked using interactive mode in which top runs indefinitely and accepts keypress to redefine how top works   A post I wrote can be found here

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When running commands  sometimes I ll want to run a command with the previous ones arguments   To do that  you can use this shortcut     mkdir  tmp new   cd        Occasionally  in lieu of using find  I ll break-out a one-line loop if I need to run a bunch of commands on a list of files     for file in   wav  do lame   file     basename   file   wav  mp3    done    Configuring the command-line history options in my  bash login  or  bashrc  is really useful   The following is a cadre of settings that I use on my Macbook Pro    Setting the following makes bash erase duplicate commands in your history   export HISTCONTROL  erasedups ignoreboth    I also jack my history size up pretty high too   Why not   It doesn t seem to slow anything down on today s microprocessors   export HISTFILESIZE 500000 export HISTSIZE 100000   Another thing that I do is ignore some commands from my history   No need to remember the exit command    export HISTIGNORE   amp       exit    You definitely want to set histappend   Otherwise  bash overwrites your history when you exit   shopt -s histappend   Another option that I use is cmdhist   This lets you save multi-line commands to the history as one command   shopt -s cmdhist   Finally  on Mac OS X  if you re not using vi mode   you ll want to reset  lt CTRL gt -S from being scroll stop   This prevents bash from being able to interpret it as forward search    stty stop

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Someone else recommended  M-x shell RET  in Emacs   I think  M-x eshell RET  is even better

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Want to get the last few lines of a log file   tail  var log syslog   Want to keep an eye on a log file for when it changes   tail -f  var log syslog   Want to quickly read over a file from the start   more  var log syslog   Want to quickly find if a file contains some text   grep  find this text   var log syslog

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As a quick calculator  say to compute a percentage     date Thu Sep 18 12 55 33 EDT 2008   answers 60   curl  http   stackoverflow com questions 68372 what-are-some-of-your-favorite-command-line-tricks-using-bash    gt  tmp html   words  awk   class  post-text    s   s  0     gt    lt   div gt     gsub   lt    gt    gt        s   print s  s          gt  length s   gt  0  s   s  0   tmp html    gt     awk   n   n   NF  END  print n      answers  awk     0-9    Answers   sub   lt h2 gt         1   print  1   tmp html    and finally     echo  words words   answers answers     words    answers   words per answer 4126 words  60 answers  68 words per answer     Not that division is truncated  not rounded   But often that s good enough for a quick calculation

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I want to mention how we can redirect top command output to file using its batch mode  -b     top -b -n 1   top out   date   s   By default  top is invoked using interactive mode in which top runs indefinitely and accepts keypress to redefine how top works   A post I wrote can be found here

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lt anything    sort   uniq -c   sort -n  will give you a count of all the different occurrences of  lt anything    Often  awk  sed  or cut help with the parsing of data in  lt anything

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Using alias can be time-saving  alias myDir    cd  this is a long directory  pwd

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Not really obscure  but one of the features I absolutely love is tab completion  Really useful when you are navigating trough an entire subtree structure  or when you are using some obscure  or long command

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I use the following a lot   The  p modifier to print a history result  E g      p   Will print the last command so you can check that it s correct before running it again  Just enter    to execute it   In a similar vein     foo  p   Will search your history for the most recent command that contained the string  foo  and print it   If you don t need to print     foo   does the search and executes it straight away

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pbcopy and pbpaste aliases for GNU Linux  alias pbcopy  xclip -selection clipboard  alias pbpaste  xclip -selection clipboard -o

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alias -- ddt  ls -trFld  dt      ddt --color        tail -n 30      Gives you the most recent files in the current directory  I use it all the time

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String multiple commands together using the  amp  amp  command     run sh  amp  amp  tail -f log txt   or  kill -9 1111  amp  amp    start sh

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Good for making an exact recursive copy backup of a directory including symlinks  rather than following them or ignoring them like cp      mkdir new dir   cd old dir   tar cf -       cd    old dir  tar xf -

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Batch extension renamer  usage  renamer txt mkd  renamer        local fn    for fn in     1   do      mv   fn     fn        2     done

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When running commands  sometimes I ll want to run a command with the previous ones arguments   To do that  you can use this shortcut     mkdir  tmp new   cd        Occasionally  in lieu of using find  I ll break-out a one-line loop if I need to run a bunch of commands on a list of files     for file in   wav  do lame   file     basename   file   wav  mp3    done    Configuring the command-line history options in my  bash login  or  bashrc  is really useful   The following is a cadre of settings that I use on my Macbook Pro    Setting the following makes bash erase duplicate commands in your history   export HISTCONTROL  erasedups ignoreboth    I also jack my history size up pretty high too   Why not   It doesn t seem to slow anything down on today s microprocessors   export HISTFILESIZE 500000 export HISTSIZE 100000   Another thing that I do is ignore some commands from my history   No need to remember the exit command    export HISTIGNORE   amp       exit    You definitely want to set histappend   Otherwise  bash overwrites your history when you exit   shopt -s histappend   Another option that I use is cmdhist   This lets you save multi-line commands to the history as one command   shopt -s cmdhist   Finally  on Mac OS X  if you re not using vi mode   you ll want to reset  lt CTRL gt -S from being scroll stop   This prevents bash from being able to interpret it as forward search    stty stop

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I ve always liked this one  Add this to your  etc inputrc or    inputrc    e A  history-search-backward   e B  history-search-forward  When you type ls  lt up-arrow gt  it will be replaced with the last command starting with  ls   or whatever else you put in

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A few years ago  I discovered the p  commands or get information about processes  ptree  pgrep  pkill  and pfiles   Of course  the mother of them all is ps  but you need to pipe the output into less  grep and or awk to make sense of the output under heavy load   top  and variants  help too

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Duplicate file finder  This will run checksums recursively from the current directory  and give back the filenames of all identical checksum results   find    -type f -print0   xargs -0 -n1 md5sum   sort -k 1 32   uniq -w 32 -d --all-repeated separate   sed -e  s   0-9a-f            You can  of course  change the path around  Maybe put it into a function or alias  and pass in the target path as a parameter

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mylittlealgorithm  lt  input txt   output txt

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type -a PROG   in order to find all the places where PROG is available  usually somewhere in   bin rather than the one in  usr bin PROG that might have been expected

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Programmable Completion   Nothing fancy  I always disable it when I m using Knoppix because it gets in the way too often  Just some basic ones   shopt -s progcomp  complete -A stopped -P              bg complete -A job     -P              fg jobs disown wait complete -A variable                readonly export complete -A variable -A function    unset complete -A setopt                  set complete -A shopt                   shopt complete -A helptopic               help complete -A alias                   alias unalias complete -A binding                 bind complete -A command                 type which                                       killall pidof complete -A builtin                 builtin complete -A disabled                enable

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You should be able to paste the following into a bash terminal window   Display ANSI colour palette   e   033   for f in 0 7  seq 6   do   no    bo      for b in n 7 0  seq 6   do     co  3 f   p             b   n        co   co 4 b  p           no    no   e   co m     p   co    e 0m      bo    bo   e 1   co m   p 1   co    e 0m    done   echo -e   no n bo  done   256 colour demo   yes    seq 232 255 seq 254 -1 233     while read i  do printf   x1b 48 5   i m n   sleep  01  done

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How to find which files match text  using find   grep -H In this example  which ruby file contains the jump string -  find   -name    rb  -exec grep -H jump

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Eliminate duplicate lines from a file   sort -u filename  gt  filename new   List all lines that do not match a condition   grep -v ajsk filename   These are not necessarily Bash specific  but hey neither is ls -thor       Some other useful cmds   prtdiag  psrinfo  prtconf - more info here and here  posts on my blog

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I have plenty of directories which I want to access quickly  CDPATH variable is solution  that speed up my work-flow enormously    export CDPATH    home gadolin sth  home gadolin dir1 importantDir   now with cd I can jump to any of sub directories of  home gadolin sth or  home gadolin dir1 importantDir without providing the full path  And also  lt tab gt  works here just like I would be there  So if there are directories  home gadolin sth 1  home gadolin sth 2  I type cd 1 wherever  and I am there

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Similar to many above  my current favorite is the keystroke  alt    Alt and     keys together  this is the same as     Inserts the last argument from the previous command  except that it s immediate and for me easier to type   Just can t be used in scripts   eg   mkdir -p  tmp test blah oops something cd  alt

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pushd and popd almost always come in handy

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I m a fan of the        and    expandos  returning  from the most recent submitted command line  the last item  first non-command item  and all non-command items  To wit  Note that the shell prints out the command first      echo foo bar baz foo bar baz   echo bang-dollar     bang-hat     bang-star     echo bang-dollar  baz bang-hat  foo bang-star  foo bar baz bang-dollar  baz bang-hat  foo bang-star  foo bar baz   This comes in handy when you  say ls filea fileb  and want to edit one of them  vi    or both of them  vimdiff     It can also be generalized to  the nth argument  like so     echo foo bar baz   echo   2 echo bar bar   Finally  with pathnames  you can get at parts of the path by appending  h and  t to any of the above expandos     ls  usr bin id  usr bin id   echo Head     h  Tail     t echo Head   usr bin Tail  id Head   usr bin Tail  id

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cd -   It s the command-line equivalent of the back button  takes you to the previous directory you were in

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Using history substiution characters    to access the current command line  in combination with       etc   E g  move a file out of the way with an  old-  prefix   mv file-with-long-name-typed-with-tab-completion txt old-

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One preferred way of navigating when I m using multiple directories in widely separate places in a tree hierarchy is to use acf func sh  listed below   Once defined  you can do  cd --   to see a list of recent directories  with a numerical menu  cd -2  to go to the second-most recent directory   Very easy to use  very handy   Here s the code     do    acd func sh    acd func 1 0 5  10-nov-2004   petar marinov  http  geocities com h2428  this is public domain  cd func        local x2 the new dir adir index   local -i cnt    if     1      --      then     dirs -v     return 0   fi    the new dir  1      -z  1     amp  amp  the new dir  HOME    if      the new dir 0 1      -      then             Extract dir N from dirs     index   the new dir 1         -z  index     amp  amp  index 1     adir   dirs   index         -z  adir     amp  amp  return 1     the new dir  adir   fi              has to be substituted by   HOME         the new dir 0 1             amp  amp  the new dir    HOME   the new dir 1            Now change to the new dir and add to the top of the stack   pushd    the new dir    gt   dev null         -ne 0     amp  amp  return 1   the new dir   pwd           Trim down everything beyond 11th entry   popd -n  11 2 gt  dev null 1 gt  dev null          Remove any other occurence of this dir  skipping the top of the stack   for   cnt 1  cnt  lt   10  cnt      do     x2   dirs    cnt  2 gt  dev null            -ne 0     amp  amp  return 0          x2 0 1             amp  amp  x2    HOME   x2 1       if       x2         the new dir       then       popd -n   cnt 2 gt  dev null 1 gt  dev null       cnt cnt-1     fi   done    return 0    alias cd cd func  if     BASH VERSION  gt   2 05a      then     ctrl w shows the menu   bind -x     C-w   cd func --    fi

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Top 10 commands again  like ctcherry s post  only shorter    history   awk    print  2      sort   uniq -c  sort -rn   head

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To be able to quickly edit a shell script you know is in your  PATH  do not try with ls       function viscr   vi   which

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lt anything    sort   uniq -c   sort -n  will give you a count of all the different occurrences of  lt anything    Often  awk  sed  or cut help with the parsing of data in  lt anything

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When navigating between two separate directories and copying files back and forth  I do this   cd  some where long src  pwd  cd  other where long dest  pwd   cp  src foo  dest  command completion will work by expanding the variable  so you can use tab completion to specify a file you re working with

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rename  Example     ls this has text to find 1 txt this has text to find 2 txt this has text to find 3 txt this has text to find 4 txt    rename  s text to find been renamed     txt   ls this has been renamed 1 txt this has been renamed 2 txt this has been renamed 3 txt this has been renamed 4 txt    So useful

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alias mycommand    verylongcommand -with -a -lot -of -parameters  alias grep  grep --color    find more than one word with grep    netstat -c  grep  msn  skype  icq

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And this one is key for me actually   set -o vi   Allan

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This prevents less  less is more  from clearing the screen at the end of a file   export LESS  -X

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sudo      Runs the last command with administrator privileges

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Ctrl   L will usually clear the screen  Works from the Bash prompt  obviously  and in GDB  and a lot of other prompts

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Here s a couple of configuration tweaks      inputrc     C-  A   history-search-backward   C-  B   history-search-forward   This works the same as  R but using the arrow keys instead  This means I can type  e g   cd  media  then hit up-arrow to go to the last thing I cd d to inside the  media  folder    I use Gnome Terminal  you may need to change the escape codes for other terminal emulators    Bash completion is also incredibly useful  but it s a far more subtle addition  In    bashrc   if   -f  etc bash completion    then        etc bash completion fi   This will enable per-program tab-completion  e g  attempting tab completion when the command line starts with evince will only show files that evince can open  and it will also tab-complete command line options    Works nicely with this also in    inputrc   set completion-ignore-case on set show-all-if-ambiguous on set show-all-if-unmodified on

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Want to get the last few lines of a log file   tail  var log syslog   Want to keep an eye on a log file for when it changes   tail -f  var log syslog   Want to quickly read over a file from the start   more  var log syslog   Want to quickly find if a file contains some text   grep  find this text   var log syslog

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A few years ago  I discovered the p  commands or get information about processes  ptree  pgrep  pkill  and pfiles   Of course  the mother of them all is ps  but you need to pipe the output into less  grep and or awk to make sense of the output under heavy load   top  and variants  help too

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Using alias can be time-saving  alias myDir    cd  this is a long directory  pwd

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while IFS  read -r line  do echo   line  done  lt  somefile txt   This is a good way to process a file line by line  Clearing IFS is needed to get whitespace characters at the front or end of the line  The  -r  is needed to get all raw characters  including backslashes

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SSH tunnel   ssh -fNR 1234 localhost 22 root 123 123 123 123

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Here s a couple of configuration tweaks      inputrc     C-  A   history-search-backward   C-  B   history-search-forward   This works the same as  R but using the arrow keys instead  This means I can type  e g   cd  media  then hit up-arrow to go to the last thing I cd d to inside the  media  folder    I use Gnome Terminal  you may need to change the escape codes for other terminal emulators    Bash completion is also incredibly useful  but it s a far more subtle addition  In    bashrc   if   -f  etc bash completion    then        etc bash completion fi   This will enable per-program tab-completion  e g  attempting tab completion when the command line starts with evince will only show files that evince can open  and it will also tab-complete command line options    Works nicely with this also in    inputrc   set completion-ignore-case on set show-all-if-ambiguous on set show-all-if-unmodified on

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If I am searching for something in a directory  but I am not sure of the file  then I just grep the files in the directory by   find   -exec grep whatIWantToFind

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alias mycommand    verylongcommand -with -a -lot -of -parameters  alias grep  grep --color    find more than one word with grep    netstat -c  grep  msn  skype  icq

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I ve always liked this one  Add this to your  etc inputrc or    inputrc    e A  history-search-backward   e B  history-search-forward  When you type ls  lt up-arrow gt  it will be replaced with the last command starting with  ls   or whatever else you put in

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As a quick calculator  say to compute a percentage     date Thu Sep 18 12 55 33 EDT 2008   answers 60   curl  http   stackoverflow com questions 68372 what-are-some-of-your-favorite-command-line-tricks-using-bash    gt  tmp html   words  awk   class  post-text    s   s  0     gt    lt   div gt     gsub   lt    gt    gt        s   print s  s          gt  length s   gt  0  s   s  0   tmp html    gt     awk   n   n   NF  END  print n      answers  awk     0-9    Answers   sub   lt h2 gt         1   print  1   tmp html    and finally     echo  words words   answers answers     words    answers   words per answer 4126 words  60 answers  68 words per answer     Not that division is truncated  not rounded   But often that s good enough for a quick calculation

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The FIGNORE environment variable is nice when you want TAB completion to ignore files or folders with certain suffixes  e g    export FIGNORE  CVS  svn      Use the IFS environment variable when you want to define an item separator other than space  e g    export IFS       This will make you able to loop through files and folders with spaces in them without performing any magic  like this     touch  with spaces  withoutspaces   for i in  ls     do echo  i  done with spaces withoutspaces   IFS       for i in  ls     do echo  i  done with spaces withoutspaces

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lt first few characters of the command  will execute the last command which matches   Example    b will run  build whatever -O -p -t -i -on     will run   a out  It works best with long and repetitive commands  like compile  build  execute  etc  It saved me sooo much time when coding and testing

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You can use the watch command in conjunction with another command to look for changes  An example of this was when I was testing my router  and I wanted to get up-to-date numbers on stuff like signal-to-noise ratio  etc   watch --interval 10 lynx -dump http   dslrouter stats html

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A few years ago  I discovered the p  commands or get information about processes  ptree  pgrep  pkill  and pfiles   Of course  the mother of them all is ps  but you need to pipe the output into less  grep and or awk to make sense of the output under heavy load   top  and variants  help too

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And this one is key for me actually   set -o vi   Allan

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cd -   It s the command-line equivalent of the back button  takes you to the previous directory you were in

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Similar to many above  my current favorite is the keystroke  alt    Alt and     keys together  this is the same as     Inserts the last argument from the previous command  except that it s immediate and for me easier to type   Just can t be used in scripts   eg   mkdir -p  tmp test blah oops something cd  alt

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Want to get the last few lines of a log file   tail  var log syslog   Want to keep an eye on a log file for when it changes   tail -f  var log syslog   Want to quickly read over a file from the start   more  var log syslog   Want to quickly find if a file contains some text   grep  find this text   var log syslog

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find -iregex      py       xml     xargs egrep -niH  a search pattern     vi -R -   Searches a pattern in all Python files and all XML files and pipes the result in a readonly Vim session

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Eliminate duplicate lines from a file   sort -u filename  gt  filename new   List all lines that do not match a condition   grep -v ajsk filename   These are not necessarily Bash specific  but hey neither is ls -thor       Some other useful cmds   prtdiag  psrinfo  prtconf - more info here and here  posts on my blog

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touch  1 2  txt   ls  12  txt 1 txt  2 txt   rm   1 rm  12  txt   history   tail -10     10007  touch  1 2  txt        10007 touch  1 2  txt   for f in   txt  do mv  f   f txt doc   done

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I use the following a lot   The  p modifier to print a history result  E g      p   Will print the last command so you can check that it s correct before running it again  Just enter    to execute it   In a similar vein     foo  p   Will search your history for the most recent command that contained the string  foo  and print it   If you don t need to print     foo   does the search and executes it straight away

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I like to construct commands with echo and pipe them to the shell     find dir -name       xargs echo rm       find dir -name       xargs echo rm   ksh -s   Why   Because it allows me to look at what s going to be done before I do it   That way if I have a horrible error  like removing my home directory   I can catch it before it happens   Obviously  this is most important for destructive or irrevocable actions

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You can use the watch command in conjunction with another command to look for changes  An example of this was when I was testing my router  and I wanted to get up-to-date numbers on stuff like signal-to-noise ratio  etc   watch --interval 10 lynx -dump http   dslrouter stats html

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du -a   sort -n   tail -99  to find the big files  or directories of files  to clean up to free up disk space

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Using alias can be time-saving  alias myDir    cd  this is a long directory  pwd

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touch  1 2  txt   ls  12  txt 1 txt  2 txt   rm   1 rm  12  txt   history   tail -10     10007  touch  1 2  txt        10007 touch  1 2  txt   for f in   txt  do mv  f   f txt doc   done

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CTRL D quits the shell

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mylittlealgorithm  lt  input txt   output txt

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I prefer reading man pages in vi  so I have the following in my  profile or  bashrc file  man          sought         usr bin man  sought   col -b   vim -R -c  set nonumber  -c  set syntax man   -

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When running a command with lots of output  like a big  make   I want to not only save the output  but also see it   make install 2  amp 1   tee E make

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Want to get the last few lines of a log file   tail  var log syslog   Want to keep an eye on a log file for when it changes   tail -f  var log syslog   Want to quickly read over a file from the start   more  var log syslog   Want to quickly find if a file contains some text   grep  find this text   var log syslog

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Insert preceding lines final parameter  ALT-   the most useful key combination ever  try it and see  for some reason no one knows about this one   Press it again and again to select older last parameters    Great when you want to do something else to something you used just a moment ago

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String multiple commands together using the  amp  amp  command     run sh  amp  amp  tail -f log txt   or  kill -9 1111  amp  amp    start sh

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dollar underscore   the last word from the previous command  Similar to    except it doesn t put its substitution in your history like    does

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sudo      Runs the last command with administrator privileges

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alias -- ddt  ls -trFld  dt      ddt --color        tail -n 30      Gives you the most recent files in the current directory  I use it all the time

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As an extension to CTRL-r to search backwards  you can auto-complete your current input with your history if you bind  history-search-backward    I typically bind it to the same key that it is in tcsh   ESC-p   You can do this by putting the following line in your  inputrc file     M-p   history-search-backward  E g   if you have previously executed  make some really painfully long target  you can type    gt  make  lt ESC p gt   and it will give you   gt  make some really painfully long target

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find -iregex      py       xml     xargs egrep -niH  a search pattern     vi -R -   Searches a pattern in all Python files and all XML files and pipes the result in a readonly Vim session

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I like to set a prompt which shows the current directory in the window title of an xterm   It also shows the time and current directory   In addition  if bash wants to report that a background job has finished  it is reported in a different colour using ANSI escape sequences   I use a black-on-light console so my colours may not be right for you if you favour light-on-black   PROMPT COMMAND  echo -e   033 0   USER    HOSTNAME        PWD   HOME    007 033 1 31m  PWD   HOME    033 1 34m   PS1     e 1 31m   t       e 0m      Make sure you understand how to use    and    correctly in your PS1 string so that bash knows how long your prompt-string actually renders on screen  This is so it can redraw your command-line correctly when you move beyond a single line command

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Using  set -o vi  from the command line  or better  in  bashrc  puts you in vi editing mode on the command line  You start in  insert  mode so you can type and backspace as normal  but if you make a  large  mistake you can hit the esc key and then use  b  and  f  to move around as you do in vi  cw to change a word  Particularly useful after you ve brought up a history command that you want to change

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This prevents less  less is more  from clearing the screen at the end of a file   export LESS  -X

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ESC   Inserts the last arguments from your last bash command   It comes in handy more than you think   cp file  to some long path   cd ESC

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Someone else recommended  M-x shell RET  in Emacs   I think  M-x eshell RET  is even better

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You changed to a new directory and want to move a file from the new directory to the old one  In one move  mv file  OLDPWD

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I use the following a lot   The  p modifier to print a history result  E g      p   Will print the last command so you can check that it s correct before running it again  Just enter    to execute it   In a similar vein     foo  p   Will search your history for the most recent command that contained the string  foo  and print it   If you don t need to print     foo   does the search and executes it straight away

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Good for making an exact recursive copy backup of a directory including symlinks  rather than following them or ignoring them like cp      mkdir new dir   cd old dir   tar cf -       cd    old dir  tar xf -

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du -a   sort -n   tail -99  to find the big files  or directories of files  to clean up to free up disk space

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type -a PROG   in order to find all the places where PROG is available  usually somewhere in   bin rather than the one in  usr bin PROG that might have been expected

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As an extension to CTRL-r to search backwards  you can auto-complete your current input with your history if you bind  history-search-backward    I typically bind it to the same key that it is in tcsh   ESC-p   You can do this by putting the following line in your  inputrc file     M-p   history-search-backward  E g   if you have previously executed  make some really painfully long target  you can type    gt  make  lt ESC p gt   and it will give you   gt  make some really painfully long target

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lt first few characters of the command  will execute the last command which matches   Example    b will run  build whatever -O -p -t -i -on     will run   a out  It works best with long and repetitive commands  like compile  build  execute  etc  It saved me sooo much time when coding and testing

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R reverse search  Hit  R  type a fragment of a previous command you want to match  and hit  R until you find the one you want  Then I don t have to remember recently used commands that are still in my history  Not exclusively bash  but also   E for end of line   A for beginning of line   U and  K to delete before and after the cursor  respectively

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I prefer reading man pages in vi  so I have the following in my  profile or  bashrc file  man          sought         usr bin man  sought   col -b   vim -R -c  set nonumber  -c  set syntax man   -

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The easiest keystrokes for me for  last argument of the last command  is     echo what the heck   what the heck   echo     heck

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Curly-Brace Expansion   Really comes in handy when running a   configure with a lot of options     configure -- prefix  usr mandir  usr man   sh libdir  usr lib64   enable- gpl pthreads bzlib lib faad  bin  mp3lame schroedinger speex theora vorbis xvid x264    pic shared postproc avfilter -lavf    disable-static    This is quite literally my configure settings for ffmpeg  Without the braces it s 409 characters   Or  even better   echo  I can count to a thousand       0 1 2 3 4 5 6 7 8 9  0 1 2 3 4 5 6 7 8 9  0 1 2 3 4 5 6 7 8 9

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When downloading a large file I quite often do   while ls -la  lt filename gt   do sleep 5  done   And then just ctrl c when I m done  or if ls returns non-zero   It s similar to the watch program but it uses the shell instead  so it works on platforms without watch   Another useful tool is netcat  or nc  If you do   nc -l -p 9100  gt  printjob prn   Then you can set up a printer on another computer but instead use the IP address of the computer running netcat  When the print job is sent  it is received by the computer running netcat and dumped into printjob prn

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More of a novelty  but it s clever     Top 10 commands used     history   awk   print  2     awk  BEGIN  FS      print  1     sort   uniq -c   sort -nr   head   Sample output    242 git   83 rake   43 cd   33 ss   24 ls   15 rsg   11 cap   10 dig    9 ping    3 vi

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Using  set -o vi  from the command line  or better  in  bashrc  puts you in vi editing mode on the command line  You start in  insert  mode so you can type and backspace as normal  but if you make a  large  mistake you can hit the esc key and then use  b  and  f  to move around as you do in vi  cw to change a word  Particularly useful after you ve brought up a history command that you want to change

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For the sheer humor factor  create an empty file  myself  and then    touch myself

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My favorite is   string string2  which takes the last command  replaces string with string2 and executes it    ehco foo bar baz bash  ehco  command not found    ehco echo foo bar baz   Bash command line history guide

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I always set my default prompt to  username hostname  current path name in full     PS1   u  h  w gt    export PS1   Saves lots of confusion when you re dealing with lots of different machines

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Similar to many above  my current favorite is the keystroke  alt    Alt and     keys together  this is the same as     Inserts the last argument from the previous command  except that it s immediate and for me easier to type   Just can t be used in scripts   eg   mkdir -p  tmp test blah oops something cd  alt

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touch  1 2  txt   ls  12  txt 1 txt  2 txt   rm   1 rm  12  txt   history   tail -10     10007  touch  1 2  txt        10007 touch  1 2  txt   for f in   txt  do mv  f   f txt doc   done

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du -a   sort -n   tail -99  to find the big files  or directories of files  to clean up to free up disk space

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I ve always been partial to   ctrl-E   move cursor to end of line ctrl-A   move cursor to beginning of line   I also use shopt -s cdable vars  then you can create bash variables to common directories   So  for my company s source tree  I create a bunch of variables like   export Dcentmain   var localdata p4ws centaur main apps core    then I can change to that directory by cd Dcentmain

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How to list only subdirectories in the current one    ls -d      It s a simple trick  but you wouldn t know how much time I needed to find that one

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I want to mention how we can redirect top command output to file using its batch mode  -b     top -b -n 1   top out   date   s   By default  top is invoked using interactive mode in which top runs indefinitely and accepts keypress to redefine how top works   A post I wrote can be found here

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Eliminate duplicate lines from a file   sort -u filename  gt  filename new   List all lines that do not match a condition   grep -v ajsk filename   These are not necessarily Bash specific  but hey neither is ls -thor       Some other useful cmds   prtdiag  psrinfo  prtconf - more info here and here  posts on my blog

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I have various typographical error corrections in aliases  alias mkae make  alias mroe less

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You should be able to paste the following into a bash terminal window   Display ANSI colour palette   e   033   for f in 0 7  seq 6   do   no    bo      for b in n 7 0  seq 6   do     co  3 f   p             b   n        co   co 4 b  p           no    no   e   co m     p   co    e 0m      bo    bo   e 1   co m   p 1   co    e 0m    done   echo -e   no n bo  done   256 colour demo   yes    seq 232 255 seq 254 -1 233     while read i  do printf   x1b 48 5   i m n   sleep  01  done

[bash] What is your single most favorite command-line trick using Bash?

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