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How-To: Bash



Documentation & References



Command Line Editing Cheat Sheet


  • CTRL + c : Kill the foreground process.
  • CTRL + z : Suspend the foreground process.
  • CTRL + d : Exit the shell.
  • CTRL + l : Clears the screen.
  • CTRL + e : Go to the end of the line.
  • CTRL + a : Go to the beginning of the line.
  • CTRL + h : Backspace.
  • CTRL + k : Clear the line after the cursor.
  • CTRL + u : Clears the line before the cursor position.
  • CTRL + k : Delete everything after the cursor, adding the killed text to the delete buffer.
  • CTRL + w : Delete the word before the cursor, adding the killed text to the delete buffer.
  • CTRL + y : Pastes the contents of the delete buffer.
  • CTRL + _ : Undoes the last edit.
  • ESC + l : Convert the word to lowercase letters.
  • ESC + l : Convert the word to uppercase letters.
  • ESC + f : Move forward a word.
  • ESC + b : Move backward one word.
  • ESC + 2 then ESC + b : Move back 2 words.
  • CTRL + r : Interactively search backwards through the command history (repeat to search again).
  • CTRL + s : Interactively search forward through the command history (repeat to search again).
  • CTRL + g : Abort the interactive search and restore the command line.
  • !! : Repeat the last command.
  • !-2 : Repeat the previous to last command.
  • !5 : Repeat command from history line 5 (run history to see the history).
  • !echo : Repeat the last command that started with echo.
  • !?date? : Repeat the last command that contains (not necessarily starts with) date.
  • !!:3 : Replaces with the third argument from the last command.
  • !!:1-2 : Replaces with the first through second arguments from the last command.
  • !!:^ : Replaces with the first argument from the last command.
  • !!:$ : Replaces with the last argument from the last command.
  • !!:$:h : Replaces with the last argument from the last command, removing the trailing pathname component.
  • !!:$:r : Replaces with the last argument from the last command, removing the trailing suffix/extension.
  • !!:$:e : Replaces with the last argument from the last command, removing all but the suffix/extension.
  • !!:* : Replaces with all arguments from the last command.
  • ^old^new^ : Repeat the last command substituting old with new.
  • !!:s/old/new/ : Repeat the last command substituting old with new (add g to the end to replace all occurrences).

Tips & Tricks


Disabling saving of the command history


This will disable saving the command history when you exit Bash:

unset HISTFILE

Clearing the command history


This will clear the command history:

history -c

Iterating over a sequence of numbers


To iterate a loop across a series of numbers use 'seq'. The following will display 'line# X' with X starting at 4 and ending at 12 with a step size of 2. The step size is optional, with a default value of 1. The ending value is also optional, when it is omitted the single value denotes the ending value with an implicit starting value of 1.

for i in $(seq 4 2 12)
do
  echo "line# $i"
done


Extended pattern matching with 'extglob'


If the extglob shell option is enabled using the shopt builtin (with shopt -s extglob), several extended pattern matching operators are recognized. In the following description, a pattern-list is a list of one or more patterns separated by a |. Composite patterns may be formed using one or more of the following sub-patterns:

  • ?(pattern-list)
    Matches zero or one occurrence of the given patterns
  • *(pattern-list)
    Matches zero or more occurrences of the given patterns
  • +(pattern-list)
    Matches one or more occurrences of the given patterns
  • @(pattern-list)
    Matches one of the given patterns
  • !(pattern-list)
    Matches anything except one of the given patterns

  • The following example will list all files ending in avi or mkv:

    ls -l *.*(avi|mkv)

    In the following example only files that do not end in avi or mkv will be listed:

    ls -l *.!(avi|mkv)


    Scripting


    Displaying GTK+ dialog boxes from the command line


    Zenity allows you to display GTK+ dialogs from shell scripts. For example the following will display an error window:

    zenity --error --text="Could not find some file."