Bash History Video Tutorial Transcription

historymanipulation.mkd

1. Overview of BASH history

   • history

2. Basic History Recall

   • !! - Previous command
   • !n - Nth previous command

3. Parameter Recall

   • !* - All parameters from the last command, excluding 0th (the command itself)
   • !:n - Nth parameter from the previous command (index starting from 1)

4. Advanced Recall

   • !?<search> - Previous command with the word <search> in it, if you want to use a command on such a recall you will need to close <search> with a ? ie., !?foo?
   • !<command> - Previous <command>

From here on any one of !!, !n, !<command>, or !?<search>? will be referred to as <history ref>

5. Advanced Parameter Recall

   • <history ref>:<n/^/$/*> - Nth, first, last, or all parameters respectively of the <history ref>

6. Basic Replace

   • ^foo^bar - Replace first occurence of foo with bar in previous command

7. Advanced Replace

   • <history ref>:s/foo/bar - Replace first occurence of foo with bar in <history ref>
     • Example: !395:s/sbiddle/shawn/
   • <history ref>:gs/foo/bar - Replace all occurences of foo with bar in <history ref>

8. Modifiers (These are essentially filters applied to a substitution)

   • <substitution>:t - The "tail" of the string, ie., the filename in a path
     • Example: !cat:t
   • <substitution>:h - The "head" of the string, ie., the path minus the filename
   • <substitution>:q - Surround the substitution with single quotes
   • <substitution>:x - Split the substitution on spaces/newlines and then surround those with quotes

Example:

> cat /foo/bar /bazz/quz
...
> echo !cat:*:x
echo '/foo/bar' '/bazz/quz'

9. History Settings All of these you can set in your .bashrc with export <setting>=<value>
   • HISTSIZE (number) - How many entries to store (defaults to 500)
   • HISTCONTROL (string) - Behaviour of the history
     • ignoredups - Don't put the command in your history if it's the sam as the previous command
     • ignorespace - Don't put the command in your history if there is a leading whitespace. Useful if you want to run some commands without having them be in the bare history file
     • ignoreboth - Both of the previous settings.