Bash history

The last commands executed on the shell are saved in the Bash history. If you want to execute a command later again, you can use the arrow keys, [Ctrl]-[r] (reverse-i-search) or the "!" sign to access previously executed commands (including all options and parameters).

history command

The history command shows all recorded commands. As an optional parameter, the number of commands displayed can be limited to the last commands called (in this example, the last 15 commands executed):

werner@lmde6:~$ history 15
 1791  pwd
 1792  cd Downloads/
 1793  ls -lah
 1794  free -m
 1795  cd
 1796  history 
 1797  vi Downloads/testfile.txt 
 1798  uptime
 1799  history | tail
 1800  man history 
 1801  man 1 history
 1802  man bash
 1803  history --help
 1804  history 10
 1805  history 15
werner@lmde6:~$ 

Executing commands again

If you want to call up a command again, Bash history offers several ways to do this.

Arrow keys

The [↑] and [↓] arrow keys can be used to easily search through the last commands called up and execute them again by pressing the [Enter] key.

[Strg]-[r]

If you want to re-execute a longer command quickly and efficiently, [Ctrl]-[r] (reverse-i-search) is very suitable.

After pressing [Ctrl]-[r], the following input prompt appears on the console:

(reverse-i-search)`':

If you now type individual characters ("pst" in this example), the bash history is automatically searched for commands that contain this character string. If the correct command is found ("pstree -C age -h -t" in this example), the command can be called up again without further input by pressing the [Enter] key:

(reverse-i-search)`pst': pstree -C age -h -t

!

If you have previously displayed the list of executed commands using the history command and you want to call up a specific command again (the 1793rd command in this example), you can do this simply by entering "!" followed by the command number:

werner@lmde6:~$ !1793
ls -lah
total 240K
drwx------ 26 werner werner 4,0K Feb 27 12:58 .
drwxr-xr-x  3 root   root   4,0K Nov 22 08:21 ..
-rw-------  1 werner werner  34K Feb 27 10:57 .bash_history
-rw-r--r--  1 werner werner  220 Nov 22 08:21 .bash_logout
-rw-r--r--  1 werner werner 3,5K Feb 27 11:36 .bashrc
drwxr-xr-x 26 werner werner 4,0K Jän 30 12:57 .cache
[...]

Change bash history size

The size of the bash history is limited by default:

werner@lmde6:~$ grep HIST .bashrc 
HISTCONTROL=ignoreboth
# for setting history length see HISTSIZE and HISTFILESIZE in bash(1)
HISTSIZE=1000
HISTFILESIZE=2000

To remove the limit, set the variables HISTSIZE and HISTFILESIZE to "-1" in ~/.bashrc using an editor such as nano or vim:

werner@lmde6:~$ vi .bashrc 
werner@lmde6:~$ grep HIST .bashrc 
HISTCONTROL=ignoreboth
# for setting history length see HISTSIZE and HISTFILESIZE in bash(1)
HISTSIZE=-1
HISTFILESIZE=-1

By executing the bashrc script, the new settings will take effect in the current shell window:

source ~/.bashrc

Author: Werner Fischer Werner Fischer, working in the Knowledge Transfer team at Thomas-Krenn, completed his studies of Computer and Media Security at FH Hagenberg in Austria. He is a regular speaker at many conferences like LinuxTag, OSMC, OSDC, LinuxCon, and author for various IT magazines. In his spare time he enjoys playing the piano and training for a good result at the annual Linz marathon relay.