The history command is very useful when you frequently work at the terminal and you want to invoke a command given in the past.But there are several options that are not so common or poorly understood, in this article we’ll see some of them in bash and zsh.
Basic usage
Show last commands in history.
Apply to bash and zsh
history
Output:
312 sudo -i 315 mkdir joom 316 cd joom 317 unzip ~/Downloads/Joomla_1.5.21_to_1.5.22-Stable-Patch_Package_ita.zip 318 cd /tmp 319 ls 320 ls -alrt 321 mkdir image 322 cd image 323 unzip ../ed ambientale.zip.html 324 cd ed ambientale
Task 1 Display Date And Time in history commands
An useful and easy thing is that to add to every single command you give the date and time they were given, this can be useful to understand when something is happened in our system.
Bash Add to your ~/.bash_profile
export HISTTIMEFORMAT='%Y-%m-%d %H:%M:%S '
Zsh Add to your ~/.zshrc
HISTFILE=~/.zsh_history
HISTSIZE=9999
SAVEHIST=9999
setopt extendedhistory
Task 2 Search for a string in your history
You know a part of the command and you want to search in your history.
Apply to bash and zsh
In the terminal, hold down Ctrl and press R to invoke “reverse-i-search. (bash)” Type a letter – like s – and you’ll get a match for the most recent command in your history that starts with s. Keep typing to narrow your match. When you reach the desired command, press Enter to execute the suggested command.
Task 3 execute the last command given as root
You gave a long command, and after that you have realized that it was necessary to be root
Apply to bash and zsh
sudo !!
You will be asked for your password, then the shell will run the last command, this is because !! is interpreted as the last command given.
Task 4 Check command history for “string” but avoid running it
Print the first occurrence of string found in the history, but don’t run it.
!string:p
!string will search your command history and execute the first command that matches ‘whatever’. If you don’t feel safe doing this put :p on the end to print without executing. Recommended when running as superuser.
Task 5 delete a line of the history
Useful when you do an error and type a password as normal command.
Apply to bash
history -d < history number >
Delete the entry with the < history number > from the command line history
Task 6 List of commands you use most often
useful in deciding what new alias to do or for the statistics.
Apply to bash and zsh
history | awk '{print $2}' | sort | uniq -c | sort -rn | head
Output:
53 aptitude
47 ip
40 ls
33 apt-get
26 cd
25 xrandr
24 man
17 history
15 rmmod
15 apt-cache
Check Also the Bash history cheatsheet
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