Go2Linux | Linux Operating System

Few tips to use with bash command history.

1. Erase duplicates in your history file
If you repeat some times the same command, like I usually do when checking memory with

free -m

You will end up with a lot of those command repeated through your command history, and if you type

history

You may see an output like this:

ls -l
ls -h
free -m
free -m
free -m
free -m
free -m

If you want to get rid of the reapeated commands, set the variable HISTCONTROL to erasedups.

export HISTCONTROL=erasedups

And the output of the command

history

will be:

 990 ls -l
 991 ls -h
 992 free -m
 993 history

2. Ignore Duplicates on bash command history, if they are in a row
If you set HISTCONTROL variable to ignoredups, it will not store repetitive commands in a row, but it will store dups if you do something like this.

ls
df
ls
ls
ls
df
df

You will see the output of

history

Like this:

 1000 ls
 1001 df
 1002 ls
 1003 df
 1004 history

3. Control which commands are stored and which are not
If you want full control over which commands will be stored by history and which will not be stored, set HISTCONTROL to ignorespace

export HISTCONTROL=ignorespace

This will cause that if a command starts with a space, it will not be stored in your bash history, so you can run

ps auxw
 df -h
ps auxw

And the output of

history

Will be:

 1015  ps auxw
 1016  ps auxw
 1017  history

4. Ignore dups and ignore space at the same time
You may set the bash variable HISTCONTROL to ignoreboth, and it will act as with ignoredups and ignorespace.

The first one is the one I prefer, how about you?

I have already written about this here but I think now is better explained.