# Keep multiple bash histories

## 2015-08-18

My use of the command line changed dramatically once I discovered guake and screen. Guake is a GUI interface that lets you open and run many terminals easily. Screen provides a similar service from the command line itself within a single terminal, which makes it extremely useful for working with remote servers.

But, when you have all of those terminals going at once, bash's regular way of tracking what commands you've used (by storing everything to ~/.bash_history) seems to break down. This is bad for reconstructing what you've done at some later point in time. Fortunately, we can configure bash to do better. To do so, add these lines to your ~/.bashrc file:

export HISTTIMEFORMAT="%s "
export HISTFILE=~/.history/history_date +"%Y-%m-%dT%H:%M:%SZ"_$$export HISTFILESIZE= export HISTSIZE=500  • HISTTIMEFORMAT appends a unix epoch timestamp before each command in the history files, which is useful for reconstructing what you've done. • HISTSIZE changes the maximum number of commands available through the history command. • HISTFILESIZE changes the maximum size of your HISTFILE. If you don't set it, the HISTFILE won't be truncated at all. • HISTFILE sets the name of the history file. We give each file a name including the current ISO8601 time date +"%Y-%m-%dT%H:%M:%SZ" and the process id of the shell $$ (in case two shells are launched in the same second).

A similar strategy for working this is to add

shopt -s histappend


to ~/.bashrc. This tells bash to append to the history file rather than overwriting it when the shell exits. The disadvantage to this is that then all of history is stored in one enormous file.