Log your console history using COMMAND_PROMPT

As per the GNU Bash doc

PROMPT_COMMAND
    If set, the value is interpreted as a command to execute before
    the printing of each primary prompt ($PS1).

The contents of this environment variable will be evaluated as a bash command just before your shell displays each prompt.

With this in mind, there’s a ton of cool stuff you could do! You could use it like PS1 to spice up your terminal with additional colors/styles, to display git repo status (a la oh-my-zsh), the exit codes or the timing of the last command run, change the terminal’s title bar… The possibilities are endless!

What I’ve been using it though, is for logging my terminal history on my dev machine.

export PROMPT_COMMAND='if [ "$(id -u)" -ne 0 ]; then echo "$(date "+%Y-%m-%d.%H:%M:%S") $(pwd) $(history 1)" >> ~/.logs/bash-history-$(date "+%Y-%m-%d").log; fi'

This prompt checks that the current user is not root and then appends the current date, working directory and command to a new file for each day, under ~/.logs, where it’s available for grep.

I first found the specific command on this HackerNews post, and don’t know the original author. There’s a heated discussion over there too, regarding the security implications of using a tool like that. I understand the ln -sf /dev/null ~/.bash_history crowd, and that’s what I would advocate for in a production setting, but the command has been really useful for some cases such as:

  • Documenting the setup of a new system
  • Creating a tutorial for someone
  • Writing automation scripts
  • Debugging someone’s workflow
  • Visualizing your .bash_history and finding patterns you should automate
  • Keep notes when I’m toying with a new tool or environment

Here’s how it looks like in practice!

tpaschalis-Lenovo-G50-30:~:% ll ~/.logs 

-rw-rw-r--. 1 tpaschalis tpaschalis     44 May 16 11:07 bash-history-2018-05-16.log
-rw-rw-r--. 1 tpaschalis tpaschalis 110921 May 21 17:26 bash-history-2018-05-21.log
-rw-rw-r--. 1 tpaschalis tpaschalis 101026 May 22 19:07 bash-history-2018-05-22.log
-rw-rw-r--. 1 tpaschalis tpaschalis  99762 May 23 17:46 bash-history-2018-05-23.log
-rw-rw-r--. 1 tpaschalis tpaschalis  37052 May 24 18:08 bash-history-2018-05-24.log
-rw-rw-r--. 1 tpaschalis tpaschalis   3618 May 25 15:38 bash-history-2018-05-25.log
-rw-rw-r--. 1 tpaschalis tpaschalis    222 May 29 10:35 bash-history-2018-05-29.log
-rw-rw-r--. 1 tpaschalis tpaschalis   7275 May 30 18:04 bash-history-2018-05-30.log

tpaschalis-Lenovo-G50-30:~:% more bash-history-2018-05-30.log

...
...
2018-05-15.13:24:02 <some-dir>tpaschalis/foo   435  mkdir ../src/qtest
2018-05-15.13:24:05 <some-dir>tpaschalis/foo   436  touch ../src/qtest/qtest.go
2018-05-15.13:24:07 <some-dir>tpaschalis/foo   437  vi ../src/qtest/qtest.go
2018-05-15.13:24:40 <some-dir>tpaschalis/foo   438  go build qtest
2018-05-15.13:24:43 <some-dir>tpaschalis/foo   439  ./qtest
2018-05-15.13:24:46 <some-dir>tpaschalis/foo   440  go clean qtest
2018-05-15.13:24:50 <some-dir>tpaschalis/foo   441  cd ~
2018-05-15.13:24:51 <some-dir>tpaschalis/foo   442  ll
Written on June 1, 2018