Display time with history command

When you are using the history command on a UNIX system, by default, you're only getting an action list with numbers but no date and/or time to complete this history. For that, you have to define an environment variable HISTTIMEFORMAT that will describe how you want to display the timestamp for each command.

To display the timestamp temporarily (during session), you can just export the variable before sending the command:

$export HISTTIMEFORMAT="%d/%m/%y %T " ; history

You will get:

2021 01/04/17 11:54:04 systemctl list-units
2022 01/04/17 11:54:10 systemctl list-unit-files
2023 01/04/17 11:54:15 cd /etc/
2024 01/04/17 11:54:33 ls -lsta
2025 01/04/17 11:54:33 ps auxw | grep apache
2026 01/04/17 11:54:35 date
2027 01/04/17 11:54:35 cd ..
2028 01/04/17 11:54:37 cd /var/log
2029 01/04/17 11:54:37 ls -lsta
2030 01/04/17 11:54:40 cat messages
2031 01/04/17 15:48:44 history
2032 01/04/17 15:48:51 export HISTTIMEFORMAT="%d/%m/%y %T " ; history

If you want to keep that display for a future session, you have to add this variable to your bash profile and reload your profile:

$echo 'export HISTTIMEFORMAT="%d/%m/%y %T "' >> ~/.bash_profile
$source ~/.bash_profile