Bash programming/Bash History

Bash Command history feature allows to recall, edit and rerun previous commands. Also allows commands to be saved using the history -a command.

Variables to control Bash History:

• HISTFILE: The default value is ~/.bash_history
• HISTFILESIZE
• HISTTIMEFORMAT

Usage

• Basic example:

export PROMPT_COMMAND='history -a'

• Advanced examples:
  • echo 'export HISTTIMEFORMAT="%d/%m/%y %T "' >> ~/.bash_profile
  • 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'
  • Sending history to syslog (needs recompiling source): Bash also support syslog capabilities at compiling time but it is not enabled by default in most distributions: https://github.com/bminor/bash/blob/d233b485e83c3a784b803fb894280773f16f2deb/config-top.h

Logging

If you wish to keep a record of your commands, you can configure bash to write a log file of entered commands.

Logging can be set up automatically by running these commands:

echo "local6.debug /var/log/commands.log" |sudo tee -a /etc/rsyslog.d/bash.conf >>/dev/null
echo "export PROMPT_COMMAND='"RETRN_VAL=\$?\;logger -p local6.debug "\"\$(whoami) \$(tty) \$(pwd) [\$\$]: \$(history 1 | sed \"s/^[ ]*[0-9]\\+[ ]*//\" ) [\$RETRN_VAL]"\"\' >>~/.bashrc
systemctl restart rsyslog

• The first line creates a configuration file for rsyslog contaning the log file destination /var/log/commands.log, which may be changed as desired. The >>/dev/null part prevents redundantly outputting the text into the command line window.
• The second adds the log line definition export PROMPT_COMMAND='RETRN_VAL=$?;logger -p local6.debug "$(whoami) $(tty) $(pwd) [$$]: $(history 1 | sed "s/^[ ]*[0-9]\+[ ]*//" ) [$RETRN_VAL]"' to ~/.bashrc, which runs upon each start of the terminal.
• The third line restarts the rsyslog service to make the changes effective.

Activities

1. Install https://github.com/ohmybash bash customization

See also

• acct