bashhistory

Bashhistory is the command history feature of the Bash shell. It records commands entered during interactive sessions, enabling users to recall, edit, and reuse previous commands. History is maintained in memory for a session and can be saved to disk for later use.

Location and size: By default, history is written to ~/.bash_history. The number of commands kept in memory is controlled by HISTSIZE, while HISTFILESIZE limits the number of lines saved to the history file. Bash can append to the history file rather than overwrite it (histappend), and timestamps can be added via HISTTIMEFORMAT.

Configuration: The behavior is controlled by environment variables such as HISTCONTROL (for ignoring duplicates and lines starting with spaces) and HISTIGNORE. The history builtin can be used to view entries, and the fc builtin can list, edit, and re-execute commands. Command substitutions and expansions use !, and PROMPT_COMMAND can be used to synchronize history after each command.

Security and privacy: Because the history may include sensitive data, access should be restricted (chmod 600 ~/.bash_history). Consider starting sensitive commands with a space if ignorespace or ignoreboth is in effect, and clearing history with history -c or unset HISTFILE. In multi-session environments, enable histappend and use history -a to append after each command to reduce loss from concurrent sessions.