Which two commands disable and then re-enable shell history recording?

• A. set +o history and set -o history
• B. set -o history and set +o history
• C. history -d and history -a
• D. unset HISTFILE and export HISTSIZE

Answer: (A)

History recording is controlled by a shell option that you can toggle with the set builtin. In Bash, you enable the option with set -o history and disable it with set +o history. When history recording is disabled, new commands you run aren’t appended to the in-session history or saved to the history file, and when you re-enable it with set -o history, recording resumes. The other options shown affect existing history entries or how much history is kept (or where it’s saved) but don’t provide a direct on/off switch for recording like these two commands do.