How to sync terminal session command history in bash?

Question

I've tried to search in ~/.bash_history for my recent commands while in a terminal session but they just weren't there. I guess this is because I have multiple terminal sessions open.

Is there a way that I can sync (ie. sync-push or sync-write-out) the current terminal session's command history into the bash_history file (without closing the session and losing that environment)?

(It would be remotely similar in idea to how the sync command stores the file-system modifications on some systems.)

I imagine I could set up bash to preserve multiple session history but the ability to push the current history buffer would still be useful in scenarios when you are working on a new machine and you accidentally forgot to set up bash the way you may would have wanted.

Answer 1

Add this line to .bashrc:

export PROMPT_COMMAND="history -a; history -n"

Open new terminal and check.

Explanation

• history -a appends new history lines to history file.
• history -n tells bash to read lines that is not read from history file to current history list of session.
• PROMPT_COMMAND: contents of this variable is run as regular command before bash show prompt. So every time after you execute a command, history -a; history -n is executed, and your bash history is synced.

Answer 2

While I like being able to share history between terminals, especially new terminals. I would not want to share each and every command as it happens, as one window is often doing a specific task, separate form other windows. I would have them merge on shell exit, or when I request.

For a long time I looked for a way to merge bash history (with timestamps), and nothing seemed acceptable to me...

Finally I just 'bit the bullet' and DIY'ed a script to merge, the on-disk ".bash_history" with the in-memory shell 'history'. Preserving timestamp ordering, and command order within those timestamps.

Now when I source this (you could make it a alias or a function as you like), I use the alias 'hc'. My current shell session is merged between disk and memory, so history is updated from other previous merges, WHEN I WANT (or on logout from that shell via ".bash_logout").

Optionally you can remove unique commands (even if multi-line), and/or removing (cleaning out) simple and/or sensitive commands, according to defined perl RE's. Adjust to suit!

This is the result... https://antofthy.gitlab.io/software/history_merge.bash.txt

Enjoy.