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I often open lots and lots of Terminals [Right now I have 7 open on this workspace] and I often search history with grep to find a command I've just written recently, but I don't want to hunt down the terminal and then scroll up and hunt for it more, etc.. Sometimes my terminals close without 'exit,' and everything I've written is lost [Sometimes I've needed something I'd written in a terminal that was killed].

So is there a way to make it so each terminal writes to .bash_history immediately? or at least once a minute, or something like that?

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    Normally I use control-r to reverse-search in the command history of one bash. More convenient than history | grep unless you need a regex. – Peter Cordes Feb 5 '18 at 11:24
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A simple solution as detailed in Update Bash History in Realtime.

It says to put those commands in the .bashrc config:

shopt -s histappend
PROMPT_COMMAND="history -a;$PROMPT_COMMAND"

The first command changes the .history file mode to append. And the second configures the history -a command to be run at each shell prompt. The -a immediately writes the current/new lines to the history file.

Related for zsh:

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    well this kind of works. I tried some more testing and it seems to only work on the first command. does it work correctly for you? – Matt Oct 16 '11 at 15:03
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Try putting this into your .bashrc: 

shopt -s histappend                      # append to history, don't overwrite it
export PROMPT_COMMAND="history -a; history -c; history -r; $PROMPT_COMMAND"

Credit here: https://stackoverflow.com/questions/103944/real-time-history-export-amongst-bash-terminal-windows/3055135

history -c clears the history of the running session. This will reduce the history counter by the amount of $HISTSIZE. history -r read the contents of $HISTFILE and insert them in to the current running session history. This will raise the history counter by the amount of lines in $HISTFILE.

I think it means that the commands are available almost immediately (you have one terminal, write echo 1, second terminal echo 2, first echo 3 and upon pressing down arrow twice, you should have echo 2 available. You must issue a command in a given terminal to have access to what has been written.

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  • Brilliant! Thanks. Wonder why those options aren't documented in man history... – artfulrobot May 17 '13 at 12:31
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    @artfulrobot: This command is a bash built-in so it is described in man bash. You can also use help history. – pabouk Jul 2 '14 at 9:32
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    I have my zsh configured to work like this: Each shell tracks its OWN history (and before that, the combined history), and every command is appended to combined history. This is different and better than always reloading history for every command for every shell, because I tend to have a different "thread of work" or "job" for each shell terminal. I think that is the difference between this with -r and -c vs just having -a. – Steven Lu Feb 25 '15 at 9:40
  • So what exactly are you using? history -c; history -r? I guess it is better for you, it would be better for me only sometimes, I often use several shells to do one job so I prefer to have the history as much combined as possible. I actually mind that command is written to history only after it finishes. typically, when I start a ssh session to one host and want to open another one while the first is still running, I have to retype it because it has not been written to history yet. – sup Feb 25 '15 at 10:36
  • I think I never stuck around long enough to figure out how to make bash simultaneously track parallel threads of history (per shell instance basis) while immediately writing history to the main history file. Zsh makes it much easier to do so, plus in addition I have defined a zsh function to write out a lot of fancy metadata to an enhanced-history file of my devising. It's become rather indispensible. Anyway, the mechanism there is precmd() and preexec() for zsh get sent args describing the entered command. It then becomes trivial to direct that to files. history -a might suffice – Steven Lu Jun 3 '15 at 4:03
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I have a large history file with about 100000 entries, and the variants that clear the history list and read the whole history file (using history -c and history -r) introduce a noticeable (maybe 0.2 second) delay before the prompt is displayed. Using history -n so that only new lines are read from the history file is faster:

shopt -s histappend
PROMPT_COMMAND='history -a;history -n'

PROMPT_COMMAND does not have to be exported because it is a shell variable.

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  • Brilliant! No more lost history when the connection gets dropped! – Tobia Jan 15 '16 at 14:45
  • This is wonderful. By appending to the file and reading from file, it will share history across multiple terminals. – wisbucky Feb 20 '18 at 19:45
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A note for all other answers (which are basically the same thing):

Setting PROMPT_COMMAND="history -a;$PROMPT_COMMAND" in the .bashrc (or friends) is enough.

Also, you can manually run history -a whenever you want to "snapshot" the history in the current session.

The command shopt -s histappend is not needed because history -a always appends new lines to the file and never overwrites it. Also, at least as of Bash 4, histappend is the default behavior.

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  • On my mac 10.13.6 it seemed it did not work without the shopt -s histappend. Also note I added it to my ~/.bash_profile – ubershmekel Aug 28 '18 at 0:51
  • Likely there's another setting somewhere in your system that disabled histappend, as that is the default behavior. I would look for it, but I don't have access to a Mac. – Guss Aug 28 '18 at 5:13

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