How do I get the command history in a screen session using Bash?

@technosaurus is right. $HISTFILE is written when bash exits, so you could exit one bash session, and start a new one, and the history should have been preserved through the file.

But I think there is a better way to solve your problem. The bash manual includes a description of the history built-in command. It allows you to save this history with history -w [filename] and read the history with history -r [filename]. If you don't provide a filename, it will use $HISTFILE.

So I would propose that you save the history inside your screen session to a specific file (or to your default $HISTFILE if you want). Then read the history file in the other bash session you want to access the history from. This way you don't have to exit the original bash session.

I use the default bash shell on my system and so might not work with other shells.

this is what I have in my ~/.screenrc file so that each new screen window gets its own command history:

Default Screen Windows With Own Command History

To open a set of default screen windows, each with their own command history file, you could add the following to the ~/.screenrc file:

screen -t "window 0" 0 bash -ic 'HISTFILE=~/.bash_history.${WINDOW} bash'
screen -t "window 1" 1 bash -ic 'HISTFILE=~/.bash_history.${WINDOW} bash'
screen -t "window 2" bash -ic 'HISTFILE=~/.bash_history.${WINDOW} bash'

Ensure New Windows Get Their Own Command History

The default screen settings mean that you create a new window using Ctrl+a c or Ctrl+a Ctrl+c. However, with just the above in your ~/.screenrc file, these will use the default ~/.bash_history file. To fix this, we will overwrite the key bindings for creating new windows. Add this to your ~/.screenrc file:

bind c screen bash -ic 'HISTFILE=~/.bash_history.${WINDOW} bash'
bind ^C screen bash -ic 'HISTFILE=~/.bash_history.${WINDOW} bash'

Now whenever you create a new screen window, it's actually launching a bash shell, setting the HISTFILE environmental variable to something that includes the current screen window's number ($WINDOW).

Command history files will be shared between screen sessions with the same window numbers.

Write Commands to $HISTFILE on Execution

As is normal bash behavior, the history is only written to the $HISTFILE file by upon exiting the shell/screen window. However, if you want commands to be written to the history files after the command is executed, and thus available immediately to other screen sessions with the same window number, you could add something like this to your ~/.bashrc file:

export PROMPT_COMMAND="history -a; history -c; history -r; ${PROMPT_COMMAND}"

screen doesn't maintain a history of the commands you type. Your shell may or may not keep a history. Since you appear to use bash, you can use the history command.

screen does appear to have a crude approximation of a history search (it merely searches the scrollback buffer for a command line. See the screen man page under the "history" command (bound to C-a { by default).