July 29, 2023

Copy a command from the shell history to a file

To copy a command from the shell history to a file run:

$ echo [event designator]:q  > file.txt

An event designator is a reference to a command line entry in the history of the shell¹. For example if you want to run the last command again, run $ !-1 or the synonym $ !!.

The q that comes after the event designator is a modifier which tells bash to enclose the substitution (e.g. !!) in single quotes (’) to prevent further expansion by the shell.². Modifiers are always preceded by a colon, i.e. :.

The > redirection operator tells the shell to redirect the output of a command - here echo - to a file which will be created if it does not exist.

So, with all of this in mind, we can for example run:

$ echo !!:q  > file.txt

which will copy the last command in the shell history to a file. Or

$ echo !-2:q > file.txt

which will copy the penultimate command in the shell history to a file.

If you can’t count how far back in the shell history the command you want to copy to a file is, run:

$ history | tail

then find our the number (n) of the command you want to copy to a file, then run:

$ echo !n:q > file.txt