exec fish trick

Often when I’m editing my fish config, I want to test out my new config. I can always run fish to run a new fish shell, which mostly works, but when I want to exit (possibly quite some time later), I go back to the original shell (without the latest config).

>*)))>< <*)))>< "how is your posture?"
$ fish
>*)))>< <*)))>< "how is your posture?"
$  # (here I hit control-d to exit)
$  # <- but I'm back to the prompt of the original shell

(yes, my prompt asks me to think about my posture. Yes, I have completely tuned it out.)

It’s a minor annoyance but luckily there’s a way to fix this behaviour: by running exec fish instead of fish. This will use exec to replace the original fish process with the new one.

>*)))>< <*)))>< "how is your posture?"
$ exec fish
>*)))>< <*)))>< "how is your posture?"
$
# at this point, sending control-d will close the shell.

For ease of running this, I have an abbr to expand ef to exec fish.

Now when I want to test out my new fish config, I just hit ef<enter> and I’m in the new shell!