Hi,

We recently added set -e in our CI script. We had something like:

#!/usr/bin/env bash

set -e

PACKAGES="cmake pkg-config fftw libogg libvorbis libsndfile libsamplerate jack sdl stk portaudio node fltk"

brew install $PACKAGES

With set -e, it failed because brew returned a non-zero exit code for already installed packages. So we had to do:

#!/usr/bin/env bash

set -e

PACKAGES="cmake pkg-config fftw libogg libvorbis libsndfile libsamplerate jack sdl stk portaudio node fltk"

# removing already installed packages from the list
for p in $(brew list); do
	PACKAGES=${PACKAGES//$p/}
done;

brew install $PACKAGES

But it's ugly and buggy. E.g. we used to have pkgconfig, so the string replacement didn't work. It now works cause we replaced it by pkg-config as it is in brew list output.

So, I'd like an option like: brew install --if-not-installed $PACKAGES which won't return a non-zero exit code if $PACKAGES contains already installed packages.

What do you think about it ? I wish i could implement it myself, but I don't know ruby and I'm not even a brew user so probably not the best option. I'm sure someone knowing ruby and brew could do this really quickly as it doesn't seem hard.