Question

I was looking for a way to check if a program is installed using Shell Script when I came across this answer which contained this code:

hash foo 2>&- || { echo >&2 "I require foo but it's not installed.  Aborting."; exit 1; }

But that code isn’t very (human) readable, what is the alternative for that syntax?

Answer 1

Readability is very subjective. I particularly think the original is very readable, once you know that || means a short-circuiting OR. So you read the original as “do this, OR this if that one fails”.

The equivalent code without using || is:

if ! hash foo 2>&-
then
    echo >&2 "I require foo but it's not installed.  Aborting."
    exit 1
fi