Many programming languages will exit 1 for unexpected exceptions at runtime (or programmer error). Eg, this Ruby program will exit 1: $ ruby -e 'raise Stan

Many programming languages will exit 1 for unexpected exceptions at runtime (or programmer error). Eg, this Ruby program will exit 1: $ ruby -e 'raise StandardError.new "oops"' Traceback (most recent call last): -e:1:in `<main>': oops (StandardError) $ echo $? 1 And so will this one: $ ruby -e 'invalid method call' Traceback (most recent call last): -e:1:in `<main>': undefined local variable or method `call' for main:Object (NameError) Did you mean? caller So, it's nice to distinguish between a possibly unexpected exceptional exit (1), and an "error case detected by the programmer", which is what I use exit (2) for.