The typical codes I see used today are: 0 = OK 1 = unexpected error 2 = usage error And then signal codes, which are either 127 or 128 (I forget which) + the

The typical codes I see used today are: 0 = OK 1 = unexpected error 2 = usage error And then signal codes, which are either 127 or 128 (I forget which) + the signal code. Anything beyond that is meaningless since because it's not enforced anywhere it's not reliable to use in scripting less you specifically target that version of the program.