Sidebar

UNIX documentation doesn't say what the actual exit code number delivered by false is, but both Esix and SCO use 255. Since TRUE is the exit code 0 and FALSE is anything else, some programs may not care that the false program exits with 255 instead of 1. However, if a program wants to distinguish between a usage error and a false answer to a question, such as "Is today the Xth weekday of this month?" the program delivers 1 when the answer is FALSE and 255 when there is a usage error.