Not the best example. The exit code it produces is exactly how it works: "The exit status is allowed to be zero when sleep is interrupted by the SIGALRM signal

Not the best example. The exit code it produces is exactly how it works: "The exit status is allowed to be zero when sleep is interrupted by the SIGALRM signal because most implementations of this utility rely on the arrival of that signal to notify them that the requested finishing time has been successfully attained." http://pubs.opengroup.org/onlinepubs/9699919799/utilities/sleep.html http://pubs.opengroup.org/onlinepubs/9699919799/utilities/sl...