John Chambers writes:

"One of the fun examples among all the copyright fuss is the extreme example of copyright claims made by AT&T some time in the 1980s. It's the /bin/true program. This is a "dummy" library program whose main function is to make it easy to write infinite loops (while true do ...) in shells scripts. The "true" program does nothing; it merely exits with a zero exit status. This can be done with an empty file that's marked executable, and that's what it was in the earliest unix system libraries. Such an empty file will be interpreted as a shell script that does nothing, and since it does this successfully, the shell exits with a zero exit status. But AT&T's lawyers decided that this was worthy of copyright protection." ...