I don't think dws missed anything, but the Anonymous Monk forgot to mention: what is being fed to the parent's stdin? If this is run from the command line without (redirection from) a file name, and without a preceding pipeline process, it will run endlessly until the person who entered the command has the presence of mind to type in data, then type in "^D" (on unix) or "^Z" (on dos/windows) to signal the end of stdin.