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.