The
ftok() function attempts to create a unique key suitable for use with the
msgget(2),
semget(2) and
shmget(2) functions given the
path of an existing file and a user-selectable
id.
The specified
path must specify an existing file that is accessible to the calling process or the call will fail. Also, note that links to files will return the same key, given the same
id.
Only the 8 least significant bits of
id are used in the key generation; the rest of the bits are ignored.