key_t
ftok(
const char *path
, int id
)
)
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.
)
function will return ((key_t)-1) if
path
does not exist or if it cannot be accessed by the calling process.
)
function originated with System V and is typically used by programs
that use the System V IPC routines.
path
in combination with the given
id
.
Thus it is quite possible for the routine to return duplicate keys
given that those fields are not 8- and 16-bit quantities like they
were on System V based systems where this library routine's ancestor
were originally created.