.nf
.B #include <sys/ipc.h>
.fi
-.PP
+.P
.BI "key_t ftok(const char *" pathname ", int " proj_id );
.SH DESCRIPTION
The
.BR semget (2),
or
.BR shmget (2).
-.PP
+.P
The resulting value is the same for all pathnames that
name the same file, when the same value of
.I proj_id
POSIX.1-2001.
.SH NOTES
On some ancient systems, the prototype was:
-.PP
+.P
.in +4n
.EX
.BI "key_t ftok(char *" pathname ", char " proj_id );
.EE
.in
-.PP
+.P
Today,
.I proj_id
is an
that is why the behavior is said to be undefined when
.I proj_id
is zero.
-.PP
+.P
Of course, no guarantee can be given that the resulting
.I key_t
is unique.