FTOK(3)                   OpenBSD Programmer's Manual                  FTOK(3)

NAME
     ftok - create IPC identifier from a pathname



SYNOPSIS
     #include <sys/types.h>
     #include <sys/ipc.h>

     key_t
     ftok(const char *path, int id);

DESCRIPTION
     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 refer to 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 sig-
     nificant bits of id are used in the key generation; the rest of the bits
     are ignored.

RETURN VALUES
     The ftok() function will return (key_t)-1 if path does not exist or if it
     cannot be accessed by the calling process.

SEE ALSO
     msgget(2),  semget(2),  shmget(2)

HISTORY
     The ftok() function originated with System V and is typically used by
     programs that use the System V IPC routines.

AUTHOR
     Thorsten Lockert <tholo@sigmasoft.com>

BUGS
     The returned key is computed based on the device and inode of the speci-
     fied 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 ancestors were originally created.

OpenBSD 2.6                      June 24, 1994                               1