NAME    [Toc]    [Back]

     ftok - create IPC identifier from a pathname

SYNOPSIS    [Toc]    [Back]

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

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

DESCRIPTION    [Toc]    [Back]

     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 significant
 bits of id are used in the key generation; the rest
of the bits
     are ignored.

RETURN VALUES    [Toc]    [Back]

     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    [Toc]    [Back]

     msgget(2), semget(2), shmget(2)

HISTORY    [Toc]    [Back]

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

AUTHORS    [Toc]    [Back]

     Thorsten Lockert <[email protected]>

BUGS    [Toc]    [Back]

     The returned key is computed based on the device  and  inode
of the specified
  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     3.6                           June      24,      1994