FTOK(3)                FreeBSD Library Functions Manual                FTOK(3)

NAME
     ftok - create IPC identifier from path name

LIBRARY
     Standard C Library (libc, -lc)

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 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.

RETURN VALUES
     The ftok() function will return -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 originates with System V and is typically used by
     programs that use the System V IPC routines.

AUTHORS
     Thorsten Lockert <tholo@sigmasoft.com>

BUGS
     The returned key is computed based on the device minor number and inode
     of the specified path in combination with the lower 8 bits of the given
     id.  Thus it is quite possible for the routine to return duplicate keys.

FreeBSD 13.1-RELEASE-p6          July 9, 2009          FreeBSD 13.1-RELEASE-p6