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NetBSD 6.1.5 - man page for ftok (netbsd section 3)

FTOK(3) 			   BSD 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.

     Only the 8 least significant 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)

STANDARDS
     The ftok() function conforms to IEEE Std 1003.1 (``POSIX.1'').

HISTORY
     The ftok() function originated 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 and inode of the specified path in combina-
     tion 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.

BSD					  April 27, 2010				      BSD


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