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

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FTOK(3) 			   BSD Library Functions Manual 			  FTOK(3)

     ftok -- create IPC identifier from path name

     Standard C Library (libc, -lc)

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

     ftok(const char *path, int id);

     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

     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.

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

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

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

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

     Thorsten Lockert <tholo@sigmasoft.com>

     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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