ftok(3) - NetBSD Manual Pages

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FTOK(3)                 NetBSD 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 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 ancestor were originally created.

NetBSD 6.0.4                    April 27, 2010                    NetBSD 6.0.4