ftok(3C)                                                           ftok(3C)




 NAME
      ftok() - create interprocess communication identifier

 SYNOPSIS
      #include <sys/ipc.h>

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

 DESCRIPTION
      All interprocess communication facilities require the user to supply a
      key to be used by the msgget(), semget(), and shmget() system calls to
      obtain interprocess communication identifiers (see msgget(2),
      semget(2), and shmget(2)).

      ftok() returns a key based on path and id that is usable in subsequent
      msgget(), semget(), and shmget() system calls.

      The parameters for the ftok() function are as follows:

           path                must be the path name of an existing file
                               that is accessible to the process.

           id                  is a character that uniquely identifies a
                               project.  Note that ftok() returns the same
                               key for linked files when called with the
                               same id and that it returns different keys
                               when called with the same file name but
                               different ids.

 RETURN VALUE
      ftok() returns (key_t) - 1 if path does not exist or if it is not
      accessible to the process.

 EXAMPLES
      The following call to ftok() returns a key associated with the file
      myfile and id A:

           key_t mykey;
                 mykey = ftok ("myfile", 'A');

 WARNINGS
      If the file whose path is passed to ftok() is removed when keys still
      refer to the file, future calls to ftok() with the same path and id
      will return an error.  If the same file is recreated, ftok() is likely
      to return a different key than it did the original time it was called.

 SEE ALSO
      intro(2), msgget(2), semget(2), shmget(2).






 Hewlett-Packard Company            - 1 -    HP-UX Release 10.20:  July 1996