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    The following form allows you to view linux man pages.

    Command:

    ftok

    
    
    
    

    SYNOPSIS

           #include <sys/types.h>
           #include <sys/ipc.h>
    
           key_t ftok(const char *pathname, int proj_id);
    
    
    

    DESCRIPTION

           The ftok() function uses the identity of the file named  by  the  given
           pathname  (which  must  refer  to an existing, accessible file) and the
           least significant 8 bits of proj_id (which must be nonzero) to generate
           a  key_t  type  System  V  IPC  key,  suitable  for use with msgget(2),
           semget(2), or shmget(2).
    
           The resulting value is the same for all pathnames that  name  the  same
           file,  when  the  same  value  of  proj_id is used.  The value returned
           should be different when the (simultaneously  existing)  files  or  the
           project IDs differ.
    
    
    

    RETURN VALUE

           On  success,  the  generated key_t value is returned.  On failure -1 is
           returned, with errno indicating the error as  for  the  stat(2)  system
           call.
    
    
    

    ATTRIBUTES

       Multithreading (see pthreads(7))
           The ftok() function is thread-safe.
    
    
    

    CONFORMING TO

           POSIX.1-2001.
    
    
    

    NOTES

           Under libc4 and libc5 (and under SunOS 4.x) the prototype was:
    
                  key_t ftok(char *pathname, char proj_id);
    
           Today proj_id is an int, but still only 8 bits are used.  Typical usage
           has an ASCII character proj_id, that is why the behavior is said to  be
           undefined when proj_id is zero.
    
           Of course no guarantee can be given that the resulting key_t is unique.
           Typically, a best effort attempt combines the given proj_id  byte,  the
           lower  16  bits of the inode number, and the lower 8 bits of the device
           number into a 32-bit result.  Collisions may easily happen, for example
           between files on /dev/hda1 and files on /dev/sda1.
    
    
    

    SEE ALSO

           msgget(2), semget(2), shmget(2), stat(2), svipc(7)
    
    
    

    GNU 2013-10-07 FTOK(3)

    
    
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