ftok man page on SuSE

Printed from http://www.polarhome.com/service/man/?qf=ftok&af=0&tf=2&of=SuSE

FTOK(3)			   Linux Programmer's Manual		       FTOK(3)

NAME
       ftok  -	convert	 a pathname and a project identifier to a System V IPC
       key

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 non-zero) to	gener‐
       ate  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.

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)

COLOPHON
       This  page  is  part of release 3.15 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

GNU				  2001-11-28			       FTOK(3)
[top]

List of man pages available for SuSE

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net