freebsd-dev/lib/libc/gen/ftok.3
Joerg Wunsch d6c9f122c8 Minor corrections. The second parameter is actually of type int
(though only char will be used), and our implementation is not really
worse than the SysV one, so there's no need to claim so in the BUGS
section.
1996-06-03 10:40:39 +00:00

86 lines
2.8 KiB
Groff

.\" Copyright (c) 1994 SigmaSoft, Th. Lockert <tholo@sigmasoft.com>
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.\" $Id: ftok.3,v 1.3 1996/02/12 07:06:23 mpp Exp $
.Dd June 24, 1994
.Os
.Dt ftok 3
.Sh NAME
.Nm ftok
.Nd create IPC identifier from path name
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/ipc.h>
.Ft key_t
.Fn ftok "const char *path" "int id" ;
.Sh DESCRIPTION
.Bf -symbolic
This function is available from the compatibility library, libcompat.
.Ef
The
.Fn ftok
function attempts to create a unique key suitable for use with the
.Xr msgget 3 ,
.Xr semget 2
and
.Xr shmget 2
functions given the
.Fa path
of an existing file and a user-selectable
.Fa id .
.Pp
The specified
.Fa 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
.Fa id .
.Sh RETURN VALUES
The
.Fn ftok
function will return -1 if
.Fa path
does not exist or if it cannot be accessed by the calling process.
.Sh SEE ALSO
.Xr semget 2 ,
.Xr shmget 2 ,
.Xr msgget 3
.Sh HISTORY
The
.Fn ftok
function originates with System V and is typically used by programs
that use the System V IPC routines.
.Sh AUTHOR
.Bl -tag
Thorsten Lockert <tholo@sigmasoft.com>
.El
.Sh BUGS
The returned key is computed based on the device minor number and inode of the
specified
.Fa path
in combination with the lower 8 bits of the given
.Fa id .
Thus is is quite possible for the routine to return duplicate keys.