freebsd-dev/lib/libcompat/SysV/ftok.3
Joerg Wunsch 85c30cfa12 Added function and man page for ftok(3), used in conjunction with
the so-called "System V IPC".

Submitted by:	jbeukema@HK.Super.Net (John Beukema)
Obtained from:  Th. Lockert <tholo@sigmasoft.com>, via NetBSD
1995-05-01 08:53:21 +00:00

89 lines
3.0 KiB
Groff

.\" Copyright (c) 1994 SigmaSoft, Th. Lockert <tholo@sigmasoft.com>
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.\" $Id: ftok.3,v 1.1 1994/06/26 16:24:57 jtc Exp $
.Dd June 24, 1994
.Os
.Dt ftok 3
.Sh NAME
.Nm ftok
.Nd create IPC indentifier from path name
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/ipc.h>
.Ft key_t
.Fn ftok "const char *path" "char 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 2 ,
.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 msgget 2 ,
.Xr semget 2 ,
.Xr shmget 2
.Sh HISTORY
The
.Fn ftok
function originate 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 and inode of the
specified
.Fa path
in combination with the given
.Fa id .
Thus is 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.