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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 f -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 .
p 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 l -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.