FTOK(3) |
FreeBSD Library Functions Manual |
FTOK(3) |
NAME
ftok —
create IPC identifier from path name
LIBRARY
Standard C Library (libc, -lc)
DESCRIPTION
The
ftok() function attempts to create a unique key suitable for use with the
msgget(2),
semget(2) and
shmget(2) functions given the
path of an existing file and a user-selectable
id.
The specified 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 id.
RETURN VALUES
The
ftok() function will return -1 if
path does not exist or if it cannot be accessed by the calling process.
HISTORY
The
ftok() function originates with System V and is typically used by programs that use the System V IPC routines.
AUTHORS
Thorsten Lockert <tholo@sigmasoft.com>
BUGS
The returned key is computed based on the device minor number and inode of the specified
path in combination with the lower 8 bits of the given
id. Thus it is quite possible for the routine to return duplicate keys.