create IPC identifier from a pathname
() function attempts to create a
unique key suitable for use with the
functions given the
of an existing file and a
The specified path
must refer to 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
. Only the 8 least significant bits of
are used in the key generation; the rest
of the bits are ignored.
() function will return (key_t)-1 if
does not exist or if it cannot be
accessed by the calling process.
() function originated with System V
and is typically used by programs that use the System V IPC routines.
The returned key is computed based on the device and inode of the specified
in combination with the given
. Thus it 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 ancestors were originally created.