call deletes a descriptor from the per-process object
If this is the last reference to the underlying object, the
object will be deactivated.
For example, on the last close of a file,
pointer associated with the file is lost;
on the last close of a
associated naming information and queued data are discarded;
and on the last close of a file holding an advisory lock,
the lock is released (see
However, the semantics of System V and
dictate that all
advisory record locks associated with a file for a given process
are removed when
file descriptor for that file is closed by that process.
When a process exits,
all associated file descriptors are freed, but since there is
a limit on active descriptors per process, the
is useful when a large quantity of file descriptors are being handled.
When a process forks (see
all descriptors for the new child process reference the same
objects as they did in the parent before the fork.
If a new process image is to then be run using
the process would normally inherit these descriptors.
Most of the descriptors can be rearranged with
or deleted with
is attempted, but since some of these descriptors may still
be needed should the
fail, it is necessary to arrange for them
to be closed when the
For this reason, the call
fcntl(d F_SETFD FD_CLOEXEC);
which arranges that a descriptor will be closed after a successful
fcntl(d F_SETFD 0);
restores the default,
which is to not close the descriptor.
Upon successful completion, a value of 0 is returned.
Otherwise, a value of \-1 is returned and the global integer variable
is set to indicate the error.