close - delete a descriptor
The close() call deletes a descriptor from the per-process
table. If this is the last reference to the underlying
object will be deactivated. For example, on the last close
of a file the
current seek pointer associated with the file is lost; on
the last close
of a socket(2) associated naming information and queued data
on the last close of a file holding an advisory lock the
lock is released.
However, the semantics of System V and IEEE Std
(``POSIX'') dictate that all fcntl(2) advisory record locks
with a file for a given process are removed when any file
that file is closed by that process (see further flock(2)).
When a process exits, all associated file descriptors are
since there is a limit on active descriptors per processes,
function call is useful when a large quantity of file descriptors are being
When a process forks (see fork(2)), all descriptors for the
process reference the same objects as they did in the parent
fork. If a new process is then to be run using execve(2),
would normally inherit these descriptors. Most of the descriptors can be
rearranged with dup2(2) or deleted with close() before the
attempted, but if some of these descriptors will still be
needed if the
execve fails, it is necessary to arrange for them to be
closed if the execve
succeeds. For this reason, the call ``fcntl(d,
F_SETFD, 1)'' is
provided, which arranges that a descriptor will be closed
after a successful
execve; the call ``fcntl(d, F_SETFD, 0)'' restores
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 errno is
set to indicate
close() will fail if:
[EBADF] D is not an active descriptor.
[EINTR] An interrupt was received.
accept(2), closefrom(2), execve(2), fcntl(2), flock(2),
close() conforms to IEEE Std 1003.1-1988 (``POSIX'').
OpenBSD 3.6 April 19, 1994
[ Back ]