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CLOSE(2V)                                                            CLOSE(2V)

       close - delete a descriptor

       int close (fd)
       int fd;

       close()  deletes a descriptor from the per-process object reference ta-
       ble.  If fd is the last reference to the underlying  object,  then  the
       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 (see socket(2)), associated naming information and
       queued data are discarded.  On the last close  of  a  file  holding  an
       advisory lock applied by flock(2), the lock is released.  (Record locks
       applied to the file by lockf(3), however, are released on any  call  to
       close()  regardless of whether fd is the last reference to the underly-
       ing object.)

       close() does not unmap any mapped pages of the object referred to by fd
       (see mmap(), munmap(2)).

       A  close  of all of a process's descriptors is automatic on exit(), but
       since there is a limit on the number of active descriptors per process,
       close() is necessary for programs that deal with many descriptors.

       When  a process forks (see fork(2v)), all descriptors for the new child
       process reference the same objects as they did in the parent before the
       fork.  If a new process is then to be run using execve(2V), the process
       would normally inherit these descriptors.  Most of the descriptors  can
       be  rearranged with dup(2V) or deleted with close() before the execve()
       is 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.  The fcntl(2V) operation F_SETFD can be used  to
       arrange  that  a descriptor will be closed after a successful execve(),
       or to restore the default behavior, which is to not close the  descrip-

       If a STREAMS (see intro(2)) file is closed, and the calling process had
       previously registered to receive a SIGPOLL signal (see  sigvec(2))  for
       events  associated  with  that  file (see I_SETSIG in streamio(4)), the
       calling process will be unregistered for  events  associated  with  the
       file.   The  last close() for a stream causes that stream to be disman-
       tled.  If the descriptor is not marked for no-delay mode and there have
       been  no signals posted for the stream, close() waits up to 15 seconds,
       for each module and driver, for any output to drain before  dismantling
       the  stream.  If the descriptor is marked for no-delay mode or if there
       are any pending signals, close() does not wait for output to drain, and
       dismantles the stream immediately.

       close() returns:

       0      on success.

       -1     on failure and sets errno to indicate the error.

       EBADF          fd is not an active descriptor.

       EINTR          A signal was caught before the close completed.

       accept(2),   dup(2V),   execve(2V),   fcntl(2V),   flock(2),  intro(2),
       open(2V), pipe(2V), sigvec(2), socket(2), socketpair(2), streamio(4)

                                21 January 1990                      CLOSE(2V)