close

CLOSE(2)                  OpenBSD Programmer's Manual                 CLOSE(2)

NAME

     close - delete a descriptor

SYNOPSIS

     #include <unistd.h>

     int
     close(int d);

DESCRIPTION

     The close() call deletes a descriptor from the per-process object
     reference table.  If this is the last reference to the underlying object,
     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(2), 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 flock(2)).  However, the semantics of System V
     and IEEE Std 1003.1-1988 (``POSIX.1'') dictate that all fcntl(2) advisory
     record locks associated with a file for a given process are removed when
     any 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 close()
     function call is useful when a large quantity of file descriptors are
     being handled.

     When a process forks (see fork(2)), 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 execve(2), the
     process would normally inherit these descriptors.  Most of the
     descriptors can be rearranged with dup2(2) or deleted with close() before
     the execve(2) is attempted, but since some of these descriptors may still
     be needed should the execve(2) fail, it is necessary to arrange for them
     to be closed when the execve(2) succeeds.  For this reason, the call
     fcntl(d, F_SETFD, FD_CLOEXEC) is provided, which arranges that a
     descriptor will be closed after a successful execve(2); the call fcntl(d,
     F_SETFD, 0) restores the default, which is to not close the descriptor.

RETURN VALUES

     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 the error.

ERRORS

     close() will fail if:

     [EBADF]            d is not an active descriptor.

     [EINTR]            An interrupt was received.

SEE ALSO

     accept(2), closefrom(2), execve(2), fcntl(2), flock(2), open(2), pipe(2),
     socket(2), socketpair(2)

STANDARDS

     close() conforms to IEEE Std 1003.1-1988 (``POSIX.1'').

HISTORY

     The close() system call first appeared in Version 1 AT&T UNIX.

OpenBSD 5.1                    November 6, 2011                    OpenBSD 5.1