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CLOSE(2)                    BSD System Calls Manual                   CLOSE(2)

NAME
     close -- delete a descriptor

SYNOPSIS
     #include <&lt;unistd.h>&gt;

     int
     close(int d);

DESCRIPTION
     The close() call deletes a descriptor d from the per-process object ref-
     erence 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 descrip-
     tors 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 descrip-
     tor 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, the value 0 is returned; otherwise the
     value -1 is returned and the global 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.

     [EIO]              An I/O error occurred while writing to the file sys-
                        tem.

SEE ALSO
     accept(2), closefrom(2), dup2(2), execve(2), fcntl(2), flock(2), open(2),
     pipe(2), socket(2), socketpair(2)

STANDARDS
     close() conforms to IEEE Std 1003.1-2008 (``POSIX.1'').

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

BSD                             March 30, 2017                             BSD