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NetBSD 6.1.5 - man page for close (netbsd section 2)

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

NAME
     close -- delete a descriptor

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <unistd.h>

     int
     close(int d);

DESCRIPTION
     The close() system 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; on the last close of a file holding an advisory lock the lock is released (see
     flock(2)).

     When a process exits, all associated descriptors are freed, but since there is a limit on
     active descriptors per processes, the close() system call is useful when a large quantity of
     file descriptors are being handled.

     When a process calls 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 is then to 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() 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 only if the execve() succeeds.  For this rea-
     son, the system call

	   fcntl(d, F_SETFD, 1);

     is provided, which arranges that a descriptor ``d'' will be closed after a successful
     execve(); the system call

	   fcntl(d, F_SETFD, 0);

     restores the default, which is to not close descriptor ``d''.

RETURN VALUES
     Upon successful completion, a value of 0 is returned.  Otherwise, a value of -1 is returned
     and 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), execve(2), fcntl(2), flock(2), open(2), pipe(2), socket(2), socketpair(2)

STANDARDS
     The close() function conforms to ISO/IEC 9945-1:1990 (``POSIX.1'').

BSD					  April 19, 1994				      BSD


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