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close(2)                    BSD System Calls Manual                   close(2)


NAME

     close -- delete a descriptor


SYNOPSIS

     #include <unistd.h>

     int
     close(int fildes);


DESCRIPTION

     The close() call deletes a descriptor from the per-process object refer-
     ence 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 dis-
     carded; on the last close of a file holding an advisory lock the lock is
     released (see further flock(2)).

     When a process exits, all associated file descriptors are freed, but
     since there is a limit on active descriptors per processes, 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 is then to 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 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.  For this reason, the call ``fcntl(d, F_SETFD, 1)'' is
     provided, which arranges that a descriptor will be closed after a suc-
     cessful execve; 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 indi-
     cate the error.


ERRORS

     The close() system call will fail if:

     [EBADF]            fildes is not a valid, active file descriptor.

     [EINTR]            Its execution was interrupted by a signal.

     [EIO]              A previously-uncommitted write(2) encountered an
                        input/output error.


SEE ALSO

     accept(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'').

4th Berkeley Distribution       April 19, 1994       4th Berkeley Distribution

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