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

     close -- delete a descriptor

     #include <unistd.h>

     close(int fildes);

     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; 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 descrip-tors descriptors
     tors 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 successful execve; the call ``fcntl(d, F_SETFD, 0)'' restores the
     default, which is to not close the descriptor.

     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.

     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.

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

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

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

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