close(2)                          SDK R4.11                         close(2)


NAME
       close - close an object associated with a file descriptor

SYNOPSIS
       #include <unistd.h>

       int  close (fildes)
       int  fildes;

   where:
       fildes    A valid, active file descriptor

DESCRIPTION
       If fildes is a valid, active descriptor, close breaks the connection
       between the descriptor indicated by fildes and the object to which it
       refers.  If fildes is the last descriptor that refers to an object
       pointer, the object pointer is "closed" by invoking the type-specific
       close operation.

       Thus, the type manager is informed only of the last close operation
       of an object pointer.  These managers (and specifically, the device
       driver close operations) should not expect to be invoked during each
       close system call.

       Upon completion of the close operation, fildes will be inactive.
       Until fildes is reallocated, subsequent operations using fildes will
       result in an EBADF error condition.

       If a STREAMS-based fildes is closed, and the calling process had
       previously registered to receive a SIGPOLL signal for events
       associated with that stream in, the calling process will be
       unregistered for events associated with the stream.  The last close
       for a stream causes the stream associated with fildes to be
       dismantled.  If ONDELAY and ONONBLOCK are clear and there have been
       no signals posted for the stream, and if there are data on the
       module's write queue, close waits up to 15 seconds (for each module
       and driver) for any output to drain before dismantling the stream.
       The time delay can be changed via an ISETCLTIME ioctl.  If ONDELAY
       or ONONBLOCK is set, or if there are any pending signals, close does
       not wait for output to drain, and dismantles the stream immediately.

       If fildes is associated with one end of a pipe, the last close causes
       a hangup to occur on the other end of the pipe.  In addition, if the
       other end of the pipe has been named [see fattach(3C)], the last
       close forces the named end to be detached [see fdetach(3C)].  If the
       named end has no open processes associated with it and becomes
       detached, the stream associated with that end is also dismantled.

       Objects are also subject to implicit close operations via the exit
       and exec operations.  When a process terminates, all active
       descriptors are closed.  When a process performs a successful exec
       operation, all active descriptors with the `close-on-exec' attribute
       are closed.  These implicit close operations are equivalent to an
       explicit close operation.

       On each close of an object, all outstanding locks owned by the
       calling process on the object are released.

ACCESS CONTROL
       None.

RETURN VALUE
       0      The object was successfully closed.

       -1     An error occurred.  errno is set to indicate the error.

DIAGNOSTICS
       Errno may be set to one of the following error codes:

       EBADF     fildes is not a valid, active descriptor.

       EINTR     Close call was interrupted.

       EIO       An i/o error occurred while reading from or writing to the
                 file system.  The fildes is inactived.

SEE ALSO
       accept(2), creat(2), dup(2), exec(2), fcntl(2), open(2), pipe(2),
       signal(2), sigset(2), socket(2), socketpair(2).


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