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OpenSolaris 2009.06 - man page for close (opensolaris section 2)

close(2)				   System Calls 				 close(2)

NAME
       close - close a file descriptor

SYNOPSIS
       #include <unistd.h>

       int close(int fildes);

DESCRIPTION
       The  close()  function  deallocates the file descriptor indicated by fildes. To deallocate
       means to make the file descriptor available for return by subsequent calls to  open(2)  or
       other  functions that allocate file descriptors. All outstanding record locks owned by the
       process on the file associated  with  the  file	descriptor  will  be  removed  (that  is,
       unlocked).

       If  close()  is interrupted by a signal that is to be caught, it will return -1 with errno
       set to EINTR and the state of fildes is unspecified. If an I/O error occurred while  read-
       ing  from  or writing to the file system during close(), it returns -1, sets errno to EIO,
       and the state of fildes is unspecified.

       When all file descriptors associated with a pipe or FIFO special file are closed, any data
       remaining in the pipe or FIFO will be discarded.

       When  all  file	descriptors associated with an open file description have been closed the
       open file description will be freed.

       If the link count of the file is 0, when all file descriptors associated with the file are
       closed, the space occupied by the file will be freed and the file will no longer be acces-
       sible.

       If a STREAMS-based (see Intro(2)) fildes is closed and the calling process was  previously
       registered  to  receive	a SIGPOLL signal (see signal(3C)) for events associated with that
       STREAM (see I_SETSIG in streamio(7I)), 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 O_NONBLOCK and O_NDELAY are not set and there  have  been
       no  signals  posted  for  the  STREAM,  and  if there is 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 I_SETCLTIME ioctl(2) request
       (see streamio(7I)). If the O_NONBLOCK or O_NDELAY flag 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 by
       fattach(3C),  then the last close() forces the named end to be detached by fdetach(3C). If
       the named end has no open file descriptors associated  with  it	and  gets  detached,  the
       STREAM associated with that end is also dismantled.

       If  fildes  refers to the master side of a pseudo-terminal, a SIGHUP signal is sent to the
       session leader, if any, for which the slave side of the pseudo-terminal is the controlling
       terminal. It is unspecified whether closing the master side of the pseudo-terminal flushes
       all queued input and output.

       If fildes refers to the slave side of a STREAMS-based pseudo-terminal, a zero-length  mes-
       sage may be sent to the master.

       When  there  is	an  outstanding cancelable asynchronous I/O operation against fildes when
       close() is called, that I/O operation is canceled. An I/O operation that is  not  canceled
       completes  as  if  the close() operation had not yet occurred. All operations that are not
       canceled will complete as if the close() blocked until the operations completed.

       If a shared memory object or a memory mapped file remains referenced  at  the  last  close
       (that  is,  a  process  has it mapped), then the entire contents of the memory object will
       persist until the memory object becomes unreferenced. If this  is  the  last  close  of	a
       shared  memory  object  or a memory mapped file and the close results in the memory object
       becoming unreferenced, and the memory object has been unlinked,	then  the  memory  object
       will be removed.

       If fildes refers to a socket, close() causes the socket to be destroyed.  If the socket is
       connection-mode, and the SO_LINGER option is set for the socket with non-zero linger time,
       and  the  socket  has  untransmitted  data,  then close() will block for up to the current
       linger interval until all data is transmitted.

RETURN VALUES
       Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno is  set  to
       indicate the error.

ERRORS
       The close() function will fail if:

       EBADF	  The fildes argument is not a valid file descriptor.

       EINTR	  The close() function was interrupted by a signal.

       ENOLINK	  The  fildes  argument is on a remote machine and the link to that machine is no
		  longer active.

       ENOSPC	  There was no free space remaining on the device containing the file.

       The close() function may fail if:

       EIO    An I/O error occurred while reading from or writing to the file system.

EXAMPLES
       Example 1 Reassign a file descriptor.

       The following example closes the file descriptor associated with standard output  for  the
       current process, re-assigns standard output to a new file descriptor, and closes the orig-
       inal file descriptor to clean up. This example assumes that the file descriptor	0,  which
       is the descriptor for standard input, is not closed.

	 #include <unistd.h>
	 ...
	 int pfd;
	 ...
	 close(1);
	 dup(pfd);
	 close(pfd);
	 ...

       Incidentally, this is exactly what could be achieved using:

	 dup2(pfd, 1);
	 close(pfd);

       Example 2 Close a file descriptor.

       In the following example, close() is used to close a file descriptor after an unsuccessful
       attempt is made to associate that file descriptor with a stream.

	 #include <stdio.h>
	 #include <unistd.h>
	 #include <stdlib.h>

	 #define LOCKFILE "/etc/ptmp"
	 ...
	 int pfd;
	 FILE *fpfd;
	 ...
	 if ((fpfd = fdopen (pfd, "w")) == NULL) {
		 close(pfd);
		 unlink(LOCKFILE);
		 exit(1);
	 }
	 ...

USAGE
       An application that used the stdio function fopen(3C) to open a file should use the corre-
       sponding fclose(3C) function rather than close().

ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Async-Signal-Safe 	   |
       +-----------------------------+-----------------------------+

SEE ALSO
       Intro(2),  creat(2),  dup(2),  exec(2),	fcntl(2), ioctl(2), open(2) pipe(2), fattach(3C),
       fclose(3C), fdetach(3C),  fopen(3C),  signal(3C),  signal.h(3HEAD),  attributes(5),  stan-
       dards(5), streamio(7I)

SunOS 5.11				   18 Oct 2005					 close(2)


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