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CLOSE(2)		   Linux Programmer's Manual		      CLOSE(2)

       close - close a file descriptor

       #include <unistd.h>

       int close(int fd);

       close()	closes	a  file descriptor, so that it no longer refers to any
       file and may be reused.	Any record locks (see fcntl(2))	 held  on  the
       file  it	 was  associated  with,	 and owned by the process, are removed
       (regardless of the file descriptor that was used to obtain the lock).

       If fd is the last file descriptor referring to the underlying open file
       description  (see open(2)), the resources associated with the open file
       description are freed; if the descriptor was the last  reference	 to  a
       file which has been removed using unlink(2), the file is deleted.

       close()	returns	 zero on success.  On error, -1 is returned, and errno
       is set appropriately.

       EBADF  fd isn't a valid open file descriptor.

       EINTR  The close() call was interrupted by a signal; see signal(7).

       EIO    An I/O error occurred.

       POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.

       Not checking the return value of close() is a common  but  nevertheless
       serious	programming error.  It is quite possible that errors on a pre-
       vious write(2) operation are first reported at the final close().   Not
       checking the return value when closing the file may lead to silent loss
       of data.	 This can especially be observed with NFS and with disk quota.
       Note  that  the	return	value should be used only for diagnostics.  In
       particular close() should not be retried after an EINTR since this  may
       cause a reused descriptor from another thread to be closed.

       A  successful  close does not guarantee that the data has been success-
       fully saved to disk, as the kernel defers writes.  It is not common for
       a  filesystem  to  flush the buffers when the stream is closed.	If you
       need to be sure that the data is physically stored, use fsync(2).   (It
       will depend on the disk hardware at this point.)

       It  is  probably	 unwise to close file descriptors while they may be in
       use by system calls in other threads in the same process.  Since a file
       descriptor  may	be reused, there are some obscure race conditions that
       may cause unintended side effects.

       When dealing with sockets, you have to be sure that there is no recv(2)
       still  blocking	on it on another thread, otherwise it might block for-
       ever, since no more messages will be send via the socket.  Be  sure  to
       use  shutdown(2)	 to  shut down all parts the connection before closing
       the socket.

       fcntl(2), fsync(2), open(2), shutdown(2), unlink(2), fclose(3)

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Linux				  2015-08-08			      CLOSE(2)