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



NAME
       close - close a file descriptor

SYNOPSIS
       #include <unistd.h>

       int close(int fd);

DESCRIPTION
       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 copy of a particular file  descriptor	the  resources
       associated  with it are freed; if the descriptor was the last reference
       to a file which has been removed using unlink(2) the file is deleted.

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

ERRORS
       EBADF  fd isn't a valid open file descriptor.

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

       EIO    An I/O error occurred.

CONFORMING TO
       SVr4, 4.3BSD, POSIX.1-2001.

NOTES
       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.

       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 re-used, 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 sent via the socket. Be sure to
       use shutdown(2) to shut down all parts the  connection  before  closing
       the socket.

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



Linux				  2001-12-13			      CLOSE(2)
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