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 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.

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; see signal(7).

       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
       previous 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 successfully saved to disk, as the kernel defers writes.  It is not common for
       a file system 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
       forever,  since no more messages will be send via the socket. Be sure to use shutdown(2) to shut down all parts the connection before clos-
       ing the socket.

SEE ALSO

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

COLOPHON

       This page is part of release 3.53 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2007-12-28								  CLOSE(2)