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
file 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.
fd isn't a
valid open file descriptor.
The close() call was
interrupted by a signal; see signal(7).
An I/O error occurred.
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. 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 file descriptor from another
thread to be closed.
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 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.
This page is part of release 4.07 of the Linux man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
|
This manpage is Copyright (C) 1992 Drew Eckhardt; and Copyright (C) 1993 Michael Haardt, Ian Jackson. %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END Modified Wed Jul 21 22:40:25 1993 by Rik Faith <faithcs.unc.edu> Modified Sat Feb 18 15:27:48 1995 by Michael Haardt Modified Sun Apr 14 11:40:50 1996 by Andries Brouwer <aebcwi.nl>: corrected description of effect on locks (thanks to Tigran Aivazian <tigransco.com>). Modified Fri Jan 31 16:21:46 1997 by Eric S. Raymond <esrthyrsus.com> Modified 2000-07-22 by Nicolás Lichtmaier <nickdebian.org> added note about close(2) not guaranteeing that data is safe on close. |