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openat.2: Convert to link to open.2
All of the openat() text has been merged into open(2), so now all we need here is a link. Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
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man2/openat.2
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man2/openat.2
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.\" This manpage is Copyright (C) 2006, Michael Kerrisk
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.TH OPENAT 2 2012-05-04 "Linux" "Linux Programmer's Manual"
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.SH NAME
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openat \- open a file relative to a directory file descriptor
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.SH SYNOPSIS
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.nf
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.B #include <fcntl.h>
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.sp
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.BI "int openat(int " dirfd ", const char *" pathname ", int " flags );
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.BI "int openat(int " dirfd ", const char *" pathname ", int " flags \
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", mode_t " mode );
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.fi
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.BR openat ():
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.PD 0
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.ad l
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.RS 4
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.TP 4
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Since glibc 2.10:
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_XOPEN_SOURCE\ >=\ 700 || _POSIX_C_SOURCE\ >=\ 200809L
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.TP
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Before glibc 2.10:
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_ATFILE_SOURCE
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.RE
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.ad
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.PD
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.SH DESCRIPTION
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The
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.BR openat ()
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system call operates in exactly the same way as
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.BR open (2),
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except for the differences described in this manual page.
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If the pathname given in
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.I pathname
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is relative, then it is interpreted relative to the directory
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referred to by the file descriptor
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.I dirfd
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(rather than relative to the current working directory of
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the calling process, as is done by
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.BR open (2)
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for a relative pathname).
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If
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.I pathname
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is relative and
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.I dirfd
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is the special value
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.BR AT_FDCWD ,
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then
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.I pathname
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is interpreted relative to the current working
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directory of the calling process (like
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.BR open (2)).
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If
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.I pathname
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is absolute, then
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.I dirfd
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is ignored.
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.SH RETURN VALUE
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On success,
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.BR openat ()
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returns a new file descriptor.
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On error, \-1 is returned and
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.I errno
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is set to indicate the error.
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.SH ERRORS
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The same errors that occur for
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.BR open (2)
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can also occur for
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.BR openat ().
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The following additional errors can occur for
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.BR openat ():
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.TP
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.B EBADF
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.I dirfd
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is not a valid file descriptor.
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.TP
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.B ENOTDIR
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.I pathname
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is relative and
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.I dirfd
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is a file descriptor referring to a file other than a directory.
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.SH VERSIONS
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.BR openat ()
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was added to Linux in kernel 2.6.16;
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library support was added to glibc in version 2.4.
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.SH CONFORMING TO
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POSIX.1-2008.
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A similar system call exists on Solaris.
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.\" The 'at' suffix in Solaris is actually double sensed. It
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.\" primarily referred to "extended *at*tributes", which are
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.\" handled by Solaris' O_XATTR flag, but was also intended
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.\" to refer to the notion of "at a relative location".
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.\"
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.\" See the following for a discussion of the inconsistent
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.\" naming of the *at() functions:
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.\" http://www.opengroup.org/austin/mailarchives/ag/msg09103.html
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.\" Subject: RE: The naming of at()s is a difficult matter
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.\" From: Don Cragun
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.\" Date: Tue, 14 Feb 2006 14:56:50 -0800 (PST)
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.\"
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.SH NOTES
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.BR openat ()
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and other similar system calls suffixed "at" are supported
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for two reasons.
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First,
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.BR openat ()
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allows an application to avoid race conditions that could
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occur when using
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.BR open (2)
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to open files in directories other than the current working directory.
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These race conditions result from the fact that some component
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of the directory prefix given to
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.BR open (2)
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could be changed in parallel with the call to
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.BR open (2).
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Such races can be avoided by
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opening a file descriptor for the target directory,
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and then specifying that file descriptor as the
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.I dirfd
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argument of
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.BR openat ().
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Second,
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.BR openat ()
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allows the implementation of a per-thread "current working
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directory", via file descriptor(s) maintained by the application.
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(This functionality can also be obtained by tricks based
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on the use of
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.IR /proc/self/fd/ dirfd,
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but less efficiently.)
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.SH SEE ALSO
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.BR faccessat (2),
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.BR fchmodat (2),
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.BR fchownat (2),
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.BR fstatat (2),
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.BR futimesat (2),
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.BR linkat (2),
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.BR mkdirat (2),
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.BR mknodat (2),
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.BR open (2),
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.BR readlinkat (2),
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.BR renameat (2),
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.BR symlinkat (2),
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.BR unlinkat (2),
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.BR utimensat (2),
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.BR mkfifoat (3),
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.BR path_resolution (7)
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.so man2/open.2
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