1 .\" Hey Emacs! This file is -*- nroff -*- source.
3 .\" This manpage is Copyright (C) 2006, Michael Kerrisk
5 .\" Permission is granted to make and distribute verbatim copies of this
6 .\" manual provided the copyright notice and this permission notice are
7 .\" preserved on all copies.
9 .\" Permission is granted to copy and distribute modified versions of this
10 .\" manual under the conditions for verbatim copying, provided that the
11 .\" entire resulting derived work is distributed under the terms of a
12 .\" permission notice identical to this one.
14 .\" Since the Linux kernel and libraries are constantly changing, this
15 .\" manual page may be incorrect or out-of-date. The author(s) assume no
16 .\" responsibility for errors or omissions, or for damages resulting from
17 .\" the use of the information contained herein. The author(s) may not
18 .\" have taken the same level of care in the production of this manual,
19 .\" which is licensed free of charge, as they might when working
22 .\" Formatted or processed versions of this manual, if unaccompanied by
23 .\" the source, must acknowledge the copyright and authors of this work.
26 .TH OPENAT 2 2009-12-13 "Linux" "Linux Programmer's Manual"
28 openat \- open a file relative to a directory file descriptor
33 .BI "int openat(int " dirfd ", const char *" pathname ", int " flags );
34 .BI "int openat(int " dirfd ", const char *" pathname ", int " flags \
39 Feature Test Macro Requirements for glibc (see
40 .BR feature_test_macros (7)):
45 Since glibc 2.10: _XOPEN_SOURCE\ >=\ 700 || _POSIX_C_SOURCE\ >=\ 200809L
52 system call operates in exactly the same way as
54 except for the differences described in this manual page.
56 If the pathname given in
58 is relative, then it is interpreted relative to the directory
59 referred to by the file descriptor
61 (rather than relative to the current working directory of
62 the calling process, as is done by
64 for a relative pathname).
74 is interpreted relative to the current working
75 directory of the calling process (like
86 returns a new file descriptor.
87 On error, \-1 is returned and
89 is set to indicate the error.
91 The same errors that occur for
95 The following additional errors can occur for
100 is not a valid file descriptor.
106 is a file descriptor referring to a file other than a directory.
109 was added to Linux in kernel 2.6.16.
112 A similar system call exists on Solaris.
113 .\" The 'at' suffix in Solaris is actually double sensed. It
114 .\" primarily referred to "extended *at*tributes", which are
115 .\" handled by Solaris' O_XATTR flag, but was also intended
116 .\" to refer to the notion of "at a relative location".
118 .\" See the following for a discussion of the inconsistent
119 .\" naming of the *at() functions:
120 .\" http://www.opengroup.org/austin/mailarchives/ag/msg09103.html
121 .\" Subject: RE: The naming of at()s is a difficult matter
123 .\" Date: Tue, 14 Feb 2006 14:56:50 -0800 (PST)
127 and other similar system calls suffixed "at" are supported
132 allows an application to avoid race conditions that could
135 to open files in directories other than the current working directory.
136 These race conditions result from the fact that some component
137 of the directory prefix given to
139 could be changed in parallel with the call to
141 Such races can be avoided by
142 opening a file descriptor for the target directory,
143 and then specifying that file descriptor as the
150 allows the implementation of a per-thread "current working
151 directory", via file descriptor(s) maintained by the application.
152 (This functionality can also be obtained by tricks based
154 .IR /proc/self/fd/ dirfd,
155 but less efficiently.)
172 .BR path_resolution (7)