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26 .TH OPENAT 2 2006-03-06 "Linux 2.6.16" "Linux Programmer's Manual"
28 openat \- open a file relative to a directory file descriptor
31 .B #define _ATFILE_SOURCE
34 .BI "int openat(int " dirfd ", const char *" pathname ", int " flags );
35 .BI "int openat(int " dirfd ", const char *" pathname ", int " flags \
41 system call operates in exactly the same way as
43 except for the differences described in this manual page.
45 If the pathname given in
47 is relative, then it is interpreted relative to the directory
48 referred to by the file descriptor
50 (rather than relative to the current working directory of
51 the calling process, as is done by
53 for a relative pathname).
63 is interpreted relative to the current working
64 directory of the calling process (like
75 returns a new file descriptor.
76 On error, \-1 is returned and
78 is set to indicate the error.
80 The same errors that occur for
84 The following additional errors can occur for
89 is not a valid file descriptor.
95 is a file descriptor referring to a file other than a directory.
98 and other similar system calls suffixed "at" are supported
103 allows an application to avoid race conditions that could
106 to open files in directories other than the current working directory.
107 These race conditions result from the fact that some component
108 of the directory prefix given to
110 could be changed in parallel with the call to
112 Such races can be avoided by
113 opening a file descriptor for the target directory,
114 and then specifying that file descriptor as the
121 allows the implementation of a per-thread "current working
122 directory", via file descriptor(s) maintained by the application.
123 (This functionality can also be obtained by tricks based
125 .IR /proc/self/fd/ dirfd,
126 but less efficiently.)
128 This system call is non-standard but is proposed
129 for inclusion in a future revision of POSIX.1.
130 A similar system call exists on Solaris.
131 .\" The 'at' suffix in Solaris is actually double sensed. It
132 .\" primarily referred to "extended *at*tributes", which are
133 .\" handled by Solaris' O_XATTR flag, but was also intended
134 .\" to refer to the notion of "at a relative location".
136 .\" See the following for a discussion of the inconsistent
137 .\" naming of the *at() functions:
138 .\" http://www.opengroup.org/austin/mailarchives/ag/msg09103.html
139 .\" Subject: RE: The naming of at()s is a difficult matter
141 .\" Date: Tue, 14 Feb 2006 14:56:50 -0800 (PST)
145 was added to Linux in kernel 2.6.16.
156 .BR path_resolution (2),