1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
|
.\" This manpage is Copyright (C) 2006, Michael Kerrisk
.\"
.\" %%%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.\" manual page may be incorrect or out-of-date.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
.\"
.TH READLINKAT 2 2013-07-31 "Linux" "Linux Programmer's Manual"
.SH NAME
readlinkat \- read value of a symbolic link relative to
a directory file descriptor
.SH SYNOPSIS
.nf
.B #include <fcntl.h> /* Definition of AT_* constants */
.B #include <unistd.h>
.sp
.BI "int readlinkat(int " dirfd ", const char *" pathname ,
.BI " char *" buf ", size_t " bufsiz );
.fi
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.BR readlinkat ():
.PD 0
.ad l
.RS 4
.TP 4
Since glibc 2.10:
_XOPEN_SOURCE\ >=\ 700 || _POSIX_C_SOURCE\ >=\ 200809L
.TP
Before glibc 2.10:
_ATFILE_SOURCE
.RE
.ad
.PD
.SH DESCRIPTION
The
.BR readlinkat ()
system call operates in exactly the same way as
.BR readlink (2),
except for the differences described in this manual page.
If the pathname given in
.I pathname
is relative, then it is interpreted relative to the directory
referred to by the file descriptor
.I dirfd
(rather than relative to the current working directory of
the calling process, as is done by
.BR readlink (2)
for a relative pathname).
If
.I pathname
is relative and
.I dirfd
is the special value
.BR AT_FDCWD ,
then
.I pathname
is interpreted relative to the current working
directory of the calling process (like
.BR readlink (2)).
If
.I pathname
is absolute, then
.I dirfd
is ignored.
Since Linux 2.6.39,
.\" commit 65cfc6722361570bfe255698d9cd4dccaf47570d
.I pathname
can be an empty string,
in which case the call operates on the file referred to by
.IR dirfd
(which may have been obtained using the
.BR open (2)
.B O_PATH
flag).
In this case,
.I dirfd
can refer to any type of file, not just a directory.
.SH "RETURN VALUE"
On success,
.BR readlinkat ()
returns the number of bytes placed in
.IR buf .
On error, \-1 is returned and
.I errno
is set to indicate the error.
.SH ERRORS
The same errors that occur for
.BR readlink (2)
can also occur for
.BR readlinkat ().
The following additional errors can occur for
.BR readlinkat ():
.TP
.B EBADF
.I dirfd
is not a valid file descriptor.
.TP
.B ENOTDIR
.I pathname
is relative and
.I dirfd
is a file descriptor referring to a file other than a directory.
.SH VERSIONS
.BR readlinkat ()
was added to Linux in kernel 2.6.16;
library support was added to glibc in version 2.4.
.SH CONFORMING TO
POSIX.1-2008.
.SH NOTES
See
.BR openat (2)
for an explanation of the need for
.BR readlinkat ().
.SH SEE ALSO
.BR openat (2),
.BR readlink (2),
.BR path_resolution (7)
|
