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1 | .\" Copyright (c) 1983, 1991, 1993 |
2 | .\" The Regents of the University of California. All rights reserved. | |
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5 | .\" modification, are permitted provided that the following conditions | |
6 | .\" are met: | |
7 | .\" 1. Redistributions of source code must retain the above copyright | |
8 | .\" notice, this list of conditions and the following disclaimer. | |
9 | .\" 2. Redistributions in binary form must reproduce the above copyright | |
10 | .\" notice, this list of conditions and the following disclaimer in the | |
11 | .\" documentation and/or other materials provided with the distribution. | |
984263bc MD |
12 | .\" 4. Neither the name of the University nor the names of its contributors |
13 | .\" may be used to endorse or promote products derived from this software | |
14 | .\" without specific prior written permission. | |
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16 | .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND | |
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28 | .\" @(#)readlink.2 8.1 (Berkeley) 6/4/93 | |
6d98f93c | 29 | .\" $FreeBSD: src/lib/libc/sys/readlink.2,v 1.17 2008/04/16 13:03:12 kib Exp $ |
984263bc | 30 | .\" |
6d98f93c | 31 | .Dd August 6, 2010 |
984263bc MD |
32 | .Dt READLINK 2 |
33 | .Os | |
34 | .Sh NAME | |
6d98f93c SW |
35 | .Nm readlink , |
36 | .Nm readlinkat | |
984263bc MD |
37 | .Nd read value of a symbolic link |
38 | .Sh LIBRARY | |
39 | .Lb libc | |
40 | .Sh SYNOPSIS | |
41 | .In unistd.h | |
42 | .Ft int | |
43 | .Fn readlink "const char *path" "char *buf" "int bufsiz" | |
6d98f93c SW |
44 | .Ft ssize_t |
45 | .Fn readlinkat "int fd" "const char *restrict path" "char *restrict buf" "size_t bufsize" | |
984263bc | 46 | .Sh DESCRIPTION |
6d98f93c SW |
47 | The |
48 | .Fn readlink | |
49 | system call | |
984263bc MD |
50 | places the contents of the symbolic link |
51 | .Fa path | |
52 | in the buffer | |
53 | .Fa buf , | |
54 | which has size | |
55 | .Fa bufsiz . | |
56 | The | |
57 | .Fn readlink | |
6d98f93c | 58 | system call does not append a |
984263bc MD |
59 | .Dv NUL |
60 | character to | |
61 | .Fa buf . | |
6d98f93c SW |
62 | .Pp |
63 | The | |
64 | .Fn readlinkat | |
65 | system call is equivalent to | |
66 | .Fn readlink | |
67 | except in the case where | |
68 | .Fa path | |
69 | specifies a relative path. | |
70 | In this case the symbolic link whose content is read relative to the | |
71 | directory associated with the file descriptor | |
72 | .Fa fd | |
73 | instead of the current working directory. | |
74 | If | |
75 | .Fn readlinkat | |
76 | is passed the special value | |
77 | .Dv AT_FDCWD | |
78 | in the | |
79 | .Fa fd | |
80 | parameter, the current working directory is used and the behavior is | |
81 | identical to a call to | |
82 | .Fn readlink . | |
984263bc | 83 | .Sh RETURN VALUES |
6d98f93c SW |
84 | The calls return the count of characters placed in the buffer |
85 | if it succeeds, or a \-1 if an error occurs, placing the error | |
984263bc MD |
86 | code in the global variable |
87 | .Va errno . | |
88 | .Sh ERRORS | |
6d98f93c SW |
89 | The |
90 | .Fn readlink | |
91 | system call | |
984263bc MD |
92 | will fail if: |
93 | .Bl -tag -width Er | |
94 | .It Bq Er ENOTDIR | |
95 | A component of the path prefix is not a directory. | |
96 | .It Bq Er ENAMETOOLONG | |
97 | A component of a pathname exceeded 255 characters, | |
98 | or an entire path name exceeded 1023 characters. | |
99 | .It Bq Er ENOENT | |
100 | The named file does not exist. | |
101 | .It Bq Er EACCES | |
102 | Search permission is denied for a component of the path prefix. | |
103 | .It Bq Er ELOOP | |
104 | Too many symbolic links were encountered in translating the pathname. | |
105 | .It Bq Er EINVAL | |
106 | The named file is not a symbolic link. | |
107 | .It Bq Er EIO | |
108 | An I/O error occurred while reading from the file system. | |
109 | .It Bq Er EFAULT | |
6d98f93c SW |
110 | The |
111 | .Fa buf | |
112 | argument | |
984263bc MD |
113 | extends outside the process's allocated address space. |
114 | .El | |
6d98f93c SW |
115 | .Pp |
116 | In addition to the errors returned by the | |
117 | .Fn readlink , | |
118 | the | |
119 | .Fn readlinkat | |
120 | may fail if: | |
121 | .Bl -tag -width Er | |
122 | .It Bq Er EBADF | |
123 | The | |
124 | .Fa path | |
125 | argument does not specify an absolute path and the | |
126 | .Fa fd | |
127 | argument is neither | |
128 | .Dv AT_FDCWD | |
129 | nor a valid file descriptor open for searching. | |
130 | .It Bq Er ENOTDIR | |
131 | The | |
132 | .Fa path | |
133 | argument is not an absolute path and | |
134 | .Fa fd | |
135 | is neither | |
136 | .Dv AT_FDCWD | |
137 | nor a file descriptor associated with a directory. | |
138 | .El | |
984263bc MD |
139 | .Sh SEE ALSO |
140 | .Xr lstat 2 , | |
141 | .Xr stat 2 , | |
142 | .Xr symlink 2 , | |
143 | .Xr symlink 7 | |
6d98f93c SW |
144 | .Sh STANDARDS |
145 | The | |
146 | .Fn readlinkat | |
147 | system call follows The Open Group Extended API Set 2 specification. | |
984263bc MD |
148 | .Sh HISTORY |
149 | The | |
150 | .Fn readlink | |
6d98f93c | 151 | system call appeared in |
984263bc | 152 | .Bx 4.2 . |
6d98f93c SW |
153 | The |
154 | .Fn readlinkat | |
155 | system call appeared in | |
156 | .Dx 2.7 . |