Add some more *at() system calls.
[dragonfly.git] / lib / libc / sys / readlink.2
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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
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32.Dt READLINK 2
33.Os
34.Sh NAME
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35.Nm readlink ,
36.Nm readlinkat
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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"
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44.Ft ssize_t
45.Fn readlinkat "int fd" "const char *restrict path" "char *restrict buf" "size_t bufsize"
984263bc 46.Sh DESCRIPTION
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47The
48.Fn readlink
49system call
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50places the contents of the symbolic link
51.Fa path
52in the buffer
53.Fa buf ,
54which has size
55.Fa bufsiz .
56The
57.Fn readlink
6d98f93c 58system call does not append a
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59.Dv NUL
60character to
61.Fa buf .
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62.Pp
63The
64.Fn readlinkat
65system call is equivalent to
66.Fn readlink
67except in the case where
68.Fa path
69specifies a relative path.
70In this case the symbolic link whose content is read relative to the
71directory associated with the file descriptor
72.Fa fd
73instead of the current working directory.
74If
75.Fn readlinkat
76is passed the special value
77.Dv AT_FDCWD
78in the
79.Fa fd
80parameter, the current working directory is used and the behavior is
81identical to a call to
82.Fn readlink .
984263bc 83.Sh RETURN VALUES
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84The calls return the count of characters placed in the buffer
85if it succeeds, or a \-1 if an error occurs, placing the error
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86code in the global variable
87.Va errno .
88.Sh ERRORS
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89The
90.Fn readlink
91system call
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92will fail if:
93.Bl -tag -width Er
94.It Bq Er ENOTDIR
95A component of the path prefix is not a directory.
96.It Bq Er ENAMETOOLONG
97A component of a pathname exceeded 255 characters,
98or an entire path name exceeded 1023 characters.
99.It Bq Er ENOENT
100The named file does not exist.
101.It Bq Er EACCES
102Search permission is denied for a component of the path prefix.
103.It Bq Er ELOOP
104Too many symbolic links were encountered in translating the pathname.
105.It Bq Er EINVAL
106The named file is not a symbolic link.
107.It Bq Er EIO
108An I/O error occurred while reading from the file system.
109.It Bq Er EFAULT
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110The
111.Fa buf
112argument
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113extends outside the process's allocated address space.
114.El
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115.Pp
116In addition to the errors returned by the
117.Fn readlink ,
118the
119.Fn readlinkat
120may fail if:
121.Bl -tag -width Er
122.It Bq Er EBADF
123The
124.Fa path
125argument does not specify an absolute path and the
126.Fa fd
127argument is neither
128.Dv AT_FDCWD
129nor a valid file descriptor open for searching.
130.It Bq Er ENOTDIR
131The
132.Fa path
133argument is not an absolute path and
134.Fa fd
135is neither
136.Dv AT_FDCWD
137nor a file descriptor associated with a directory.
138.El
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139.Sh SEE ALSO
140.Xr lstat 2 ,
141.Xr stat 2 ,
142.Xr symlink 2 ,
143.Xr symlink 7
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144.Sh STANDARDS
145The
146.Fn readlinkat
147system call follows The Open Group Extended API Set 2 specification.
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148.Sh HISTORY
149The
150.Fn readlink
6d98f93c 151system call appeared in
984263bc 152.Bx 4.2 .
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153The
154.Fn readlinkat
155system call appeared in
156.Dx 2.7 .