1.\" $OpenBSD: readlink.2,v 1.13 2011/07/18 23:04:40 matthew Exp $ 2.\" $NetBSD: readlink.2,v 1.7 1995/02/27 12:35:54 cgd Exp $ 3.\" 4.\" Copyright (c) 1983, 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)readlink.2 8.1 (Berkeley) 6/4/93 32.\" 33.Dd $Mdocdate: July 18 2011 $ 34.Dt READLINK 2 35.Os 36.Sh NAME 37.Nm readlink , 38.Nm readlinkat 39.Nd read value of a symbolic link 40.Sh SYNOPSIS 41.Fd #include <fcntl.h> 42.Fd #include <unistd.h> 43.Ft int 44.Fn readlink "const char *path" "char *buf" "size_t bufsiz" 45.Ft ssize_t 46.Fn readlinkat "int fd" "const char *path" "char *buf" "size_t bufsiz" 47.Sh DESCRIPTION 48The 49.Fn readlink 50function places the contents of the symbolic link 51.Fa path 52in the buffer 53.Fa buf , 54which has size 55.Fa bufsiz . 56.Nm readlink 57does not append a 58.Dv NUL 59character to 60.Fa buf . 61.Pp 62The 63.Fn readlinkat 64function is equivalent to 65.Fn readlink 66except that where 67.Fa path 68specifies a relative path, 69the symbolic link whose contents are read is determined relative to 70the directory associated with file descriptor 71.Fa fd 72instead of the current working directory. 73.Pp 74If 75.Fn readlinkat 76is passed the special value 77.Dv AT_FDCWD 78(defined in 79.In fcntl.h ) 80in the 81.Fa fd 82parameter, the current working directory is used 83and the behavior is identical to a call to 84.Fn readlink . 85.Sh RETURN VALUES 86The call returns the count of characters placed in the buffer 87if it succeeds, or a \-1 if an error occurs, placing the error 88code in the global variable 89.Va errno . 90.Sh ERRORS 91.Fn readlink 92and 93.Fn readlinkat 94will fail if: 95.Bl -tag -width Er 96.It Bq Er ENOTDIR 97A component of the path prefix is not a directory. 98.It Bq Er ENAMETOOLONG 99A component of a pathname exceeded 100.Dv {NAME_MAX} 101characters, or an entire path name exceeded 102.Dv {PATH_MAX} 103characters. 104.It Bq Er ENOENT 105The named file does not exist. 106.It Bq Er EACCES 107Search permission is denied for a component of the path prefix. 108.It Bq Er ELOOP 109Too many symbolic links were encountered in translating the pathname. 110.It Bq Er EINVAL 111The named file is not a symbolic link. 112.It Bq Er EIO 113An I/O error occurred while reading from the file system. 114.It Bq Er EFAULT 115.Fa buf 116or 117.Fa path 118extends outside the process's allocated address space. 119.El 120.Pp 121Additionally, 122.Fn readlinkat 123will fail if: 124.Bl -tag -width Er 125.It Bq Er EBADF 126The 127.Fa path 128argument does not specify an absolute path and the 129.Fa fd 130argument is neither 131.Dv AT_FDCWD 132nor a valid file descriptor open for reading. 133.El 134.Sh SEE ALSO 135.Xr lstat 2 , 136.Xr stat 2 , 137.Xr symlink 2 , 138.Xr symlink 7 139.Sh STANDARDS 140The 141.Fn readlink 142and 143.Fn readlinkat 144functions conform to 145.St -p1003.1-2008 . 146.Sh HISTORY 147The 148.Fn readlink 149function call appeared in 150.Bx 4.2 . 151The 152.Fn readlinkat 153function call appeared in 154.Ox 5.0 . 155