1.\" $NetBSD: readlink.2,v 1.7 1995/02/27 12:35:54 cgd Exp $ 2.\" 3.\" Copyright (c) 1983, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)readlink.2 8.1 (Berkeley) 6/4/93 35.\" 36.Dd June 4, 1993 37.Dt READLINK 2 38.Os BSD 4.2 39.Sh NAME 40.Nm readlink , 41.Nm readlinkat , 42.Nm freadlink 43.Nd read value of a symbolic link 44.Sh SYNOPSIS 45.Fd #include <unistd.h> 46.Ft ssize_t 47.Fo readlink 48.Fa "const char *restrict path" 49.Fa "char *restrict buf" 50.Fa "size_t bufsize" 51.Fc 52.Ft ssize_t 53.Fo readlinkat 54.Fa "int fd" "const char *restrict path" "char *restrict buf" "size_t bufsize" 55.Fc 56.Ft ssize_t 57.Fo freadlink 58.Fa "int fd" "char *restrict buf" "size_t bufsize" 59.Fc 60.Sh DESCRIPTION 61.Fn readlink 62places the contents of the symbolic link 63.Fa path 64in the buffer 65.Fa buf , 66which has size 67.Fa bufsize . 68.Nm Readlink 69does not append a 70.Dv NUL 71character to 72.Fa buf . 73.Pp 74The 75.Fn readlinkat 76system call is equivalent to 77.Fn readlink 78except in the case where 79.Fa path 80specifies a relative path. 81In this case the symbolic link whose content is read relative to the 82directory associated with the file descriptor 83.Fa fd 84instead of the current working directory. 85If 86.Fn readlinkat 87is passed the special value 88.Dv AT_FDCWD 89in the 90.Fa fd 91parameter, the current working directory is used and the behavior is 92identical to a call to 93.Fn readlink . 94The 95.Fn freadlink 96system call returns the same information about an open symbolic link file referenced by descriptor 97.Fa fd . 98.Sh RETURN VALUES 99The call returns the count of characters placed in the buffer 100if it succeeds, or a -1 if an error occurs, placing the error 101code in the global variable 102.Va errno . 103.Sh ERRORS 104.Fn readlink 105will fail if: 106.Bl -tag -width Er 107.\" =========== 108.It Bq Er EACCES 109Search permission is denied for a component of the path prefix. 110.\" =========== 111.It Bq Er EFAULT 112.Fa Buf 113extends outside the process's allocated address space. 114.\" =========== 115.It Bq Er EINVAL 116The named file is not a symbolic link. 117.\" =========== 118.It Bq Er EIO 119An I/O error occurred while reading from the file system. 120.\" =========== 121.It Bq Er ELOOP 122Too many symbolic links are encountered in translating the pathname. 123This is taken to be indicative of a looping symbolic link. 124.\" =========== 125.It Bq Er ENAMETOOLONG 126A component of a pathname exceeded 127.Dv {NAME_MAX} 128characters, or an entire path name 129(possibly expanded by a symbolic link) exceeded 130.Dv {PATH_MAX} 131characters. 132.\" =========== 133.It Bq Er ENOENT 134The named file does not exist. 135.\" =========== 136.It Bq Er ENOTDIR 137A component of the path prefix is not a directory. 138.El 139.Pp 140In addition to the errors returned by the 141.Fn readlink , 142the 143.Fn readlinkat 144may fail if: 145.Bl -tag -width Er 146.It Bq Er EBADF 147The 148.Fa path 149argument does not specify an absolute path and the 150.Fa fd 151argument is neither 152.Dv AT_FDCWD 153nor a valid file descriptor open for searching. 154.It Bq Er ENOTDIR 155The 156.Fa path 157argument is not an absolute path and 158.Fa fd 159is neither 160.Dv AT_FDCWD 161nor a file descriptor associated with a directory. 162.El 163.Sh LEGACY SYNOPSIS 164.Fd #include <unistd.h> 165.Pp 166.Ft int 167.br 168.Fo readlink 169.Fa "const char *path" 170.Fa "char *buf" 171.Fa "int bufsize" 172.Fc ; 173.Pp 174The function type and the type of 175.Fa bufsize 176have changed. 177.Sh SEE ALSO 178.Xr lstat 2 , 179.Xr stat 2 , 180.Xr symlink 2 , 181.Xr compat 5 , 182.Xr symlink 7 183.Sh STANDARDS 184The 185.Fn readlinkat 186system call is expected to conform to POSIX.1-2008 . 187.Sh HISTORY 188The 189.Fn readlink 190function call appeared in 191.Bx 4.2 . 192The 193.Fn readlinkat 194system call appeared in OS X 10.10. 195The 196.Fn freadlink 197system call appeared in macOS 13.0. 198