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.\" $OpenBSD: readlink.2,v 1.19 2015/05/31 23:54:25 schwarze Exp $
.\" $NetBSD: readlink.2,v 1.7 1995/02/27 12:35:54 cgd Exp $
.\"
.\" Copyright (c) 1983, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" @(#)readlink.2 8.1 (Berkeley) 6/4/93
.\"
.Dd $Mdocdate: May 31 2015 $
.Dt READLINK 2
.Os
.Sh NAME
.Nm readlink ,
.Nm readlinkat
.Nd read value of a symbolic link
.Sh SYNOPSIS
.In unistd.h
.Ft ssize_t
.Fn readlink "const char *restrict path" "char *restrict buf" "size_t bufsiz"
.In fcntl.h
.In unistd.h
.Ft ssize_t
.Fn readlinkat "int fd" "const char *path" "char *buf" "size_t bufsiz"
.Sh DESCRIPTION
The
.Fn readlink
function places the contents of the symbolic link
.Fa path
in the buffer
.Fa buf ,
which has size
.Fa bufsiz .
.Fn readlink
does not append a
.Dv NUL
character to
.Fa buf .
.Pp
The
.Fn readlinkat
function is equivalent to
.Fn readlink
except that where
.Fa path
specifies a relative path,
the symbolic link whose contents are read is determined relative to
the directory associated with file descriptor
.Fa fd
instead of the current working directory.
.Pp
If
.Fn readlinkat
is passed the special value
.Dv AT_FDCWD
(defined in
.In fcntl.h )
in the
.Fa fd
parameter, the current working directory is used
and the behavior is identical to a call to
.Fn readlink .
.Sh RETURN VALUES
The call returns the count of characters placed in the buffer
if it succeeds, or a \-1 if an error occurs, placing the error
code in the global variable
.Va errno .
.Sh ERRORS
.Fn readlink
and
.Fn readlinkat
will fail if:
.Bl -tag -width Er
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded
.Dv NAME_MAX
characters, or an entire pathname (including the terminating NUL)
exceeded
.Dv PATH_MAX
bytes.
.It Bq Er ENOENT
The named file does not exist.
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.It Bq Er EINVAL
The named file is not a symbolic link.
.It Bq Er EIO
An I/O error occurred while reading from the file system.
.It Bq Er EFAULT
.Fa buf
or
.Fa path
extends outside the process's allocated address space.
.El
.Pp
Additionally,
.Fn readlinkat
will fail if:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa path
argument specifies a relative path and the
.Fa fd
argument is neither
.Dv AT_FDCWD
nor a valid file descriptor.
.It Bq Er ENOTDIR
The
.Fa path
argument specifies a relative path and the
.Fa fd
argument is a valid file descriptor but it does not reference a directory.
.It Bq Er EACCES
The
.Fa path
argument specifies a relative path but search permission is denied
for the directory which the
.Fa fd
file descriptor references.
.El
.Sh SEE ALSO
.Xr lstat 2 ,
.Xr stat 2 ,
.Xr symlink 2 ,
.Xr symlink 7
.Sh STANDARDS
The
.Fn readlink
and
.Fn readlinkat
functions conform to
.St -p1003.1-2008 .
.Sh HISTORY
The
.Fn readlink
system call first appeared in
.Bx 4.1c .
The
.Fn readlinkat
system call has been available since
.Ox 5.0 .
|
