.\" Copyright (c) 1994
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Jan-Simon Pendry.
.\"
.\" 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. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. 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
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\"
.\"     @(#)realpath.3	8.2 (Berkeley) 2/16/94
.\" $FreeBSD: src/lib/libc/stdlib/realpath.3,v 1.13 2003/03/27 20:48:53 fjoe Exp $
.\"
.Dd April 5, 2008
.Dt REALPATH 3
.Os
.Sh NAME
.Nm realpath
.Nd returns the canonicalized absolute pathname
.\" .Sh LIBRARY
.\" .Lb libc
.Sh SYNOPSIS
.In stdlib.h
.Ft "char *"
.Fo realpath
.Fa "const char *restrict file_name"
.Fa "char *restrict resolved_name"
.Fc
.Sh DESCRIPTION
The
.Fn realpath
function resolves all symbolic links, extra
.Dq /
characters, and references to
.Pa /./
and
.Pa /../
in
.Fa file_name .
If the
.Fa resolved_name
argument
is non-NULL, the resulting absolute pathname is copied there (it
.Em must
refer to a buffer capable of storing at least
.Dv PATH_MAX
characters).
.Pp
As a permitted extension to the standard, if
.Fa resolved_name
is NULL, 
memory is allocated for the resulting absolute pathname, and is returned by
.Fn realpath .
This memory should be freed by a call to
.Xr free 3
when no longer needed.
.Pp
The
.Fn realpath
function will resolve both absolute and relative paths
and return the absolute pathname corresponding to
.Fa file_name .
All components of
.Fa file_name
must exist when
.Fn realpath
is called.
.Sh "RETURN VALUES"
On success, the
.Fn realpath
function returns the address of the resulting absolute pathname, which is
.Fa resolved_name
if it was non-NULL, or the address of newly allocated memory.
If an error occurs,
.Fn realpath
returns
.Dv NULL .
If
.Fa resolved_name
was non-NULL, it will
contains the pathname which caused the problem.
.Sh ERRORS
The function
.Fn realpath
may fail and set the external variable
.Va errno
for any of the errors specified for the library functions
.Xr alloca 3 ,
.Xr getattrlist 2 ,
.Xr getcwd 3 ,
.Xr lstat 2 ,
.Xr readlink 2 ,
.Xr stat 2 ,
and
.Xr strdup 3 .
.\" .Sh CAVEATS
.\" This implementation of
.\" .Fn realpath
.\" differs slightly from the Solaris implementation.
.\" The
.\" .Bx 4.4
.\" version always returns absolute pathnames,
.\" whereas the Solaris implementation will,
.\" under certain circumstances, return a relative
.\" .Fa resolved_name
.\" when given a relative
.\" .Fa file_name .
.Sh LEGACY SYNOPSIS
.Fd #include <sys/param.h>
.Fd #include <stdlib.h>
.Pp
The include file
.In sys/param.h
is necessary.
.Sh LEGACY DESCRIPTION
In legacy mode,
the last component of
.Fa file_name
does not need to exist when
.Fn realpath
is called.
.Sh "SEE ALSO"
.Xr free 3 ,
.Xr getcwd 3 ,
.Xr compat 5
.Sh HISTORY
The
.Fn realpath
function first appeared in
.Bx 4.4 .