realpath.3

早期freebsd实现

.\" Copyright (c) 1994
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.\" This code is derived from software contributed to Berkeley by
.\" Jan-Simon Pendry.
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.\"     @(#)realpath.3	8.2 (Berkeley) 2/16/94
.\"
.Dd "February 16, 1994"
.Dt REALPATH 3
.Os
.Sh NAME
.Nm realpath
.Nd returns the canonicalized absolute pathname
.Sh SYNOPSIS
.Fd #include <sys/param.h>
.Fd #include <stdlib.h>
.Ft "char *"
.Fn realpath "const char *pathname" "char resolvedname[MAXPATHLEN]"
.Sh DESCRIPTION
The
.Fn realpath
function resolves all symbolic links, extra
.Dq /
characters and references to
.Pa /./
and
.Pa /../
in
.Fa pathname ,
and copies the resulting absolute pathname into
the memory referenced by
.Fa resolvedname .
The
.Fa resolvedname
argument
.Em must
refer to a buffer capable of storing at least
.Dv MAXPATHLEN
characters.
.Pp
The 
.Fn realpath
function will resolve both absolute and relative paths
and return the absolute pathname corresponding to
.Fa pathname .
All but the last component of
.Fa pathname
must exist when
.Fn realpath
is called.
.Sh "RETURN VALUES"
The
.Fn realpath
function returns
.Fa resolved_name
on success.
If an error occurs,
.Fn realpath
returns
.Dv NULL ,
and
.Fa resolved_name
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 chdir 2 ,
.Xr close 2 ,
.Xr fchdir 2 ,
.Xr lstat 2 ,
.Xr open 2 ,
.Xr readlink 2
and
.Xr getcwd 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_path
when given a relative
.Fa pathname .
.Sh "SEE ALSO"
.Xr getcwd 3
.Sh HISTORY
The
.Fn realpath
function call first appeared in
.Bx 4.4 .