file::spec::mac.3

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

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However, this approach is limited to the first arguments following
\&\*(L"root\*(R" (again, see \f(CW\*(C`Unix\->canonpath()\*(C'\fR ). If there are more
arguments that move up the directory tree, an invalid path going
beyond root can be created.
.RE
.RS 2
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As you've seen, you can force \f(CW\*(C`catdir()\*(C'\fR to create an absolute path
by passing either an empty string or a path that begins with a volume
name as the first argument. However, you are strongly encouraged not
to do so, since this is done only for backward compatibility. Newer
versions of File::Spec come with a method called \f(CW\*(C`catpath()\*(C'\fR (see
below), that is designed to offer a portable solution for the creation
of absolute paths.  It takes volume, directory and file portions and
returns an entire path. While \f(CW\*(C`catdir()\*(C'\fR is still suitable for the
concatenation of \fIdirectory names\fR, you are encouraged to use
\&\f(CW\*(C`catpath()\*(C'\fR to concatenate \fIvolume names\fR and \fIdirectory
paths\fR. E.g.
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.Vb 2
\&    $dir      = File::Spec\->catdir("tmp","sources");
\&    $abs_path = File::Spec\->catpath("MacintoshHD:", $dir,"");
.Ve
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yields
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.Vb 1
\&    "MacintoshHD:tmp:sources:" .
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.RE
.IP "catfile" 2
.IX Item "catfile"
Concatenate one or more directory names and a filename to form a
complete path ending with a filename. Resulting paths are \fBrelative\fR
by default, but can be forced to be absolute (but avoid this).
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\&\fB\s-1IMPORTANT\s0 \s-1NOTE:\s0\fR Beginning with version 1.3 of this module, the
resulting path is relative by default and \fInot\fR absolute. This
decision was made due to portability reasons. Since
\&\f(CW\*(C`File::Spec\->catfile()\*(C'\fR returns relative paths on all other
operating systems, it will now also follow this convention on Mac \s-1OS\s0.
Note that this may break some existing scripts.
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The last argument is always considered to be the file portion. Since
\&\f(CW\*(C`catfile()\*(C'\fR uses \f(CW\*(C`catdir()\*(C'\fR (see above) for the concatenation of the
directory portions (if any), the following with regard to relative and
absolute paths is true:
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.Vb 2
\&    catfile("")     = ""
\&    catfile("file") = "file"
.Ve
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but
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.Vb 3
\&    catfile("","")        = rootdir()         # (e.g. "HD:")
\&    catfile("","file")    = rootdir() . file  # (e.g. "HD:file")
\&    catfile("HD:","file") = "HD:file"
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This means that \f(CW\*(C`catdir()\*(C'\fR is called only when there are two or more
arguments, as one might expect.
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Note that the leading \*(L":\*(R" is removed from the filename, so that
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.Vb 1
\&    catfile("a","b","file")  = ":a:b:file"    and
\&
\&    catfile("a","b",":file") = ":a:b:file"
.Ve
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give the same answer.
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To concatenate \fIvolume names\fR, \fIdirectory paths\fR and \fIfilenames\fR,
you are encouraged to use \f(CW\*(C`catpath()\*(C'\fR (see below).
.IP "curdir" 2
.IX Item "curdir"
Returns a string representing the current directory. On Mac \s-1OS\s0, this is \*(L":\*(R".
.IP "devnull" 2
.IX Item "devnull"
Returns a string representing the null device. On Mac \s-1OS\s0, this is \*(L"Dev:Null\*(R".
.IP "rootdir" 2
.IX Item "rootdir"
Returns a string representing the root directory.  Under MacPerl,
returns the name of the startup volume, since that's the closest in
concept, although other volumes aren't rooted there. The name has a
trailing \*(L":\*(R", because that's the correct specification for a volume
name on Mac \s-1OS\s0.
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If Mac::Files could not be loaded, the empty string is returned.
.IP "tmpdir" 2
.IX Item "tmpdir"
Returns the contents of \f(CW$ENV\fR{\s-1TMPDIR\s0}, if that directory exits or the
current working directory otherwise. Under MacPerl, \f(CW$ENV\fR{\s-1TMPDIR\s0} will
contain a path like \*(L"MacintoshHD:Temporary Items:\*(R", which is a hidden
directory on your startup volume.
.IP "updir" 2
.IX Item "updir"
Returns a string representing the parent directory. On Mac \s-1OS\s0, this is \*(L"::\*(R".
.IP "file_name_is_absolute" 2
.IX Item "file_name_is_absolute"
Takes as argument a path and returns true, if it is an absolute path.
If the path has a leading \*(L":\*(R", it's a relative path. Otherwise, it's an
absolute path, unless the path doesn't contain any colons, i.e. it's a name
like \*(L"a\*(R". In this particular case, the path is considered to be relative
(i.e. it is considered to be a filename). Use \*(L":\*(R" in the appropriate place
in the path if you want to distinguish unambiguously. As a special case,
the filename '' is always considered to be absolute. Note that with version
1.2 of File::Spec::Mac, this does no longer consult the local filesystem.
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E.g.
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.Vb 4
\&    File::Spec\->file_name_is_absolute("a");             # false (relative)
\&    File::Spec\->file_name_is_absolute(":a:b:");         # false (relative)
\&    File::Spec\->file_name_is_absolute("MacintoshHD:");  # true (absolute)
\&    File::Spec\->file_name_is_absolute("");              # true (absolute)
.Ve
.IP "path" 2
.IX Item "path"
Returns the null list for the MacPerl application, since the concept is
usually meaningless under Mac \s-1OS\s0. But if you're using the MacPerl tool under
\&\s-1MPW\s0, it gives back \f(CW$ENV\fR{Commands} suitably split, as is done in
:lib:ExtUtils:MM_Mac.pm.
.IP "splitpath" 2
.IX Item "splitpath"
.Vb 2
\&    ($volume,$directories,$file) = File::Spec\->splitpath( $path );
\&    ($volume,$directories,$file) = File::Spec\->splitpath( $path, $no_file );
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Splits a path into volume, directory, and filename portions.
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On Mac \s-1OS\s0, assumes that the last part of the path is a filename unless
\&\f(CW$no_file\fR is true or a trailing separator \*(L":\*(R" is present.
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The volume portion is always returned with a trailing \*(L":\*(R". The directory portion
is always returned with a leading (to denote a relative path) and a trailing \*(L":\*(R"
(to denote a directory). The file portion is always returned \fIwithout\fR a leading \*(L":\*(R".
Empty portions are returned as empty string ''.
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The results can be passed to \f(CW\*(C`catpath()\*(C'\fR to get back a path equivalent to
(usually identical to) the original path.
.IP "splitdir" 2
.IX Item "splitdir"
The opposite of \f(CW\*(C`catdir()\*(C'\fR.
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.Vb 1
\&    @dirs = File::Spec\->splitdir( $directories );
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\&\f(CW$directories\fR should be only the directory portion of the path on systems
that have the concept of a volume or that have path syntax that differentiates
files from directories. Consider using \f(CW\*(C`splitpath()\*(C'\fR otherwise.
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Unlike just splitting the directories on the separator, empty directory names
(\f(CW""\fR) can be returned. Since \f(CW\*(C`catdir()\*(C'\fR on Mac \s-1OS\s0 always appends a trailing
colon to distinguish a directory path from a file path, a single trailing colon
will be ignored, i.e. there's no empty directory name after it.
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Hence, on Mac \s-1OS\s0, both
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.Vb 2
\&    File::Spec\->splitdir( ":a:b::c:" );    and
\&    File::Spec\->splitdir( ":a:b::c" );
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yield:
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.Vb 1
\&    ( "a", "b", "::", "c")
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while
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.Vb 1
\&    File::Spec\->splitdir( ":a:b::c::" );
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yields:
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.Vb 1
\&    ( "a", "b", "::", "c", "::")
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.IP "catpath" 2
.IX Item "catpath"
.Vb 1
\&    $path = File::Spec\->catpath($volume,$directory,$file);
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Takes volume, directory and file portions and returns an entire path. On Mac \s-1OS\s0,
\&\f(CW$volume\fR, \f(CW$directory\fR and \f(CW$file\fR are concatenated.  A ':' is inserted if need be. You
may pass an empty string for each portion. If all portions are empty, the empty
string is returned. If \f(CW$volume\fR is empty, the result will be a relative path,
beginning with a ':'. If \f(CW$volume\fR and \f(CW$directory\fR are empty, a leading \*(L":\*(R" (if any)
is removed form \f(CW$file\fR and the remainder is returned. If \f(CW$file\fR is empty, the
resulting path will have a trailing ':'.
.IP "abs2rel" 2
.IX Item "abs2rel"
Takes a destination path and an optional base path and returns a relative path
from the base path to the destination path:
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.Vb 2
\&    $rel_path = File::Spec\->abs2rel( $path ) ;
\&    $rel_path = File::Spec\->abs2rel( $path, $base ) ;
.Ve
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Note that both paths are assumed to have a notation that distinguishes a
directory path (with trailing ':') from a file path (without trailing ':').
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If \f(CW$base\fR is not present or '', then the current working directory is used.
If \f(CW$base\fR is relative, then it is converted to absolute form using \f(CW\*(C`rel2abs()\*(C'\fR.
This means that it is taken to be relative to the current working directory.
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If \f(CW$path\fR and \f(CW$base\fR appear to be on two different volumes, we will not
attempt to resolve the two paths, and we will instead simply return
\&\f(CW$path\fR.  Note that previous versions of this module ignored the volume
of \f(CW$base\fR, which resulted in garbage results part of the time.
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If \f(CW$base\fR doesn't have a trailing colon, the last element of \f(CW$base\fR is
assumed to be a filename.  This filename is ignored.  Otherwise all path
components are assumed to be directories.
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If \f(CW$path\fR is relative, it is converted to absolute form using \f(CW\*(C`rel2abs()\*(C'\fR.
This means that it is taken to be relative to the current working directory.
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Based on code written by Shigio Yamaguchi.
.IP "rel2abs" 2
.IX Item "rel2abs"
Converts a relative path to an absolute path:
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.Vb 2
\&    $abs_path = File::Spec\->rel2abs( $path ) ;
\&    $abs_path = File::Spec\->rel2abs( $path, $base ) ;
.Ve
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Note that both paths are assumed to have a notation that distinguishes a
directory path (with trailing ':') from a file path (without trailing ':').
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If \f(CW$base\fR is not present or '', then \f(CW$base\fR is set to the current working
directory. If \f(CW$base\fR is relative, then it is converted to absolute form
using \f(CW\*(C`rel2abs()\*(C'\fR. This means that it is taken to be relative to the
current working directory.
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If \f(CW$base\fR doesn't have a trailing colon, the last element of \f(CW$base\fR is
assumed to be a filename.  This filename is ignored.  Otherwise all path
components are assumed to be directories.
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If \f(CW$path\fR is already absolute, it is returned and \f(CW$base\fR is ignored.
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Based on code written by Shigio Yamaguchi.
.SH "AUTHORS"
.IX Header "AUTHORS"
See the authors list in \fIFile::Spec\fR. Mac \s-1OS\s0 support by Paul Schinder
<[e-mail]> and Thomas Wegner <[e-mail]>.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright (c) 2004 by the Perl 5 Porters.  All rights reserved.
.PP
This program is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
See File::Spec and File::Spec::Unix.  This package overrides the
implementation of these methods, not the semantics.