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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.\" ========================================================================
.\"
.IX Title "File::Spec::Mac 3"
.TH File::Spec::Mac 3 "2008-01-23" "perl v5.10.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
File::Spec::Mac \- File::Spec for Mac OS (Classic)
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& require File::Spec::Mac; # Done internally by File::Spec if needed
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Methods for manipulating file specifications.
.SH "METHODS"
.IX Header "METHODS"
.IP "canonpath" 2
.IX Item "canonpath"
On Mac \s-1OS\s0, there's nothing to be done. Returns what it's given.
.IP "\fIcatdir()\fR" 2
.IX Item "catdir()"
Concatenate two or more directory names to form a path separated by colons
(\*(L":\*(R") ending with a directory. Resulting paths are \fBrelative\fR by default,
but can be forced to be absolute (but avoid this, see below). Automatically
puts a trailing \*(L":\*(R" on the end of the complete path, because that's what's
done in MacPerl's environment and helps to distinguish a file path from a
directory path.
.Sp
\&\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\->catdir()\*(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.
.Sp
The intended purpose of this routine is to concatenate \fIdirectory names\fR.
But because of the nature of Macintosh paths, some additional possibilities
are allowed to make using this routine give reasonable results for some
common situations. In other words, you are also allowed to concatenate
\&\fIpaths\fR instead of directory names (strictly speaking, a string like \*(L":a\*(R"
is a path, but not a name, since it contains a punctuation character \*(L":\*(R").
.Sp
So, beside calls like
.Sp
.Vb 3
\&    catdir("a") = ":a:"
\&    catdir("a","b") = ":a:b:"
\&    catdir() = ""                    (special case)
.Ve
.Sp
calls like the following
.Sp
.Vb 5
\&    catdir(":a:") = ":a:"
\&    catdir(":a","b") = ":a:b:"
\&    catdir(":a:","b") = ":a:b:"
\&    catdir(":a:",":b:") = ":a:b:"
\&    catdir(":") = ":"
.Ve
.Sp
are allowed.
.Sp
Here are the rules that are used in \f(CW\*(C`catdir()\*(C'\fR; note that we try to be as
compatible as possible to Unix:
.RS 2
.IP "1." 2
The resulting path is relative by default, i.e. the resulting path will have a
leading colon.
.IP "2." 2
A trailing colon is added automatically to the resulting path, to denote a
directory.
.IP "3." 2
Generally, each argument has one leading \*(L":\*(R" and one trailing \*(L":\*(R"
removed (if any). They are then joined together by a \*(L":\*(R". Special
treatment applies for arguments denoting updir paths like \*(L"::lib:\*(R",
see (4), or arguments consisting solely of colons (\*(L"colon paths\*(R"),
see (5).
.IP "4." 2
When an updir path like \*(L":::lib::\*(R" is passed as argument, the number
of directories to climb up is handled correctly, not removing leading
or trailing colons when necessary. E.g.
.Sp
.Vb 2
\&    catdir(":::a","::b","c")    = ":::a::b:c:"
\&    catdir(":::a::","::b","c")  = ":::a:::b:c:"
.Ve
.IP "5." 2
Adding a colon \*(L":\*(R" or empty string "" to a path at \fIany\fR position
doesn't alter the path, i.e. these arguments are ignored. (When a "\*(L"
is passed as the first argument, it has a special meaning, see
(6)). This way, a colon \*(R":\*(L" is handled like a \*(R".\*(L" (curdir) on Unix,
while an empty string \*(R"" is generally ignored (see
\&\f(CW\*(C`Unix\->canonpath()\*(C'\fR ). Likewise, a \*(L"::\*(R" is handled like a \*(L"..\*(R"
(updir), and a \*(L":::\*(R" is handled like a \*(L"../..\*(R" etc.  E.g.
.Sp
.Vb 2
\&    catdir("a",":",":","b")   = ":a:b:"
\&    catdir("a",":","::",":b") = ":a::b:"
.Ve
.IP "6." 2
If the first argument is an empty string "" or is a volume name, i.e. matches
the pattern /^[^:]+:/, the resulting path is \fBabsolute\fR.
.IP "7." 2
Passing an empty string "" as the first argument to \f(CW\*(C`catdir()\*(C'\fR is
like passing\f(CW\*(C`File::Spec\->rootdir()\*(C'\fR as the first argument, i.e.
.Sp
.Vb 1
\&    catdir("","a","b")          is the same as
\&
\&    catdir(rootdir(),"a","b").
.Ve
.Sp
This is true on Unix, where \f(CW\*(C`catdir("","a","b")\*(C'\fR yields \*(L"/a/b\*(R" and
\&\f(CW\*(C`rootdir()\*(C'\fR is \*(L"/\*(R". Note that \f(CW\*(C`rootdir()\*(C'\fR on Mac \s-1OS\s0 is the startup
volume, which is the closest in concept to Unix' \*(L"/\*(R". This should help
to run existing scripts originally written for Unix.
.IP "8." 2
For absolute paths, some cleanup is done, to ensure that the volume
name isn't immediately followed by updirs. This is invalid, because
this would go beyond \*(L"root\*(R". Generally, these cases are handled like
their Unix counterparts:
.Sp
.Vb 10
\& Unix:
\&    Unix\->catdir("","")                 =  "/"
\&    Unix\->catdir("",".")                =  "/"
\&    Unix\->catdir("","..")               =  "/"              # can\*(Aqt go beyond root
\&    Unix\->catdir("",".","..","..","a")  =  "/a"
\& Mac:
\&    Mac\->catdir("","")                  =  rootdir()         # (e.g. "HD:")
\&    Mac\->catdir("",":")                 =  rootdir()
\&    Mac\->catdir("","::")                =  rootdir()         # can\*(Aqt go beyond root
\&    Mac\->catdir("",":","::","::","a")   =  rootdir() . "a:"  # (e.g. "HD:a:")
.Ve