Perl Modules about File

文件存取与处理 

Cwd             取得现行工作目录的路径名 
DirHandle       提供处理目录代码的对象方法 
Fcntl           载入C的Fcntl.h中的定义 

File::Basename 分割文件名数据 

File::CheckTree 对一连串文件串做许多测试 
File::Copy      拷贝文件或文件句柄 
File::Find      寻找文件 
File::Path      产生或移除一连串目录 
FileCache       允许打开多于系统限制的文件句柄 
FileHandle      提供处理文件句柄的对象方法 

File::Find

Traverse a directory tree.

find() does a depth-first search over the given @directories in the order they are given.

finddepth() works just like find() except that it invokes the &wanted function for a directory after invoking it for the directory's contents. It does a postorder traversal instead of a preorder traversal, working from the bottom of the directory tree up where find() works from the top of the tree down.

#!/usr/bin/perl
use warnings;
use strict;
use File::Find;
print "find():\n";
find(\&wanted,'.');
print "\n\n";

print "finddepth():\n"
finddepth(\&wanted,'.');

sub wanted {
        print $File::Find::name,"\n" if ($_ =~ /^test/);
        print "*";
}

其中有三个变量：

1.$File::Find::dir  :当前处理的目录名

2.$_                :当前处理的文件名

3.$File::Find::name :目录加文件名

find是在进行目录测试后在进行目录内容的测试。从目录树根往下。

finddepth 是先内容后目录，从叶子往树根。

wanted函数是一个回调函数。回调函数是指：一般不自己调用而是由别的程序调用，这里是由find调用。find两个参数第一个是对遍历到文件的行为，一个是待查找的目录。

%option

The first argument to find() is either a code reference to your &wanted function, or a hash reference describing the operations to be performed for each file. 

1. wanted : The value should be a code reference. This code reference is described in the wanted function , The &wanted subroutine is mandatory
2. bydepth : Reports the name of a directory only AFTER all its entries have been reported. Entry point finddepth() is a shortcut for specifying { bydepth => 1 } in the first argument offind().
3. preprocess : The value should be a code reference. This code reference is used to preprocess the current directory.The name of the currently processed directory is in $File::Find::dir. It is called with a list of strings (actually file/directory names) and is expected to return a list of strings.The code can be used to sort the file/directory names alphabetically, numerically, or to filter out directory entries based on their name alone. When follow or follow_fast are in effect, preprocess is a no-op(空操作).
4. postprocess : The value should be a code reference. It is invoked just before leaving the currently processed directory.This hook is handy for summarizing a directory, such as calculating its disk usage. When follow or follow_fast are in effect, postprocess is a no-op.
5. follow : Causes symbolic links to be followed
6. follow_fast：
   

File::Password