Perl的DATA文件句柄

有太屡次写完一个perl程序，须要另外新建一个文件来测试，每次以为很繁琐，但又不得不这么作。没想到原来perl已经提供了解决方案，这就是DATA。php

使用很简单，见下面这个例子：html

1 #!/usr/bin/perl
2 
3 while (<DATA>) {
4         print;
5 }
6 
7 __DATA__
8 hello perl

输出结果: hello perlide

这个用法太方便太perl了，之后不再须要使用新建文件的笨方法了。post

下面是解释：测试

<IN>能够从打开的句柄IN中得到数据，<STDIN>能够从标准输入接收数据，相似地，<DATA> 文件句柄能够直接从执行它的脚本中获取数据，而不是从命令行或者从另外一个文件里获取。<DATA> 所读取的数据保存在每一个脚本末尾的特殊常量__DATA__以后，同时这个常量也标志着脚本的逻辑结束。url

注意：脚本中有两个while(<DATA>)将只有前一个起做用，由于前一个已经读到了文件结尾。好比如下示例：spa

 1 #!/usr/bin/perl -w
 2 use strict;
 3 
 4 while (<DATA>) {
 5         print "$_";
 6 }
 7 
 8 while (<DATA>) {
 9         print;
10 }
11 
12 __DATA__
13 hello world

输出结果:.net

hello world命令行

而不是:code

hello world

DATA

A Virtual File In Perl

It has been occurred a lot of times that one has to test a code using data from a file. It can be anything like checking for a pattern in a file to taking some input. If you want to check the code without opening the file and reading it. One can use the __DATA__ marker provided by perl as a pseudo-datafile.

Steps to follow:1) At the end of the code use __DATA__ marker and copy paste or write the contents of the file you wish to test exactly from the next line of _DATA_.2) Use while (){ -- your code here -- }.#!/usr/bin/perluse strict;use warnings;while () {chomp $_; print "Found" if $_ =~ /(t\w+)/; print $1;}__DATA__hello there how r uOutput of the above program will be “there”.