perl 3.08 根据模板生成文件

>经常会有根据一些模板来生成配置文件或者cgi 页面的需求，这时候我们可以使用template模块
文档： http://search.cpan.org/~abw/Template-Toolkit-2.24/lib/Template.pm
安装： yum -y install perl-Template-Toolkit

*该模块允许template 文件中有perl 语句块，你可以理解成jsp 页面中的jsp 语句*

#直接上code
```perl
#!/usr/bin/perl
use warnings;
use strict;
use Template;

my $config = {
    INCLUDE_PATH => '/root/', #要操作的文件所在目录
    POST_CHOMP => 1,  #删除不需要的换行符，比如perl 语句块后面的
    EVAL_PERL => 1,   #允许执行perl 语句块
};
my $template = Template->new($config);  #创建这个对象

#现在我们来定义需要替换的变量
my $value = "the value";
my %hash = ("first" => "111","second" => "222");
my @list = qw( lala wawa haha );
my $vars = {
    var1 => $value,
    var2 => \%hash,
    var3 => \@list,
};

my $input = 'file';  #作为模板的文件
#$template->process($input, $vars, './abc')   用这种写法可以指定输出的文件，默认STDOUT
$template->process($input, $vars) || die $template->error();
```
#尝试运行
```bash
[root@test ~]# cat file
This is the file:
==[% var1 %]==
==[% var2.first %]==[% var2.second %]==
==[% var3.0 %]==[% var3.1 %]==[% var3.2 %]==

[% SET n = 0 %]
[% FOREACH THE_VALUE IN var3 %][% n = n + 1 %]
==[% n %]==>==[% THE_VALUE %]==
[% END %]

[root@test ~]# ./template.pl
This is the file:
==the value==
==111==222==
==lala==wawa==haha==

==1==>==lala==
==2==>==wawa==
==3==>==haha==

```
***
#更多template 的写法 （从文档中copy 来的）
##获得值
```
[%   GET variable %]    # 'GET' 可以省略
[%       variable %]
[%       hash.key %]
[%         list.n %]
[%     code(args) %]
[% obj.meth(args) %]
[%  "value: $var" %]
[%  CALL variable %]    #不会打印出来
```
##赋值
```
[% SET variable = value %]    # 'SET' 可以省略
[%     variable = other_variable
       variable = 'literal text @ $100'
       variable = "interpolated text: $var"
       list     = [ val, val, val, val, ... ]
       list     = [ val..val ]
       hash     = { var => val, var => val, ... }
%]
[% DEFAULT variable = value %]   #只有variable为空值时候才会赋值
```
##导入文件
```
[% INSERT legalese.txt %]   #导入一个文件
[% INCLUDE template %]      #导入并处理文件
[% INCLUDE template  var = val, ... %]
[% PROCESS template %]      #导入并处理文件，这里声明的变量是全局的，可以在以后使用
[% PROCESS template  var = val, ... %]
```
##foreach
```
[% FOREACH variable IN [ val, val, val ] %]    
[% FOREACH variable IN list %]                 
   The variable is set to [% variable %]
[% END %]
```
##while
```
[% WHILE condition %]
    content
[% END %]
```
##if
```
[% IF condition %]
    content
[% ELSIF condition %]
    content
[% ELSE %]
    content
[% END %]
```
##unless
```
[% UNLESS condition %]
    content
[% ELSIF condition %]
    content
[% ELSE %]
    content
[% END %]
```
##switch/case
```
[% SWITCH variable %]
    [% CASE val1 %]
        content
    [% CASE [ val2, val3 ] %]
        content
    [% CASE %]         
        content
[% END %]
```
##run perl code  (需要 EVAL_PERL = 1)
```
[% PERL %]
my $a = 1;
my $b = 2;
my $c = $a + $b;
print "a + b = $c\n";
[% END %]
```
##其他
```
[% NEXT %]  #用于foreach/while 
[% LAST %]  #用于foreach/while 
```

乱读天书， 不求甚解

乱读天书，不求甚解