Perl——正则表达式(四)查找替换s///

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转自http://blog.csdn.net/blog_abel/article/details/40589227 侵删

一. 介绍

使用 s/regex/replacement/modifiers 进行查找替换

二. 实例

(1) s///

1 $f = "'quoted words'";  
2 #进行模式匹配,下面方法去除''单引号  
3 if($f =~ s/^'(.*)'$/$1/) { #true, $1指的是引用了第一组(.*)的内容, ^$这两个字符用来表示开始与结束  
4   
5     print "matches","\n"; # mathces  
6     print $f,"\n";        # quoted words  
7                           # 注意 标量$f 匹配后本身内容发生了变化  
8 }

(2) s///r

用它进行匹配后,原始标量的值不会发生变化，可以把新值赋值给一个新的标量

1 $f = "'quoted words'";  
2 #进行模式匹配,下面方法去除''单引号  
3 $n = $f =~ s/^'(.*)'$/$1/r;  
4   
5 print "matches","\n";  
6 print $f,"\n"; # quoted words   # 注意 标量$f 匹配后本身内容无变化  
7       
8 print $n,"\n"; # 'quoted words' # 注意 $n

(3) s///g 多次查找替换

1 $z = "time hcat to feed the cat hcat";  
2 $z =~ s/cat/AAA/g;#替换多次  
3 print $z,"\n"; #结果为 time hAAA to feed the AAA hAAA

(4) s///e 求值

1 # reverse all the words in a string  
2 $x = "the cat in the hat";  
3 $x =~ s/(\w+)/reverse $1/ge; # $x contains "eht tac ni eht tah"  
4   
5 # convert percentage to decimal  
6 $x = "A 39% hit rate";  
7 $x =~ s!(\d+)%!$1/100!e; # $x contains "A 0.39 hit rate"