Perl——正则表达式(四) 查找替换s///

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///

 $f = "'quoted words'";
 #进行模式匹配,下面方法去除''单引号
 if($f =~ s/^'(.*)'$/$/) { #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  

     print "matches","\n"; # mathces
     print $f,"\n";        # quoted words
                           # 注意 标量$f 匹配后本身内容发生了变化
 }  

(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

 $f = "'quoted words'";
 #进行模式匹配,下面方法去除''单引号
 $n = $f =~ s/^'(.*)'$/$/r;  

 print "matches","\n";
 print $f,"\n"; # quoted words   # 注意 标量$f 匹配后本身内容无变化  

 print $n,"\n"; # 'quoted words' # 注意 $n  

 

(3) s///g 多次查找替换

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

 

(4) s///e 求值

 # reverse all the words in a string
 $x = "the cat in the hat";
 $x =~ s/(\w+)/reverse $/ge; # $x contains "eht tac ni eht tah"  

 # convert percentage to decimal
 $x = "A 39% hit rate";
 $x =~ s!(\d+)%!$/!e; # $x contains "A 0.39 hit rate"  

(5) s/// 可以用 s!!! , s{}{} , s{}// 进行替换