perl正则表达式小问题

ld462370527

testfile

1. 44235

复制代码

下面程序是匹配44开头的美国邮编的。注：美国邮编是5位数字。
test.pl

1. #!/usr/bin/perl -w
   
2. 
   
3. open(FILENAME, "testfile");
   
4. 
   
5. while (<FILENAME>) {
   
6.     $count = () = m/(?:[^4]\d\d\d\d|\d[^4]\d\d\d)*(44\d\d\d)?/g;
   
7.     print "number of matched: " . $count . "\n";
   
8. }
   

复制代码

1. root@ubuntu:/home/teddy/regex/LRE# ./test.pl  
   
2. number of matched: 3

复制代码

这是在看精通表达式遇到的一个问题。写的一个测试程序。
运行test.pl结果是匹配3次。怎么会匹配3次呢？应该两次才对啊。求解。

TrishaTie

我运行出的结果是： number of matched: 2

TrishaTie

这样写是嘛意思啊，求教， $count = () = m/(?:[^4]\d\d\d\d|\d[^4]\d\d\d)*(44\d\d\d)?/g;  回复 1# ld462370527


   

ld462370527

回复 3# TrishaTie

你可以把第六行改成下面六七行，应该就能理解了：

1. #!/usr/bin/perl -w
   
2. 
   
3. open(FILENAME, "testfile");
   
4. 
   
5. while (<FILENAME>) {
   
6.     @zips = m/(?:[^4]\d\d\d\d|\d[^4]\d\d\d)*(44\d\d\d)?/g;
   
7.     $count = @zips;
   
8.     print "number of matched: " . $count . "\n";
   
9. }

复制代码

对了 运行结果是2么，你用的什么系统？还有perl的版本号是多少？Thanks~
我用的centos ubuntu都是结果为3。

1. [root@localhost ~]# perl -v
   
2. 
   
3. This is perl, v5.10.1 (*) built for x86_64-linux-thread-multi
   
4. 
   
5. [root@localhost ~]# cat /etc/issue
   
6. CentOS release 6.4 (Final)
   
7. Kernel \r on an \m
   
8. 
   
9. [root@localhost ~]# ./test.pl
   
10. number of matched: 3

复制代码

1. root@ubuntu:/home/teddy/regex/LRE# perl -v
   
2. 
   
3. This is perl 5, version 14, subversion 2 (v5.14.2) built for x86_64-linux-gnu-thread-multi
   
4. 
   
5. root@ubuntu:/home/teddy/regex/LRE# cat /etc/issue
   
6. Ubuntu 12.04.2 LTS \n \l
   
7. 
   
8. root@ubuntu:/home/teddy/regex/LRE# ./test.pl
   
9. number of matched: 3

复制代码

   

TrishaTie

系统：windows 2012, 远程机  Perl版本：5.8.7  比较老  呵呵



回复 4# ld462370527


   

ld462370527

回复 5# TrishaTie

THANKS~ 用win7 perl 5.18测试的也是3。应该是版本的问题。具体细节只能等待大神啦。


   

yestreenstars

回复 6# ld462370527

跟版本没关系，出现3的原因是多了个换行符，如果你在循环开头用了chomp，结果就是2了。
   

ld462370527

回复 7# yestreenstars
感谢！
   

substr函数

怎么会匹配2次呢？

jason680

回复 1# ld462370527

$ cat test.pl
while (<DATA>) {
    $cnt = 0;
    #chomp;
    while(m/(?:[^4]\d\d\d\d|\d[^4]\d\d\d)*(44\d\d\d)?/g){
      print ++$cnt,",PREMATCH=<$`>,MATCH=<$&>,POSTMATCH=<$'>\n";
    }
}
__DATA__
44235


# without chomp that match 3 times
$ perl test.pl
1,PREMATCH=<>,MATCH=<44235>,POSTMATCH=<
>
2,PREMATCH=<44235>,MATCH=<>,POSTMATCH=<
>
3,PREMATCH=<44235
>,MATCH=<>,POSTMATCH=<>

# with chomp that match 2 times
$ perl test.pl
1,PREMATCH=<>,MATCH=<44235>,POSTMATCH=<>
2,PREMATCH=<44235>,MATCH=<>,POSTMATCH=<>