pattern比对 （grep）
字符串 命令 /pattern/修饰词
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命令
=~ 表示比對符合pattern
!~ 表示比對不符合pattern
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修饰词
i 不計大小寫
x 在模式中忽略空格
g 继续比对，继续寻找，相当于find next |
例子 ：扫描文件gogo,找含有want的行
#!/usr/bin/perl
$file="/home/macg/perltest/gogo";
&gotest($file);
sub gotest{
my(@tmp)=@_;
open (MYFILE, $tmp[0]) || die ("Could not open file");
my($line,$newline);
while ($line=<MYFILE>) {
if($newline=($line=~/want/)) { 行中查找含有want
print "found\n";
print "\$line is:$line";
print "\$newline is:$newline \n";
} else {
print "not found\n";
print "\$line is:$line";
print "\$newline is:$newline \n";
}
}
close(MYFILE);
}
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[macg@localhost perltest]$ ./tip.pl
not found
$line is:I glad to be Los angle
$newline is:
found
$line is:I want to be Los angle
$newline is:1
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缺省的，模式定界符为反斜线/，但其可用字母m自行指定，如：
m!/u/jqpublic/perl/prog1! 等价于 /\/u\/jqpublic\/perl\/prog1/
而且换成其他字符后，/就不属于特殊字符了，不必加\/了
pattern
\d或\d+ 任意数字 [0-9]
\D或\D+ 除数字外的任意字符
/[\da-z]/ 等同于/[0-9a-z]/
^ /^def/ 只匹配以def打头的字符串
$
/\\/ 转义字符
/\*+/
pattern中标点都要加\
[] 意味着匹配一组字符中的一个
* + ? . 通配符
*+不能作为首字符，所以任意字符必须用显示表示法[0-9a-zA-Z]
$line=~
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syntax error at ./address.pl line 6, near "out @int_hwaddress"
Quantifier follows nothing in regex; marked by <-- HERE in m at ./address.pl line 41
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改为
$line=~/[0-9a-zA-Z]+:[0-9a-fA-F]+:[0-9a-fA-F]+:[0-9a-fA-F]+:[0-9a-fA-F]+:[0-9a-fA-F]+/
.
pattern中空格就是" "
if(($input=~/^ping$/i)||($input=~/^ping $/i))
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macg>ping
command:[ping xxx.xxx.xxx.xxx]
macg>ping 带一个空格
command:[ping xxx.xxx.xxx.xxx]
IEI-nTracker>ping 带两个空格
Use of uninitialized value in concatenation (.) or string at /nettracker/ntshell/ntshell
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| if(($input=~/^ping$/i)||($input=~/^ping +$/i)) |
IEI-nTracker>ping 多个空格
command:[ping xxx.xxx.xxx.xxx]
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if($_[0]=~/^ping +[0-9a-zA-Z\.]+$/i)
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相当于"ping xxxxx"或"ping xxxx"
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=~/want/是等于，还是含有？？？
当然是包含
等于其实就是exactly匹配，/^wang$/
格式匹配（不是包含性符合），通常用于一些特殊格式输入时用（比如IP地址）
#!/usr/bin/perl
$file="/home/macg/perltest/gogo";
&gotest($file);
sub gotest{
my(@tmp)=@_;
open (MYFILE, $tmp[0]) || die ("Could not open file");
my($line,$newline);
while ($line=<MYFILE>) {
if ($line =~ /\d+\.\d+\.\d+\.\d+/) {
print "$line";
print "the ip add is good\n";
} else {
print "$line";
print "the ip add is a error\n";
}
}
close(MYFILE);
}
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[macg@localhost perltest]$ cat gogo
202.106.0.20
10.0.0.as
[macg@localhost perltest]$ ./tip.pl
202.106.0.20
the ip add is good
10.0.0.as
the ip add is a error
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上面这个例子也不对，会出下面的错：包含以外的错误,所以应该加^ $
[macg@localhost perltest]$ cat gogo
202.106.0.20
10.0.0.as
10.0.0.1 as
改成 if ($line =~ /^\d+\.\d+\.\d+\.\d+$/) {
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[macg@localhost perltest]$ ./tip.pl
202.106.0.20
the ip add is good
10.0.0.as
the ip add is a error
10.0.0.1 as
the ip add is a error |
/want/g与/want/的区别：指针后移,相当于find next
$line="inet addr:192.168.10.17 Bcast:192.168.10.255 Mask:255.255.255.0";
$line=~/(\d+)\.(\d+)\.(\d+)\.(\d+)/;
print "$&\n"; $&查询结果
$line=~/(\d+)\.(\d+)\.(\d+)\.(\d+)/;
print "$&\n";
$line=~/(\d+)\.(\d+)\.(\d+)\.(\d+)/;
print "$&\n";
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[root@nm testpl]# ./tip.pl
192.168.10.17
192.168.10.17
192.168.10.17
几次的查找都相同，因为每次都是回到“首部”找“一次”
找到一个，就返回值1，并停止比对
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加g
$line="inet addr:192.168.10.17 Bcast:192.168.10.255 Mask:255.255.255.0";
$line=~/(\d+)\.(\d+)\.(\d+)\.(\d+)/g;
print "$&\n";
$line=~/(\d+)\.(\d+)\.(\d+)\.(\d+)/g;
print "$&\n";
$line=~/(\d+)\.(\d+)\.(\d+)\.(\d+)/g;
print "$&\n";
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[root@nm testpl]# ./tip.pl
192.168.10.17
192.168.10.255
255.255.255.0
加g后，好象文件指针一样，查一次，指针就移一格
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“或”下的比对，匹配的先后顺序很重要, 尤其是包含型的，要把精确的放前面
if (($ret=($line=~/eth[0-5]/))||($ret=($line=~/eth[0-5]:[0-5]/)))
{
print "$&:";
$found=1;
} elsif ($found)
{
print $line;
$found=0;
}
}
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[mac@nm testpl]$ ./address.pl
eth0: inet addr:10.4.3.117 Bcast:10.4.255.255 Mask:255.255.0.0
eth0: inet addr:192.168.10.117 Bcast:192.168.10.255 Mask:255.255.255.0
eth0: inet addr:192.168.1.142 Bcast:192.168.1.255 Mask:255.255.255.0
eth1: BROADCAST MULTICAST MTU:1500 Metric:1
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改成精确的放前面
if (($ret=($line=~/eth[0-5]:[0-5]/))||($ret=($line=~/eth[0-5]/)))
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[mac@nm testpl]$ ./address.pl
eth0: inet addr:10.4.3.117 Bcast:10.4.255.255 Mask:255.255.0.0
eth0:1: inet addr:192.168.10.117 Bcast:192.168.10.255 Mask:255.255.255.0
eth0:2: inet addr:192.168.1.142 Bcast:192.168.1.255 Mask:255.255.255.0
eth1: BROADCAST MULTICAST MTU:1500 Metric:1
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先查到精确，就会跳过模糊的（部分的），否则会用模糊的（部分的）代替精确的
$line =~ /want/ 完成，只返回1和null
即比对不修改=~左边字符串
与比对截然不同，替换是修改=~左边字符串的
my($line,$newline);
while ($line=<MYFILE>) {
if($newline=($line=~/want/)) {
print "found\n";
print "\$line is:$line";
print "\$newline is:$newline \n";
} else {
print "not found\n";
print "\$line is:$line";
print "\$newline is:$newline \n";
}
}
close(MYFILE);
}
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[macg@localhost perltest]$ ./tip.pl
not found
$line is:I glad to be Los angle
$newline is:
found
$line is:I want to be Los angle
$newline is:1
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如何能找到比对结果？ 用$&
while ($line=<MYFILE>) {
if ($line =~ /want/) {
print "$line";
print "\$\& is $&\n";
print "good\n";
} else {
print "$line";
print " error\n";
}
}
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[macg@localhost perltest]$ ./tip.pl
I want go to LA. and I also want to be NY. $line没发生变化
$& is want $&是比对结果
good
But I glad to be D.C.
error
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注意if ($line=~/want/)和赋值毫无关系，所以不存在$line值改变的问题，$line只是操作符号=~左边的一个元素而已，所以也不存在返回值给$line的问题
$& $` $' 的含义
while ($line=<MYFILE>) {
if ($line =~ /want/g) {
print "good\n";
print "$line";
print $& . "\n";
print $` . "\n";
print $' . "\n";
print "good\n";
} else {
print " error\n";
print "$line";
}
}
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[macg@localhost perltest]$ ./tip.pl
good
I want go to LA. and I also want to be NY.
want $& $&是最后一个match，也可算是结果
I $` match之前的所有字符
go to LA. and I also want to be NY. $' match之后的所有字符 |
!~ 比对不符合pattern （其实没什么用，因为用if ( =~ ) else即可）
perl可以将pattern再细分 ,再用$1,$2,$3,$4表示这些子match
步骤：
1.对想单独提出来的子pattern加( )
2.再用$1,$2来表示if ($line =~ /^(\d+)\.(\d+)\.(\d+)\.(\d+)$/) {
print "good \n";
print $line;
print $& . "\n";
print $1,"\n";
print $2,"\n";
print $3,"\n";
print $4,"\n";
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[macg@localhost perltest]$ ./tip.pl
good
202.106.0.20
202.106.0.20
202
106
0
20
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修饰词i 不计大小写
if ($line =~ /want/i) {
print "good \n";
print $line;
print $& . "\n";
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[macg@localhost perltest]$ ./tip.pl
good
I WANT TO go to
WANT
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修饰词x 在模式中忽略空格
/\d{2} ([\W]) \d{2} \1 \d{2}/x 等价于 /\d{2}([\W])\d{2}\1\d{2}/
替换格式
命令与修饰词基本上与比对相同格式： string command s/pattern/欲置換的字串/修饰词
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命令与比对相同
=~ 先比对符合(=~)再替换
!~ 比对不符合(!~)再替换
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基本替换(后面替换前面)
$line =~s/want/hate/i;
print "good \n";
print "\$line is :$line";
print "\$\& is : $&", "\n";
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[macg@localhost perltest]$ ./tip.pl
good
$line is :I hate TO go to 与比对截然不同，替换是修改=~左边字符串的
$& is : WANT 替换里的$&和就是比对的$&
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修饰词i,不计大小写
$line =~s/want/hate/i; 將 $line中的 want 或 WANT,Want 換成 hate
刪除（替换为空）
单纯的删除一般没用，实际应用中，基本上都用全域删除(g)
$line =~s/want//i;
print "\$line is :$line";
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[macg@localhost perltest]$ ./tip.pl
$line is :I TO go to
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g全域替换，替换所有的，缺省替换是查找到第一符合的就替换，然后停止
$line =~s/want/hate/ig; 修饰词可以连写
print "good \n";
print "\$line is :$line"
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[macg@localhost perltest]$ cat gogo
I WANT TO go to NY. And I also want to be DC.
I glad to go to
[macg@localhost perltest]$ ./tip.pl
$line is :I hate TO go to NY. And I also hate to be DC.
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替换g与比对的g的不同
- 比对g是find next,所以需要与while等合用
- 替换不需要用循环语句，一句就能实现所有替换，即：替换不需要find and find next,替换可以find all in one time.
e选项把替换部分的字符串看作表达式，在替换之前先计算其值
$string = "0abc1";
$string =~ s/[a-zA-Z]+/$& x 2/e; 将中间的字符（非数字）成倍
now $string = "0abcabc1"
$&是查找结果
转换格式
string command tr/字元集/欲轉換的字元集/修饰词
string command y/字元集/欲轉換的字元集/修饰词
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命令：=~ !~
修饰词：
d 刪除
s 將重覆刪除
c 非转换：將不在指定字元集中的字元(包括換行字元)，換成欲轉換的字元集
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最基本的转换：字符串小写换大写
$line =~tr/a-z/A-Z/;
print "\$line is :$line";
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[macg@localhost perltest]$ cat gogo
I WANT TO go to NY. And I also want to be DC.
[macg@localhost perltest]$ ./tip.pl
good
$line is :I WANT TO GO TO NY. AND I ALSO WANT TO BE DC.
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转换和替换一样，也是修改string
删除: =~tr/要删除的字符//d
全域替换删除和转换删除等价
全域替换删除 $line =~tr/\t//g;
转换删除 $line =~tr/\t//d;
$line =~tr/\t//; 删除所有TAB 转化所有TAB为空//
print "\$line is :$line";
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[macg@localhost perltest]$ ./tip.pl
$line is :I WANT TO go to NY. And I also want to be DC.
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发觉TAB没删掉，其实不是没删掉，只是只删了第一个TAB而已
$line =~tr/\t//d;
print "\$line is :$line";
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[macg@localhost perltest]$ ./tip.pl
good
$line is :I WANT TO go to NY. And I also want to be DC.
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删除重复字符： =~ tr/a-zA-Z//s; 这功能没什么实际用途
$line=~ tr/a-zA-Z//s;
print "\$line is :$line";
[macg@localhost perltest]$ cat gogo
I WANTWANT TO go to NNYY. And I also wWant to be DC.
[macg@localhost perltest]$ ./tip.pl
good
$line is :I WANTWANT TO go to NY. And I also wWant to be DC.
tr转换不支持!~ 只支持=~ 因为修饰词c就相当于!~了
$text="1 abc 23 PID";
$text =~ tr/[0-9]c; [0-90]c即非数字
一个CGI控件值的解码的示范程序:
$value="%A4T%A4K%21";
$value=~s/%([a-fA-F0-9][a-fA-F0-9])/pack("C",hex($1))/eg;
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s替换%字符串，
并把符合的字符串传给$1，
把$1通过e运算pack("C",hex($1))进行解码处理
pack("C",hex($1))把$1找到的十六进制数值转成十进制的码
C代表unsigned char value的意
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posted on 2012-03-10 15:44
xzc 阅读(8208)
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