perl 老版本模式分组问题

romanticsong

perl 版本5.8.8

文本内容

<param name="UserPassword" type="encrypt">b273290137C725168F52F3D7E1EA8670</param>


需要将红色部分的文字替换为新的字符串

本人菜鸟写的perl语句为：

#B="UserPassword"
#C="encrypt"
perl -ne 'use 5.010;s/(<param name="'$B'" type="'$C'">)(?:.*?)(<\/param>)/\1'$A'\2/;print $_'  xxx.xml

当变量$A的值为 数字开头的字符串时，就会出问题，例如A="123456" 这类字符串时，perl无法得出正确的结果

由于perl版本较低，分组模式引用又不能使用\g{1} 这种方法

求助各位高人，如何解决该问题？

jason680

回复 1# romanticsong

1. shell variable use %ENV, ex: %ENV{"B"}
$ export B="UserPassword"
$ perl -e 'print "shell \$B=$ENV{B}\n"'   
shell $B=UserPassword

2. \1 change to $1 ==> ${1}

perldoc perlre
   Warning on \1 Instead of $1
       Some people get too used to writing things like:

           $pattern =~ s/(\W)/\\\1/g;

       This is grandfathered (for \1 to \9) for the RHS of a substitute to
       avoid shocking the sed addicts, but it's a dirty habit to get into.
       That's because in PerlThink, the righthand side of an "s///" is a
       double-quoted string.  "\1" in the usual double-quoted string means a
       control-A.  The customary Unix meaning of "\1" is kludged in for
       "s///".  However, if you get into the habit of doing that, you get
       yourself into trouble if you then add an "/e" modifier.

           s/(\d+)/ \1 + 1 /eg;            # causes warning under -w

       Or if you try to do

           s/(\d+)/\1000/;

       You can't disambiguate that by saying "\{1}000", whereas you can fix it
       with "${1}000".  The operation of interpolation should not be confused
       with the operation of matching a backreference.  Certainly they mean
       two different things on the left side of the "s///".

romanticsong

回复 2# jason680


perl -ne 's/(<param name="'$B'" type="'$C'">)(?:.*?)(<\/param>)/${1}'$A'${2}/;print $_'  xxx.xml


感谢大牛，将\1 修改为 ${1}解决了