On Fri, Apr 30, 2010 at 10:40 PM, C.DeRykus <dery...@gmail.com> wrote:
> On Apr 30, 3:55 am, learn.tech...@gmail.com (Amit Saxena) wrote:
> > Hello everybody,
> >
> > Can we perform substitution to the matched pattern inside a regular
> > expression so that the modified pattern gets returned instead of earlier
> > matched one ?
> >
> > As a reference, in the following code below, I want to perform the
> > substitution of "~" character with "_" character to the value of "\3"
> inside
> > a regular expression so that $3 ultimately becomes "are___you___fine?"
> > instead of "are~~~you~~~fine?".
> >
> > I tried checking with the perl docs but of no help. The only hope is
> using
> > "(?{})" which not only is experimental but also doesn't allow me to
> modify
> > the value of "\3" inside a regular expression.
> >
> > Note : The reason why I want a solution entirely based on regular
> expression
> > because this regular expression will be used in a tool which supports
> usage
> > of perl regular expression inside its configuration file.
> >
> > The source code as well as the output is mentioned below.
> >
> > Please suggest.
> >
> >
> ==========================================================================================
> >
> > [r...@host1 ~]#
> > [r...@host1 ~]# cat check.pl
> > #!/usr/bin/perl
> >
> > use strict;
> > use warnings;
> >
> > my $text1 = q/hello~~~how~~~are~~~you~~~fine?~~~OK/;
> > my $regex1 =
> qr/^([^\~]+)\~\~\~([^\~]+)(?:\~\~\~){0,1}(.*)\~\~\~([^\~]+)$/;
> >
> > print "\n";
> > print "text1 is [$text1]\n\n";
> >
> > print "regex1 is [$regex1]\n\n";
> >
> > if ( $text1 =~ /$regex1/ )
> > {
> > print "Regular expression matched\n\n";
> >
> > print "Field 1 : [$1]\n";
> > print "Field 2 : [$2]\n";
> > print "Field 3 : [$3]\n";
> > print "Field 4 : [$4]\n";
> >
> > print "\n";}
> >
> > else
> > {
> > print "Regular expressing didn't matched\n\n";}
> >
> > [r...@host1 ~]#
> > [r...@host1 ~]# perl check.pl
> >
> > text1 is [hello~~~how~~~are~~~you~~~fine?~~~OK]
> >
> > regex1 is [(?-xism:^([^~]+)~~~([^~]+)(?:~~~){0,1}(.*)~~~([^~]+)$)]
> >
> > Regular expression matched
> >
> > Field 1 : [hello]
> > Field 2 : [how]
> > Field 3 : [are~~~you~~~fine?]
> > Field 4 : [OK]
>
> Not exclusively a regex but here's an option:
>
> my $regex1 = qr/^( # field 1 - new capture
> ([^~]+) # field 2
> ~~~
> ([^~]+) # field 3
> (?:~~~){0,1}
> ) # end field 1 (needed for
> length)
> (.*) # target field 4
> ~~~
> ([^~]+)$ # final field 5
> /x;
> if ( $text1 =~ /$regex1/ )
> {
> ( my $target = $4 ) =~ tr/~/_/;
> substr( $text1, length($1), length($4), $target ); # extra
> substr arg
> }
>
> orig: [hello~~~how~~~are~~~you~~~fine?~~~OK]
> change: [hello~~~how~~~are___you___fine?~~~OK]
>
>
> Perl 5.10 has named captures which'd make this more readable.
>
> --
> Charles DeRykus
>
>
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>
>
Thanks Charles but this will not work as the tool only accepts perl regular
expressions but not any perl code statements etc.
Thanks anyway.
Regards,
Amit Saxena
