On May 5, 7:02 am, learn.tech...@gmail.com (Amit Saxena) wrote:
> 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
>
> > --
> > To unsubscribe, e-mail: beginners-unsubscr...@perl.org
> > For additional commands, e-mail: beginners-h...@perl.org
> >http://learn.perl.org/
>
> Thanks Charles but this will not work as the tool only accepts perl regular
> expressions but not any perl code statements etc.
>
Sorry, my follow-on with the s{}{} missed the regex requirement.
--
Charles DeRykus
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