On Mon, Mar 1, 2010 at 11:27 PM, John W. Krahn <jwkr...@shaw.ca> wrote:
> raphael() wrote: > >> Hi, >> > > Hello, > > > I am trying to understand WWW::Mechanize >> > > Did you also look at these pages: > > > http://search.cpan.org/~petdance/WWW-Mechanize-1.60/lib/WWW/Mechanize/Examples.pod<http://search.cpan.org/%7Epetdance/WWW-Mechanize-1.60/lib/WWW/Mechanize/Examples.pod> > > http://search.cpan.org/~petdance/WWW-Mechanize-1.60/lib/WWW/Mechanize/FAQ.pod<http://search.cpan.org/%7Epetdance/WWW-Mechanize-1.60/lib/WWW/Mechanize/FAQ.pod> > > http://search.cpan.org/~petdance/WWW-Mechanize-1.60/lib/WWW/Mechanize/Cookbook.pod<http://search.cpan.org/%7Epetdance/WWW-Mechanize-1.60/lib/WWW/Mechanize/Cookbook.pod> > > > > I understand that the downloaded content is stored in content(). >> Why am I not able to use a regex on it in scalar form? >> >> ------code------ >> >> use strict; >> use warnings; >> use WWW::Mechanize; >> >> my $mech = WWW::Mechanize->new(); >> $mech->get("http://checkip.dyndns.org";); >> my $last_page = $mech->content(); # last page fetched >> >> # this works if I store content in an array @last_page >> # for ( @last_page ) { >> # if ( m/([\d+.]+)/ ) { >> # print "$1\n"; >> # } >> # } >> > > $mech->content() returns a scalar value so that is the same as saying: > > if ( $last_page[ 0 ] =~ m/([\d+.]+)/ ) { > > print "$1\n"; > } > > > # ( my $ip ) = grep/(\d+\.)/, $last_page; >> > > grep() returns the list items that match the expression /(\d+\.)/. The > regular expression is only used to determine which items to return, it has > no effect on the content of those items. If you want to effect the contents > of the list then you have to use map() instead. > > > > ( my $ip = $last_page ) =~ m/([\d+\.]+)/; >> print "$ip\n"; >> >> ------end------ >> >> my $ip gets the whole source page as its value. >> >> -- >> Got it while writing out this post :) >> -- >> >> Now the question becomes what is the difference between these two? >> >> ( my $ip = $last_page ) =~ m/([\d+\.]+)/; >> > > That is the same as: > > my $ip = $last_page; > $ip =~ m/([\d+\.]+)/; > > You are not doing anything with the string stored in $1. > > And BTW, '+' is not a valid IP address character. > > > > ( my $ip ) = ( $last_page ) =~ m/([\d+\.]+)/; >> > > That is equivalent to: > > my $ip; > if ( $last_page =~ m/([\d+\.]+)/ ) { > $ip = $1; > > } > > > I think the above one is "wrong syntax" for using list context? >> > > No, you *have* to use list context or $ip will be assigned the result of > the match operator (true or false) and not the contents of the capturing > parentheses. > > > > Also how can I make grep work? >> >> ( my $ip ) = grep/(\d+\.)/, $last_page; >> > > You can't, grep() doesn't work that way. What you are looking for is > map(): > > ( my $ip ) = map /([\d.]+)/, $last_page; > > Or, since you are not actually using a list, use the /g global option to > the match operator: > > ( my $ip ) = $last_page =~ /[\d.]+/g; > > Note that this will return a list of [\d.]+ strings but only the first one > will be stored in $ip and the rest will be discarded. > > > > > John > -- > The programmer is fighting against the two most > destructive forces in the universe: entropy and > human stupidity. -- Damian Conway > > -- > To unsubscribe, e-mail: beginners-unsubscr...@perl.org > For additional commands, e-mail: beginners-h...@perl.org > http://learn.perl.org/ > > > Cool! I have to admit that is a "detailed" answer. Also thanks for clearing out the differences between these two.. ( my $ip = $last_page ) =~ m/([\d+\.]+)/; ( my $ip ) = ( $last_page ) =~ m/([\d+\.]+)/; Just to clear out any misunderstanding "by above one" I meant ( my $ip = $last_page ) =~ m/([\d+\.]+)/; Now am I getting this right that this is the *wrong syntax* to get list context. Your post was very helpful since I didn't know about parenthesis (or lack of it) to capture values. I always did use parenthesis to capture values like ( my $ip ) = $last_page =~ m/*(*[\d+\.]+*)*/g; Now I *know* this works ( my $ip ) = $last_page =~ m/[\d+\.]+/g; Thanks again John.
