what regex to extract all data except within <> in perl? - regex

Question

I have string
Message <Network=Data Center> All Verified
I need to extract all string except one in angular brackets
I tried
m/(?![^<]*\\>)/s
Not giving desired result.

Answer 1

Removing <..> regions
It's easier to remove the <..> parts from the string and then deal with the remaining string.
Try this oneliner:
cat file | perl -pne 's/<[^>]*?>//g;'
For your sample input, this is the output:
Message All Verified
Notice the non-greedy quantifier ? is used in the regex. Also, because this is a oneliner, the s/// search-and-replace construct is applied to $_ implicit variable (which is a line from standard input). So after search & replace has run in this oneliner, the $_ will be altered(there will be no <..> regions in it). Also the -p was used in order to print the variable $_ after running the block of code. You can read more about Perl commandline switches in perlrun.
This is one solution. Below there is another one:
Capturing regions outside of <..>
On the other hand, you can(if you want) match the parts outside of the <..> regions.
In order to do that let's build a regex. First, we want a < or > free region. The following regex matches just that
$p = ([^<>]*).
Next, we want to match everything before <, and for that we can write (?:$p<) and everything after >, and that's (?:>$p).
Now if we assemble all those parts together we get (?:>$p)|(?:$p<).
Notice that (?:) is a non-capturing group.
So now there are two capturing groups (the two $p you see above) but only one will match at a time, so some of the captures will be undef. We'll have to filter those out.
Finally, we can assemble all the captures, and we're done.
cat file | perl -ne '$p="([^<>]*)";#x=grep{defined} m{(?:>$p)|(?:$p<)}g; print join(" ",#x)."\n";'
Parse::Yapp parser
You might think that using Parser::Yapp for this particular problem is a bit too much(usually, if you have something complicated to parse, you would use a grammar and a parser generator), but .. why not.. :)
Ok, so we need a grammar, here's one right here grammar_file.yp:
#header
%%
#rules
expression:
| exterior '<' interior '>' exterior
| exterior
;
exterior:
| TOK { $_[0]->YYData->{DATA} .= $_[1]; }
| expression
;
interior: TOK;
%%
#footer
sub Error { my ($parser)=shift; }
sub Lexer {
use Data::Dumper;
my($parser)=shift;
$parser->YYData->{INPUT} or return('',undef);
#$parser->YYData->{INPUT}=~s/^\s+//;
for ($parser->YYData->{INPUT}) {
return ('TOK',$1) if(s/^([^<>]+)//);
return ( $1,$1) if(s/^([<>])//);
};
}
You will notice in the grammar above that the interior is completely ignored, and only the terminals from exterior are collected.
Here's a small program that will use the parser(MyParser.pm generated from grammar_file.yp) parse.pl:
#!/usr/bin/env perl
use strict;
use warnings;
use MyParser;
my $parser=MyParser->new;
$parser->YYData->{INPUT} = "Message <Network=Data Center> All Verified";
my $value=$parser->YYParse(
yylex => \&MyParser::Lexer,
yyerror => \&MyParser::Error,
#yydebug => 0x1F,
);
my $nberr=$parser->YYNberr();
my $data=$parser->YYData->{DATA};
print "Result=$data"
And now a Makefile and we're done:
generate_parser_module:
yapp -m MyParser grammar_file.yp;
run:
perl parse.pl
all: generate_parser_module
Note
Some more Parser generators can be found here
Regexp::Grammars
Parse::RecDescent
Marpa::XS or Marpa::R2

Answer 2

You can do it other way: just remove the string in the angular brackets:
s#<.*>##
Or if > is not allowed:
s#<[^>]*>##

Answer 3

You can use sed for that:
cat yourfile |sed 's/<.*>//g' > newfile
If you need perl:
perl -i -pe "s/<.*?>//g" yourfile

Answer 4

Here is a compact approach. The following regex will capture your strings into Group 1:
<[^>]+>|([^<>]*)
What we are interested in here is not the overall match, but just the Group 1 matches.
So we need to iterate over Group 1 matches. I don't code in Perl, but following a recipe from the perlretut tutorial, this should do it:
while ($x =~ /<[^>]+>|([^<>]*)/g) {
print "$1","\n";
}
Please give it a try and let me know if it works for you.