I've had the pleasure of hacking through three types of flat text file recently. They are So I have been parsing a lot of flat text files. The RFC's are HTML, but there's a lot of fluff at the beginning and at the end, so I've been using the belowmentioned loop to extract the 'meat'. The drinks are also HTML, but have different crap around them. The CIF files are not HTML, and I cant really strip a lot of data from them -- but I want to be able to strip them out of other data.

So with these three programs (in about 2 weeks) I have had to use some sort of start parsing - parse - stop parsing loop three times. I've even pondered writing a small module to do it for me (not for CPAN, probably would post it here, but just something to keep in my homedir to ease future scripts). This is something that has undoubtedly been done zillions of times. After all, what is perl but a <!- pathologically eclectic RUBBISH lister!!!!!! ->parser?

So whilst working on making my code readable, I stumbled upon (see Using arrays of qr!! to simplify larger RE's for readability (code). and Optimization for readability and speed (code)) the use of arrays of qr!! and iterate through them when matching text. This allows some flexibility (i.e., mulitple "start" and "finish" conditions), and it also is pretty clear to read (as it reduces the size of the individual regular expressions).

But looking over the code, I dont get a good "satisfied" feeling re-using it. So, here it is, and I'd like to know what others would do instead: 

my @beginnings =
( qr{This is valid</a>},
  qr{[So]+(?:IS|isnt) this}, 
);

my @endings =
( qr{(?:we) Should not [be] [Pp]arsing after},
  qr{either (o|f) these [Ll]ines},
);

sub isbeg {
  my $test = shift;
  foreach (@beginnings) { return undef unless $test =~ $_ }
  $test;
}

sub isend {
  my $test = shift;
  foreach (@endings) { return undef unless $test =~ $_}
  $test;
}

# here is the part I dislike, partially because of the $parsing variab
+le
# it just doesnt seem as "clean" as something some of
# you would write.

  my $parsing;
  foreach my $line (@lines) {
    $parsing++ if isbeg( $line );
    push @extracted, "$line\n" if $parsing;
    last if isend( $line );
  }

[download]
I'm familiar with HTML::TokeParser and HTML::Parser, but since I do this a lot on non-HTML files, I'd like to extract the good parts with my loop and use the parsing modules to parse the stuff I want to parse (rather than the gristle).

thanks
hermano deppon

--
Laziness, Impatience, Hubris, and Generosity.

In reply to Parse Loops with flat text files. (code) by deprecated

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