Re: Regex to match 20 chars of some digits followed by some spaces

I can't see any good reason to use Parse::RecDescent to parse fixed width records. This would seem to be using a A-bomb to crack a walnut. Surely you would be better off to unpack the data into a structure and validate from there?

In addition to the examples above you can for fun autogenerate one that does the job you want - rather ugly but it does work.

for ( reverse 1..20 ) {
    $re .= sprintf "\\d{%d} {%d}|", $_, 20-$_;
}
chop $re;
$re = qr/^(?:$re)$/;
print $re, $/;

@tests = (
    '01234567890123456789', # OK
    '123                 ', # OK
    '123               ',   # NOK
    '123 123             ', # NOK
    '                    ', # NOK
    '123c                ', # NOK
);

for(@tests){
    print m/$re/ ? "'$_' #OK\n" : "'$_' #NOK\n"
}

__DATA__
(?-xism:^(?:\d{20} {0}|\d{19} {1}|\d{18} {2}|\d{17} {3}|\d{16} {4}|\d{
+15} {5}|\d{14} {6}|\d{13} {7}|\d{12} {8}|\d{11} {9}|\d{10} {10}|\d{9}
+ {11}|\d{8} {12}|\d{7} {13}|\d{6} {14}|\d{5} {15}|\d{4} {16}|\d{3} {1
+7}|\d{2} {18}|\d{1} {19})$)
'01234567890123456789' #OK
'123                 ' #OK
'123               ' #NOK
'123 123             ' #NOK
'                    ' #NOK
'123c                ' #NOK
[download]

cheers

tachyon

Comment on Re: Regex to match 20 chars of some digits followed by some spaces Download Code

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Re: Re: Regex to match 20 chars of some digits followed by some spaces by leriksen (Curate) on Dec 19, 2003 at 03:20 UTC
Not all the text I am parsing is fixed width, just this bit. The rest is somewhat like this (deboned to protect client) `document : checkpoint address report(s?) doctrailer report : report1 \| report2 \| report3 \| ... report1 : lt[100] report1_cost_centre(s?) lt[200] report1_cost_centre : lt[300] report1_txn(s?) lt[400] report1_txn : lt[500] lt[600] page_break(?) lt[700] lt : "<LT$arg[0]>" lt_data lt_data : /[^\\]*/ lt_end {$return = $item{__PATTERN1__} ...` [download] but for 15 different reports, hundreds of lt records, lots of options, repeats and alternations. +++++++++++++++++ #!/usr/bin/perl use warnings;use strict;use brain;	[reply] [d/l]
Re: Re: Re: Regex to match 20 chars of some digits followed by some spaces by tachyon (Chancellor) on Dec 19, 2003 at 03:35 UTC
Ah that makes more sense. If you have to deal with fixed width records you may find this sub handy: $str = 'first name EOFlast name EOFaddress field + EOF'; my @rec_def = ( [ 'first_name', 20 ], [ 'last_name', 20 ], [ 'address', 30 ], ); sub parse_fixed_width { my ( $record, $rec_def ) = @_; my %struct; my $offset = 0; for my $rec(@$rec_def) { $struct{$rec->[0]} = substr $record, $offset, $rec->[1]; $offset += $rec->[1]; } return length($record) == $offset ? \%struct : ''; } use Data::Dumper; print Dumper parse_fixed_width( $str, \@rec_def ); __DATA__ $VAR1 = { 'first_name' => 'first name EOF', 'address' => 'address field EOF', 'last_name' => 'last name EOF' }; [download] cheers tachyon	[reply] [d/l]