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To begin with your concrete example ...

The specification looks something like -- fieldA is from character 9 to 14
my $TEMPLATE = '@8A6'; # oops, originally posted without the quotes while (<DATA>) { my @fields = unpack $TEMPLATE, $_; # for output try pack or printf }

This generalizes. The template for unpack should be machine-generated, to avoid off-by-one errors and other typos.

In what follows, let's suppose you have collected a list of column specifications. Each specification tells you

  • a field name,
  • an offset, and
  • the width of the field in your fixed-width extract.
You might get this from a config file of some sort, or as the result set from a database query, if you happen to have saved your parse specifications in a database table.

use DBI; my $dbh = ... my $sth = $dbh->prepare( 'SELECT field, offset, width' . ' FROM Source_Field' . ' WHERE source = ?;' ); my $source = 'input_file.txt'; $sth->execute($source); my $template; my @fields; while (my $column_spec = $sth->fetchrow_hashref() ) { my ($field, $offset, $width) = @$column_spec{qw(field offset width)}; $template .= "\@${offset}A$width"; push @fields, $field; } open my $reader, '<', $source; while (<$reader>) { my %value_of; my @values = unpack($template, $_); @value_of{@fields} = @values; # you've got your current record in a hash # print it or save it somewhere }

In reply to Re: framework for data parsing by Narveson
in thread framework for data parsing by sam700

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