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Fixed length file layout - cut2fmt 2

by Anonymous Monk
on Jul 22, 2002 at 06:40 UTC ( #183957=snippet: print w/replies, xml ) Need Help??
Description: You've all seen the Perl Cookbook cut2fmt function which relieves you of some of the work setting up a unpack TEMPLATE. I often need to go one further and get fields out of a record in a non-contiguous way, ie. skip bytes. This is similar to what you do in languages like SAS - and it makes life very easy when working with files. I slightly modified the cut2fmt program from the Perl Cookbook to do this. WARNING - hasn't been through exhaustive testing, and it's yours to do what you want with.
# cut2fmt part 2

sub cut2fmt2 {
  my(@positions) = @_;
  my $template = '';
  my $lastpos = 1;
  foreach $fld (@positions) {
    ($place,$len) = split(/-/,$fld);
    if ($lastpos<=$place) {
      $template .= "x" . ($place - $lastpos) . " ";
      $place += $len;
    $template .= "A" . ($len) . " ";
    $lastpos = $place;
  $template .= "A*";
  return $template;

# Pick out fields from a fixed length file record
# by defining start pos - len eg. 8-3 = get 3 Alpha char from posn 8.
# use the string this sub returns in your unpack (or pack!) statement.

$fmt = cut2fmt2("8-3","14-6","20-3","26-2","30-1");
print "$fmt\n";
# Returns: x7 A3 x3 A6 x0 A3 x3 A2 x2 A1 A*
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