How do I read fixed-length records in Perl?

Question

What\'s the best way to read a fixed length record in Perl. I know to read a file like:

ABCDE 302
DEFGC 876

I can do

while         


        

Answer 1

Update: For the definitive answer, see Jonathan Leffler's answer below.

I wouldn't use this for just two fields (I'd use pack/unpack directly), but for 20 or 50 or so fields I like to use Parse::FixedLength (but I'm biased). E.g. (for your example) (Update: also, you can use $/ and <> as an alternative to read($fh, $buf, $buf_length)...see below):

use Parse::FixedLength;

my $pfl = Parse::FixedLength->new([qw(
  key:5
  blank:1
  value:3
)]);
# Assuming trailing newline
# (or add newline to format above and remove "+ 1" below)
my $data_length = $pfl->length() + 1;

{
  local $/ = \$data_length;
  while() {
    my $data = $pfl->parse($_);
    print "$data->{key}:$data->{value}\n";
    # or
    print $data->key(), ":", $data->value(), "\n";
  }
}

There are some similar modules that make pack/unpack more "friendly" (See the "See Also" section of Parse::FixedLength).

Update: Wow, this was meant to be an alternative answer, not the official answer...well, since it is what it is, I should include some of Jonathan Leffler's more straight forward code, which is likely how you should usually do it (see pack/unpack docs and Jonathan Leffler's node below):

$_ = "ABCDE 302";
my($key, $blank, $value) = unpack "A5A1A3";