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hi

I have a binary file, the first bytes is represent the record type and the second byte represent the record length. Due to that, i have to read the second byte to get total record length and read the record base on the length.

sample data as below

84 47 00 0c 00 00 11 0a 03 50 35 04 00 64 0a 04
16 12 00 1e 00 1d 00 00 65 09 08 54 52 03 2f 82
05 10 00 02 6e 06 0b a8 53 11 67 00 00 00 7a 7f
00 69 4a 42 47 48 4a 41 0c 00 6a 53 54 4d 44 54
4f 1c 00 66 04 00 00
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After i read the record length and substr the record. The substr result is not running properly. It was not substr the record based on the length. Why this is happened and below is the output of my program:

RECORD TAG    : 84
RECORD LENGTH : 71
RECORD        : 000c0000110a
RECORD TAG    : 03
RECORD LENGTH : 80
RECORD        : 350400640a
RECORD TAG    : 04
RECORD LENGTH : 22
RECORD        : 12001e001d00006509085452032f82051000026e060b
RECORD TAG    : 04
RECORD LENGTH : 22
RECORD        : 120021001b00006509084480900f82051000046e0608
RECORD TAG    : 03
RECORD LENGTH : 39
[download]

This is my code

#!/usr/bin/perl -w

use Cwd;
use warnings;
use strict;
use Getopt::Long;

use constant FILEHDR => 4;
use constant CDRLEN  => 286;

my ($trace, $help, $infile);
my $swap = '';
my $indir  = getcwd;
my $outdir = getcwd;

GetOptions (
    "h|help"    => \$help,
    "filename|f=s"    => \$infile,
    "swap|s"    => \$swap,
    "input|i=s"    => \$indir,
    "output|o=s"    => \$outdir,
    "trace|t"    => \$trace
) or usage();


sub usage {
    exit;
}

my $outfile = $infile;
my $data;

if ($infile) {
    #open (OUTPUT, ">$outdir/$outfile");
    open (DATA, "$indir/$infile");
    binmode DATA;
    
    while ($data = <DATA>) {
        my $tag    = unpack "H2", substr $data,0,1,'';
        my $length = unpack "C", substr $data,0,1,'';

        if ($length == 0x81) {
            $length = unpack "C", substr $data,0,1,'';
        }

        my $template = 'H' . $length*2;
        my $rec      = unpack $template, substr $data,0,$length,'';

        printf ("RECORD TAG    : %s\n", $tag);
        printf ("RECORD LENGTH : %s\n", $length);
        printf ("RECORD        : %s\n", $rec);
    }

    close(DATA);
    #close(OUTPUT);
}
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Please help me..

In reply to Problem on substr record on binary file by bh_perl

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