http://www.perlmonks.org?node_id=991770

zing has asked for the wisdom of the Perl Monks concerning the following question:

Hi all ,this perl code uses the three text files(included after the code).Im getting this error -- Unknown format list.txt. at code.pl line 30, <$fh> line 41.

code.pl

 #!/usr/bin/perl  
use strict;  
use warnings;  
use List::Util qw/ max /;  
  
my @matrix;  
my $path = '.'; # (current directory - '.') or path to data files  
  
my @file = qw/list.txt one.txt another.txt/;  
  
for my $file ( @file ) {  
    my %data;  
    my @substrate;  
  
    open my $fh, "<", "$path/$file"  
        or die "Unable to open $file for reading. $!";  
  
    while (<$fh>) {  
        if (/^substrate/) {  
            @substrate = /\d+/g;  
        }  
        elsif (/^product/) {  
            while (/(\d+)/g) {  
                for my $sub (@substrate) {  
                    $data{$sub}{$1} = 1 ;  
                }  
            }  
        }  
        else {  
            die "Unknown format $file. $!";      
        }  
    }  
    close $fh or die "Unable to close $file. $!";  
  
    print "Processing file: $file\n";  
    process(%data);  
  
    push @matrix, \%data;  
}  
  
for my $i (0 .. $#matrix) {  
    for my $j ($i+1 .. $#matrix) {  
        print "Combining $file[$i] and $file[$j]\n";  
        my %data = combine($matrix[$i], $matrix[$j]);  
        process(%data);  
    }      
}  
  
sub process {  
    my %data = @_;  
    my %seen;  
  
    my @product = sort {$a <=> $b}  
                  grep ! $seen{$_}++,  
                  map keys %$_, values %data;  
  
    # to get column width for print  
    my $wid = 1 + max map length, @product;  
  
    printf "%7s" . "%${wid}s" x @product . "\n", 'prod->', @product;  
  
    for my $substrate (sort {$a <=> $b} keys %data) {  
        printf "%7s", $substrate;  
        printf "%${wid}s", $data{$substrate}{$_} || '-' for @product; 
+ 
        print "\n";  
    }  
    printf "\n%5s\n%5s\n%s\n\n", '^', '|', 'substrate';  
}  
  
  
sub combine {  
    my ($matrix1, $matrix2) = @_;  
    my %new_hash = %$matrix1;  
  
    for my $substrate (keys %$matrix2) {  
        $new_hash{$substrate}{$_} = 1 for keys %{ $matrix2->{$substrat
+e} };      
    }  
    return %new_hash;  
}

[download]
-----3 DATA FILES---

list.txt

substrate: 1 2
product: 3
substrate: 6 9
product: 8 10
substrate: 3
product: 6
substrate: 9
product: 5
substrate: 5
product: 2
substrate: 3
product: 9
substrate: 8
product: 9
substrate: 8
product: 1
substrate: 7
product: 11
substrate: 19
product: 17
substrate: 14
product: 13
substrate: 14
product: 11
substrate: 18
product: 19
substrate: 7 14
product: 15
substrate: 7 16
product: 7 17
substrate: 5
product: 6
substrate: 18 15
product: 7
substrate: 7 8
product: 8 18
substrate: 6
product: 9
substrate: 11
product: 12

[download]
one.txt 
substrate[s]: 3649
product[s]: 3419 3648
substrate[s]: 3645
product[s]: 3647
substrate[s]: 3659
product[s]: 3647
substrate[s]: 3675
product[s]: 3674
substrate[s]: 3674
product[s]: 3490 3489
substrate[s]: 3489
product[s]: 3490
substrate[s]: 3490
product[s]: 3485
substrate[s]: 3485
product[s]: 3486
substrate[s]: 3486
product[s]: 3488
substrate[s]: 3488
product[s]: 3487
substrate[s]: 3487
product[s]: 3877
substrate[s]: 3877
product[s]: 3419
substrate[s]: 3182
product[s]: 1875
substrate[s]: 2809
product[s]: 3182
substrate[s]: 3186
product[s]: 2809

[download]
another.txt 
substrate[s]: 3647
product[s]: 3419 3248
substrate[s]: 3645
product[s]: 3641
substrate[s]: 3609
product[s]: 3645
substrate[s]: 3685
product[s]: 3374
substrate[s]: 3674
product[s]: 3390 3490
substrate[s]: 3491
product[s]: 3490
substrate[s]: 3490
product[s]: 3485
substrate[s]: 3489
product[s]: 3486
substrate[s]: 3986
product[s]: 3488
substrate[s]: 3499
product[s]: 3487
substrate[s]: 3287
product[s]: 3877
substrate[s]: 3877
product[s]: 3419
substrate[s]: 3182
product[s]: 1875
substrate[s]: 2809
product[s]: 3182
substrate[s]: 3186
product[s]: 2809

[download]

Replies are listed 'Best First'.
Re: Bad file descriptor error
by Corion (Patriarch) on Sep 05, 2012 at 08:11 UTC

    Maybe you want to improve your error message to also output the offending line, instead of only outputting the number of the offending line?

    die "Unknown format in file '$file' line $. : [$_]";

    [download]
[reply]
[d/l]
      Sorry for that,but this is the only error Im getting :- 
      Unknown format list.txt. Bad file descriptor at code.pl line 30, <$fh>
+ line 41.

      [download]
[reply]
[d/l]
        And what is on the line 41 of list.txt? An empty line?
        لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ
[reply]

        So, have you looked at line 30?

        What have you done to improve the error message that line 30 produces?

        Maybe consider reading die to find out what that subroutine does.

[reply]
Re: Bad file descriptor error
by choroba (Cardinal) on Sep 05, 2012 at 08:14 UTC
    How is the title related to the question?
    لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ
[reply]

      Oh - I completely missed that.

      The title in the question likely stems from a erroneous use of $! in the die message.

      As an explanation to the OP, please read perlvar about $!. It rightly says there:

      Many system or library calls set errno if they fail, to indicate the cause of failure.

      Using $! in situations that are not immediately after a related system call is usually wrong.

[reply]
[d/l]
[select]

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