Re: [PLUG] Simple Perl question

[Walt Mankowski via plug <plug@lists.phillylinux.org>]

Hi Eric,

I'm not 100% sure I'm following your logic, but it looks like you're
trying to treat $output as a string where you're appending one binary
digit at a time. If that's the case, then try changing `+=` to `.=` so
you're appending instead of adding.

That said, I think you're going about it the wrong way. Perl's pack()
function will convert integers to binary for you without doing all
this work. Here's an example:

#!/usr/bin/env perl

my $output = 0;
while (<<>>) {
    chomp;
    my @nums = split ',';
    for my $num (@nums) {
        $output *= 2;
        $output += 1 if $num;
    }
    printf STDERR "%b\n", $output;
    print pack ("i", $output);
}

----

Sample run:

% perl cvs2bin.pl input.csv | xxd -b
110101
00000000: 00110101 00000000 00000000 00000000                    5...

Hope this helps!

Walt

On Mon, Oct 14, 2024 at 07:17:35PM -0400, Eric Lucas via plug wrote:
> I'm trying to quickly put together a little utility in perl to help me with
> a task.
> 
> The object is to take a csv file containing a row of either 0, 1, or ,  and
> write it out as a binary file that matches the csv input.
> 
> Here's the code:
> 
> #! /usr/bin/perl
> my @line;
> my $char;
> my $output;
> my $binOut = 1;
> 
> my $file = shift @ARGV or die "ERROR: You gotta give me a file name!\n";
> 
> open $FILE, '<', $file or die "BAH!\n" ;
> 
> while (@line = split(//,<$FILE>)) {
>     my $count = @line;
>     for (my $x=0; $x<$count; $x++) {
>         if ($line[$x] =~ /1/) {
>             print "one " if ($binOut == 0);
>             $output += 0b1;
>         }elsif ($line[$x] =~ /0/) {
>             print "zero " if ($binOut == 0);
>             $output += 0b0;
>         }
>     }
>     print $output if ($binOut == 1);
>     print "\n" if ($binOut == 0);
>     $output = "";
> }
> close $FILE;
> __END__
> 
> A typical input is a single line of ASCII characters:  "0,0,1,1,0,1,0,1,"
> 
> I expect the output to be, in binary, a single byte: 00110101
> 
> When I debug it with $binOut = 0 I get:  zero zero one one zero one zero one
> So far, so good.
> 
> With $binOut = 1
> ./cvs2bin.pl input.csv |xxd -b
> 00000000: 00110100
> 
> My question is, why does the ultimate "1" appear to become a zero?
> Program error?
> File error?
> xxd error?
> 
> Thanks,
> 
> Eric Lucas

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