Re: Why Is Writing to a Binary File so Hard?

You are converting characters to the integer value of their codepoints with the unpack(), and you end up printing those integers. At some point you need to convert integers back to characters with chr().

The smallest change to fix this problem in your code would probably be to replace the print lines:

#   print "$c";
    print chr($c);
#   print $out $c;
    print $out chr($c);
[download]

An alternative would be to make the whole thing much simpler by treating the line directly without converting to integers at all:

    while (my $line = <$in>) {
        $line =~ s/\n/\r/;  # replace LF with CR in the line
        print $out $line;   # and output it
    }
[download]

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Re^2: Why Is Writing to a Binary File so Hard? by NetWallah (Canon) on Feb 01, 2024 at 00:21 UTC
Minor tweak to allow reading of a line containing "0" : `while (defined(my $line = <$in>)) { chomp $line; # Zap trailing "\n" efficiently print $out $line,"\r"; }` [download] "If it happens once, it's a bug. If it happens twice, it's a feature. If it happens more than twice, it's a design philosophy."	[reply] [d/l]
Re^3: Why Is Writing to a Binary File so Hard? by afoken (Chancellor) on Feb 01, 2024 at 09:29 UTC
Minor tweak to allow reading of a line containing "0" : `while (defined(my $line = <$in>)) { chomp $line; # Zap trailing "\n" efficiently print $out $line,"\r"; }` [download] Not required: `#!/usr/bin/perl use strict; use warnings; use autodie; open my $out,'>:raw',"file.tmp"; print $out "a line\na second line\n0"; close $out; open my $in,'<:raw',"file.tmp"; while (my $line=<$in>) { chomp $line; print "read: $line\n"; } close $in;` [download] `>perl foo.pl read: a line read: a second line read: 0 >` [download] Any line but the last in a file always contains a trailing newline, so $line is guaranteed to be true for all but the last line, and reading empty lines and lines containing only "0" is no problem for all but the last line: `>perl -E '"0\n" and say "true"' true >perl -E '"\n" and say "true"' true >perl -E '"0" or say "false"' false > perl -E '"" or say "false"' false >perl -E 'undef or say "false"' false >` [download] The last line WOULD BE a problem if perl would check for truth. But in the special case of readline a.k.a. `<HANDLE>`, it checks for definedness, not for truth. Quoting perlfunc: readline EXPR readline Reads from the filehandle whose typeglob is contained in EXPR (or from `*ARGV` if EXPR is not provided). In scalar context, each call reads and returns the next line until end-of-file is reached, whereupon the subsequent call returns undef. [...] This is the internal function implementing the `<EXPR>` operator, but you can use it directly. [...]If either a `readline` expression or an explicit assignment of a `readline` expression to a scalar is used as a `while`/`for` condition, then the condition actually tests for definedness of the expression's value, not for its regular truth value. (Emphasis mine) Alexander -- Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)	[reply] [d/l] [select]
Re^2: Why Is Writing to a Binary File so Hard? by jmlynesjr (Deacon) on Feb 01, 2024 at 01:07 UTC
The regex would eliminate one of the loops. Thanks for the reply. James There's never enough time to do it right, but always enough time to do it over...	[reply]

readline EXPR

readline