This just a very short FYI for anyone who is interested in why read() would refuse to read the "right" number of bytes from a file. In the following snippet I am slurping an entire file and verifying that I read the expected number of bytes. I was getting the error message "Read 3157 but expected 3158 bytes from 002971DD46D2CB2286256BAC002C26FB.xml" and it didn't immediately occur to me that because of the implicit new-line handling on text files, a single \r character had been removed and my $expected was differing from my $got value.

One application of binmode() later and my code worked. This isn't a revelation, perlfunc already documents this but since I had to think about it for moment today I figured I'd just share and let this be a reminder to anyone else who might get something out of it.

sub readfile {
    my $fname = shift;
    my $fdata;
    open XML, "<", $fname or die "Couldn't open $fname: $!";
    binmode XML or die "Couldn't binmode $fname: $!";
    
    my $expected = -s XML;
    my $got = read XML, $fdata, $expected;
    $expected == $got or
      die "Read $got but expected $expected bytes from $fname: $!";
    close XML or die "Couldn't close $fname: $!";

    return \ $fdata;
}

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In reply to Remember to binmode text files by diotalevi

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