Hello,

The following code is supposed to check for "illegal" characters in a text file that I pass to it.
I define illegal as ordinates 0-8, 11-31 or >126. 
BEGIN{
  @ARGV == 1  or warn "\n\tUsage: $0 FILE\n\n" and exit 255;
  $in=shift;
  warn "Error: Can't read input file $in\n" and exit 255
    if ! -s $in;
}

open (INFILE, $in) or die "Can't open $in for reading\n";

while (<INFILE>) {
  $line = $_;
  chomp $line;
  @character=split /\.*/;
  while (@character){
    my $character = shift @character;
    $ord = ord($character);
    if ($ord>126) {
      print "$in contains illegal character \(ord:\ ", "$ord\) on line
+ $.";
    }
    elsif ($ord<32) {
      if ($ord<9) {
        print "$in contains illegal character \(ord:\ ", "$ord\) on li
+ne $.";
      }
      if ($ord>10) {
        print "$in contains illegal character \(ord:\ ", "$ord\) on li
+ne $.";
      }
    }
  }
}

close (INFILE);

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That gives the expected results for most of my text files, e.g. a text file that contains ^Z on line 15 will yield:

test.txt contains illegal character (ord: 26) on line 15

However if the input text file contains a line commencing with "." (period), I get output like this:

test.txt contains illegal character (ord: 0) on line 23

Can anyone explain (in terms a newbie can understand) why it thinks a "." at the start of a line is a Null character?

Thanks.

In reply to Rogue Null (ordinate 0) characters in text files by paulnovl

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