Looking for NULLS in a string

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

Hello fellow Monks, Is it possible in a regular expression (or some other way) to match the null character? For an application here at work, I attempted to write a perl "record scrubber" that walks through a record and looks for Null bytes. Unfortunately, it does not match to \000 or \x00; that is to say, given a line like this: HELLO\0\0GOODBYE A C program would find the two nulls between Hello and Goodbye but perl apparently doesn't. Is there a way to do this? here is my code:

while (<INFILE>)
{
    $CurrentLine = $_;
    $WordPos = 0;

    if ($Line =~ /\000/)
    {
        print "Found nulls at line $Line file position: ";
         }

}
[download]

Comment on Looking for NULLS in a string Download Code

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Re: Looking for NULLS in a string by dreadpiratepeter (Priest) on Sep 20, 2002 at 14:43 UTC
One thing I am noticing right off is that the $Line variable you are matching against does not appear to contain anything useful. I'm hoping that is a transcription error and not a sign (along with the lack of my's) that you are not using strict. Which would have told you about the misnaming of $CurrentLine to $Line. If this is indeed a transcription error I apologize and point out that \0 is the proper metacharacter for null in the Perl regular expression (See p163 of the Camel book). Hope this helps, -pete "Pain heals. Chicks dig scars. Glory lasts forever."	[reply]
Re: Looking for NULLS in a string by blokhead (Monsignor) on Sep 20, 2002 at 14:40 UTC
Your code `if ($Line =~ /\000/)` is searching within the `$Line` variable, however, I don't think that's what you want. You want to match within `$CurrentLine`, right? `if ($CurrentLine =~ /\000/)`. However, if all you want to do is find the string offset of a single character, use the `index` function, which will be much more efficient. blokhead	[reply] [d/l] [select]
Re: Looking for NULLS in a string by Zaxo (Archbishop) on Sep 20, 2002 at 16:12 UTC
`while (<INFILE>) { local $" = ', '; my @positions; push @positions, pos() while /\000/g; print 'Found nulls at line ', $. , ', positions ' "@positions.$/" if @positions; }` [download] `$.` is the line number maintained by the diamond operator. `$"` is the record seperator for stringified arrays. pos() is the last match position maintained by the regex engine. After Compline, Zaxo	[reply] [d/l]
Re: Looking for NULLS in a string by zentara (Cardinal) on Sep 20, 2002 at 16:02 UTC
I think you just want =~ /\0/ This script will strip out Nulls from a test file. `#!/usr/bin/perl use warnings; open(IH,"<null-bytes-test-in") or die $!; @in = (<IH>); close IH; open(OH,"+>null-bytes-test-out"); foreach $line (@in){ $line =~ s/\0//g; print OH $line; } close OH;` [download]	[reply] [d/l]