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How to detect binary chars in a file using preg_match in PHP 5?

Posted on 2009-04-10
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Last Modified: 2012-05-06
What pattern could I use to detect whether a file contains non-printable chars using preg_match (or ereg)?

The logic in the conditional below could be reversed depending upon the easiest pattern.

Thanks in advance.
$fileBuffer = file_get_contents($filePath);	
$pattern = '/pattern??/';
$result = preg_match($pattern, $fileBuffer);
if (false === $result)
    return "binary file";
else
    return "text file";

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Question by:DigitalDave1
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8 Comments
 
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Expert Comment

by:LordOfPorts
ID: 24120236
The is_binary http://us2.php.net/is_binary function might be of interest.
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Expert Comment

by:LordOfPorts
ID: 24120246
My mistake, sorry, is_binary is available starting with PHP 6.
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Author Comment

by:DigitalDave1
ID: 24120249
Yes I saw is_binary(). But we are running PHP 5.x.

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Assisted Solution

by:Ray Paseur
Ray Paseur earned 1500 total points
ID: 24120253
I use a "clean_string()" function to remove not only binary characters, but also unwanted characters.  The code snippet just tests for numbers, but you can add all the alpha and special characters to the REGEX.

So something like this...

$str = "12345";
if (!is_clean_numeric_string($str)) die("BAD NUMBER!");

HTH, ~Ray
function is_clean_numeric_string($string) // Q-N-D IS IT NUMERIC?
{ 
   $str = trim(ereg_replace(" +", " ", $string));
   $new = ereg_replace("[^0-9]", "?", $str);
	
   if ($new != $str) 
   {
      return FALSE; 
   } else {
      return ( $new ); 
   }
}

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Expert Comment

by:LordOfPorts
ID: 24120255
Try using is_string http://us2.php.net/manual/en/function.is-string.php on $fileBuffer:
$fileBuffer = file_get_contents($filePath);     
 
$result = is_string($fileBuffer);
 
if (false === $result)
    return "binary file";
else
    return "text file";

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Accepted Solution

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Ray Paseur earned 1500 total points
ID: 24120266
For a more expanded view of things, the pattern [\x00-\x1f] matches all control characters including the NUL.
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Author Comment

by:DigitalDave1
ID: 24126414
Worked out a preg_match pattern to test for the non-printing chars that exclude \n \r \t  etc.:

$pattern = '/[\x00-\x08\x0E-\x1F\x7F]/';

Thanks for the clues that led to this idea.


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LVL 111

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by:Ray Paseur
ID: 24126507
Thanks for the points -- it's a good question! ~Ray
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