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I find myself needing to use Perl more and more since PHP's regular expressions leave me wondering what is going on half the time as they simply don't respond as they should (as they do when I use Perl, for example)... i had been using this method to call perl (before i started trying to do this with regular expressions).. passing in a regex string as a variable causes all sorts of problems, such as using " ( )" anywhere makes it not work, among other things.. I am wondering if there is a better way to do this, than the string of variables after the perl filename method as it seems to have some glaring limiations.. thanks for any info.

the way I do it currently:

$file = "/pathtomy/perlscript.pl $var1 $var2 $var3" ;
    ob_start();
passthru($file);
$perlreturn = ob_get_contents();
ob_end_clean();
return $perlreturn;
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  • What issues are you having with PHP's regex? They are supposed to be perl compatible. Commented Aug 16, 2010 at 4:50
  • I seem to have a lot of issues, I don't have a full example off hand but it just doesn't respond the same as it does with perl, I don't know what it is about preg but, using special characters like { gives me problems, even when I escape it with \{ or [ { ] Commented Aug 16, 2010 at 4:59
  • It sounds like you may be falling victim to the trap lurking in most languages that lack regexs as a native language feature. You have to write regexs using strings, and the backslash is both the string escape character and the regex escape character. Therefore, you have to double all your backslashes, or else they're treated as string escapes and the regex engine never sees them. So to match a literal brace, you have to say "\\{" and not "\{". Commented Aug 16, 2010 at 7:50
  • 1
    @NullUserException no, they're PCRE. Despite the name, PCRE is not the same thing as Perl regexes. :) Commented Aug 16, 2010 at 13:07

2 Answers 2

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2

For the general case, you'll want to use escapeshellarg. Blindly wrapping everything in single quotes works most of the time but will fail when one of your arguments contains a single quote!

string escapeshellarg  ( string $arg )

escapeshellarg() adds single quotes around a string and quotes/escapes any existing single quotes allowing you to pass a string directly to a shell function and having it be treated as a single safe argument. This function should be used to escape individual arguments to shell functions coming from user input. The shell functions include exec(), system() and the backtick operator.

Using a simple Perl program that prints its command-line arguments

#! /usr/bin/perl

$" = "][";  # " fix StackOverflow highlighting
print "[@ARGV]\n";

and then a modified version of the PHP program from your question

<?php

$var1 = "I'm a";
$var2 = "good boy,";
$var3 = "I am.";

$file = "./prog.pl " . implode(" ",
                         array_map("escapeshellarg",
                           array($var1,$var2,$var3)));
echo "command=", $file, "\n";

ob_start();
passthru($file);
$perlreturn = ob_get_contents();
ob_end_clean();
echo "return=", $perlreturn;

?>

we see the following output:

$ php prog.php 
command=./prog.pl 'I'\''m a' 'good boy,' 'I am.'
return=[I'm a][good boy,][I am.]
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0

Try to use quotation marks:

$file = "/pathtomy/perlscript.pl '$var1' '$var2' '$var3'" ;
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3 Comments

sounds simple enough.. I guess I didn't think of it that way as I that makes sense now that I think about it as perl wouldn't see it with the quotations the way I was doing it since the entire filestring is enclosed in quotations
@Rick it's not perl, it's the shell that's getting in between when you use passthru.
This code can create serious problems with strings that contain single quotes. Please use gbacon's answer instead.

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