Signaficance of the sign #

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May 14th, 2009, 12:38 PM

taneem

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Signaficance of the sign #

Hello Mates,
A very basic question. How does the sign '#' effects any RE. For example the following RE

Code:

#(alert|cmd|passthru|eval|exec|system|fopen|fsockopen|file|file_get_contents|readfile|unlink)(\s*)\(  (.*?)\)#si

. What's the signaficance of the sign '#'. If anyone can kindly help me with this, that woudl be very much appreciated. Thank you.

May 14th, 2009, 02:27 PM

prometheuzz

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Assuming it is a Perl, PHP or some similar regex flavour, it probably is just a delimiter.
Most of the times, the forward slash is used, but you can use other delimiters, like the hash character (#).

May 15th, 2009, 03:23 AM

taneem

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Quote:

Originally Posted by prometheuzz

Assuming it is a Perl, PHP or some similar regex flavour, it probably is just a delimiter.
Most of the times, the forward slash is used, but you can use other delimiters, like the hash character (#).

Thank you, mate. I was using RE in PHP. Thankx.

May 15th, 2009, 03:39 AM

prometheuzz

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Quote:

Originally Posted by taneem

Thank you, mate. I was using RE in PHP. Thankx.

No problem.
Most of the time you see people using the forward slash:

PHP Code:


		
			
'/some-regex-here/'

But when you want to match a forward slash in your regex, you would need to escape it, otherwise the regex engine "thinks" your regex terminates too early:

PHP Code:


		
			
'/some-regex\/here/'

in which case many people use another delimiter so that they need not escape the slash:

PHP Code:


		
			
'#some-regex/here#'

HTH

May 15th, 2009, 04:08 AM

taneem

Contributing User

Join Date: Jan 2008

Posts: 59

Time spent in forums: 12 h 24 m 7 sec
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Quote:

Originally Posted by prometheuzz

No problem.
Most of the time you see people using the forward slash:

PHP Code:


		
			
'/some-regex-here/'

But when you want to match a forward slash in your regex, you would need to escape it, otherwise the regex engine "thinks" your regex terminates too early:

PHP Code:


		
			
'/some-regex\/here/'

in which case many people use another delimiter so that they need not escape the slash:

PHP Code:


		
			
'#some-regex/here#'

HTH

Got it. RE is quite a handly tool to stop hackers in terms of form input. That's why I need to learn them good. Thankx.

Signaficance of the sign #

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