REGEX to find STRING between two values

Question

I have a string being received from a monitoring system, the string contains 3 variables that I am interested in the variables are pre/post fixed with c=VAR1; e=VAR2; s=VAR3; so I want to grab the text in between for example c= ; but am having limited success, these are a few of the REGEXs I have tested with:

c=([^;]+);
.+c=(.+);.+
(?<=c=\()(.*?)(?=\;*\))
c=(.*);

A full alert string would look similar to:

alert c=Vari Able1; e=Vari Able2; s=Vari Able3;

But none seem to return in the way I would expect.

Any help is much appreciated.

Thanks!

Brad Christie · Accepted Answer · 2012-09-25 21:46:26Z

1

You can use something like:

(\w+)=([^;]+)

Which would grab all values (key and value), but if you're after only the c value:

c=([^;]+)

Should capture everything between the = and ; (([^;]+) captures every character that's not a semi-colon, repeated 1 or more times.).

answered Sep 25, 2012 at 21:46

Brad Christie

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4 Comments

Brad Christie Over a year ago

@Isaac: Oops, typo. Yes, forgot the quantifier. Good catch.

Brad Christie Over a year ago

@Isaac: Lol, indeed. Can you tell it's after 5? ;p

Andrew Reynolds Over a year ago

This seems like it should do what I need and when I run it in a REGEX tester it finds what I need but it isn't working in the native tool I am using for this work, however that's not your problem so thank you for your answer!

Brad Christie Over a year ago

@AndrewReynolds: Where is the application? There are different versions and applications of REGEX. Unfortunately there is no "one size fits all", though 90% of the patterns translate cross-platform/application.

John Woo · Accepted Answer · 2012-09-26 03:52:24Z

0

Try something like this,

(?<=((alert)?.*=)).*?(?=;)

See Lookahead and Lookbehind Zero-Width Assertions.

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answered Sep 26, 2012 at 3:52

John Woo

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1 Comment

Andrew Reynolds Over a year ago

So this one gives me: REGEX: Compile failed at offset 18: lookbehind assertion is not fixed length as an error in my debugger

Nelson Benítez León · Accepted Answer · 2012-09-26 15:01:14Z

0

Your first regex is good, but only working for c variable, this is a variation working for all three variables:

[ces]=([^;]+);

that will look for your c , e and s variables.

In PHP you could execute it like this:

$string = 'c=VAR1; e=VAR2; s=VAR3;';
preg_match_all("/([ces])=([^;]+);/", $string, $out, PREG_PATTERN_ORDER);
$tot = count($out[1]);
for ($i=0;$i<$tot;$i++) {
    echo $out[1][$i]; //will echo 'c' , 'e' , 's' respectively
    echo $out[2][$i]; //will echo 'VAR1' , 'VAR2' , 'VAR3' respectively
}

Update: Answer to a OP's question in comments

The above loop is for dinamically assign the values found, so if the regex found 4 , 5 or 10 vars the for will loop all of them. But if you are sure your string has only 3 vars in it, you could assign them directly in one go, like this:

$string = 'c=VAR1; e=VAR2; s=VAR3;';
preg_match_all("/([ces])=([^;]+);/", $string, $out, PREG_PATTERN_ORDER);
$$out[1][0] = $out[2][0]; // var $c is created with VAR1 value
$$out[1][1] = $out[2][1]; // var $e is created with VAR1 value
$$out[1][2] = $out[2][2]; // var $s is created with VAR1 value

echo $c; //will output VAR1
echo $e; //will output VAR2
echo $s; //will output VAR3

I'm using PHP variable variables in above code.

edited Sep 26, 2012 at 15:01

answered Sep 25, 2012 at 21:53

Nelson Benítez León

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2 Comments

Andrew Reynolds Over a year ago

Question on this - would doing them in one hit allow me assign them to separate variables? Or would it only ever find the first one, I see in your PHP you have a FOR loop counter so I assume this is how you assign each of them but in the native tool I am using for my work that isn't possible I have 3 variables all running a slightly different REGEX on the same string to pick out the text it is interested in.

Nelson Benítez León Over a year ago

I updated my answer to include your question about FOR loop, consider giving upvote if you find it useful :-)

Andrew Reynolds · Accepted Answer · 2012-09-26 18:50:41Z

0

So the ultimate solution to this question was I need to find out a little more about the tool I was using, specifically the REGEX engine... as it turns out it uses PCRE so the final REGEX was:

'(?<=c=)[^;]*'
'(?<=e=)[^;]*'
'(?<=s=)[^;]*'

In the tool that exists within the software I was reconfiguring this gave me the three variables I needed to correctly interpret my monitor system alerts.

Thanks all!

answered Sep 26, 2012 at 18:50

Andrew Reynolds

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