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!

Answer 1

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!

Answer 2

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.

Answer 3

Try something like this,

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

See Lookahead and Lookbehind Zero-Width Assertions.

RegexBuddy ScreenShot

Answer 4

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.).