Argument Parsing with Perl Compatible Regular Expressions

[krumms]

Hi all,

My regular expression skills are still forming, and I'm having trouble with the following:

$var_matches = array();
$match = '/(.+?)=(\'(.+?)\')|("(.+?)")|(\$([\w\d]+))/';
preg_match_all( $match, $args, $var_matches, PREG_SET_ORDER );

Basically, $args is a string that contains a whitespace-delimited set of the following:
a='b'
a="b"
a=$b

So an example value for $args would be:

$args = "a='b' c=\"d\" e=$f"

Obviously my regular expression is wrong. Can anybody explain why? Or, at least, provide a regular expression I can use (I'm quite happy to figure out the workings by myself! :))

Thanks a lot,
Tom L

[xblue]

I think you misunderstood the use of parenthesis with alternation.

Parenthesis are used for two purposes: to capture sub-pattern you want to reuse or to group parts of the pattern, either to apply quantifiers to a sequence of characters, or to limit alternation to a certain part of the pattern. Example of the latter:

"/H(i|ello)/"
Here both pattern would match either "Hi" or "Hello", but if we omitted the parenthesis, the latter would match "Hi" or "ello".

what you are doing is:
"/H(i)|(ello)/"
which would match "Hi" or "ello" as well, with the only difference that you can reuse 'i' and 'ello' as matches of a sub-pattern.

And a lot of backslashes seem to have been stripped by the forum, or are they missing?

btw \w includes digits already, no need to use [\w\d].

[krumms]

Great, thanks a lot.

My regular expression now looks something like this:

$match = '/\s*(.+?)=(\'.+?\'|".+?"|\$\w+)/';

It's not perfect, but its much closer to what I want. Thanks very much!

And yes, it was the forums stripping the backslashes 🙂