RegEx: How to Split String into Words

Questions & Suggestions
#1

I continue to struggle with translating a RegEx pattern that works in the Online RegEx tool to one that works in the KM action for Search Using Regular Expression. BTW, I know this is easily done in JavaScript, but I need it to work in just KM.

###How to I make this pattern work in KM:
/"[^"]*"|[^:]+/g

For the string "10:05:12:00" it should return 4 match groups, but it shows only one.

####The pattern from the online tool:
/"[^"]*"|[^:]+/g

####The pattern in KM:
"[^"]*"|[^:]+

It should be showing 4 capture groups in the KM Action.

I've tried the various ICU Flag Options, but none of them helped.

#2

Matches and groups are not quite the same – capturing groups are defined by brackets.

#3

and the KM action is certainly more convenient than this:

(function (s) {
	'use strict';
	
	// Get a reference to a Keyboard Maestro variable (existing or new)
	function kmVar(k) {
		var kme = Application("Keyboard Maestro Engine"),
			vs = kme.variables,
			vks = vs.where({name:k});
				
		return vks.length ? vks[0] :
			vs.push(kme.Variable({'name': k})) && vs[k];
	}

	return s.split(':').map(function (x, i) {
		var k = 'gp ' + i;
		
		kmVar(k).value = x;
		
		return kmVar(k).value();
	});
	
})('10:05:12:00');
#4

Thanks, Rob.

I understand that. But why does the Online tool identify the matched groups with /"[^"]*"|[^:]+/g but KM does not?

The pattern you show for KM is completely different from the Online pattern, which works online.

There should be a pattern that works in KM that does not require you to specify the exact number of words to match.

BTW, you stated “bracket”, but your example shows parenthesis.
Isn’t the “[ ]” considered brackets, as shown in the Online pattern?

#5

But why does the Online tool identify the matched groups with /"[^"]*"|[^:]+/g

It doesn’t.

Matches ≠ groups.

The online tool is showing matches. Your regex contains no groups.

( it uses no parentheses )

#6

Re parentheses - yes, there may be a dialectal variation in Anglic there : - )

To standardise a bit on {braces} vs [square brackets] vs (parentheses),

the square brackets enclose character classes,
and the parentheses enclose groups.

Without parentheses there are no capturing groups.

#7

OK, so what is the group syntax that will identify/capture n number of matches?

#8

If you want n separate captures you need n separate groups.

(as in my example above)

(Otherwise you are just defining one big group)

#9

I have noticed many discussions about RegEx that include a RegEx.split() function.

In fact the ICU RegEx, which KM uses, supports it.
I’m wondering if it is accessible from KM:

###ICU split() function

Using split()

ICU’s split() function is similar in concept to Perl’s – it will split a string into fields, with a regular expression match defining the field delimiters and the text between the delimiters being the field content itself.

Suppose you have a string of words separated by spaces

`UnicodeString s = “dog cat   giraffe”;`

This code will extract the individual words from the string.

UErrorCode status = U_ZERO_ERROR;
RegexMatcher m(“\\s+”, 0, status); 
const int maxWords = 10;
UnicodeString words[maxWords];    
int numWords = m.split(s, words, maxWords, status);

After the split(),

> Variable	value
> numWords	3
> words[0]	“dog”
> words[1]	“cat”
> words[2]	“giraffe”
> words[3 to 9]	“”
#10

From KM you can use the JavaScript String.split() function, which takes either a regex or a string literal as an argument.

#11

Thanks, Rob.
But as you’ve seen, many people are uncomfortable with scripts, especially changing them. So, I’m trying to come up with a KM only solution, where the KM user need only change a few settings/variable in KM to use.

#12

As others have noted, there are no groups in the pattern. You have added the "g" modifier to the end of the online version, and that means "global", which means repeat the search multiple times and return each match. That is, it returns a list of matches.

Keyboard Maestro users, being used to Keyboard Maestro's nice and orthogonal behaviour, should then immediately think of the For Each action, which is the action you use when you want to deal with a list of things.

In this case, the "Substrings In" collection, and the matching option will return each match.

2 Likes
#13

Perhaps we should, but I, for one, do not immediately think of the KM For Each action.
Sorry Peter, but it is just not intuitive to me. Perhaps it is to others.

But let’s use this as a teaching opportunity.

I still don’t get how to use the For Each action, to extract each of the words into a different KM variable. It would be nice to have KM arrays, but it seems that to use them will always convert the array elements into numbers.

So if you will lay out how to do this, I’ll update the KM wiki on RegEx to provide this as a great example. I would like to use the “:” as the word delimiter, and return all characters between them as a “word”.

Thanks.

#14

This is in no way, shape, or form intuitive for newbies. You have to know about the action, and you have to know a bit of RegEx.

But. Once you've used it a time or two it becomes a useful tool in the toolbox.

Open the Keyboard Maestro Engine Log in the Console.app to see the macro work.

~/Library/Logs/Keyboard Maestro/Engine.log

In the RegEx I'm using 2-digits as the substgring, and the Positive Lookahead Assertion of colon (:slight_smile: OR end-of-line as the substring-separator.

-Chris

For Each Substring Match.kmmacros (2.6 KB)

#15

I didn’t say it was intuitive.

But I will say when using Keyboard Maestro, whenever you hit a problem that deals with a list of things, the For Each action is the pace to look. Keyboard Maestro has no other places where it iterates over a collection of items.

As I say, it is not intuitive - what solution to this sort of problem would be intuitive? I can’t think of any.

Instead, once learnt, it is knowledge that applies across a range of problems within Keyboard Maestro - this is the best I know how to do…

#16

The For each > Substrings option is excellent.

Perhaps, if users are getting to it via a notion of splitting, it might be useful to make for each > substrings appear as a hit for searches on split by inserting the word split in a relevant wiki paragraph somewhere ?

#17

OK, let’s figure out how to add this to the wiki so that users who don’t know KM or programming will know how to proceed. After all, the wiki is for those who don’t know KM fully, right?

I guess what I’m saying is that, in the wiki, we need to connect RegEx with For Each, and provide some examples.

#18

####Also, I want to make it easy for KM users to go from creating/testing a RegEx expression in a tool like RegEx101.com to KM.

So I just got this suggestion for creating multiple groups:

/("[^"]*"|[^:]+)/g

How to we instruct the KM user to implement this in KM?
Is the answer anytime a RegEx tool uses the global flag /g that the KM user needs to use the For Each Action?

See https://regex101.com/r/jN0uT2/1

Pasted image720Ă—350 39.7 KB

1 Like
#19

Chris, I'm probably doing something wrong, but this is not working for me. It only shows a notification for "12"

#20

2/3 comments:

  1. by \d(2) I would guess that you meant \d{2} or \d\d

    ( \d(2) looks for a digit followed by the number two, which it places in a distinct capture group.
    The latter two look for two digits. \d\d may be quicker to parse and execute,
    as well as quicker to write, and perhaps a bit less error-prone.)

  2. As you found, quite easy for confusion about the difference between regex groups and regex matches to arise. If you do want to write learning materials, it would probably be good to make a quick edit to ensure that you are not using the terms interchangeably. (See yellow bubble above - the tool doesn't auto-find 4 groups, it finds four matches).

  3. If simplicity is the goal, and splitting is the first metaphor that comes to mind, perhaps you can try a search and replace with : --> \n, and then loop through the resulting lines