Golang Regexp Quote submatch

Question

I am trying to extract a submatch value from a regexp but to all for it to disregard a set of quotes if necessary. So far I have this:

url: http://play.golang.org/p/lcKLKmi1El

package main

import "fmt"
import "regexp"

func main() {
  authRegexp := regexp.MustCompile("^token=(?:\"(.*)\"|(.*))$")

  matches := authRegexp.FindStringSubmatch("token=llll")
  fmt.Println("MATCHES", matches, len(matches))

  matches = authRegexp.FindStringSubmatch("token=\"llll\"")
  fmt.Println("MATCHES", matches, len(matches))
}

Input::Expected Matches

token=llll::[token=llll llll]

token="llll"::[token="llll" llll]

Also note that I want to test for either no quotes, or a single set of quotes. I don't want to be able to have mismatched quotes or anything.

How do I get rid of the empty string that is returned? Is there a better regex to get rid of the quotes?

Are you parsing attributes? http://stackoverflow.com/questions/317053/regular-expression-for-extracting-tag-attributes — Alex Netkachov, Jul 28 '15 at 17:04
Yes kind of. I want to be able to have a pair or double quotes or no quotes at all. Perhaps this is more complicated? — Gary, Jul 28 '15 at 17:17
Sorry, it is still a bit unclear to me. Do you simply want to get the value without quotes? In this case just get everything after `=` and trim `"`. — Alex Netkachov, Jul 28 '15 at 17:24
Actually, would be nice to have several use cases like `input-output`. — Alex Netkachov, Jul 28 '15 at 17:24
Sorry for the ambiguity, I have added an input and expected matches section. — Gary, Jul 28 '15 at 17:50

score 2 · Accepted Answer · answered Jul 28 '15 at 18:04

2

Ok, that's it: http://play.golang.org/p/h2w-9-XFAt

Regex: ^token="?([^"]*)"?$

MATCHES [token=llll llll] 2
MATCHES [token="llll" llll] 2

answered Jul 28 '15 at 18:04

Alex Netkachov

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Although this allows for unbalanced quotes. – James Buck Jul 28 '15 at 21:24
Definitely. That's why I'd asked for test cases. – Alex Netkachov Jul 28 '15 at 21:30
1

"I dont want to be able to have mismatched quotes or anything" - I just assumed he didn't want to allow this kind of thing. Just wanted to raise his attention to it in case it produces some unexpected behaviour. – James Buck Jul 28 '15 at 21:39

score 1 · Answer 2 · answered Jul 28 '15 at 17:22

1

Try the following:

authRegexp := regexp.MustCompile("^token=(.*?|\".*?\")$")
Demo here.

answered Jul 28 '15 at 17:22

James Buck

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The second match is: `MATCHES [token="llll" "llll"] 2` Is it possible not to have the quotes in the match? – Gary Jul 28 '15 at 17:23
@Gary Unfortunately then, the best other way I can think of doing it is the way you initially said but having an empty group. This is because when `"` are included, capturing group 3 will be empty, but when there are no quotes group 2 will by empty - either way you are left with 1 empty group. It would be easy to get rid of the quotes in my method if the Go regex engine supported lookbehinds or conditionals, but it does not. – James Buck Jul 28 '15 at 17:45

Golang Regexp Quote submatch

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