golang regex to find a string but only extract the substring within it

Question

I have a two strings like this

mystr = "xyz/10021abc/f123"
mystr2 = "abc/10021abd/c222"

I want to extract 10021abc and 10021abd. I came up with

r = regexp.MustCompile(`(?:xyz\/|abc\/)(.+)\/`)

But when I want to extract the match using this:

fmt.Println(r.FindString(mystr))

It returns the entire string. How should I change my regex?

You already have it, it is in the first capture group. See stackoverflow.com/questions/30483652/… — The fourth bird
– The fourth bird, Commented Sep 16, 2022 at 7:13

mkopriva · Accepted Answer · 2022-09-16 06:50:47Z

3

You can use FindStringSubmatch.

var re = regexp.MustCompile(`(?:xyz\/|abc\/)(.+)\/`)
var s1 = "xyz/10021abc/f123"
var s2 = "abc/10021abd/c222"

fmt.Println(re.FindStringSubmatch(s1)[1])
fmt.Println(re.FindStringSubmatch(s2)[1])

https://go.dev/play/p/C93DbfzVv3a

answered Sep 16, 2022 at 6:50

mkopriva

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9 Comments

drdot Over a year ago

This program crash when there is no match

mkopriva Over a year ago

Of course it does. Any Go slice index expression will crash if there isn't enough elements in the slice. The standard approach is to check the slice's length before indexing. But that was not your question.

drdot Over a year ago

I already know how to do this. My Q is how to change the regex

drdot Over a year ago

It is a regex skill Q rather than a go programming Q if that makes sense ;)

drdot Over a year ago

I am happy to take this answer if you think updating regex to just match the substring I need is too hard

|

Tim Biegeleisen · Accepted Answer · 2022-09-16 06:49:48Z

1

You could use a regex replacement here:

var mystr = "xyz/10021abc/f123"
var re = regexp.MustCompile(`^.*?/|/.*$`)
var output = re.ReplaceAllString(mystr, "")
fmt.Println(output)  // 10021abc

answered Sep 16, 2022 at 6:49

Tim Biegeleisen

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