Regex for string after string pattern

Question

I have a string like this (4 words separated by dot)

Exactfoobar.foobar-_nocaps.foobar-_nocaps.foobar-_caps

I need to write a regex to find the pattern as above.

There could be 4 or more fields separated by a dot
The first word should be exactly Exactfoobar.
The 2nd and 3rd word can't have caps but can have -_
The 4th word and so on can have caps with -_

I was thinking of using groups but its not working here:

^Exactfoobar\.([a-z0-9][a-z0-9_\-.])+([a-z0-9][a-zA-Z0-9_\-.])+$

How should I think about matching a string after another string. Is it possible?

Trying this in golang but cant seem to get the above regex right

package main

import (
    "fmt"
    "regexp"
)

func main() {

    var validID = regexp.MustCompile(`^ Exactfoobar\.([a-z0-9][a-z0-9_\-.])+([a-z0-9][a-z0-9_\-.])+$`)

    fmt.Println(validID.MatchString("Exactfoobar.somestring.some_other-string.someStringwithCaps"))


}

Result:

false

Thanks

why not split on the dot character then discard the first element (since it would always be `Exactfoobar`)? That way you don't need regex, which should be a lot faster and more readable. — Olian04, Jun 27 '19 at 21:46

score 1 · Accepted Answer · answered Jun 27 '19 at 21:45

1

You may use

^Exactfoobar(?:\.[a-z0-9][a-z0-9_-]*){2}(?:\.[a-zA-Z0-9][a-zA-Z0-9_-]*)+$

See the regex demo

^ - Start of string
Exactfoobar - some word
(?:\.[a-z0-9][a-z0-9_-]*){2} - two repetitions of a ., then a lowercase letter or digit and then 0+ lowercase letters or digits, _ or -
(?:\.[a-zA-Z0-9][a-zA-Z0-9_-]*)+ - 1 or more repetitions of
- \. - dot
- [a-zA-Z0-9] - a letter or digit
- [a-zA-Z0-9_-]* - 0+ letters, digits or _ or -
$ - end of string.

answered Jun 27 '19 at 21:45

Wiktor Stribiżew

607,720
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thanks @Wiktor! this worked like I was thinking. What does `?:` mean – Sumitk Jun 28 '19 at 03:25
@Sumitk See [What is a non-capturing group? What does (?:) do?](https://stackoverflow.com/questions/3512471/what-is-a-non-capturing-group-what-does-do). – Wiktor Stribiżew Jun 28 '19 at 06:45

score 0 · Answer 2 · answered Jun 27 '19 at 21:52

0

^Exactfoobar(?:\.[a-z0-9_\-]+){2}(?:\.[A-Za-z0-9_\-]+)+$

https://regex101.com/r/PJ9V0L/1

answered Jun 27 '19 at 21:52

danielb

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4
10
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This is a wrong solution, see [your regex demo](https://regex101.com/r/8ebzJv/1). The words must begin with a letter or digit. – Wiktor Stribiżew Jun 27 '19 at 21:55
I guess you're right, although that wasn't an explicit requirement – danielb Jun 27 '19 at 22:21

Regex for string after string pattern

2 Answers2