是否可以使用Go.Regexp匹配除常量字符串以外的所有内容？

Question

I have found many similar questions that do not work with the Go regex syntax.

The string that I am attempting to match against is in the form of anything/anything/somestring. With the pattern \/.*\/.*\/(.*), I will match somestring, but I am trying to match anything except strings that contain somestring.

Most answers propose using something like \/.*\/.*\/((?!somestring).*), however in golang regexp I get: ? The preceding token is not quantifiable.

For clarification: /test/test/MATCH would produce a match while /test/test/somestring would not. Is this possible with the (limited) Go regex syntax?

Answer 1

The anything/anything/somestring should not be expressed as \/.*\/.*\/(.*). The first .* matches up to the last but one / in the string. You need to use a negated character class [^/] (not the / should not be escaped in Go regex).

Since RE2 that Go uses does not support lookaheads, you need to capture (as JimB mentions in the comments) all three parts you are interested in, and after checking the capture group #1 value, decide what to return:

package main

import (
    "fmt"
    "regexp"
)

func main() {
    s := "anything/anything/somestring"
    r := regexp.MustCompile(`^[^/]+/[^/]+/(.*)`)
    val := r.FindStringSubmatch(s)
    // fmt.Println(val[1]) // -> somestring
    if len(val) > 1 && val[1] != "somestring" { // val has more than 1 element and is not equal to somestring?
        fmt.Println(val[1])      // Use val[1]
    } else {
        fmt.Println("No match")  // Else, report no match
    }
}

See the Go demo