skip regex chars until search using golang - regex

Question

This will skip the 1st 2 characters and start matching left to right
re := regexp.MustCompile("(^.{2})(\\/path\\/subpath((\\/.*)|()))")
fmt.Println(re.MatchString("c:/path/subpath/path/subpath/")) // true
fmt.Println(re.MatchString("c:/patch/subpath/path/subpath/")) // false
notice the second one doesnt hit. even though /path/subpath exists in the string. This is perfect.
now if if dont know how many characters to skip and want to start search at the 1st '/' then i tried this
re2 := regexp.MustCompile("([^\\/])(\\/path\\/subpath((\\/.*)|()))")
fmt.Println(re2.MatchString("cddddd:/path/subpath/path/subpath")) // true
which is perfect. but if i change the 1st path
fmt.Println(re2.MatchString("cddddd:/patch/subpath/path/subpath")) // this is true as well
I don't want the last one to match the second /path/subpath. I want to be able to search in the 1st group, start the second group from there and do a left to right match.
Any help would be great appreciated.

Answer 1

It pays to be more precise about what you want, state what you want in absolute terms, not like "second first should not match third". Instead, say;
I want to capture the path if it begins with /path/subpath in the second group. If a path contains /path/subpath somewhere in later than the beginning, then I don't want that to match.
Also, slashes are not special in regex, so you don't need to double-escape them for nothing.
The third expression, does this:
capture everything that is not a slash from the start anchor
delimit group 1 from group 2 by :
require /path/subpath to be the at the top of the path
capture whatever remains
This may be what you want:
package main
import (
"fmt"
"regexp"
)
func main() {
paths := []string{
"c:/path/subpath/path/subpath/",
"c:/patch/subpath/path/subpath/",
"cddddd:/path/subpath/path/subpath",
}
re1 := regexp.MustCompile("(^.{2})(/path/subpath(/.*))")
re2 := regexp.MustCompile("([^/])(/path/subpath((/.*)|()))")
re3 := regexp.MustCompile(`^([^/]+):/path/subpath(/.*)`)
for i, re := range []*regexp.Regexp{re1, re2, re3} {
i++
for _, s := range paths {
fmt.Println(i, re.MatchString(s), s)
if re.MatchString(s) {
matches := re.FindStringSubmatch(s)
for m, g := range matches {
m++
if m > 1 {
fmt.Printf("\n\t%d %v", m, g)
}
}
}
println()
}
println()
}
}
Output
$ go run so-regex-path.go
(...)
3 true c:/path/subpath/path/subpath/
2 c
3 /path/subpath/
3 false c:/patch/subpath/path/subpath/
3 true cddddd:/path/subpath/path/subpath
2 cddddd
3 /path/subpath