Issue with regex in Golang-CodePudding

I am trying to create a regex to parse specific string .

The current string is abcd_1.263.0.15-8zz00df.yml and I want to parse only 1.263.0.15-8zz00df out of it.

Tried already with this expression "_\K.*(?=\.)" but its not working in Golan and giving me pattern error. Can someone please help with this?

CodePudding user response：

Go uses RE2 regex engine, that does not support lookaheads, lookbehinds and other PCRE goodies like \K

See this comparison of the different regex engines.

You could however use this regex:

[^_-] -[^.]

See this demo.

Explained:

[^_-]    # a charter that is not "_" or "-", one or more times
-        # a literal "-"
[^.]     # a character that is not a dot, one or more times

CodePudding user response：

Edit: You can simply use the regular expression:

_(.*)\.

The * matches greedily, which means that it will match everything until the last '.' - this is exactly what you need. Your match is in group 1.

Why are you using the \K matcher? Your regular expression works like this:

_(.*)(?=\.)

and group 1 contains your match.

Note: a very helpful tool to test regular expressions is this site: https://regexr.com/

CodePudding user response：

Just reposting one of @mkopriva snippet with a sentence,

not everything needs to be done with regular expressions :

    s := "abcd_1.263.0.15-8zz00df.yml"

    if i := strings.IndexByte(s, '_'); i > -1 {
        s = s[i 1:]
    }
    if i := strings.LastIndexByte(s, '.'); i > -1 {
        s = s[:i]
    }

    fmt.Println(s)

playground