Regex to match after string before space using RE2

Question

I am new to RE2 syntax regex, I want to match first word comes after specific string.

For example:

java.lang.OutOfMemoryError: Java heap space Error sending periodic event java.lang.NullPointerException: Java heap space Error sending periodic event

I want to capture anything comes after java.lang. so I can get OutOfMemoryError, NullPointerException errors. I know in Python and PCRE we can do this using positive lookbehind and regex will be - (?<=java.lang.).*?(?=\s), but this is not working for RE2.

Answer 1

You may use

java\.lang\.([^\s:]+)

Details

• java\.lang\. - a java.lang. substring
• ([^\s:]+) - Capturing group 1: one or more characters other than whitespace and :.

NOTE: If you need to get all text between java.lang. and : followed with whitespace, use java\.lang\.(.*?):\s.

See the regex demo and the Go demo:

package main

import (
    "fmt"
    "regexp"
)

func main() {
    regex := regexp.MustCompile(`java\.lang\.([^\s:]+)`)
    result := regex.FindStringSubmatch("java.lang.OutOfMemoryError: Java heap space Error sending periodic event")
    fmt.Printf("%q", result[1])
}