package main
import (
"regexp"
"fmt"
)
func main() {
var re = regexp.MustCompile(`\A((?:(?!127\.0\.0\.1\s)[\s\S])*?)(?:\Z|127\.0\.0\.1\s+(?!localhost)\S+\n|(127\.0\.1\.1\s+\S+(?![\s\S]*\n127\.0\.0\.1\s)\n))`)
var str = []byte(`127.0.1.1 myhost
1.1.1.1 bla
127.0.0.1 bla
2.2.2.2 bla
`)
var substitution = []byte("\1\2127.0.0.1 localhost\n")
var count = 1 // negative counter is equivalent to global case (replace all)
str = re.ReplaceAllStringFunc(str, func(s string) string {
if count == 0 {
return s
}
count -= 1
return re.ReplaceAllString(s, substitution)
})
fmt.Println(string(str))
}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Golang, please visit: https://golang.org/pkg/regexp/