IP Address with CIDR Notation in GO
Match IPv4 addresses with CIDR prefix notation such as 10.0.0.0/8 or 192.168.1.0/24.
Try it in the GO tester →Pattern
regexGO
(?:(?:25[0-5]|2[0-4]\d|[01]?\d\d?)\.){3}(?:25[0-5]|2[0-4]\d|[01]?\d\d?)\/(?:3[0-2]|[12]?\d) (flags: g)Go (RE2) code
goGo
package main
import (
"fmt"
"regexp"
)
func main() {
re := regexp.MustCompile(`(?:(?:25[0-5]|2[0-4]\d|[01]?\d\d?)\.){3}(?:25[0-5]|2[0-4]\d|[01]?\d\d?)\/(?:3[0-2]|[12]?\d)`)
input := `10.0.0.0/8`
for _, match := range re.FindAllString(input, -1) {
fmt.Println(match)
}
}Uses `regexp.MustCompile` (panics on bad patterns at startup) and `FindAllString` for all matches.
How the pattern works
The IPv4 portion uses alternation to strictly validate each octet in the 0–255 range (same as the standalone IPv4 pattern). \/(?:3[0-2]|[12]?\d) appends a / and a CIDR prefix constrained to 0–32.
Examples
Input
10.0.0.0/8Matches
10.0.0.0/8
Input
192.168.1.0/24Matches
192.168.1.0/24
Input
999.0.0.0/33No match
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