Private IP Address (RFC 1918) in GO
Match IPv4 addresses in the RFC 1918 private ranges: 10/8, 192.168/16, and 172.16/12.
Try it in the GO tester →Pattern
regexGO
\b(?:10(?:\.\d{1,3}){3}|192\.168(?:\.\d{1,3}){2}|172\.(?:1[6-9]|2\d|3[01])(?:\.\d{1,3}){2})\b (flags: g)Go (RE2) code
goGo
package main
import (
"fmt"
"regexp"
)
func main() {
re := regexp.MustCompile(`\b(?:10(?:\.\d{1,3}){3}|192\.168(?:\.\d{1,3}){2}|172\.(?:1[6-9]|2\d|3[01])(?:\.\d{1,3}){2})\b`)
input := `Servers at 10.0.0.5 and 192.168.1.20`
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
Three top-level alternatives cover the three reserved private ranges. 10(?:\.\d{1,3}){3} matches 10.x.x.x. 192\.168(?:\.\d{1,3}){2} matches 192.168.x.x. 172\.(?:1[6-9]|2\d|3[01]) constrains the second octet to the 16–31 sub-range, then (?:\.\d{1,3}){2} matches the last two octets. \b boundaries prevent partial-IP matches inside longer numbers.
Examples
Input
Servers at 10.0.0.5 and 192.168.1.20Matches
10.0.0.5192.168.1.20
Input
172.16.50.1 is private; 172.32.0.1 is notMatches
172.16.50.1
Input
Public IP 8.8.8.8No match
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