Identifiers

Kubernetes Label (key=value)

Validate Kubernetes label `key=value` pairs per the K8s naming spec.

Available in

JavaScript / ECMAScript code

jsJavaScript

const re = new RegExp("^([a-zA-Z0-9](?:[\\w.\\-]{0,61}[a-zA-Z0-9])?)=([a-zA-Z0-9](?:[\\w.\\-]{0,61}[a-zA-Z0-9])?)?$", "");
const input = "app=myapp";
const matches = [...input.matchAll(re)];
console.log(matches.map(m => m[0]));

Uses `String.prototype.matchAll` for global iteration (Node 12+ / all modern browsers).

Python (re) code

pyPython

import re

pattern = re.compile(r"^([a-zA-Z0-9](?:[\w.\-]{0,61}[a-zA-Z0-9])?)=([a-zA-Z0-9](?:[\w.\-]{0,61}[a-zA-Z0-9])?)?$")
input_text = "app=myapp"
for m in pattern.finditer(input_text):
    print(m.group(0))

Stdlib `re` module — no third-party dependency. Works on Python 3.6+.

Go (RE2) code

goGo

package main

import (
	"fmt"
	"regexp"
)

func main() {
	re := regexp.MustCompile(`^([a-zA-Z0-9](?:[\w.\-]{0,61}[a-zA-Z0-9])?)=([a-zA-Z0-9](?:[\w.\-]{0,61}[a-zA-Z0-9])?)?$`)
	input := `app=myapp`
	for _, match := range re.FindAllString(input, -1) {
		fmt.Println(match)
	}
}

Uses `regexp.MustCompile` (panics on bad patterns at startup) and `FindAllString` for all matches.

Pattern

regexengine-agnostic

^([a-zA-Z0-9](?:[\w.\-]{0,61}[a-zA-Z0-9])?)=([a-zA-Z0-9](?:[\w.\-]{0,61}[a-zA-Z0-9])?)?$

Raw source: ^([a-zA-Z0-9](?:[\w.\-]{0,61}[a-zA-Z0-9])?)=([a-zA-Z0-9](?:[\w.\-]{0,61}[a-zA-Z0-9])?)?$

How it works

Both key and value follow the same rule: 1–63 chars, must start AND end with alphanumeric, can contain underscores/dots/hyphens in the middle. The value group is optional (empty values are allowed). Anchored with ^ and $ for strict full-string matching.