Identifiersflags: g

Docker Image Tag

Match Docker image references with an explicit tag — e.g. nginx:1.21, mycorp/service:v2.3.1.

Available in

JavaScript / ECMAScript code

jsJavaScript

const re = new RegExp("\\b[a-z0-9]+(?:[._\\-\\/][a-z0-9]+)*:[\\w.\\-]+\\b", "g");
const input = "FROM nginx:1.21";
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"\b[a-z0-9]+(?:[._\-\/][a-z0-9]+)*:[\w.\-]+\b")
input_text = "FROM nginx:1.21"
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(`\b[a-z0-9]+(?:[._\-\/][a-z0-9]+)*:[\w.\-]+\b`)
	input := `FROM nginx:1.21`
	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

\b[a-z0-9]+(?:[._\-\/][a-z0-9]+)*:[\w.\-]+\b   (flags: g)

Raw source: \b[a-z0-9]+(?:[._\-\/][a-z0-9]+)*:[\w.\-]+\b

How it works

Image name is lowercase alphanumerics with optional . _ - / separators for registry paths. Tag follows the colon and can include letters, digits, dots, hyphens, and underscores.