File & Pathflags: gm

Dockerfile ENV Instruction

Match Dockerfile `ENV KEY=value` (or `ENV KEY value`) instructions, capturing key and value.

Available in

JavaScript / ECMAScript code

jsJavaScript

const re = new RegExp("^ENV\\s+([A-Z_][A-Z0-9_]*)(?:[=\\s]+)(.+)$", "gm");
const input = "ENV NODE_VERSION=20.10.0\\nENV PORT 3000";
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"^ENV\s+([A-Z_][A-Z0-9_]*)(?:[=\s]+)(.+)$", re.MULTILINE)
input_text = "ENV NODE_VERSION=20.10.0\nENV PORT 3000"
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(`(?m)^ENV\s+([A-Z_][A-Z0-9_]*)(?:[=\s]+)(.+)$`)
	input := `ENV NODE_VERSION=20.10.0\nENV PORT 3000`
	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

^ENV\s+([A-Z_][A-Z0-9_]*)(?:[=\s]+)(.+)$   (flags: gm)

Raw source: ^ENV\s+([A-Z_][A-Z0-9_]*)(?:[=\s]+)(.+)$

How it works

^ENV anchors to the line start (m flag enables per-line). \s+ requires whitespace. ([A-Z_][A-Z0-9_]*) captures the key (uppercase + underscores by convention). [=\s]+ matches either the modern `=` separator or the legacy whitespace separator. (.+)$ captures the rest of the line as the value.