Go (RE2)

Dockerfile ENV Instruction in GO

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

Try it in the GO tester →

Pattern

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

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.

How the pattern 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.

Examples

Input

ENV NODE_VERSION=20.10.0\nENV PORT 3000

Matches

  • ENV NODE_VERSION=20.10.0
  • ENV PORT 3000

Input

ENV DATABASE_URL=postgres://localhost/db

Matches

  • ENV DATABASE_URL=postgres://localhost/db

Input

FROM node:20

No match

—

Same pattern, other engines

JavaScript / ECMAScript

Supported

See how this pattern looks (and behaves) in JavaScript's built-in RegExp.

Python (re)

Supported

See how this pattern looks (and behaves) in Python's stdlib `re` module.

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