Go (RE2)

Unix Environment Variable Reference in GO

Match Unix shell environment variable references in both $VAR and ${VAR} forms.

Try it in the GO tester →

Pattern

regexGO
\$\{?([A-Z_][A-Z0-9_]*)\}?   (flags: g)

Go (RE2) code

goGo
package main

import (
	"fmt"
	"regexp"
)

func main() {
	re := regexp.MustCompile(`\$\{?([A-Z_][A-Z0-9_]*)\}?`)
	input := `Path is $HOME/.config`
	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

\$ matches the literal dollar sign. \{? optionally matches an opening brace. ([A-Z_][A-Z0-9_]*) captures the variable name: must start with a letter or underscore, followed by letters, digits, or underscores. \}? optionally matches the closing brace.

Examples

Input

Path is $HOME/.config

Matches

  • $HOME

Input

export ${DATABASE_URL}

Matches

  • ${DATABASE_URL}

Input

no variables here

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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