Text Processingflags: g

Unix Environment Variable Reference

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

Available in

JavaScript / ECMAScript code

jsJavaScript

const re = new RegExp("\\$\\{?([A-Z_][A-Z0-9_]*)\\}?", "g");
const input = "Path is $HOME/.config";
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-Z_][A-Z0-9_]*)\}?")
input_text = "Path is $HOME/.config"
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-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.

Pattern

regexengine-agnostic

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

Raw source: \$\{?([A-Z_][A-Z0-9_]*)\}?

How it 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.