POSIX Environment Variable Name (Uppercase Convention) Regex for JavaScript

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching posix environment variable name (uppercase convention), ported and verified for JavaScript. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your JavaScript project — whether you're validating in an Express middleware, a Next.js API route, or a client-side form.

Javascript Implementation

// POSIX Environment Variable Name (Uppercase Convention)
// ReDoS-safe | RegexVault — Dev & Systems > Environment

const posixEnvironmentVariableNameUppercaseConventionRegex = /^[A-Z_][A-Z0-9_]{0,254}$/;

function validatePosixEnvironmentVariableNameUppercaseConvention(input: string): boolean {
  return posixEnvironmentVariableNameUppercaseConventionRegex.test(input);
}

// Example
console.log(validatePosixEnvironmentVariableNameUppercaseConvention("PATH")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Dev & Systems > Environment category and carries a ReDoS-safe certification. That matters for JavaScript developers because especially critical in long-running Node.js event loops where a ReDoS vulnerability can block the entire process. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

POSIX variables are case-sensitive and conventionally uppercase. Lowercase variables (PATH vs path) are different on Linux. On Windows, environment variables are case-insensitive.