What is the regex for dotenv line?

The regex pattern for dotenv line is `^[A-Z_][A-Z0-9_]*=.*$`. This pattern validates .env file line (key=value format).

How do I use this regex in JavaScript?

In JavaScript, create the regex with `const regex = /^[A-Z_][A-Z0-9_]*=.*$/;` and test with `regex.test(yourValue)`. It returns `true` if the value matches.

How do I use this regex in Python?

In Python, use `import re; re.match(r'^[A-Z_][A-Z0-9_]*=.*$', value)`. The raw string prefix (`r`) prevents Python from interpreting backslashes as escape characters.

Is this regex case-sensitive?

By default, yes. To make it case-insensitive, add the `i` flag in JavaScript (`/^[A-Z_][A-Z0-9_]*=.*$/i`) or use `re.IGNORECASE` in Python.

Regex for Dotenv Line

Regex Pattern

^[A-Z_][A-Z0-9_]*=.*$

.env file line (KEY=value format)

Quick Answer

The regex pattern for dotenv line is `^[A-Z_][A-Z0-9_]*=.*$`. .env file line (KEY=value format). This works in JavaScript, Python, Ruby, PHP, Java, and most regex engines that support PCRE syntax.

Test Examples

Input	Result
DATABASE_URL=postgres://localhost/db	✓ Matches
NODE_ENV=production	✓ Matches
SECRET_KEY=abc123	✓ Matches
# comment	✗ No match
lowercase=bad	✗ No match
=no-key	✗ No match

Code Examples

javascript

const regex = /^[A-Z_][A-Z0-9_]*=.*$/;
const isValid = regex.test(value);

python

import re
pattern = r'^[A-Z_][A-Z0-9_]*=.*$'
if re.match(pattern, value):
    print("valid")

ruby

pattern = /^[A-Z_][A-Z0-9_]*=.*$/
if value =~ pattern
  puts "valid"
end

php

if (preg_match('/^[A-Z_][A-Z0-9_]*=.*$/', $value)) {
    echo "valid";
}

java

String pattern = "^[A-Z_][A-Z0-9_]*=.*$";
boolean isValid = value.matches(pattern);

Frequently Asked Questions

Related Regex Patterns

JavaScript Variable Name

Valid JavaScript variable/identifier name

Python Variable Name

Valid Python identifier name

CSS Class Name

Valid CSS class name (starts with letter, underscore, or hyphen)

CSS ID Selector

CSS ID selector starting with #

JSON Key

JSON object key (quoted string followed by colon)

Semantic Version (Strict)

Strict semantic versioning (MAJOR.MINOR.PATCH)