Pattern

Regex for Shell variable assignment

Bash variable assignment — NAME=value.

The Shell variable assignment regex is ^[A-Za-z_][A-Za-z0-9_]*= — copy it below, or open it in the explainer for a token-by-token breakdown.

The pattern

^[A-Za-z_][A-Za-z0-9_]*=

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What it matches

HOME=/root
my_var=hello
PATH=/usr/bin:/bin
x=42

What it doesn't match

1var=oops
my var=spaces
HOME =/root

Notes & gotchas

Matches a shell variable name followed by =. No spaces allowed around the = sign in bash. The value can be anything; this regex matches just the start.

Code in your language

Use the explainer's Code tab to generate ready-to-paste snippets in JavaScript, Python, Java, .NET, Go, Ruby, and PHP for this pattern.

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Token-by-token breakdown

Every part of the pattern, left to right:

Token	Meaning
`^`	start of string (or line in multiline mode)
`[A-Za-z_]`	any of: uppercase letters, lowercase letters, “_”
`[A-Za-z0-9_]*`	zero or more: any of: uppercase letters, lowercase letters, digits, “_”
`=`	literal text “=”

About this pattern

Developer-oriented patterns help with code analysis, log parsing, and data transformation. Use these in build scripts, CI tools, IDE search-and-replace, and code review utilities.

Quick usage in different languages

This exact pattern — with the correct escaping and idioms for each language:

JavaScript: /^[A-Za-z_][A-Za-z0-9_]*=/.test(value)
Python: re.match(r"^[A-Za-z_][A-Za-z0-9_]*=", value)
Java: Pattern.compile("^[A-Za-z_][A-Za-z0-9_]*=").matcher(value).matches()
C# / .NET: Regex.IsMatch(value, @"^[A-Za-z_][A-Za-z0-9_]*=")
Go: regexp.MustCompile(`^[A-Za-z_][A-Za-z0-9_]*=`).MatchString(value)
Ruby: /^[A-Za-z_][A-Za-z0-9_]*=/.match?(value)
PHP: preg_match('~^[A-Za-z_][A-Za-z0-9_]*=~', $value)

The explainer’s Code tab regenerates these for any pattern you paste, and the downloadable cheat sheet bundles the breakdown, all seven snippets, and the pitfalls below onto one printable page.

Common pitfalls

Anchored to the whole string. This pattern uses ^, so it requires the entire input to match. To find it inside a longer text, drop the anchors and use the global (g) flag.
ASCII letters only. [a-zA-Z] excludes accented and non-Latin letters (é, ü, ß, ñ, and non-Latin scripts). For international input use Unicode properties like \p{L} with the u flag.
Validate beyond format. Matching the format doesn't guarantee the value is real. Confirm the shell variable assignment against a source of truth (database, API, or checksum) where it matters.

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