Shebang Line Regex for Python

What this pattern does

This page provides a well-structured, multi-part regular expression for matching shebang line, ported and verified for Python. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your Python project — whether you're validating in a Django view, a FastAPI endpoint, or a standalone data processing script.

Python Implementation

# Shebang Line
# ReDoS-safe | RegexVault — Dev & Systems > Shell

import re

shebang_line_pattern = re.compile(r'^#!(/(?:[a-zA-Z0-9._\-]+/)*[a-zA-Z0-9._\-]+)((?:\s+[^\s]+)*)$')

def validate_shebang_line(value: str) -> bool:
    return bool(shebang_line_pattern.fullmatch(value))

# Example
print(validate_shebang_line("#!/bin/bash"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Dev & Systems > Shell category and carries a ReDoS-safe certification. That matters for Python developers because particularly important in Python web servers where CPU-bound regex operations can stall concurrent request handling. 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

Groups: 1=interpreter path, 2=arguments. The env idiom (#!/usr/bin/env python3) is preferred for portability. The shebang must be the first two characters of the file.