shebang-command 2.0.0: shebangCommand

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify shebangCommand in pkg:npm/shebang-command@2.0.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/shebang-command@2.0.0
Demonstrate these symbols/APIs:
  - shebangCommand
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:6baff35ddc4863c5241f27a173a17373516ede5d08e70d024cad6ca094226858","constraints":{"executionContext":"node"},"contract":["shebangCommand extracts command name from env-based shebang","shebangCommand extracts direct binary name from standard shebang","shebangCommand preserves arguments for direct binary shebangs","shebangCommand handles shebangs with whitespace after hashbang","shebangCommand returns null for non-shebang strings, empty strings, and omitted arguments"],"goal":"verify shebangCommand in pkg:npm/shebang-command@2.0.0","kind":"HOW","packages":["pkg:npm/shebang-command@2.0.0"],"schemaVersion":1,"symbols":["shebangCommand"]},"contractCommand":["node","test/contract.js"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"cjs","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/shebang-command@2.0.0"],"schemaVersion":1,"subject":"pkg:npm/shebang-command@2.0.0","symbols":["shebangCommand"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-shebang-command",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-shebang-command",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "shebang-command": "2.0.0"
      }
    },
    "node_modules/shebang-command": {
      "version": "2.0.0",
      "resolved": "https://registry.npmjs.org/shebang-command/-/shebang-command-2.0.0.tgz",
      "integrity": "sha512-kHxr2zZpYtdmrN1qDjrrX/Z1rR1kG8Dx+gkpK1G4eXmvXswmcE1hTWBWYUzlraYw1/yZp6YuDY77YtvbN0dmDA==",
      "license": "MIT",
      "dependencies": {
        "shebang-regex": "^3.0.0"
      },
      "engines": {
        "node": ">=8"
      }
    },
    "node_modules/shebang-regex": {
      "version": "3.0.0",
      "resolved": "https://registry.npmjs.org/shebang-regex/-/shebang-regex-3.0.0.tgz",
      "integrity": "sha512-7++dFhtcx3353uBaq8DDR4NuxBetBzC7ZQOhmTQInHEd6bSrXdiEyzCvG07Z44UYdLShWUyXt5M/yhz8ekcb1A==",
      "license": "MIT",
      "engines": {
        "node": ">=8"
      }
    }
  }
}

{
  "name": "sample-shebang-command",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification sample for shebang-command",
  "main": "src/index.js",
  "scripts": {
    "test": "node test/contract.js"
  },
  "dependencies": {
    "shebang-command": "2.0.0"
  },
  "license": "MIT-0"
}

{
  "schemaVersion": 1,
  "goal": "verify shebangCommand in pkg:npm/shebang-command@2.0.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/shebang-command@2.0.0"
  ],
  "symbols": [
    "shebangCommand"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

'use strict';

const shebangCommand = require('shebang-command');

/**
 * Extracts the command from a shebang line.
 * @param {string} string - A shebang string.
 * @returns {string|null} - The extracted command or null if not a valid shebang.
 */
function extractCommand(string) {
  return shebangCommand(string);
}

module.exports = {
  shebangCommand,
  extractCommand
};

'use strict';

const assert = require('assert');
const shebangCommand = require('shebang-command');
const { extractCommand } = require('../src/index.js');

// 1. shebangCommand extracts command name from env-based shebang
{
  assert.strictEqual(shebangCommand('#!/usr/bin/env node'), 'node');
  assert.strictEqual(shebangCommand('#!/usr/bin/env python3'), 'python3');
  assert.strictEqual(extractCommand('#!/usr/bin/env node'), 'node');
}

// 2. shebangCommand extracts direct binary name from standard shebang
{
  assert.strictEqual(shebangCommand('#!/bin/bash'), 'bash');
  assert.strictEqual(shebangCommand('#!/bin/sh'), 'sh');
  assert.strictEqual(shebangCommand('/usr/bin/node'), null);
}

// 3. shebangCommand preserves arguments for direct binary shebangs
{
  assert.strictEqual(shebangCommand('#!/bin/sh -e'), 'sh -e');
  assert.strictEqual(shebangCommand('#!/usr/bin/python3 -u'), 'python3 -u');
}

// 4. shebangCommand handles shebangs with whitespace after hashbang
{
  assert.strictEqual(shebangCommand('#! /usr/bin/env node'), 'node');
  assert.strictEqual(shebangCommand('#! /bin/bash'), 'bash');
}

// 5. shebangCommand returns null for non-shebang strings, empty strings, and omitted arguments
{
  assert.strictEqual(shebangCommand('console.log("hello")'), null);
  assert.strictEqual(shebangCommand(''), null);
  assert.strictEqual(shebangCommand(), null);
  assert.strictEqual(extractCommand(''), null);
}

console.log('Contract tests passed successfully.');