\n\n# flagged-respawn\n\n[![NPM version][npm-image]][npm-url] [![Downloads][downloads-image]][npm-url] [![Build Status][ci-image]][ci-url] [![Coveralls Status][coveralls-image]][coveralls-url]\n\nA tool for respawning node binaries when special flags are present.\n\n## What is it?\n\nSay you wrote a command line tool that runs arbitrary javascript (e.g. task runner, test framework, etc). For the sake of discussion, let's pretend it's a testing harness you've named `testify`.\n\nEverything is going splendidly until one day you decide to test some code that relies on a feature behind a v8 flag in node (`--harmony`, for example). Without much thought, you run `testify --harmony spec tests.js`.\n\nIt doesn't work. After digging around for a bit, you realize this produces a [`process.argv`](http://nodejs.org/docs/latest/api/process.html#process_process_argv) of:\n\n`['node', '/usr/local/bin/test', '--harmony', 'spec', 'tests.js']`\n\nCrap. The `--harmony` flag is in the wrong place! It should be applied to the **node** command, not our binary. What we actually wanted was this:\n\n`['node', '--harmony', '/usr/local/bin/test', 'spec', 'tests.js']`\n\nFlagged-respawn fixes this problem and handles all the edge cases respawning creates, such as:\n\n- Providing a method to determine if a respawn is needed.\n- Piping stderr/stdout from the child into the parent.\n- Making the parent process exit with the same code as the child.\n- If the child is killed, making the parent exit with the same signal.\n\nTo see it in action, clone this repository and run `npm install` / `npm run respawn` / `npm run nospawn`.\n\n## Sample Usage\n\n```js\n#!/usr/bin/env node\n\nconst flaggedRespawn = require('flagged-respawn');\n\n// get a list of all possible v8 flags for the running version of node\nconst v8flags = require('v8flags').fetch();\n\nflaggedRespawn(v8flags, process.argv, function (ready, child) {\n if (ready) {\n console.log('Running!');\n // your cli code here\n } else {\n console.log('Special flags found, respawning.');\n }\n if (process.pid !== child.pid) {\n console.log('Respawned to PID:', child.pid);\n }\n});\n```\n\n## API\n\n### flaggedRespawn(flags, argv, [ forcedFlags, ] callback) : Void\n\nRespawns the script itself when _argv_ has special flag contained in _flags_ and/or _forcedFlags_ is not empty. Because members of _flags_ and _forcedFlags_ are passed to `node` command, each of them needs to be a node flag or a V8 flag.\n\n#### Forbid respawning\n\nIf `--no-respawning` flag is given in _argv_, this function does not respawned even if _argv_ contains members of flags or _forcedFlags_ is not empty. (This flag is also used internally to prevent from respawning more than once).\n\n#### Parameter:\n\n| Parameter | Type | Description |\n| :------------ | :-------------: | :--------------------------------------------------------------------------------------- |\n| _flags_ | Array | An array of node flags and V8 flags which are available when present in _argv_. |\n| _argv_ | Array | Command line arguments to respawn. |\n| _forcedFlags_ | Array or String | An array of node flags or a string of a single flag and V8 flags for respawning forcely. |\n| _callback_ | function | A called function when not respawning or after respawned. |\n\n- **callback(ready, proc, argv) : Void**\n\n _callback_ function is called both when respawned or not, and it can be distinguished by callback's argument: _ready_. (_ready_ indicates whether a process spawned its child process (false) or not (true), but it does not indicate whether a process is a spawned child process or not. _ready_ for a spawned child process is true.)\n\n _argv_ is an array of command line arguments which is respawned (when _ready_ is false) or is passed current process except flags within _flags_ and `--no-respawning` (when _ready_ is true).\n\n **Parameter:**\n\n | Parameter | Type | Description |\n | :-------- | :-----: | :------------------------------------------------------------------- |\n | _ready_ | boolean | True, if not respawning and is ready to execute main function. |\n | _proc_ | object | Child process object if respawned, otherwise current process object. |\n | _argv_ | Array | An array of command line arguments. |\n\n## License\n\nMIT\n\n\n[downloads-image]: https://img.shields.io/npm/dm/flagged-respawn.svg?style=flat-square\n[npm-url]: https://www.npmjs.com/package/flagged-respawn\n[npm-image]: https://img.shields.io/npm/v/flagged-respawn.svg?style=flat-square\n\n[ci-url]: https://github.com/gulpjs/flagged-respawn/actions?query=workflow:dev\n[ci-image]: https://img.shields.io/github/workflow/status/gulpjs/flagged-respawn/dev?style=flat-square\n\n[coveralls-url]: https://coveralls.io/r/gulpjs/flagged-respawn\n[coveralls-image]: https://img.shields.io/coveralls/gulpjs/flagged-respawn/master.svg?style=flat-square\n\n","_attachments":{},"homepage":"https://github.com/gulpjs/flagged-respawn#readme","bugs":{"url":"https://github.com/gulpjs/flagged-respawn/issues"},"license":"MIT"}
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