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How to use the watch function from fs

Find comprehensive JavaScript fs.watch code examples handpicked from public code repositorys.

fs.watch is a Node.js method used to monitor changes in a file or directory.

README.md?plain=1

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const [cmd, , source, ...argv] = process.argv
// console.log('abc', cmd, source, argv)
const childProcess = spawn(cmd, [source, ...argv])
childProcess.stdout.pipe(process.stdout)
childProcess.stderr.pipe(process.stderr)
const watcher = fs.watch(resolve(__dirname, source), () => {
    console.log('File changed, reloading.')
    childProcess.kill()
    watcher.close()
    watch()

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fs.js

GitHub: blockcollider/bcnode

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exports.unlink = co.promisify(fs.unlink);
exports.unlinkSync = fs.unlinkSync;
exports.unwatchFile = fs.unwatchFile;
exports.utimes = co.promisify(fs.utimes);
exports.utimesSync = fs.utimesSync;
exports.watch = fs.watch;
exports.watchFile = fs.watchFile;
exports.write = co.promisify(fs.write);
exports.writeSync = fs.writeSync;
exports.writeFile = co.promisify(fs.writeFile);

How does fs.watch work?

fs.watch is a method in the Node.js file system module (fs) that allows developers to monitor changes in a file or directory. The method takes two arguments: the path to the file or directory to watch and an optional configuration object with various options such as persistent (whether to keep the process running as long as files are being watched) and recursive (whether to watch all subdirectories). When fs.watch is called, it starts monitoring the specified file or directory and emits events when changes occur, such as when a file is created, modified, or deleted. The type of event emitted depends on the operating system and the type of change. Developers can listen for these events using the watcher.on('event', callback) syntax, where 'event' is the name of the event being listened to (e.g., 'change', 'rename', etc.) and callback is a function that will be called when the event occurs. Note that fs.watch is not always reliable, particularly on some platforms such as macOS. In such cases, developers may want to consider using third-party libraries such as chokidar for more reliable file watching capabilities.

linkWorkspaceDeps.js

GitHub: iTwin/viewer-components-react

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const targetPath = getTargetLibPath(package.name, package.libDirName);

copyChangedFiles(package.name, sourcePath, targetPath);

let lastChange = undefined;
fs.watch(sourcePath, { recursive: true }, () => {
  const now = new Date();
  if (now === lastChange) {
    return;
  }

anubis.js

GitHub: anubiskun/anubisbot-MD

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    }
}
anubis.type = type
anubis.anubiskun = S_WHATSAPP_NET
Object.freeze(global.reload)
fs.watch(Path.join(__dirname, 'plugins'), global.reload)
const libCon = require('./library/conector')
anubis.ev.on('connection.update', async (update) => {
    const { connection, lastDisconnect } = update
    if (connection === 'connecting') console.log('sabar ngab lagi nyoba menghubungkan!')

Ai Example

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const fs = require("fs");

fs.watch("myFile.txt", (eventType, filename) => {
  console.log(`Event type is: ${eventType}`);
  if (filename) {
    console.log(`Filename provided: ${filename}`);
  } else {
    console.log("Filename not provided");
  }
});

In this example, the fs.watch function is used to watch for changes to a file named myFile.txt. When changes are detected, the function specified as the second argument is called with two arguments: eventType and filename. eventType indicates the type of event that triggered the callback, such as 'change' or 'rename'. If the event was triggered by a change to a file, filename indicates the name of the file that was changed.

preload.js

GitHub: Michael-Vanderford/electron-file-manager

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// } else {
//     sidebar_items.append('No devices found.')
// }

// fs.watch('/mnt/', (e, filename) => {
//     localStorage.setItem('sidebar', 1);
//     show_sidebar();
//     get_devices();
// })

+ 2 other calls in file

application.js

GitHub: Aslijia/pomelo2

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var pfile = require(realpath)
this.set(key, pfile[this.env] ? pfile[this.env] : pfile)

if (!!realpath && !!reload) {
    var self = this
    fs.watch(realpath, function (event, filename) {
        if (event === 'change') {
            delete require.cache[require.resolve(realpath)]
            self.loadConfigBaseApp(key, val)
        }

finder.js

GitHub: AxelRothe/wranglebot

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join(...paths) {
  return path.join(...paths);
}

watch(pathToFolder, callback) {
  return fs.watch(pathToFolder, callback);
}

async checkDiskSpace(pathToDevice) {
  return new Promise((resolve) => {

MessageStrategy.js

GitHub: dmzoneill/Chuckbot

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static watch() {
  if (MessageStrategy.watcher != null) {
    MessageStrategy.watcher.close()
  }

  fs.watch(strategies_dir, (event, filename) => {
    if (filename) {
      MessageStrategy.update_strategy(filename)
    }
  })

main.js

GitHub: ghostpariah/thunder-canyon

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readyFolders();

console.log("************database done");
setTimeout(() => {
    backupDB();
    fs.watch(white_board, (event, filename) => {
        if (filename) {
            if (fsWait) return;
            fsWait = setTimeout(() => {
                fsWait = false;

+ 4 other calls in file

index.js

GitHub: Monuwarhussen/CSE---3200-project

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// Other platforms use non-polling fs_watch.
if (undef(opts, 'usePolling') && !opts.useFsEvents) {
  opts.usePolling = isMacos;
}

// Always default to polling on IBM i because fs.watch() is not available on IBM i.
if(isIBMi) {
  opts.usePolling = true;
}

development-server.js

GitHub: TIBCOSoftware/spotfire-mod-verticalline

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if (files.find((fileName) => fileName == manifestName)) {
    const manifestPath = path.join(rootDirectoryAbsolutePath, manifestName);

    await readExternalResources();
    fs.watch(manifestPath, {}, readExternalResources);

    async function readExternalResources() {
        let content = await readFile(manifestPath, { encoding: "utf-8" });

verify_download2.js

GitHub: MalickGalant/malikblog

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function checkFileExists(filePath, timeout=15000) {
  return new Promise((resolve, reject) => {
    const dir = path.dirname(filePath);
    const basename = path.basename(filePath);


    const watcher = fs.watch(dir, (eventType, filename) => {
      if (eventType === 'rename' && filename === basename) {
        clearTimeout(timer);
        watcher.close();
        resolve();

fs-read.js

GitHub: Mike7323/Mike-s-construction

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}


// fs.watch
{
  assert.throws(() => {
    fs.watch(blockedFile, () => {});
  }, common.expectsError({
    code: 'ERR_ACCESS_DENIED',
    permission: 'FileSystemRead',
    resource: path.toNamespacedPath(blockedFile),

+ 3 other calls in file

test-fs-options-immutable.js

GitHub: vladimir-andreevich/node.js-14-windows-7

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  fs.appendFileSync(fileName, 'ABCD', options);
  fs.appendFile(fileName, 'ABCD', options, common.mustCall(errHandler));
}


if (!common.isIBMi) { // IBMi does not support fs.watch()
  const watch = fs.watch(__filename, options, common.mustNotCall());
  watch.close();
}


{

test-fs-assert-encoding-error.js

GitHub: vladimir-andreevich/node.js-14-windows-7

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assert.throws(() => {
  fs.appendFileSync('path', 'data', options);
}, expectedError);


assert.throws(() => {
  fs.watch('path', options, common.mustNotCall());
}, expectedError);


assert.throws(() => {
  fs.realpath('path', options, common.mustNotCall());

main.js

GitHub: xyzuniverse/xyzbot

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  global.plugins[filename] = require(path.join(
    pluginFolder,
    name,
    filename
  ));
  fs.watch(pluginFolder + "/" + name, global.reload);
} catch (e) {
  logger.error(e);
  delete global.plugins[filename];
}

+ 3 other calls in file

Other functions in fs

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