How to use child_process - 10 common examples

setTimeout(function () {
                client.destroy();
                if (!fs.existsSync(rootDir + 'tmp/node_modules/' + appName + '.js-controller')) {
                    console.log('installJsController: no js-controller => install from git');

                    child_process.execSync('npm install https://github.com/' + appName + '/' + appName + '.js-controller/tarball/master --prefix ./  --production', {
                        cwd:   rootDir + 'tmp/',
                        stdio: [0, 1, 2]
                    });
                } else {
                    console.log('Setup js-controller...');
                    let __pid;
                    if (debug) {
                        // start controller
                        child_process.exec('node ' + appName + '.js setup first', {
                            cwd: rootDir + 'tmp/node_modules/' + appName + '.js-controller',
                            stdio: [0, 1, 2]
                        });
                    } else {
                        child_process.fork(appName + '.js', ['setup', 'first'], {
                            cwd:   rootDir + 'tmp/node_modules/' + appName + '.js-controller',
                            stdio: [0, 1, 2, 'ipc']
                        });
                    }
                }

                // let npm install admin and run setup
                checkIsControllerInstalled(function () {
                    let _pid;

                    if (fs.existsSync(rootDir + 'node_modules/' + appName + '.js-controller/' + appName + '.js')) {

console.log('Install adapter...');
    var startFile = 'node_modules/' + appName + '.js-controller/' + appName + '.js';
    // make first install
    if (debug) {
        child_process.execSync('node ' + startFile + ' add ' + customName + ' --enabled false', {
            cwd:   rootDir + 'tmp',
            stdio: [0, 1, 2]
        });
        checkIsAdapterInstalled(function (error) {
            if (error) console.error(error);
            console.log('Adapter installed.');
            if (cb) cb();
        });
    } else {
        // add controller
        var _pid = child_process.fork(startFile, ['add', customName, '--enabled', 'false'], {
            cwd:   rootDir + 'tmp',
            stdio: [0, 1, 2, 'ipc']
        });

        waitForEnd(_pid, function () {
            checkIsAdapterInstalled(function (error) {
                if (error) console.error(error);
                console.log('Adapter installed.');
                if (cb) cb();
            });
        });
    }
}

// See the License for the specific language governing permissions and
// limitations under the License.

'use strict';

var assert = require('assert');
var cp = require('child_process');
var glob = require('glob');
var path = require('path');
var tmp = require('tmp');

var expressVersion = '4.15.3';

// Setup
var express_dir = tmp.dirSync().name;
cp.execFileSync('git', ['clone', '--branch', expressVersion,
    'https://github.com/strongloop/express.git', '--depth', '1', express_dir]);
var test_glob = path.join(express_dir, 'test', '*.js');
var error;
process.chdir(express_dir);

// Remove name to allow for cyclic dependency
console.log('Updating express metadata');
cp.execFileSync('sed', ['-i.bak', 's/"express"/"e"/', 'package.json']);

// Install express as its own dependency
console.log('Installing express dependencies');
cp.execFileSync('npm', ['--version'], { stdio: 'inherit' });
cp.execFileSync('npm', ['install']);
cp.execFileSync('npm', ['install', 'express@' + expressVersion]);

// Reformat tests to use newly installed express

const child = new ChildProcess();

  [null, 0, 1, NaN, true, false, {}, 'foo'].forEach((args) => {
    common.expectsError(() => {
      child.spawn({ file: 'foo', args });
    }, {
      code: 'ERR_INVALID_ARG_TYPE',
      type: TypeError,
      message: 'The "options.args" property must be of type Array. ' +
               `Received type ${typeName(args)}`
    });
  });
}

// Test that we can call spawn
const child = new ChildProcess();
child.spawn({
  file: process.execPath,
  args: ['--interactive'],
  cwd: process.cwd(),
  stdio: 'pipe'
});

assert.strictEqual(child.hasOwnProperty('pid'), true);
assert(Number.isInteger(child.pid));

// Try killing with invalid signal
common.expectsError(
  () => { child.kill('foo'); },
  { code: 'ERR_UNKNOWN_SIGNAL', type: TypeError }
);

'use strict';

const common = require('../common');
const assert = require('assert');
const { ChildProcess } = require('child_process');
assert.strictEqual(typeof ChildProcess, 'function');

function typeName(value) {
  return typeof value;
}

{
  // Verify that invalid options to spawn() throw.
  const child = new ChildProcess();

  [undefined, null, 'foo', 0, 1, NaN, true, false].forEach((options) => {
    common.expectsError(() => {
      child.spawn(options);
    }, {
      code: 'ERR_INVALID_ARG_TYPE',
      type: TypeError,
      message: 'The "options" argument must be of type Object. ' +
               `Received type ${typeName(options)}`
    });
  });
}

{
  // Verify that spawn throws if file is not a string.
  const child = new ChildProcess();

// var input = prefs.file.input;
  var w = prefs.dimensions.width || 320;
  var h = prefs.dimensions.height || 240;
  var fps = prefs.fps || 24;
  var stats = prefs.color.stats_mode || 'full';
  // var colors = prefs.color.colors || 256;
  var transparency = (prefs.color.alpha?1:0) || 0;
  var colors = prefs.color.count || 256;

  var scaleCmd = "scale="+w+":"+h;

  var vf = util.format("fps=%s,%s:flags=lanczos,palettegen=stats_mode=%s:max_colors=%s:reserve_transparent=%s", fps, scaleCmd, stats, colors, transparency);

  if(ffmpeg_ps) ffmpeg_ps.kill();

  ffmpeg_ps = spawn(ffmpeg_path, ["-i", input, "-vf", vf, "-f", "image2", "-vcodec", "png", "pipe:1"])
  var data = [];
  ffmpeg_ps.stdout.on('data',function(d){
    data.push(d);
  });
  ffmpeg_ps.stderr.on('data',function(d){
    // console.log("stderr",d.toString());
  });
  ffmpeg_ps.on('close',function(){
    event.sender.send('paletteResult', Buffer.concat(data).toString('base64'));
  });
})
ipcMain.on('cancelProcess', (event,opts) => {

const { exec } = require('child_process');
const semver = require('semver');

const currentDir = process.cwd();

exec('tns --version', (err, stdout, stderr) => {
  if (err) {
    // node couldn't execute the command
    console.log(`tns --version err: ${err}`);
    return;
  }

  const tnsVersion = semver.major(stdout);

  // execute 'tns plugin build' for {N} version > 4. This command builds .aar in platforms/android folder.
  if (tnsVersion >= 4) {
    console.log(`executing 'tns plugin build' in ${currentDir}`);
    exec(`cd ${currentDir} && tns plugin build`);
  }
});

await fs.move(path.join(dest, 'gitignore'), path.join(dest, '.gitignore'))
  }
  if (fs.pathExistsSync(path.join(dest, 'gitignore'))) {
    fs.removeSync(path.join(dest, 'gitignore'))
  }

  if (isCLI) {
    console.log(
      `Installing dependencies with: ${
        isYarn
          ? chalk.hex(ChalkColor.yarn)('Yarn')
          : chalk.hex(ChalkColor.npm)('NPM')
      }...`
    )
    // We install react-static separately to ensure we always have the latest stable release
    execSync(`cd "${name}" && ${isYarn ? 'yarn' : 'npm install'}`)
    console.log('')
  }

  timeEnd(chalk.green(`[\u2713] Project "${name}" created`))

  console.log(`
  ${chalk.green('To get started:')}

    cd "${name}" ${
    !isCLI
      ? `&& ${
          isYarn
            ? chalk.hex(ChalkColor.yarn)('yarn')
            : chalk.hex(ChalkColor.npm)('npm install')
        }`
      : ''

if (process.platform === 'win32') {
        const TASK_KILL = 'C:\\Windows\\System32\\taskkill.exe';
        // when killing a process in Windows its child processes are *not* killed but become root processes.
        // Therefore we use TASKKILL.EXE
        try {
            cp.execSync(`${TASK_KILL} /F /T /PID ${processId}`);
        }
        catch (err) {
            console.log('Error killing process tree: ' + err);
        }
    }
    else {
        // on linux and OS X we kill all direct and indirect child processes as well
        try {
            const cmd = path.join(__dirname, '../../../scripts/terminateProcess.sh');
            cp.spawnSync(cmd, [processId.toString()]);
        }
        catch (err) {
            console.log('Error killing process tree: ' + err);
        }
    }
}
exports.killTree = killTree;

let cliOpts = ['start',
      '--port', this.opts.packagerPort,
      '--projectRoots', root,
      '--assetRoots', root,
    ];

    if (options.reset) {
      cliOpts.push('--reset-cache');
    }
    
    // Run the copy of Node that's embedded in Electron by setting the
    // ELECTRON_RUN_AS_NODE environment variable
    // Note: the CLI script sets up graceful-fs and sets ulimit to 4096 in the
    // child process
    let packagerProcess = child_process.fork(this.opts.cliPath, cliOpts, {
      cwd: path.dirname(path.dirname(this.opts.cliPath)),
      env: {
        ...process.env,
        NODE_PATH: null,
        ELECTRON_RUN_AS_NODE: 1,
      },
      silent: true,
    });
    process.on('exit', () => {
      packagerProcess.kill();
    });
    this._packager = packagerProcess;
    this._packager.stdout.setEncoding('utf8');
    this._packager.stderr.setEncoding('utf8');
    this._packager.stdout.on('data', (data) => {
      this.emit('stdout', data);