code: async function main() {
    // Initialize the application.
    process.title = 'Which.js';
  
    // Parse the command line arguments.
    program.name('which')
      .description('Find the instances of an executable in the system path.')
      .version(packageVersion, '-v, --version')
      .option('-a, --all', 'list all instances of executables found (instead of just the first one)')
      .option('-s, --silent', 'silence the output, just return the exit code (0 if any executable is found, otherwise 1)')
      .arguments('<command>').action(command => program.executable = command)
      .parse(process.argv);
  
    if (!program.executable) {
      program.outputHelp();
      process.exitCode = 64;
      return;
    }
  
    // Run the program.
    let executables = await which(program.executable, {all: program.all});
    if (!program.silent) {
      if (!Array.isArray(executables)) executables = [executables];
      for (const path of executables) console.log(path);
    }
  }
docs: Application entry point.
  @return {Promise<void>} Completes when the program is terminated.