$ cat pipe.js 
require('shelljs/global')
echo('files with o\'s in the name:\n' + ls().grep('o'));

$ shjs pipe.js 
/home/pelle/pipe.js:3
echo('files with o\'s in the name:\n' + ls().grep('o'));
                                             ^
TypeError: ls(...).grep is not a function
    at Object.<anonymous> (/home/pelle/pipe.js:3:46)
    at Module._compile (module.js:413:34)
    at Object.Module._extensions..js (module.js:422:10)
    at Module.load (module.js:357:32)
    at Function.Module._load (module.js:314:12)
    at Function.Module.runMain (module.js:447:10)
    at startup (node.js:141:18)
    at node.js:933:3