learnyounode/exercises/my_first_io/problem.md

Learn You The Node.js For Much Win! An intro to Node.js via a set of self-guided workshops.

Create a file named `my-first-io.js`.

Write a program that uses a single **synchronous** filesystem operation to read a file and print the number of newlines (\n) it contains to the console (stdout), similar to running `cat file | wc -l`.

The full path to the file to read will be provided as the first command-line argument (i.e., process.argv[2]). You do not need to make your own test file.

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## HINTS

To perform a filesystem operation you are going to need the `fs` module from the Node core library. To load this kind of module, or any other "global" module, use the following incantation:

```js
const fs = require('fs')
```

Now you have the full `fs` module available in a variable named `fs`.

All synchronous (or blocking) filesystem methods in the `fs` module end with 'Sync'. To read a file, you'll need to use `fs.readFileSync('/path/to/file')`. This method will *return* a `Buffer` object containing the complete contents of the file.

Documentation on the `fs` module can be found by pointing your browser here:
  {rootdir:/docs-nodejs/fs.html}

`Buffer` objects are Node's way of efficiently representing arbitrary arrays of data, whether it be ascii, binary or some other format. `Buffer` objects can be converted to strings by simply calling the `toString()` method on them. e.g. `const str = buf.toString()`.

Documentation on `Buffer`s can be found by pointing your browser here:
  {rootdir:/docs-nodejs/buffer.html}

If you're looking for an easy way to count the number of newlines in a string, recall that a JavaScript `String` can be `.split()` into an array of substrings and that '\n' can be used as a delimiter. Note that the test file does not have a newline character ('\n') at the end of the last line, so using this method you'll end up with an array that has one more element than the number of newlines.

Check to see if your program is correct by running this command:

```sh
$ {appname} verify my-first-io.js
```