npm package: @stdlib/fs-read-file
Description: Read the entire contents of a file.
Author: The Stdlib Authors
Latest version: 0.2.3

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<details>
  <summary>
    About stdlib...
  </summary>
  <p>We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.</p>
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</details>

# Read File

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> Read the entire contents of a file.

<section class="installation">

## Installation

```bash
npm install @stdlib/fs-read-file
```

</section>

<section class="usage">

## Usage

```javascript
var readFile = require( '@stdlib/fs-read-file' );
```

#### readFile( file\[, options], clbk )

Asynchronously reads the entire contents of a file.

```javascript
readFile( __filename, onFile );

function onFile( error, data ) {
    if ( error ) {
        throw error;
    }
    console.log( data );
}
```

The function accepts the same `options` and has the same defaults as [`fs.readFile()`][node-fs].

#### readFile.sync( file\[, options] )

Synchronously reads the entire contents of a `file`.

```javascript
var out = readFile.sync( __filename );
if ( out instanceof Error ) {
    throw out;
}
console.log( out );
```

The function accepts the same `options` and has the same defaults as [`fs.readFileSync()`][node-fs].

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   The difference between this API and [`fs.readFileSync()`][node-fs] is that [`fs.readFileSync()`][node-fs] will throw if an `error` is encountered (e.g., if given a non-existent `path`) and this API will return an `error`. Hence, the following anti-pattern


    ```javascript
    var fs = require( 'fs' );

    var file = '/path/to/file.js';

    // Check for existence to prevent an error being thrown...
    if ( fs.existsSync( file ) ) {
        file = fs.readFileSync( file );
    }
    ```

    can be replaced by an approach which addresses existence via `error` handling.

    ```javascript
    var readFile = require( '@stdlib/fs-read-file' );

    var file = '/path/to/file.js';

    // Explicitly handle the error...
    file = readFile.sync( file );
    if ( file instanceof Error ) {
        // You choose what to do...
        console.error( file.message );
    }
    ```

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var readFile = require( '@stdlib/fs-read-file' );

/* Sync */

var file = readFile.sync( __filename, 'utf8' );
// returns <string>

console.log( file instanceof Error );
// => false

file = readFile.sync( 'beepboop', {
    'encoding': 'utf8'
});
// returns <Error>

console.log( file instanceof Error );
// => true

/* Async */

readFile( __filename, onFile );
readFile( 'beepboop', onFile );

function onFile( error, data ) {
    if ( error ) {
        if ( error.code === 'ENOENT' ) {
            console.error( 'File does not exist.' );
        } else {
            throw error;
        }
    } else {
        console.log( data );
    }
}
```

</section>

<!-- /.examples -->



<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

## See Also

-   <span class="package-name">[`@stdlib/fs-read-file-cli`][@stdlib/fs-read-file-cli]</span><span class="delimiter">: </span><span class="description">CLI package for use as a command-line utility.</span>
-   <span class="package-name">[`@stdlib/fs-exists`][@stdlib/fs/exists]</span><span class="delimiter">: </span><span class="description">test whether a path exists on the filesystem.</span>
-   <span class="package-name">[`@stdlib/fs-open`][@stdlib/fs/open]</span><span class="delimiter">: </span><span class="description">open a file.</span>
-   <span class="package-name">[`@stdlib/fs-read-dir`][@stdlib/fs/read-dir]</span><span class="delimiter">: </span><span class="description">read the entire contents of a directory.</span>
-   <span class="package-name">[`@stdlib/fs-read-json`][@stdlib/fs/read-json]</span><span class="delimiter">: </span><span class="description">read a file as JSON.</span>
-   <span class="package-name">[`@stdlib/fs-write-file`][@stdlib/fs/write-file]</span><span class="delimiter">: </span><span class="description">write data to a file.</span>

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->


<section class="main-repo" >

* * *

## Notice

This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].

#### Community

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

</section>

<!-- /.stdlib -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="links">

[@stdlib/fs-read-file-cli]: https://www.npmjs.com/package/@stdlib/fs-read-file-cli

[npm-image]: http://img.shields.io/npm/v/@stdlib/fs-read-file.svg
[npm-url]: https://npmjs.org/package/@stdlib/fs-read-file

[test-image]: https://github.com/stdlib-js/fs-read-file/actions/workflows/test.yml/badge.svg?branch=v0.2.3
[test-url]: https://github.com/stdlib-js/fs-read-file/actions/workflows/test.yml?query=branch:v0.2.3

[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/fs-read-file/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/fs-read-file?branch=main

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-->

[chat-image]: https://img.shields.io/badge/zulip-join_chat-brightgreen.svg
[chat-url]: https://stdlib.zulipchat.com

[stdlib]: https://github.com/stdlib-js/stdlib

[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors

[cli-section]: https://github.com/stdlib-js/fs-read-file#cli
[cli-url]: https://github.com/stdlib-js/fs-read-file/tree/cli
[@stdlib/fs-read-file]: https://github.com/stdlib-js/fs-read-file/tree/main

[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules

[deno-url]: https://github.com/stdlib-js/fs-read-file/tree/deno
[deno-readme]: https://github.com/stdlib-js/fs-read-file/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/fs-read-file/tree/umd
[umd-readme]: https://github.com/stdlib-js/fs-read-file/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/fs-read-file/tree/esm
[esm-readme]: https://github.com/stdlib-js/fs-read-file/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/fs-read-file/blob/main/branches.md

[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/fs-read-file/main/LICENSE

[node-fs]: https://nodejs.org/api/fs.html

<!-- <related-links> -->

[@stdlib/fs/exists]: https://www.npmjs.com/package/@stdlib/fs-exists

[@stdlib/fs/open]: https://www.npmjs.com/package/@stdlib/fs-open

[@stdlib/fs/read-dir]: https://www.npmjs.com/package/@stdlib/fs-read-dir

[@stdlib/fs/read-json]: https://www.npmjs.com/package/@stdlib/fs-read-json

[@stdlib/fs/write-file]: https://www.npmjs.com/package/@stdlib/fs-write-file

<!-- </related-links> -->

</section>

<!-- /.links -->