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https://github.com/stdlib-js/fs-read-file

Read the entire contents of a file.
https://github.com/stdlib-js/fs-read-file

async file filesystem fs javascript node node-js nodejs open path read readfile readfilesync stdlib sync

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Read the entire contents of a file.

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README 

        



  

    About stdlib...

  

  
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.


  
The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.


  
When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.


  
To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!



# Read File



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



> Read the entire contents of a file.



## Installation



```bash

npm install @stdlib/fs-read-file

```



Alternatively,



-   To load the package in a website via a `script` tag without installation and bundlers, use the [ES Module][es-module] available on the [`esm`][esm-url] branch (see [README][esm-readme]).

-   If you are using Deno, visit the [`deno`][deno-url] branch (see [README][deno-readme] for usage intructions).

-   For use in Observable, or in browser/node environments, use the [Universal Module Definition (UMD)][umd] build available on the [`umd`][umd-url] branch (see [README][umd-readme]).

-   To use as a general utility for the command line, install the corresponding [CLI package][cli-section] globally.



The [branches.md][branches-url] file summarizes the available branches and displays a diagram illustrating their relationships.



To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.



## 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].



## 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 );

    }

    ```



## Examples



```javascript

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



/* Sync */



var file = readFile.sync( __filename, 'utf8' );

// returns 



console.log( file instanceof Error );

// => false



file = readFile.sync( 'beepboop', {

    'encoding': 'utf8'

});

// returns 



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 );

    }

}

```



* * *



## CLI



## Installation



To use as a general utility, install the CLI package globally



```bash

npm install -g @stdlib/fs-read-file-cli

```



### Usage



```text

Usage: read-file [options] 



Options:



  -h,    --help                Print this message.

  -V,    --version             Print the package version.

  --enc, --encoding encoding   Encoding.

         --flag flag           Flag. Default: 'r'.

```



### Notes



-   Relative file paths are resolved relative to the current working directory.

-   Errors are written to `stderr`.

-   File contents are written to `stdout`.



### Examples



```bash

$ read-file ./README.md



```



* * *



## See Also



-   [`@stdlib/fs-exists`][@stdlib/fs/exists]: test whether a path exists on the filesystem.

-   [`@stdlib/fs-open`][@stdlib/fs/open]: open a file.

-   [`@stdlib/fs-read-dir`][@stdlib/fs/read-dir]: read the entire contents of a directory.

-   [`@stdlib/fs-read-json`][@stdlib/fs/read-json]: read a file as JSON.

-   [`@stdlib/fs-write-file`][@stdlib/fs/write-file]: write data to a file.



* * *



## 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 © 2016-2024. The Stdlib [Authors][stdlib-authors].



[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=main

[test-url]: https://github.com/stdlib-js/fs-read-file/actions/workflows/test.yml?query=branch:main



[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



[chat-image]: https://img.shields.io/gitter/room/stdlib-js/stdlib.svg

[chat-url]: https://app.gitter.im/#/room/#stdlib-js_stdlib:gitter.im



[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



[@stdlib/fs/exists]: https://github.com/stdlib-js/fs-exists



[@stdlib/fs/open]: https://github.com/stdlib-js/fs-open



[@stdlib/fs/read-dir]: https://github.com/stdlib-js/fs-read-dir



[@stdlib/fs/read-json]: https://github.com/stdlib-js/fs-read-json



[@stdlib/fs/write-file]: https://github.com/stdlib-js/fs-write-file