Read the entire contents of a file.
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> Read the entire contents of a file.
``bash`
npm install @stdlib/fs-read-file
`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].
- 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 );
}
`
`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 );
}
}
`
- [@stdlib/fs-read-file-cli][@stdlib/fs-read-file-cli]: CLI package for use as a command-line utility.
- [@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.
*
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]
---
See [LICENSE][stdlib-license].
Copyright © 2016-2026. The Stdlib [Authors][stdlib-authors].
[@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
[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
[@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