About stdlib...

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Read File

Read the entire contents of a file.

Installation

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 available on the esm branch (see README).
• If you are using Deno, visit the deno branch (see README for usage intructions).
• For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch (see README).
• To use as a general utility for the command line, install the corresponding CLI package globally.

The branches.md 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

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

readFile( file[, options], clbk )

Asynchronously reads the entire contents of a file.

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().

readFile.sync( file[, options] )

Synchronously reads the entire contents of a file.

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().

Notes

• The difference between this API and fs.readFileSync() is that fs.readFileSync() 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

  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.

  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

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 );
    }
}

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CLI

Installation

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

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

Usage

Usage: read-file [options] <filepath>

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

$ read-file ./README.md
<file_contents>

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See Also

• @stdlib/fs-exists: test whether a path exists on the filesystem.
• @stdlib/fs-open: open a file.
• @stdlib/fs-read-dir: read the entire contents of a directory.
• @stdlib/fs-read-json: read a file as JSON.
• @stdlib/fs-write-file: write data to a file.

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Notice

This package is part of 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, see the main project repository.

Community

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License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.