213 lines
3.9 KiB
Markdown
213 lines
3.9 KiB
Markdown
<!--
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@license Apache-2.0
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Copyright (c) 2018 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# Read File
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> Read the entire contents of a file.
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<section class="usage">
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## Usage
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```javascript
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var readFile = require( '@stdlib/fs/read-file' );
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```
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#### readFile( file\[, options], clbk )
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Asynchronously reads the entire contents of a file.
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```javascript
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readFile( __filename, onFile );
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function onFile( error, data ) {
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if ( error ) {
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throw error;
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}
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console.log( data );
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}
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```
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The function accepts the same `options` and has the same defaults as [`fs.readFile()`][node-fs].
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#### readFile.sync( file\[, options] )
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Synchronously reads the entire contents of a `file`.
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```javascript
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var out = readFile.sync( __filename );
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if ( out instanceof Error ) {
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throw out;
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}
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console.log( out );
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```
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The function accepts the same `options` and has the same defaults as [`fs.readFileSync()`][node-fs].
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</section>
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<!-- /.usage -->
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<section class="notes">
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## Notes
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- 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
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```javascript
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var fs = require( 'fs' );
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var file = '/path/to/file.js';
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// Check for existence to prevent an error being thrown...
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if ( fs.existsSync( file ) ) {
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file = fs.readFileSync( file );
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}
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```
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can be replaced by an approach which addresses existence via `error` handling.
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```javascript
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var readFile = require( '@stdlib/fs/read-file' );
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var file = '/path/to/file.js';
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// Explicitly handle the error...
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file = readFile.sync( file );
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if ( file instanceof Error ) {
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// You choose what to do...
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console.error( file.message );
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}
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```
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</section>
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<!-- /.notes -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var readFile = require( '@stdlib/fs/read-file' );
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/* Sync */
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var file = readFile.sync( __filename, 'utf8' );
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// returns <string>
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console.log( file instanceof Error );
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// => false
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file = readFile.sync( 'beepboop', {
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'encoding': 'utf8'
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});
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// returns <Error>
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console.log( file instanceof Error );
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// => true
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/* Async */
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readFile( __filename, onFile );
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readFile( 'beepboop', onFile );
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function onFile( error, data ) {
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if ( error ) {
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if ( error.code === 'ENOENT' ) {
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console.error( 'File does not exist.' );
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} else {
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throw error;
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}
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} else {
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console.log( data );
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}
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}
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```
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</section>
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<!-- /.examples -->
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* * *
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<section class="cli">
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## CLI
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<section class="usage">
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### Usage
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```text
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Usage: read-file [options] <filepath>
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Options:
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-h, --help Print this message.
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-V, --version Print the package version.
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--enc, --encoding encoding Encoding.
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--flag flag Flag. Default: 'r'.
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```
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</section>
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<!-- /.usage -->
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<section class="notes">
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### Notes
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- Relative file paths are resolved relative to the current working directory.
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- Errors are written to `stderr`.
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- File contents are written to `stdout`.
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</section>
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<!-- /.notes -->
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<section class="examples">
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### Examples
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```bash
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$ read-file ./README.md
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<file_contents>
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```
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</section>
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<!-- /.examples -->
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</section>
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<!-- /.cli -->
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<section class="links">
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[node-fs]: https://nodejs.org/api/fs.html
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</section>
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<!-- /.links -->
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