Node.js filehandle.readFile()方法

原文:https://www . geesforgeks . org/node-js-file handle-read file-method/

filehandle.readFile()方法用于异步读取文件内容。此方法将整个文件读入缓冲区。它异步读取文件的全部内容。

语法:

filehandle.readFile( options )

参数:该方法如上所述接受单个参数，如下所述:

  • Option: Code of the saved file. Its default value is "utf8". It is an object or a string.
    • Code: is a string or empty. Default: blank

返回值:返回一个承诺。

  • Commitment will be solved by the contents of the document. If the encoding is not specified with options.encoding, the data will be returned as a buffer object. Otherwise, the data will be a string.
  • If the option is a string, specify the encoding.
  • The file handle must support reading.

示例:读取文件‘gfg . txt’的文件内容

注意:“gfg . txt”应出现在目录中，并带有以下文本:

GeeksforGeeks - A computer science portal for geeks

文件名:app.js

// Node.js program to demonstrate the   
// fsPromises.truncate() Method

// Import the filesystem module 
const fs = require('fs');
const fsPromises = fs.promises;

// Using the async function to
// ReadFile using filehandle
async function doReadFile() {
    let filehandle = null;
    try {

        // Using the filehandle method
        filehandle = 
        await fsPromises.open('GFG.txt', 'r+');

        var data = 
        await filehandle.readFile("utf8");

        console.log(data);
    } catch (e) {
        console.log("Error", e);
    }
}

doReadFile().catch((error) => {
    console.log("Error", error)
});

使用以下命令运行 app.js 文件:

node app.js

输出:

GeeksforGeeks - A computer science portal for geeks

参考:T2】https://nodejs . org/dist/latest-v 14 . x/docs/API/fs . html # fs _ file handle _ readfile _ options

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