node . js | fs . writelefilesync()方法
原文:https://www . geesforgeks . org/node-js-fs-write filesync-method/
Node.js 的“fs”模块实现了文件的输入输出操作。fs 模块中的方法可以是同步的，也可以是异步的。异步函数有一个回调函数作为指示异步函数完成的最后一个参数。与同步方法相比，Node.js 开发人员更喜欢异步方法，因为异步方法在程序执行过程中从不阻塞程序，而后者会阻塞程序。阻塞主线程是 Node.js 中的弊端，因此同步函数应该只用于调试或者在没有其他选项可用的时候。fs.writeFileSync()是一种同步方法。如果指定的文件不存在，fs.writeFileSync()将创建一个新文件。“readline-sync”模块也用于在运行时启用用户输入。 语法:
fs.writeFileSync( file, data, options )
参数:该方法接受三个参数，如上所述，如下所述:
- 文件:它是一个字符串、缓冲区、网址或文件描述整数，表示必须写入的文件路径。使用文件描述符将使其行为类似于 fs.write()方法。
- 数据:它是一个字符串、Buffer、TypedArray 或 DataView，将被写入文件。
- 选项:它是一个字符串或对象，可用于指定将影响输出的可选参数。它有三个可选参数:
- 编码:是指定文件编码的字符串。默认值为“utf8”。
- 模式:指定文件模式的整数。默认值为 0o666。
- 标志:它是一个字符串，指定写入文件时使用的标志。默认值为“w”。
以下示例说明了 Node.js 中的fs . writelefilesync()方法:
例 1:
// Node.js program to demonstrate the
// fs.writeFileSync() method
// Import the filesystem module
const fs = require('fs');
let data = "This is a file containing a collection"
+ " of programming languages.\n"
+ "1\. C\n2\. C++\n3\. Python";
fs.writeFileSync("programming.txt", data);
console.log("File written successfully\n");
console.log("The written has the following contents:");
console.log(fs.readFileSync("programming.txt", "utf8"));
输出:
File written successfully
The written has the following contents:
This is a file containing a collection of programming languages.
1\. C
2\. C++
3\. Python
例 2:
// Node.js program to demonstrate the
// fs.writeFileSync() method
// Import the filesystem module
const fs = require('fs');
// Writing to the file 5 times
// with the append file mode
for (let i = 0; i < 5; i++) {
fs.writeFileSync("movies.txt",
"Movie " + i + "\n",
{
encoding: "utf8",
flag: "a+",
mode: 0o666
});
}
console.log("File written successfully 5 times\n");
console.log("The written file has the following contents:");
console.log(fs.readFileSync("movies.txt", "utf8"));
输出:
File written successfully 5 times
The written file has the following contents:
Movie 0
Movie 1
Movie 2
Movie 3
Movie 4
参考:T2【https://nodejs . org/API/fs . html # fs _ fs _ writelefilesync _ file _ data _ options
示例 3: 使用 readline 模块从用户处获取文件名和文件数据的运行时输入
// Write Javascript code here
var readline = require('readline-sync');
var fs = require("fs");
var path = readline.question("Enter file name/path: ");
console.log("Entered path : " + path);
var data = readline.question("Enter file data: ");
//synchronous functions may throw errors
//which can be handled using try-catch block
try {
fs.writeFileSync(path, data,{flag:'a+'}); //'a+' is append mode
console.log("File written successfully");
} catch(err) {
console.error(err);
}
console.log("-----------------------------------------------");
try{
const data = fs.readFileSync(path,{encoding: "utf8"});
console.log("File content is as follows:");
// Display the file data
console.log(data);
}catch(err){
console.log(err);
}
输出
示例 4: 使用缓冲区从用户处获取使用 readline 模块的文件数据的运行时输入
// Write Javascript code here
var fs = require("fs");
var readline = require('readline-sync');
var path = readline.question("Enter file name/path: ");
console.log("Entered path : " + path);
// 1024 specifies the buffer size. We can limit
// the data size by this approach
var buf = new Buffer.alloc(1024);
buf = readline.question("Enter data:");
try {
fs.writeFileSync(path, buf,{flag:'a+'});
console.log("File written successfully");
} catch(err) {
console.error(err);
}
console.log("-----------------------------------------------");
try{
const data = fs.readFileSync(path,{encoding: "utf8"});
console.log("File content is as follows:");
// Display the file data
console.log(data);
}catch(err){
console.log(err);
}
输出
版权属于：月萌API www.moonapi.com，转载请注明出处
