node文件流的读取与写入

1、文件流写入

const fs = require("fs");

const ws = fs.createWriteStream("test.txt",{
    flags:"w",
    encoding:"utf-8"
});

for(let i = 0;i < 10000;i++){
    ws.write("第"+i+"行\r\n",{
        encoding:"utf-8"
    },(err)=>{
        if(err) console.log("文件写入失败");
        console.log("正在写入...");
    });
}
ws.end();//标记文件写入完成

ws.on("open",()=>{
    console.log("文件被打开");
})

ws.on("ready",()=>{
    console.log("文件已准备就绪，即将开始写入");
})

ws.on("close",()=>{//文件写入完成后会触发
    console.log("文件关闭,禁止写入");
});

ws.on("error",()=>{
    console.log("文件写入失败");
});

2、文件流读取

const fs = require("fs");

const rs = fs.createReadStream("test.txt",{flags:"r",encoding:"utf-8"});//创建读取文件入口

let str = "";
rs.on("data",(chunk)=>{//监听数据的流入
    str += chunk;
});

rs.on("open",()=>{
    console.log("文件已打开");
}).on("ready",()=>{
    console.log("文件已准备就绪，即将读取");
}).on("end",()=>{
    console.log(str);
    console.log("文件流读取完成");
}).on("error",()=>{
    console.log("读取文件失败");
});

3、读取某个文件，写入到另一个文件中

const fs = require("fs");

const rs = fs.createReadStream("test.txt");
const ws = fs.createWriteStream("testcopy.txt",{encoding:"utf-8"});

rs.on("data",(chunk)=>{
    console.log(chunk.length);
    ws.write(chunk);
});

rs.on("close",()=>{
    console.log("文件流读取完成");
    ws.end();
}).on("error",()=>{
    console.log("文件流读取出错");
});

ws.on("close",()=>{
    console.log("文件写入完成");
});

4、使用pipe可实现第三个案例，pipe的原理类似于第三个案例

rs.pipe(ws);