nodejs writeSync 的position不起作用呢

Question

import * as fs from 'fs';
import * as path from 'path';
class BreakFileSave{
    constructor(protected option: IOptione) {
        this.init();
    }
    protected init() {
        let filePath =  path.resolve(this.option.path+'/'+this.option.hash+'.'+this.option.subffix.toLowerCase());
        console.log(filePath);
        if(fs.existsSync(filePath)) {
            console.log('文件存在');
        }else{
            console.log('文件不存在');
            let buffer = Buffer.alloc(this.option.size);
            let res = fs.writeFileSync(filePath, buffer);
        }
        this.test(filePath)
    }
    test(filePath: string) {
        let fd = fs.openSync(filePath, 'a+');
        let buf = Buffer.from('dd2', 'utf8');
        fs.writeSync(fd, buf ,0,buf.length,8);
        fs.closeSync(fd);
    }
}

每次写入都是在文件的末尾

Answer 1

nodejs fs 的文档 里说：

On Linux, positional writes don't work when the file is opened in append mode. The kernel ignores the position argument and always appends the data to the end of the file.

用 a+ 模式打卡就只能想末尾写。你得看下文档，换一个你需要的打开方式。