NODE.JS --为什么我们要使用: COPYFILE_FICLONE和COPYFILE_FICLONE_FORCE --它是干什么用的？

Question

伙计们，我正在通过阅读NODE.JS文档来学习node.js。

我首先开始学习fs模块。

在学习的同时，我看到了这个解释：

“

”模式是一个可选的整数，它指定复制操作的行为。可以创建一个掩码，该掩码由两个或多个值的按位OR组成(例如，fs.constants.COPYFILE_EXCL two fs.constants.COPYFILE_FICLONE)。

在https://nodejs.org/api/fs.html#fscopyfilesrc-dest-mode-callback

我不明白COPYFILE_FICLONE和COPYFILE_FICLONE_FORCE为什么要使用这两种模式

我研究了“如何复制写”的工作，我发现这些网站：https://www.geeksforgeeks.org/copy-on-write/ https://www.computerhope.com/jargon/c/copy-on-write.htm和我仍然不明白

也许我以为你们能帮我，我能理解为什么

    //*  Module   *//
let fs = require('fs');

    //* Variables *//
source = 'source.txt';
destination = 'hesyy.txt';

    //* call back function for error *//
function callback(err) {
    if (!err){
        console.log("source.txt copied to destination");
    } else throw err;
}

const {COPYFILE_EXCL} = fs.constants; // the copy operation will fail if dest already exists.
const {COPYFILE_FICLONE} = fs.constants; // the copy operation will attempt to create a copy-on-write reflink. if the platform does not support copy-on-write,then a fallback copy mechanism is used.
const {COPYFILE_FICLONE_FORCE} = fs.constants; // the copy operation will attempt to create a copy-on-write reflink. if the platform does not support copy-on-write, then the operation will fail.

       // fs.copyFile(source,destination,callback);
       // fs.copyFile(source,destination,COPYFILE_EXCL,callback);
       // fs.copyFile(source,destination,COPYFILE_FICLONE,callback);
        fs.copyFile(source,destination,COPYFILE_FICLONE_FORCE,err => {
            if (!err) {
                console.log("Copied");
            }else{
                console.log("err yo:",err);
            }
        });

运行:节点copyFile.js和我通过使用COPYFILE_FICLONE_FORCE结果获得了错误：

err yo: [Error: ENOSYS: function not implemented, copyfile 'C:\Users\CENSORED\Desktop\nodejss\fs\fs.copyFile\source.txt' -> 'C:\Users\CENSORED\Desktop\nodejss\fs\fs.copyFile\hessyy.txt'] {
  errno: -4054,
  code: 'ENOSYS',
  syscall: 'copyfile',
  path: 'C:\\Users\\CENSORED\\Desktop\\nodejss\\fs\\fs.copyFile\\source.txt',
  dest: 'C:\\Users\\CENSORED\\Desktop\\nodejss\\fs\\fs.copyFile\\hessyy.txt'
}

Answer 1

根据医生的说法：

mode is an optional integer that specifies the behavior of the copy operation. It is possible to create a mask consisting of the bitwise OR of two or more values (e.g. fs.constants.COPYFILE_EXCL | fs.constants.COPYFILE_FICLONE).

fs.constants.COPYFILE_EXCL: The copy operation will fail if dest already exists.
fs.constants.COPYFILE_FICLONE: The copy operation will attempt to create a copy-on-write reflink. If the platform does not support copy-on-write, then a fallback copy mechanism is used.
fs.constants.COPYFILE_FICLONE_FORCE: The copy operation will attempt to create a copy-on-write reflink. If the platform does not support copy-on-write, then the operation will fail.

所以您使用的是WINDOWS，有些标志/函数是不可用的。