fs.copyFile(src, dest[, flags], callback)


异步地将 src 拷贝到 dest。 默认情况下,如果 dest 已经存在,则会被覆盖。 除了可能的异常,完成回调没有其他参数。 Node.js 不保证拷贝操作的原子性。 如果在打开目标文件进行写入后发生错误,Node.js 将尝试删除目标文件。

flags 是一个可选的整数,指定拷贝操作的行为。 可以创建由两个或多个值的按位或组成的掩码(比如 fs.constants.COPYFILE_EXCL | fs.constants.COPYFILE_FICLONE)。

  • fs.constants.COPYFILE_EXCL - 如果 dest 已存在,则拷贝操作将失败。
  • fs.constants.COPYFILE_FICLONE - 拷贝操作将尝试创建写时拷贝(copy-on-write)链接。如果平台不支持写时拷贝,则使用后备的拷贝机制。
  • fs.constants.COPYFILE_FICLONE_FORCE - 拷贝操作将尝试创建写时拷贝链接。如果平台不支持写时拷贝,则拷贝操作将失败。
const fs = require('fs');

// 默认情况下将创建或覆盖目标文件。
fs.copyFile('源文件.txt', '目标文件.txt', (err) => {
  if (err) throw err;
  console.log('源文件已拷贝到目标文件');
});

如果第三个参数是数字,则它指定 flags:

const fs = require('fs');
const { COPYFILE_EXCL } = fs.constants;

// 通过使用 COPYFILE_EXCL,如果目标文件存在,则操作将失败。
fs.copyFile('源文件.txt', '目标文件.txt', COPYFILE_EXCL, callback);

Asynchronously copies src to dest. By default, dest is overwritten if it already exists. No arguments other than a possible exception are given to the callback function. Node.js makes no guarantees about the atomicity of the copy operation. If an error occurs after the destination file has been opened for writing, Node.js will attempt to remove the destination.

flags 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.
const fs = require('fs');

// destination.txt will be created or overwritten by default.
fs.copyFile('source.txt', 'destination.txt', (err) => {
  if (err) throw err;
  console.log('source.txt was copied to destination.txt');
});

If the third argument is a number, then it specifies flags:

const fs = require('fs');
const { COPYFILE_EXCL } = fs.constants;

// By using COPYFILE_EXCL, the operation will fail if destination.txt exists.
fs.copyFile('source.txt', 'destination.txt', COPYFILE_EXCL, callback);