[英]Fastest way to copy a file in Node.js
The project that I am working on (Node.js) implies lots of operations with the file system (copying, reading, writing, etc.).我正在从事的项目 (Node.js) 涉及对文件系统的大量操作(复制、读取、写入等)。
Which methods are the fastest?哪些方法最快?
Use the standard built-in way fs.copyFile
:使用标准的内置方式fs.copyFile
:
const fs = require('fs');
// File 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 you have to support old end-of-life versions of Node.js - here is how you do it in versions that do not support fs.copyFile
:如果您必须支持旧的 Node.js 生命周期结束版本 - 以下是在不支持fs.copyFile
的版本中如何做到这一点:
const fs = require('fs');
fs.createReadStream('test.log').pipe(fs.createWriteStream('newLog.log'));
Same mechanism, but this adds error handling:相同的机制,但这增加了错误处理:
function copyFile(source, target, cb) {
var cbCalled = false;
var rd = fs.createReadStream(source);
rd.on("error", function(err) {
done(err);
});
var wr = fs.createWriteStream(target);
wr.on("error", function(err) {
done(err);
});
wr.on("close", function(ex) {
done();
});
rd.pipe(wr);
function done(err) {
if (!cbCalled) {
cb(err);
cbCalled = true;
}
}
}
Since Node.js 8.5.0 we have the new fs.copyFile and fs.copyFileSync methods.从 Node.js 8.5.0 开始,我们有了新的fs.copyFile和fs.copyFileSync方法。
Usage example:使用示例:
var fs = require('fs');
// File "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');
});
I was not able to get the createReadStream/createWriteStream
method working for some reason, but using the fs-extra npm module it worked right away.由于某种原因,我无法使createReadStream/createWriteStream
方法工作,但使用fs-extra npm 模块它立即工作。 I am not sure of the performance difference though.我不确定性能差异。
npm install --save fs-extra
var fs = require('fs-extra');
fs.copySync(path.resolve(__dirname, './init/xxx.json'), 'xxx.json');
Fast to write and convenient to use, with promise and error management:编写速度快,使用方便,具有承诺和错误管理:
function copyFile(source, target) {
var rd = fs.createReadStream(source);
var wr = fs.createWriteStream(target);
return new Promise(function(resolve, reject) {
rd.on('error', reject);
wr.on('error', reject);
wr.on('finish', resolve);
rd.pipe(wr);
}).catch(function(error) {
rd.destroy();
wr.end();
throw error;
});
}
The same with async/await syntax:与 async/await 语法相同:
async function copyFile(source, target) {
var rd = fs.createReadStream(source);
var wr = fs.createWriteStream(target);
try {
return await new Promise(function(resolve, reject) {
rd.on('error', reject);
wr.on('error', reject);
wr.on('finish', resolve);
rd.pipe(wr);
});
} catch (error) {
rd.destroy();
wr.end();
throw error;
}
}
Well, usually it is good to avoid asynchronous file operations.嗯,通常最好避免异步文件操作。 Here is the short (ie no error handling) sync example:这是简短的(即没有错误处理)同步示例:
var fs = require('fs');
fs.writeFileSync(targetFile, fs.readFileSync(sourceFile));
If you don't care about it being async, and aren't copying gigabyte-sized files, and would rather not add another dependency just for a single function:如果您不关心它是异步的,并且不复制千兆字节大小的文件,并且宁愿不为单个功能添加另一个依赖项:
function copySync(src, dest) {
var data = fs.readFileSync(src);
fs.writeFileSync(dest, data);
}
Mike Schilling's solution with error handling with a shortcut for the error event handler. Mike Schilling 的错误处理解决方案和错误事件处理程序的快捷方式。
function copyFile(source, target, cb) {
var cbCalled = false;
var rd = fs.createReadStream(source);
rd.on("error", done);
var wr = fs.createWriteStream(target);
wr.on("error", done);
wr.on("close", function(ex) {
done();
});
rd.pipe(wr);
function done(err) {
if (!cbCalled) {
cb(err);
cbCalled = true;
}
}
}
You may want to use async/await, since node v10.0.0
it's possible with the built-in fs Promises API
.您可能想要使用异步/等待,因为node v10.0.0
可以使用内置的fs Promises API
。
Example:例子:
const fs = require('fs')
const copyFile = async (src, dest) => {
await fs.promises.copyFile(src, dest)
}
Note:笔记:
As of
node v11.14.0, v10.17.0
the API is no longer experimental.从node v11.14.0, v10.17.0
,API 不再是实验性的。
More information:更多信息:
const fs = require("fs");
fs.copyFileSync("filepath1", "filepath2"); //fs.copyFileSync("file1.txt", "file2.txt");
This is what I personally use to copy a file and replace another file using Node.js:)这是我个人使用 Node.js 复制文件和替换另一个文件的方式:)
For fast copies you should use the fs.constants.COPYFILE_FICLONE
flag.对于快速复制,您应该使用fs.constants.COPYFILE_FICLONE
标志。 It allows (for filesystems that support this) to not actually copy the content of the file.它允许(对于支持此功能的文件系统)不实际复制文件的内容。 Just a new file entry is created, but it points to aCopy-on-Write "clone" of the source file.只是创建了一个新文件条目,但它指向源文件的写时复制“克隆”。
To do nothing/less is the fastest way of doing something;)什么都不做/少做是做某事的最快方式;)
https://nodejs.org/api/fs.html#fs_fs_copyfile_src_dest_flags_callback https://nodejs.org/api/fs.html#fs_fs_copyfile_src_dest_flags_callback
let fs = require("fs");
fs.copyFile(
"source.txt",
"destination.txt",
fs.constants.COPYFILE_FICLONE,
(err) => {
if (err) {
// TODO: handle error
console.log("error");
}
console.log("success");
}
);
Using promises instead:改用承诺:
let fs = require("fs");
let util = require("util");
let copyFile = util.promisify(fs.copyFile);
copyFile(
"source.txt",
"destination.txt",
fs.constants.COPYFILE_FICLONE
)
.catch(() => console.log("error"))
.then(() => console.log("success"));
Use Node.js's built-in copy function使用 Node.js 内置的复制功能
It provides both async and sync version:它同时提供异步和同步版本:
const fs = require('fs');
// File "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');
});
fs.copyFileSync(src, dest[, mode]) fs.copyFileSync(src, dest[, mode])
The project that I am working on (Node.js) implies lots of operations with the file system (copying, reading, writing, etc.).我正在处理的项目(Node.js)包含文件系统的许多操作(复制,读取,写入等)。
Which methods are the fastest?哪些方法最快?
You can do it using the fs-extra
module very easily:您可以使用fs-extra
模块非常轻松地做到这一点:
const fse = require('fs-extra');
let srcDir = 'path/to/file';
let destDir = 'pat/to/destination/directory';
fse.moveSync(srcDir, destDir, function (err) {
// To move a file permanently from a directory
if (err) {
console.error(err);
} else {
console.log("success!");
}
});
Or要么
fse.copySync(srcDir, destDir, function (err) {
// To copy a file from a directory
if (err) {
console.error(err);
} else {
console.log("success!");
}
});
I wrote a little utility to test the different methods:我写了一个小工具来测试不同的方法:
https://www.npmjs.com/package/copy-speed-test https://www.npmjs.com/package/copy-speed-test
run it with运行它
npx copy-speed-test --source someFile.zip --destination someNonExistentFolder
It does a native copy using child_process.exec(), a copy file using fs.copyFile and it uses createReadStream with a variety of different buffer sizes (you can change buffer sizes by passing them on the command line. run npx copy-speed-test -h for more info).它使用 child_process.exec() 进行本机复制,使用 fs.copyFile 进行复制文件,并使用具有各种不同缓冲区大小的 createReadStream(您可以通过在命令行上传递它们来更改缓冲区大小。运行 npx copy-speed-测试 -h 以获得更多信息)。
Mike's solution , but with promises:迈克的解决方案,但有承诺:
const FileSystem = require('fs');
exports.copyFile = function copyFile(source, target) {
return new Promise((resolve,reject) => {
const rd = FileSystem.createReadStream(source);
rd.on('error', err => reject(err));
const wr = FileSystem.createWriteStream(target);
wr.on('error', err => reject(err));
wr.on('close', () => resolve());
rd.pipe(wr);
});
};
Improvement of one other answer.改进另一个答案。
Features:特征:
promise
, which makes it easier to use in a larger project.它返回一个promise
,这使得它更容易在更大的项目中使用。Usage:用法:
var onePromise = copyFilePromise("src.txt", "dst.txt");
var anotherPromise = copyMultiFilePromise(new Array(new Array("src1.txt", "dst1.txt"), new Array("src2.txt", "dst2.txt")));
Code:代码:
function copyFile(source, target, cb) {
console.log("CopyFile", source, target);
var ensureDirectoryExistence = function (filePath) {
var dirname = path.dirname(filePath);
if (fs.existsSync(dirname)) {
return true;
}
ensureDirectoryExistence(dirname);
fs.mkdirSync(dirname);
}
ensureDirectoryExistence(target);
var cbCalled = false;
var rd = fs.createReadStream(source);
rd.on("error", function (err) {
done(err);
});
var wr = fs.createWriteStream(target);
wr.on("error", function (err) {
done(err);
});
wr.on("close", function (ex) {
done();
});
rd.pipe(wr);
function done(err) {
if (!cbCalled) {
cb(err);
cbCalled = true;
}
}
}
function copyFilePromise(source, target) {
return new Promise(function (accept, reject) {
copyFile(source, target, function (data) {
if (data === undefined) {
accept();
} else {
reject(data);
}
});
});
}
function copyMultiFilePromise(srcTgtPairArr) {
var copyFilePromiseArr = new Array();
srcTgtPairArr.forEach(function (srcTgtPair) {
copyFilePromiseArr.push(copyFilePromise(srcTgtPair[0], srcTgtPair[1]));
});
return Promise.all(copyFilePromiseArr);
}
The project that I am working on (Node.js) implies lots of operations with the file system (copying, reading, writing, etc.).我正在处理的项目(Node.js)包含文件系统的许多操作(复制,读取,写入等)。
Which methods are the fastest?哪些方法最快?
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