fs.readFile(path[, options], callback)

版本历史

版本	变更
v18.0.0	Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`.
v16.0.0	The error returned may be an `AggregateError` if more than one error is returned.
v15.2.0, v14.17.0	The options argument may include an AbortSignal to abort an ongoing readFile request.
v10.0.0	The `callback` parameter is no longer optional. Not passing it will throw a `TypeError` at runtime.
v7.6.0	The `path` parameter can be a WHATWG `URL` object using `file:` protocol.
v7.0.0	The `callback` parameter is no longer optional. Not passing it will emit a deprecation warning with id DEP0013.
v5.1.0	The `callback` will always be called with `null` as the `error` parameter in case of success.
v5.0.0	The `path` parameter can be a file descriptor now.
v0.1.29	新增于: v0.1.29

path <string> | <Buffer> | <URL> | <integer> 文件名或文件描述符
options <Object> | <string>
- encoding <string> | <null> 默认值： null
- flag <string> 参见文件系统 flags 支持。默认值: 'r'。
- signal <AbortSignal> 允许中止正在进行的 readFile 操作
callback <Function>
- err <Error> | <AggregateError>
- data <string> | <Buffer>

异步地读取文件的全部内容。

🌐 Asynchronously reads the entire contents of a file.

import { readFile } from 'node:fs';

readFile('/etc/passwd', (err, data) => {
  if (err) throw err;
  console.log(data);
});

回调函数会传入两个参数 (err, data)，其中 data 是文件的内容。

🌐 The callback is passed two arguments (err, data), where data is the contents of the file.

如果未指定编码，则返回原始缓冲区。

🌐 If no encoding is specified, then the raw buffer is returned.

如果 options 是字符串，则它指定了编码方式：

🌐 If options is a string, then it specifies the encoding:

import { readFile } from 'node:fs';

readFile('/etc/passwd', 'utf8', callback);

当路径是一个目录时，fs.readFile() 和 fs.readFileSync() 的行为取决于平台。在 macOS、Linux 和 Windows 上，会返回一个错误。在 FreeBSD 上，会返回目录内容的表示。

🌐 When the path is a directory, the behavior of fs.readFile() and fs.readFileSync() is platform-specific. On macOS, Linux, and Windows, an error will be returned. On FreeBSD, a representation of the directory's contents will be returned.

import { readFile } from 'node:fs';

// macOS, Linux, and Windows
readFile('<directory>', (err, data) => {
  // => [Error: EISDIR: illegal operation on a directory, read <directory>]
});

//  FreeBSD
readFile('<directory>', (err, data) => {
  // => null, <data>
});

可以使用 AbortSignal 中止正在进行的请求。如果请求被中止，回调将使用 AbortError 调用：

🌐 It is possible to abort an ongoing request using an AbortSignal. If a request is aborted the callback is called with an AbortError:

import { readFile } from 'node:fs';

const controller = new AbortController();
const signal = controller.signal;
readFile(fileInfo[0].name, { signal }, (err, buf) => {
  // ...
});
// When you want to abort the request
controller.abort();

fs.readFile() 函数会将整个文件缓存在内存中。为了尽量减少内存消耗，在可能的情况下，建议使用 fs.createReadStream() 进行流式处理。

🌐 The fs.readFile() function buffers the entire file. To minimize memory costs, when possible prefer streaming via fs.createReadStream().

中止正在进行的请求并不会中止单个操作系统请求，而是中止内部缓冲 fs.readFile 所执行的操作。

🌐 Aborting an ongoing request does not abort individual operating system requests but rather the internal buffering fs.readFile performs.