Node.js fs.close()方法
fs.close()方法用于异步关闭给定的文件描述符，从而清除与之关联的文件。这将允许文件描述符被其他文件重用。在文件描述符上执行其他操作时调用 fs.close()可能会导致未定义的行为。
语法:
fs.close( fd, callback )
参数:该方法接受两个参数，如上所述，如下所述:
- FD: is an integer that represents the file descriptor of the file to be closed.
- Callback: is a function that will be called when the method is executed.
- err: This is an error that will be thrown if the method fails.
下面的例子说明了 Node.js 中的 fs.close()方法:
示例 1: 此示例显示了文件描述符的关闭。
// Node.js program to demonstrate the
// fs.close() method
// Import the filesystem module
const fs = require('fs');
// Get the file descriptor of the given path
file_descriptor = fs.openSync("example.txt");
console.log("The file descriptor is:", file_descriptor);
// Close the file descriptor
fs.close(file_descriptor, (err) => {
if (err)
console.error('Failed to close file', err);
else {
console.log("\n> File Closed successfully");
}
});
输出:
The file descriptor is: 3
> File Closed successfully
示例 2: 此示例显示了关闭文件描述符并尝试再次访问该关闭的文件描述符。
// Node.js program to demonstrate the
// fs.close() method
// Import the filesystem module
const fs = require('fs');
// Get the file descriptor of the given path
file_descriptor = fs.openSync("example.txt");
console.log("The file descriptor is:", file_descriptor);
console.log("\n> Finding the stats of the file");
try {
// Attempting to find stats of file before closing
statsObj = fs.fstatSync(file_descriptor);
console.log("Stats of the file generated");
// Closing the file descriptor
console.log("\n> Closing the file descriptor");
fs.close(file_descriptor, (err) => {
if (err)
console.error("Failed to close file", err);
else {
console.log("File Closed successfully");
try {
// Attempting to find stats of file after closing
console.log("\n> Finding the stats of the file again");
statsObj = fs.fstatSync(file_descriptor);
console.log("Stats of the file generated");
}
catch (err) {
console.error("Cannot find stats of file", err);
}
}
});
} catch (err) {
console.error("Cannot find stats of file", err);
}
输出:
The file descriptor is: 3
> Finding the stats of the file
Stats of the file generated
> Closing the file descriptor
File Closed successfully
> Finding the stats of the file again
Cannot find stats of file Error: EBADF: bad file descriptor, fstat
at Object.fstatSync (fs.js:897:3)
at G:\tutorials\nodejs-fs-close\index.js:42:23
at FSReqCallback.oncomplete (fs.js:146:23) {
fd: 3,
errno: -4083,
syscall: 'fstat',
code: 'EBADF'
}
参考:T2】https://nodejs.org/api/fs.html#fs_fs_close_fd_callback
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