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How to use the open function from fs

Find comprehensive JavaScript fs.open code examples handpicked from public code repositorys.

fs.open is a function in the Node.js fs module that opens a file for reading or writing, or creates the file if it does not exist.

00005-nodejs-file-system.md?plain=1

GitHub: ddean2009/www.flydean.com

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* fs.createReadStream(): 创建可读的文件流。
* fs.createWriteStream(): 创建可写的文件流。
* fs.link(): 新建指向文件的硬链接。
* fs.mkdir(): 新建文件夹。
* fs.mkdtemp(): 创建临时目录。
* fs.open(): 设置文件模式。
* fs.readdir(): 读取目录的内容。
* fs.readFile(): 读取文件的内容。相关方法：fs.read()。
* fs.readlink(): 读取符号链接的值。
* fs.realpath(): 将相对的文件路径指针（.、..）解析为完整的路径。

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+ 5 other calls in file

btrfs.js

GitHub: wisnuc/appifi

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  }
}


// btrfs clone, callback version
const btrfsClone = (dst, src, callback) => 
  fs.open(src, 'r', (err, srcFd) => err 
    ? callback(err) 
    : fs.open(dst, 'w', (err, dstFd) => {
        let error
        if (err) {

+ 5 other calls in file

How does fs.open work?

fs.open is a function in the Node.js fs module that opens a file for reading or writing, or creates the file if it does not exist.

When called, fs.open takes two required arguments: the path of the file to open or create, and a string indicating the file mode to use. The file mode specifies the permissions to use when creating the file, as well as whether the file should be opened for reading, writing, or both.

For example, to open a file for reading, we could call fs.open like this:

javascript
const fs = require('fs');

fs.open('myfile.txt', 'r', (err, fd) => {
  if (err) throw err;
  // do something with the file descriptor (fd)
});

In this example, we use fs.open to open the file 'myfile.txt' for reading. The second argument 'r' specifies that the file should be opened in read-only mode.

When fs.open is called with the file path and mode, it returns a file descriptor (fd) that can be used to read from or write to the file. We pass a callback function that will be called with an error if one occurred, or the file descriptor if the file was opened successfully.

Similarly, we can use fs.open to create a new file for writing by using the 'w' mode:

javascript
fs.open('newfile.txt', 'w', (err, fd) => {
  if (err) throw err;
  // do something with the file descriptor (fd)
});

In this example, we use fs.open to create a new file 'newfile.txt' for writing. The second argument 'w' specifies that the file should be opened in write-only mode, creating a new file if it does not exist or overwriting the existing file if it does.

The fs.open function is useful for working with files in Node.js, allowing us to read and write files in a variety of modes depending on our needs.

createBigFile.js

GitHub: wisnuc/appifi

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  callback(err)
})

ws.on('finish', () => {
  if (error) return
  fs.open(filePath, 'r+', (err, fd) => {
    if (err) return callback(err)
    fs.ftruncate(fd, size, err => {
      fs.close(fd, x => x)
      if (err) {

test-fs-chmod.js

GitHub: alibaba/AliOS-nodejs

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let mode_async;
let mode_sync;


// Need to hijack fs.open/close to make sure that things
// get closed once they're opened.
fs._open = fs.open;
fs._openSync = fs.openSync;
fs.open = open;
fs.openSync = openSync;
fs._close = fs.close;

Ai Example

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const fs = require("fs");

fs.open("myfile.txt", "r", (err, fd) => {
  if (err) {
    console.error(err);
    return;
  }

  // Read from the file using the file descriptor
  const buffer = Buffer.alloc(1024);
  fs.read(fd, buffer, 0, buffer.length, null, (err, bytesRead, buffer) => {
    if (err) throw err;

    console.log(`Read ${bytesRead} bytes: ${buffer.toString()}`);

    // Close the file descriptor when we're done
    fs.close(fd, (err) => {
      if (err) throw err;
      console.log("File closed successfully");
    });
  });
});

In this example, we use fs.open to open the file 'myfile.txt' for reading. The second argument 'r' specifies that the file should be opened in read-only mode. When fs.open is called with the file path and mode, it returns a file descriptor (fd) that can be used to read from the file. We pass a callback function that will be called with an error if one occurred, or the file descriptor if the file was opened successfully. We then read from the file using fs.read, passing the file descriptor, a buffer to read the data into, and a callback function that will be called with the number of bytes read and the buffer of data. When we're done reading, we close the file descriptor using fs.close, passing the file descriptor and a callback function that will be called when the file is closed. This is just one example of how fs.open can be used in Node.js to work with files. We could also use it to open a file for writing or both reading and writing, depending on our needs.

test-fs-error-messages.js

GitHub: nwjs/node

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  assert.strictEqual(err.code, 'ENOENT');
  assert.strictEqual(err.syscall, 'open');
  return true;
};

fs.open(nonexistentFile, 'r', 0o666, common.mustCall(validateError));

assert.throws(
  () => fs.openSync(nonexistentFile, 'r', 0o666),
  validateError

test-fs-truncate.js

GitHub: grangerecords/anyka

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if (er) return cb(er);
fs.stat(filename, function(er, stat) {
  if (er) return cb(er);
  assert.equal(stat.size, 1024 * 16);

  fs.open(filename, 'w', function(er, fd) {
    if (er) return cb(er);
    fs.ftruncate(fd, 1024, function(er) {
      if (er) return cb(er);
      fs.stat(filename, function(er, stat) {

index.js

GitHub: alancnet/await-file

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 * * `a+` - Open file for reading and appending. The file is created if it does not exist.
 * * `ax+` - Like `a+` but fails if `path` exists.
 * The exclusive flag `x` (`O_EXCL` flag in [open(2)](http://man7.org/linux/man-pages/man2/open.2.html)) ensures that `path` is newly created. On POSIX systems, `path` is considered to exist even if it is a symlink to a non-existent file. The exclusive flag may or may not work with network file systems.
 * `flags` can also be a number as documented by [open(2)](http://man7.org/linux/man-pages/man2/open.2.html); commonly used constants are available from `fs.constants`. On Windows, flags are translated to their equivalent ones where applicable, e.g. `O_WRONLY` to `FILE_GENERIC_WRITE`, or `O_EXCL|O_CREAT` to `CREATE_NEW`, as accepted by `CreateFileW`.
 * On Linux, positional writes don't work when the file is opened in append mode. The kernel ignores the position argument and always appends the data to the end of the file.
 * *Note: The behavior of fs.open() is platform specific for some flags. As such, opening a directory on OS X and Linux with the 'a+' flag - see example below - will return an error. In contrast, on Windows and FreeBSD, a file descriptor will be returned.*
 * @param mode Sets the file mode (permission and sticky bits), but only if the file was created. It defaults to `0666`, readable and writable.
 * @returns Returns an integer representing the file descriptor.
 */
function open(path, flags, mode) { return promisify(fs.open, arguments); }

+ 5 other calls in file

index.js

GitHub: Monuwarhussen/CSE---3200-project

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  if (typeof this.fd === 'number' && this.closeAfter)
    fs.close(this.fd, () => {})
}

open () {
  fs.open(this.path, this.oflags, (er, fd) => this.onopen(er, fd))
}

onopen (er, fd) {
  if (er) {

+ 2 other calls in file

index.js

GitHub: srinanoo/sirius-batch-node

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//     //     output = "User Created!";
//     // });
    
// }

// fs.open("username.txt", 'r', function (err, file) {
//     if (err) 
//         console.log("No User!"); 
//     else
//         console.log("Success!");

temp.js

GitHub: ds-sampaio/ClicouChegouApp

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/* FILES */


function open(affixes, callback) {
  var filePath = generateName(affixes, 'f-');
  fs.open(filePath, RDWR_EXCL, 0600, function(err, fd) {
    if (!err) {
      deleteFileOnExit(filePath);
    }
    if (callback) {

tmp.js

GitHub: ds-sampaio/ClicouChegouApp

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// gets a temporary filename
tmpName(opts, function _tmpNameCreated(err, name) {
  if (err) return cb(err);

  // create and open the file
  fs.open(name, CREATE_FLAGS, opts.mode || FILE_MODE, function _fileCreated(err, fd) {
    if (err) return cb(err);

    if (opts.discardDescriptor) {
      return fs.close(fd, function _discardCallback(err) {

replace.js

GitHub: RumanSanghera/Receipt-Scanner

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p.on('error', reject)
let flag = 'r+'
const onopen = (er, fd) => {
  if (er && er.code === 'ENOENT' && flag === 'r+') {
    flag = 'w+'
    return fs.open(opt.file, flag, onopen)
  }

  if (er) {
    return reject(er)

+ 3 other calls in file

fs-read.js

GitHub: Mike7323/Mike-s-construction

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    permission: 'FileSystemRead',
    resource: path.toNamespacedPath(__dirname),
  }));
}


// fs.open
{
  assert.throws(() => {
    fs.open(blockedFile, 'r', () => {});
  }, common.expectsError({

+ 9 other calls in file

test-fs-chmod-mask.js

GitHub: vladimir-andreevich/node.js-14-windows-7

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}

{
  const file = path.join(tmpdir.path, `fchmod-async-${suffix}.txt`);
  fs.writeFileSync(file, 'test', 'utf-8');
  fs.open(file, 'w', common.mustSucceed((fd) => {
    fs.fchmod(fd, input, common.mustSucceed(() => {
      assert.strictEqual(fs.fstatSync(fd).mode & 0o777, mode);
      fs.close(fd, assert.ifError);
    }));

+ 4 other calls in file

test-fs-open-mode-mask.js

GitHub: vladimir-andreevich/node.js-14-windows-7

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data.js

GitHub: hridoyraisul/RAW-NODE-JS-PROJECT

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const lib = {};


lib.basedir = path.join(__dirname,'/../.data/');


lib.create = (dir, file, data, callback) => {
    fs.open(lib.basedir+dir+'/'+file+'.json','wx',(createError, fileDescriptor) => {
        if (!createError && fileDescriptor){
            const stringData = JSON.stringify(data);
            fs.writeFile(fileDescriptor, stringData,(writingError) => {
                if (!writingError){

data.js

GitHub: AlessandroMarc/nodejs-masterclass

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lib.baseDir = path.join(__dirname, '/../.data/');


// Write data to a file
lib.create = function(dir, file, data, callback) {
  // Open the file for writing
  fs.open(lib.baseDir + dir + '/' + file + '.json', 'wx', function(err, fileDescriptor) {
    if (!err && fileDescriptor) {
      // Convert data to string
      var stringData = JSON.stringify(data);

data.js

GitHub: protickr/raw-nodejs-project

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// update existing file 
lib.update = (dir, file, data, callback) => {
    // open file to update 
    fs.open(lib.basedir + dir + '/' + file + '.json', 'r+', (err, fileDescriptor)=>{
        if(!err && fileDescriptor){
            // convert the data to string 
            const stringData = JSON.stringify(data);

data.js

GitHub: icaromagnago/pizza-delivery-nodejs-api

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    }
  })
};


lib.update = (dir, file, data, callback) => {
  fs.open(`${lib.baseDir}${dir}/${file}.json`, 'r+', (err, fileDescriptor) => {
    if (!err && fileDescriptor) {
      const stringData = JSON.stringify(data);


      // Truncate the file

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