Source Code: lib/fs.js
\nThe fs module provides an API for interacting with the file system in a\nmanner closely modeled around standard POSIX functions.
To use this module:
\nconst fs = require('fs');\nAll file system operations have synchronous and asynchronous forms.
\nThe asynchronous form always takes a completion callback as its last argument.\nThe arguments passed to the completion callback depend on the method, but the\nfirst argument is always reserved for an exception. If the operation was\ncompleted successfully, then the first argument will be null or undefined.
const fs = require('fs');\n\nfs.unlink('/tmp/hello', (err) => {\n if (err) throw err;\n console.log('successfully deleted /tmp/hello');\n});\nExceptions that occur using synchronous operations are thrown immediately and\nmay be handled using try…catch, or may be allowed to bubble up.
const fs = require('fs');\n\ntry {\n fs.unlinkSync('/tmp/hello');\n console.log('successfully deleted /tmp/hello');\n} catch (err) {\n // handle the error\n}\nThere is no guaranteed ordering when using asynchronous methods. So the\nfollowing is prone to error because the fs.stat() operation may complete\nbefore the fs.rename() operation:
fs.rename('/tmp/hello', '/tmp/world', (err) => {\n if (err) throw err;\n console.log('renamed complete');\n});\nfs.stat('/tmp/world', (err, stats) => {\n if (err) throw err;\n console.log(`stats: ${JSON.stringify(stats)}`);\n});\nTo correctly order the operations, move the fs.stat() call into the callback\nof the fs.rename() operation:
fs.rename('/tmp/hello', '/tmp/world', (err) => {\n if (err) throw err;\n fs.stat('/tmp/world', (err, stats) => {\n if (err) throw err;\n console.log(`stats: ${JSON.stringify(stats)}`);\n });\n});\nIn busy processes, use the asynchronous versions of these calls. The synchronous\nversions will block the entire process until they complete, halting all\nconnections.
\nMost asynchronous fs functions allow the callback argument to be omitted.\nHowever, this usage is deprecated. When the callback is omitted, a default\ncallback is used that rethrows errors. To get a trace to the original call site,\nset the NODE_DEBUG environment variable:
$ cat script.js\nfunction bad() {\n require('fs').readFile('/');\n}\nbad();\n\n$ env NODE_DEBUG=fs node script.js\nfs.js:88\n throw backtrace;\n ^\nError: EISDIR: illegal operation on a directory, read\n <stack trace.>\nMost fs operations accept filepaths that may be specified in the form of\na string, a Buffer, or a URL object using the file: protocol.
String form paths are interpreted as UTF-8 character sequences identifying\nthe absolute or relative filename. Relative paths will be resolved relative\nto the current working directory as specified by process.cwd().
Example using an absolute path on POSIX:
\nconst fs = require('fs');\n\nfs.open('/open/some/file.txt', 'r', (err, fd) => {\n if (err) throw err;\n fs.close(fd, (err) => {\n if (err) throw err;\n });\n});\nExample using a relative path on POSIX (relative to process.cwd()):
fs.open('file.txt', 'r', (err, fd) => {\n if (err) throw err;\n fs.close(fd, (err) => {\n if (err) throw err;\n });\n});\nPaths specified using a Buffer are useful primarily on certain POSIX\noperating systems that treat file paths as opaque byte sequences. On such\nsystems, it is possible for a single file path to contain sub-sequences that\nuse multiple character encodings. As with string paths, Buffer paths may\nbe relative or absolute:
Example using an absolute path on POSIX:
\nfs.open(Buffer.from('/open/some/file.txt'), 'r', (err, fd) => {\n if (err) throw err;\n fs.close(fd, (err) => {\n if (err) throw err;\n });\n});\nOn Windows, Node.js follows the concept of per-drive working directory. This\nbehavior can be observed when using a drive path without a backslash. For\nexample fs.readdirSync('C:\\\\') can potentially return a different result than\nfs.readdirSync('C:'). For more information, see\nthis MSDN page.
For most fs module functions, the path or filename argument may be passed\nas a WHATWG URL object. Only URL objects using the file: protocol\nare supported.
const fs = require('fs');\nconst fileUrl = new URL('file:///tmp/hello');\n\nfs.readFileSync(fileUrl);\nfile: URLs are always absolute paths.
Using WHATWG URL objects might introduce platform-specific behaviors.
On Windows, file: URLs with a host name convert to UNC paths, while file:\nURLs with drive letters convert to local absolute paths. file: URLs without a\nhost name nor a drive letter will result in a throw:
// On Windows :\n\n// - WHATWG file URLs with hostname convert to UNC path\n// file://hostname/p/a/t/h/file => \\\\hostname\\p\\a\\t\\h\\file\nfs.readFileSync(new URL('file://hostname/p/a/t/h/file'));\n\n// - WHATWG file URLs with drive letters convert to absolute path\n// file:///C:/tmp/hello => C:\\tmp\\hello\nfs.readFileSync(new URL('file:///C:/tmp/hello'));\n\n// - WHATWG file URLs without hostname must have a drive letters\nfs.readFileSync(new URL('file:///notdriveletter/p/a/t/h/file'));\nfs.readFileSync(new URL('file:///c/p/a/t/h/file'));\n// TypeError [ERR_INVALID_FILE_URL_PATH]: File URL path must be absolute\nfile: URLs with drive letters must use : as a separator just after\nthe drive letter. Using another separator will result in a throw.
On all other platforms, file: URLs with a host name are unsupported and will\nresult in a throw:
// On other platforms:\n\n// - WHATWG file URLs with hostname are unsupported\n// file://hostname/p/a/t/h/file => throw!\nfs.readFileSync(new URL('file://hostname/p/a/t/h/file'));\n// TypeError [ERR_INVALID_FILE_URL_PATH]: must be absolute\n\n// - WHATWG file URLs convert to absolute path\n// file:///tmp/hello => /tmp/hello\nfs.readFileSync(new URL('file:///tmp/hello'));\nA file: URL having encoded slash characters will result in a throw on all\nplatforms:
// On Windows\nfs.readFileSync(new URL('file:///C:/p/a/t/h/%2F'));\nfs.readFileSync(new URL('file:///C:/p/a/t/h/%2f'));\n/* TypeError [ERR_INVALID_FILE_URL_PATH]: File URL path must not include encoded\n\\ or / characters */\n\n// On POSIX\nfs.readFileSync(new URL('file:///p/a/t/h/%2F'));\nfs.readFileSync(new URL('file:///p/a/t/h/%2f'));\n/* TypeError [ERR_INVALID_FILE_URL_PATH]: File URL path must not include encoded\n/ characters */\nOn Windows, file: URLs having encoded backslash will result in a throw:
// On Windows\nfs.readFileSync(new URL('file:///C:/path/%5C'));\nfs.readFileSync(new URL('file:///C:/path/%5c'));\n/* TypeError [ERR_INVALID_FILE_URL_PATH]: File URL path must not include encoded\n\\ or / characters */\nOn POSIX systems, for every process, the kernel maintains a table of currently\nopen files and resources. Each open file is assigned a simple numeric\nidentifier called a file descriptor. At the system-level, all file system\noperations use these file descriptors to identify and track each specific\nfile. Windows systems use a different but conceptually similar mechanism for\ntracking resources. To simplify things for users, Node.js abstracts away the\nspecific differences between operating systems and assigns all open files a\nnumeric file descriptor.
\nThe fs.open() method is used to allocate a new file descriptor. Once\nallocated, the file descriptor may be used to read data from, write data to,\nor request information about the file.
fs.open('/open/some/file.txt', 'r', (err, fd) => {\n if (err) throw err;\n fs.fstat(fd, (err, stat) => {\n if (err) throw err;\n // use stat\n\n // always close the file descriptor!\n fs.close(fd, (err) => {\n if (err) throw err;\n });\n });\n});\nMost operating systems limit the number of file descriptors that may be open\nat any given time so it is critical to close the descriptor when operations\nare completed. Failure to do so will result in a memory leak that will\neventually cause an application to crash.
", "type": "module", "displayName": "File descriptors" }, { "textRaw": "Threadpool usage", "name": "threadpool_usage", "desc": "All file system APIs except fs.FSWatcher() and those that are explicitly\nsynchronous use libuv's threadpool, which can have surprising and negative\nperformance implications for some applications. See the\nUV_THREADPOOL_SIZE documentation for more information.
The fs.promises API provides an alternative set of asynchronous file system\nmethods that return Promise objects rather than using callbacks. The\nAPI is accessible via require('fs').promises or require('fs/promises').
A FileHandle object is a wrapper for a numeric file descriptor.\nInstances of FileHandle are distinct from numeric file descriptors\nin that they provide an object oriented API for working with files.
If a FileHandle is not closed using the\nfilehandle.close() method, it might automatically close the file descriptor\nand will emit a process warning, thereby helping to prevent memory leaks.\nPlease do not rely on this behavior because it is unreliable and\nthe file may not be closed. Instead, always explicitly close FileHandles.\nNode.js may change this behavior in the future.
Instances of the FileHandle object are created internally by the\nfsPromises.open() method.
Unlike the callback-based API (fs.fstat(), fs.fchown(), fs.fchmod(), and\nso on), a numeric file descriptor is not used by the promise-based API. Instead,\nthe promise-based API uses the FileHandle class in order to help avoid\naccidental leaking of unclosed file descriptors after a Promise is resolved or\nrejected.
Alias of filehandle.writeFile().
When operating on file handles, the mode cannot be changed from what it was set\nto with fsPromises.open(). Therefore, this is equivalent to\nfilehandle.writeFile().
Modifies the permissions on the file. The Promise is resolved with no\narguments upon success.
Changes the ownership of the file then resolves the Promise with no arguments\nupon success.
Closes the file descriptor.
\nconst fsPromises = require('fs').promises;\nasync function openAndClose() {\n let filehandle;\n try {\n filehandle = await fsPromises.open('thefile.txt', 'r');\n } finally {\n if (filehandle !== undefined)\n await filehandle.close();\n }\n}\nAsynchronous fdatasync(2). The Promise is resolved with no arguments upon\nsuccess.
Read data from the file.
\nbuffer is the buffer that the data will be written to.
offset is the offset in the buffer to start writing at.
length is an integer specifying the number of bytes to read.
position is an argument specifying where to begin reading from in the file.\nIf position is null, data will be read from the current file position,\nand the file position will be updated.\nIf position is an integer, the file position will remain unchanged.
Following successful read, the Promise is resolved with an object with a\nbytesRead property specifying the number of bytes read, and a buffer\nproperty that is a reference to the passed in buffer argument.
Asynchronously reads the entire contents of a file.
\nThe Promise is resolved with the contents of the file. If no encoding is\nspecified (using options.encoding), the data is returned as a Buffer\nobject. Otherwise, the data will be a string.
If options is a string, then it specifies the encoding.
The FileHandle has to support reading.
If one or more filehandle.read() calls are made on a file handle and then a\nfilehandle.readFile() call is made, the data will be read from the current\nposition till the end of the file. It doesn't always read from the beginning\nof the file.
Read from a file and write to an array of ArrayBufferViews
The Promise is resolved with an object containing a bytesRead property\nidentifying the number of bytes read, and a buffers property containing\na reference to the buffers input.
position is the offset from the beginning of the file where this data\nshould be read from. If typeof position !== 'number', the data will be read\nfrom the current position.
Retrieves the fs.Stats for the file.
Asynchronous fsync(2). The Promise is resolved with no arguments upon\nsuccess.
Truncates the file then resolves the Promise with no arguments upon success.
If the file was larger than len bytes, only the first len bytes will be\nretained in the file.
For example, the following program retains only the first four bytes of the\nfile:
\nconst fs = require('fs');\nconst fsPromises = fs.promises;\n\nconsole.log(fs.readFileSync('temp.txt', 'utf8'));\n// Prints: Node.js\n\nasync function doTruncate() {\n let filehandle = null;\n try {\n filehandle = await fsPromises.open('temp.txt', 'r+');\n await filehandle.truncate(4);\n } finally {\n if (filehandle) {\n // Close the file if it is opened.\n await filehandle.close();\n }\n }\n console.log(fs.readFileSync('temp.txt', 'utf8')); // Prints: Node\n}\n\ndoTruncate().catch(console.error);\nIf the file previously was shorter than len bytes, it is extended, and the\nextended part is filled with null bytes ('\\0'):
const fs = require('fs');\nconst fsPromises = fs.promises;\n\nconsole.log(fs.readFileSync('temp.txt', 'utf8'));\n// Prints: Node.js\n\nasync function doTruncate() {\n let filehandle = null;\n try {\n filehandle = await fsPromises.open('temp.txt', 'r+');\n await filehandle.truncate(10);\n } finally {\n if (filehandle) {\n // Close the file if it is opened.\n await filehandle.close();\n }\n }\n console.log(fs.readFileSync('temp.txt', 'utf8')); // Prints Node.js\\0\\0\\0\n}\n\ndoTruncate().catch(console.error);\nThe last three bytes are null bytes ('\\0'), to compensate the over-truncation.
Change the file system timestamps of the object referenced by the FileHandle\nthen resolves the Promise with no arguments upon success.
This function does not work on AIX versions before 7.1, it will resolve the\nPromise with an error using code UV_ENOSYS.
Write buffer to the file.
The Promise is resolved with an object containing a bytesWritten property\nidentifying the number of bytes written, and a buffer property containing\na reference to the buffer written.
offset determines the part of the buffer to be written, and length is\nan integer specifying the number of bytes to write.
position refers to the offset from the beginning of the file where this data\nshould be written. If typeof position !== 'number', the data will be written\nat the current position. See pwrite(2).
It is unsafe to use filehandle.write() multiple times on the same file\nwithout waiting for the Promise to be resolved (or rejected). For this\nscenario, use fs.createWriteStream().
On Linux, positional writes do not work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
" }, { "textRaw": "`filehandle.write(string[, position[, encoding]])`", "type": "method", "name": "write", "meta": { "added": [ "v10.0.0" ], "changes": [ { "version": "v14.0.0", "pr-url": "https://github.com/nodejs/node/pull/31030", "description": "The `string` parameter won't coerce unsupported input to strings anymore." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise}", "name": "return", "type": "Promise" }, "params": [ { "textRaw": "`string` {string}", "name": "string", "type": "string" }, { "textRaw": "`position` {integer}", "name": "position", "type": "integer" }, { "textRaw": "`encoding` {string} **Default:** `'utf8'`", "name": "encoding", "type": "string", "default": "`'utf8'`" } ] } ], "desc": "Write string to the file. If string is not a string, then\nan exception will be thrown.
The Promise is resolved with an object containing a bytesWritten property\nidentifying the number of bytes written, and a buffer property containing\na reference to the string written.
position refers to the offset from the beginning of the file where this data\nshould be written. If the type of position is not a number the data\nwill be written at the current position. See pwrite(2).
encoding is the expected string encoding.
It is unsafe to use filehandle.write() multiple times on the same file\nwithout waiting for the Promise to be resolved (or rejected). For this\nscenario, use fs.createWriteStream().
On Linux, positional writes do not work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
" }, { "textRaw": "`filehandle.writeFile(data, options)`", "type": "method", "name": "writeFile", "meta": { "added": [ "v10.0.0" ], "changes": [ { "version": "v14.0.0", "pr-url": "https://github.com/nodejs/node/pull/31030", "description": "The `data` parameter won't coerce unsupported input to strings anymore." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise}", "name": "return", "type": "Promise" }, "params": [ { "textRaw": "`data` {string|Buffer|Uint8Array}", "name": "data", "type": "string|Buffer|Uint8Array" }, { "textRaw": "`options` {Object|string}", "name": "options", "type": "Object|string", "options": [ { "textRaw": "`encoding` {string|null} **Default:** `'utf8'`", "name": "encoding", "type": "string|null", "default": "`'utf8'`" } ] } ] } ], "desc": "Asynchronously writes data to a file, replacing the file if it already exists.\ndata can be a string or a buffer. The Promise will be resolved with no\narguments upon success.
The encoding option is ignored if data is a buffer.
If options is a string, then it specifies the encoding.
The FileHandle has to support writing.
It is unsafe to use filehandle.writeFile() multiple times on the same file\nwithout waiting for the Promise to be resolved (or rejected).
If one or more filehandle.write() calls are made on a file handle and then a\nfilehandle.writeFile() call is made, the data will be written from the\ncurrent position till the end of the file. It doesn't always write from the\nbeginning of the file.
Write an array of ArrayBufferViews to the file.
The Promise is resolved with an object containing a bytesWritten property\nidentifying the number of bytes written, and a buffers property containing\na reference to the buffers input.
position is the offset from the beginning of the file where this data\nshould be written. If typeof position !== 'number', the data will be written\nat the current position.
It is unsafe to call writev() multiple times on the same file without waiting\nfor the previous operation to complete.
On Linux, positional writes don't work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
" } ], "properties": [ { "textRaw": "`fd` {number} The numeric file descriptor managed by the `FileHandle` object.", "type": "number", "name": "fd", "meta": { "added": [ "v10.0.0" ], "changes": [] }, "desc": "The numeric file descriptor managed by the `FileHandle` object." } ] } ], "methods": [ { "textRaw": "`fsPromises.access(path[, mode])`", "type": "method", "name": "access", "meta": { "added": [ "v10.0.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise}", "name": "return", "type": "Promise" }, "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`mode` {integer} **Default:** `fs.constants.F_OK`", "name": "mode", "type": "integer", "default": "`fs.constants.F_OK`" } ] } ], "desc": "Tests a user's permissions for the file or directory specified by path.\nThe mode argument is an optional integer that specifies the accessibility\nchecks to be performed. Check File access constants for possible values\nof mode. It is possible to create a mask consisting of the bitwise OR of\ntwo or more values (e.g. fs.constants.W_OK | fs.constants.R_OK).
If the accessibility check is successful, the Promise is resolved with no\nvalue. If any of the accessibility checks fail, the Promise is rejected\nwith an Error object. The following example checks if the file\n/etc/passwd can be read and written by the current process.
const fs = require('fs');\nconst fsPromises = fs.promises;\n\nfsPromises.access('/etc/passwd', fs.constants.R_OK | fs.constants.W_OK)\n .then(() => console.log('can access'))\n .catch(() => console.error('cannot access'));\nUsing fsPromises.access() to check for the accessibility of a file before\ncalling fsPromises.open() is not recommended. Doing so introduces a race\ncondition, since other processes may change the file's state between the two\ncalls. Instead, user code should open/read/write the file directly and handle\nthe error raised if the file is not accessible.
Asynchronously append data to a file, creating the file if it does not yet\nexist. data can be a string or a Buffer. The Promise will be\nresolved with no arguments upon success.
If options is a string, then it specifies the encoding.
The path may be specified as a FileHandle that has been opened\nfor appending (using fsPromises.open()).
Changes the permissions of a file then resolves the Promise with no\narguments upon succces.
Changes the ownership of a file then resolves the Promise with no arguments\nupon success.
Asynchronously copies src to dest. By default, dest is overwritten if it\nalready exists. The Promise will be resolved with no arguments upon success.
Node.js makes no guarantees about the atomicity of the copy operation. If an\nerror occurs after the destination file has been opened for writing, Node.js\nwill attempt to remove the destination.
\nmode is an optional integer that specifies the behavior\nof the copy operation. It is possible to create a mask consisting of the bitwise\nOR of two or more values (e.g.\nfs.constants.COPYFILE_EXCL | fs.constants.COPYFILE_FICLONE).
fs.constants.COPYFILE_EXCL: The copy operation will fail if dest already\nexists.fs.constants.COPYFILE_FICLONE: The copy operation will attempt to create a\ncopy-on-write reflink. If the platform does not support copy-on-write, then a\nfallback copy mechanism is used.fs.constants.COPYFILE_FICLONE_FORCE: The copy operation will attempt to\ncreate a copy-on-write reflink. If the platform does not support copy-on-write,\nthen the operation will fail.const {\n promises: fsPromises,\n constants: {\n COPYFILE_EXCL\n }\n} = require('fs');\n\n// destination.txt will be created or overwritten by default.\nfsPromises.copyFile('source.txt', 'destination.txt')\n .then(() => console.log('source.txt was copied to destination.txt'))\n .catch(() => console.log('The file could not be copied'));\n\n// By using COPYFILE_EXCL, the operation will fail if destination.txt exists.\nfsPromises.copyFile('source.txt', 'destination.txt', COPYFILE_EXCL)\n .then(() => console.log('source.txt was copied to destination.txt'))\n .catch(() => console.log('The file could not be copied'));\nChanges the permissions on a symbolic link then resolves the Promise with\nno arguments upon success. This method is only implemented on macOS.
Changes the ownership on a symbolic link then resolves the Promise with\nno arguments upon success.
Changes the access and modification times of a file in the same way as\nfsPromises.utimes(), with the difference that if the path refers to a\nsymbolic link, then the link is not dereferenced: instead, the timestamps of\nthe symbolic link itself are changed.
Upon success, the Promise is resolved without arguments.
Asynchronous link(2). The Promise is resolved with no arguments upon success.
Asynchronous lstat(2). The Promise is resolved with the fs.Stats object\nfor the given symbolic link path.
Asynchronously creates a directory then resolves the Promise with either no\narguments, or the first directory path created if recursive is true.
The optional options argument can be an integer specifying mode (permission\nand sticky bits), or an object with a mode property and a recursive\nproperty indicating whether parent directories should be created. Calling\nfsPromises.mkdir() when path is a directory that exists results in a\nrejection only when recursive is false.
Creates a unique temporary directory and resolves the Promise with the created\ndirectory path. A unique directory name is generated by appending six random\ncharacters to the end of the provided prefix. Due to platform\ninconsistencies, avoid trailing X characters in prefix. Some platforms,\nnotably the BSDs, can return more than six random characters, and replace\ntrailing X characters in prefix with random characters.
The optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use.
fsPromises.mkdtemp(path.join(os.tmpdir(), 'foo-'))\n .catch(console.error);\nThe fsPromises.mkdtemp() method will append the six randomly selected\ncharacters directly to the prefix string. For instance, given a directory\n/tmp, if the intention is to create a temporary directory within /tmp, the\nprefix must end with a trailing platform-specific path separator\n(require('path').sep).
Asynchronous file open that returns a Promise that, when resolved, yields a\nFileHandle object. See open(2).
mode sets the file mode (permission and sticky bits), but only if the file was\ncreated.
Some characters (< > : \" / \\ | ? *) are reserved under Windows as documented\nby Naming Files, Paths, and Namespaces. Under NTFS, if the filename contains\na colon, Node.js will open a file system stream, as described by\nthis MSDN page.
Asynchronously open a directory. See opendir(3).
Creates an fs.Dir, which contains all further functions for reading from\nand cleaning up the directory.
The encoding option sets the encoding for the path while opening the\ndirectory and subsequent read operations.
Example using async iteration:
\nconst fs = require('fs');\n\nasync function print(path) {\n const dir = await fs.promises.opendir(path);\n for await (const dirent of dir) {\n console.log(dirent.name);\n }\n}\nprint('./').catch(console.error);\nReads the contents of a directory then resolves the Promise with an array\nof the names of the files in the directory excluding '.' and '..'.
The optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe filenames. If the encoding is set to 'buffer', the filenames returned\nwill be passed as Buffer objects.
If options.withFileTypes is set to true, the resolved array will contain\nfs.Dirent objects.
const fs = require('fs');\n\nasync function print(path) {\n const files = await fs.promises.readdir(path);\n for (const file of files) {\n console.log(file);\n }\n}\nprint('./').catch(console.error);\nAsynchronously reads the entire contents of a file.
\nThe Promise is resolved with the contents of the file. If no encoding is\nspecified (using options.encoding), the data is returned as a Buffer\nobject. Otherwise, the data will be a string.
If options is a string, then it specifies the encoding.
When the path is a directory, the behavior of fsPromises.readFile() is\nplatform-specific. On macOS, Linux, and Windows, the promise will be rejected\nwith an error. On FreeBSD, a representation of the directory's contents will be\nreturned.
Any specified FileHandle has to support reading.
Asynchronous readlink(2). The Promise is resolved with the linkString upon\nsuccess.
The optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe link path returned. If the encoding is set to 'buffer', the link path\nreturned will be passed as a Buffer object.
Determines the actual location of path using the same semantics as the\nfs.realpath.native() function then resolves the Promise with the resolved\npath.
Only paths that can be converted to UTF8 strings are supported.
\nThe optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe path. If the encoding is set to 'buffer', the path returned will be\npassed as a Buffer object.
On Linux, when Node.js is linked against musl libc, the procfs file system must\nbe mounted on /proc in order for this function to work. Glibc does not have\nthis restriction.
Renames oldPath to newPath and resolves the Promise with no arguments\nupon success.
Removes the directory identified by path then resolves the Promise with\nno arguments upon success.
Using fsPromises.rmdir() on a file (not a directory) results in the\nPromise being rejected with an ENOENT error on Windows and an ENOTDIR\nerror on POSIX.
The Promise is resolved with the fs.Stats object for the given path.
Creates a symbolic link then resolves the Promise with no arguments upon\nsuccess.
The type argument is only used on Windows platforms and can be one of 'dir',\n'file', or 'junction'. Windows junction points require the destination path\nto be absolute. When using 'junction', the target argument will\nautomatically be normalized to absolute path.
Truncates the path then resolves the Promise with no arguments upon\nsuccess. The path must be a string or Buffer.
Asynchronous unlink(2). The Promise is resolved with no arguments upon\nsuccess.
Change the file system timestamps of the object referenced by path then\nresolves the Promise with no arguments upon success.
The atime and mtime arguments follow these rules:
Dates, or a\nnumeric string like '123456789.0'.NaN, Infinity or\n-Infinity, an Error will be thrown.Asynchronously writes data to a file, replacing the file if it already exists.\ndata can be a string or a buffer. The Promise will be resolved with no\narguments upon success.
The encoding option is ignored if data is a buffer.
If options is a string, then it specifies the encoding.
Any specified FileHandle has to support writing.
It is unsafe to use fsPromises.writeFile() multiple times on the same file\nwithout waiting for the Promise to be resolved (or rejected).
The following constants are exported by fs.constants.
Not every constant will be available on every operating system.
\nTo use more than one constant, use the bitwise OR | operator.
Example:
\nconst fs = require('fs');\n\nconst {\n O_RDWR,\n O_CREAT,\n O_EXCL\n} = fs.constants;\n\nfs.open('/path/to/my/file', O_RDWR | O_CREAT | O_EXCL, (err, fd) => {\n // ...\n});\nThe following constants are meant for use with fs.access().
| Constant | \nDescription | \n
|---|---|
F_OK | \n Flag indicating that the file is visible to the calling process.\n This is useful for determining if a file exists, but says nothing\n about rwx permissions. Default if no mode is specified. | \n
R_OK | \n Flag indicating that the file can be read by the calling process. | \n
W_OK | \n Flag indicating that the file can be written by the calling\n process. | \n
X_OK | \n Flag indicating that the file can be executed by the calling\n process. This has no effect on Windows\n (will behave like fs.constants.F_OK). | \n
The following constants are meant for use with fs.copyFile().
| Constant | \nDescription | \n
|---|---|
COPYFILE_EXCL | \n If present, the copy operation will fail with an error if the\n destination path already exists. | \n
COPYFILE_FICLONE | \n If present, the copy operation will attempt to create a\n copy-on-write reflink. If the underlying platform does not support\n copy-on-write, then a fallback copy mechanism is used. | \n
COPYFILE_FICLONE_FORCE | \n If present, the copy operation will attempt to create a\n copy-on-write reflink. If the underlying platform does not support\n copy-on-write, then the operation will fail with an error. | \n
The following constants are meant for use with fs.open().
| Constant | \nDescription | \n
|---|---|
O_RDONLY | \n Flag indicating to open a file for read-only access. | \n
O_WRONLY | \n Flag indicating to open a file for write-only access. | \n
O_RDWR | \n Flag indicating to open a file for read-write access. | \n
O_CREAT | \n Flag indicating to create the file if it does not already exist. | \n
O_EXCL | \n Flag indicating that opening a file should fail if the\n O_CREAT flag is set and the file already exists. | \n
O_NOCTTY | \n Flag indicating that if path identifies a terminal device, opening the\n path shall not cause that terminal to become the controlling terminal for\n the process (if the process does not already have one). | \n
O_TRUNC | \n Flag indicating that if the file exists and is a regular file, and the\n file is opened successfully for write access, its length shall be truncated\n to zero. | \n
O_APPEND | \n Flag indicating that data will be appended to the end of the file. | \n
O_DIRECTORY | \n Flag indicating that the open should fail if the path is not a\n directory. | \n
O_NOATIME | \n Flag indicating reading accesses to the file system will no longer\n result in an update to the atime information associated with\n the file. This flag is available on Linux operating systems only. | \n
O_NOFOLLOW | \n Flag indicating that the open should fail if the path is a symbolic\n link. | \n
O_SYNC | \n Flag indicating that the file is opened for synchronized I/O with write\n operations waiting for file integrity. | \n
O_DSYNC | \n Flag indicating that the file is opened for synchronized I/O with write\n operations waiting for data integrity. | \n
O_SYMLINK | \n Flag indicating to open the symbolic link itself rather than the\n resource it is pointing to. | \n
O_DIRECT | \n When set, an attempt will be made to minimize caching effects of file\n I/O. | \n
O_NONBLOCK | \n Flag indicating to open the file in nonblocking mode when possible. | \n
UV_FS_O_FILEMAP | \n When set, a memory file mapping is used to access the file. This flag\n is available on Windows operating systems only. On other operating systems,\n this flag is ignored. | \n
The following constants are meant for use with the fs.Stats object's\nmode property for determining a file's type.
| Constant | \nDescription | \n
|---|---|
S_IFMT | \n Bit mask used to extract the file type code. | \n
S_IFREG | \n File type constant for a regular file. | \n
S_IFDIR | \n File type constant for a directory. | \n
S_IFCHR | \n File type constant for a character-oriented device file. | \n
S_IFBLK | \n File type constant for a block-oriented device file. | \n
S_IFIFO | \n File type constant for a FIFO/pipe. | \n
S_IFLNK | \n File type constant for a symbolic link. | \n
S_IFSOCK | \n File type constant for a socket. | \n
The following constants are meant for use with the fs.Stats object's\nmode property for determining the access permissions for a file.
| Constant | \nDescription | \n
|---|---|
S_IRWXU | \n File mode indicating readable, writable, and executable by owner. | \n
S_IRUSR | \n File mode indicating readable by owner. | \n
S_IWUSR | \n File mode indicating writable by owner. | \n
S_IXUSR | \n File mode indicating executable by owner. | \n
S_IRWXG | \n File mode indicating readable, writable, and executable by group. | \n
S_IRGRP | \n File mode indicating readable by group. | \n
S_IWGRP | \n File mode indicating writable by group. | \n
S_IXGRP | \n File mode indicating executable by group. | \n
S_IRWXO | \n File mode indicating readable, writable, and executable by others. | \n
S_IROTH | \n File mode indicating readable by others. | \n
S_IWOTH | \n File mode indicating writable by others. | \n
S_IXOTH | \n File mode indicating executable by others. | \n
The following flags are available wherever the flag option takes a\nstring.
'a': Open file for appending.\nThe file is created if it does not exist.
'ax': Like 'a' but fails if the path exists.
'a+': Open file for reading and appending.\nThe file is created if it does not exist.
'ax+': Like 'a+' but fails if the path exists.
'as': Open file for appending in synchronous mode.\nThe file is created if it does not exist.
'as+': Open file for reading and appending in synchronous mode.\nThe file is created if it does not exist.
'r': Open file for reading.\nAn exception occurs if the file does not exist.
'r+': Open file for reading and writing.\nAn exception occurs if the file does not exist.
'rs+': Open file for reading and writing in synchronous mode. Instructs\nthe operating system to bypass the local file system cache.
This is primarily useful for opening files on NFS mounts as it allows\nskipping the potentially stale local cache. It has a very real impact on\nI/O performance so using this flag is not recommended unless it is needed.
\nThis doesn't turn fs.open() or fsPromises.open() into a synchronous\nblocking call. If synchronous operation is desired, something like\nfs.openSync() should be used.
'w': Open file for writing.\nThe file is created (if it does not exist) or truncated (if it exists).
'wx': Like 'w' but fails if the path exists.
'w+': Open file for reading and writing.\nThe file is created (if it does not exist) or truncated (if it exists).
'wx+': Like 'w+' but fails if the path exists.
flag can also be a number as documented by open(2); commonly used constants\nare available from fs.constants. On Windows, flags are translated to\ntheir equivalent ones where applicable, e.g. O_WRONLY to FILE_GENERIC_WRITE,\nor O_EXCL|O_CREAT to CREATE_NEW, as accepted by CreateFileW.
The exclusive flag 'x' (O_EXCL flag in open(2)) causes the operation to\nreturn an error if the path already exists. On POSIX, if the path is a symbolic\nlink, using O_EXCL returns an error even if the link is to a path that does\nnot exist. The exclusive flag may or may not work with network file systems.
On Linux, positional writes don't work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
\nModifying a file rather than replacing it may require the flag option to be\nset to 'r+' rather than the default 'w'.
The behavior of some flags are platform-specific. As such, opening a directory\non macOS and Linux with the 'a+' flag, as in the example below, will return an\nerror. In contrast, on Windows and FreeBSD, a file descriptor or a FileHandle\nwill be returned.
// macOS and Linux\nfs.open('<directory>', 'a+', (err, fd) => {\n // => [Error: EISDIR: illegal operation on a directory, open <directory>]\n});\n\n// Windows and FreeBSD\nfs.open('<directory>', 'a+', (err, fd) => {\n // => null, <fd>\n});\nOn Windows, opening an existing hidden file using the 'w' flag (either\nthrough fs.open() or fs.writeFile() or fsPromises.open()) will fail with\nEPERM. Existing hidden files can be opened for writing with the 'r+' flag.
A call to fs.ftruncate() or filehandle.truncate() can be used to reset\nthe file contents.
A class representing a directory stream.
\nCreated by fs.opendir(), fs.opendirSync(), or\nfsPromises.opendir().
const fs = require('fs');\n\nasync function print(path) {\n const dir = await fs.promises.opendir(path);\n for await (const dirent of dir) {\n console.log(dirent.name);\n }\n}\nprint('./').catch(console.error);\nAsynchronously close the directory's underlying resource handle.\nSubsequent reads will result in errors.
\nA Promise is returned that will be resolved after the resource has been\nclosed.
Asynchronously close the directory's underlying resource handle.\nSubsequent reads will result in errors.
\nThe callback will be called after the resource handle has been closed.
Synchronously close the directory's underlying resource handle.\nSubsequent reads will result in errors.
" }, { "textRaw": "`dir.read()`", "type": "method", "name": "read", "meta": { "added": [ "v12.12.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise} containing {fs.Dirent|null}", "name": "return", "type": "Promise", "desc": "containing {fs.Dirent|null}" }, "params": [] } ], "desc": "Asynchronously read the next directory entry via readdir(3) as an\nfs.Dirent.
After the read is completed, a Promise is returned that will be resolved with\nan fs.Dirent, or null if there are no more directory entries to read.
Directory entries returned by this function are in no particular order as\nprovided by the operating system's underlying directory mechanisms.\nEntries added or removed while iterating over the directory may or may not be\nincluded in the iteration results.
" }, { "textRaw": "`dir.read(callback)`", "type": "method", "name": "read", "meta": { "added": [ "v12.12.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error}", "name": "err", "type": "Error" }, { "textRaw": "`dirent` {fs.Dirent|null}", "name": "dirent", "type": "fs.Dirent|null" } ] } ] } ], "desc": "Asynchronously read the next directory entry via readdir(3) as an\nfs.Dirent.
After the read is completed, the callback will be called with an\nfs.Dirent, or null if there are no more directory entries to read.
Directory entries returned by this function are in no particular order as\nprovided by the operating system's underlying directory mechanisms.\nEntries added or removed while iterating over the directory may or may not be\nincluded in the iteration results.
" }, { "textRaw": "`dir.readSync()`", "type": "method", "name": "readSync", "meta": { "added": [ "v12.12.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {fs.Dirent|null}", "name": "return", "type": "fs.Dirent|null" }, "params": [] } ], "desc": "Synchronously read the next directory entry via readdir(3) as an\nfs.Dirent.
If there are no more directory entries to read, null will be returned.
Directory entries returned by this function are in no particular order as\nprovided by the operating system's underlying directory mechanisms.\nEntries added or removed while iterating over the directory may or may not be\nincluded in the iteration results.
" }, { "textRaw": "`dir[Symbol.asyncIterator]()`", "type": "method", "name": "[Symbol.asyncIterator]", "meta": { "added": [ "v12.12.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {AsyncIterator} of {fs.Dirent}", "name": "return", "type": "AsyncIterator", "desc": "of {fs.Dirent}" }, "params": [] } ], "desc": "Asynchronously iterates over the directory via readdir(3) until all entries have\nbeen read.
Entries returned by the async iterator are always an fs.Dirent.\nThe null case from dir.read() is handled internally.
See fs.Dir for an example.
Directory entries returned by this iterator are in no particular order as\nprovided by the operating system's underlying directory mechanisms.\nEntries added or removed while iterating over the directory may or may not be\nincluded in the iteration results.
" } ], "properties": [ { "textRaw": "`path` {string}", "type": "string", "name": "path", "meta": { "added": [ "v12.12.0" ], "changes": [] }, "desc": "The read-only path of this directory as was provided to fs.opendir(),\nfs.opendirSync(), or fsPromises.opendir().
A representation of a directory entry, which can be a file or a subdirectory\nwithin the directory, as returned by reading from an fs.Dir. The\ndirectory entry is a combination of the file name and file type pairs.
Additionally, when fs.readdir() or fs.readdirSync() is called with\nthe withFileTypes option set to true, the resulting array is filled with\nfs.Dirent objects, rather than strings or Buffers.
Returns true if the fs.Dirent object describes a block device.
Returns true if the fs.Dirent object describes a character device.
Returns true if the fs.Dirent object describes a file system\ndirectory.
Returns true if the fs.Dirent object describes a first-in-first-out\n(FIFO) pipe.
Returns true if the fs.Dirent object describes a regular file.
Returns true if the fs.Dirent object describes a socket.
Returns true if the fs.Dirent object describes a symbolic link.
The file name that this fs.Dirent object refers to. The type of this\nvalue is determined by the options.encoding passed to fs.readdir() or\nfs.readdirSync().
A successful call to fs.watch() method will return a new fs.FSWatcher\nobject.
All fs.FSWatcher objects emit a 'change' event whenever a specific watched\nfile is modified.
Emitted when something changes in a watched directory or file.\nSee more details in fs.watch().
The filename argument may not be provided depending on operating system\nsupport. If filename is provided, it will be provided as a Buffer if\nfs.watch() is called with its encoding option set to 'buffer', otherwise\nfilename will be a UTF-8 string.
// Example when handled through fs.watch() listener\nfs.watch('./tmp', { encoding: 'buffer' }, (eventType, filename) => {\n if (filename) {\n console.log(filename);\n // Prints: <Buffer ...>\n }\n});\nEmitted when the watcher stops watching for changes. The closed\nfs.FSWatcher object is no longer usable in the event handler.
Emitted when an error occurs while watching the file. The errored\nfs.FSWatcher object is no longer usable in the event handler.
Stop watching for changes on the given fs.FSWatcher. Once stopped, the\nfs.FSWatcher object is no longer usable.
When called, requests that the Node.js event loop not exit so long as the\nFSWatcher is active. Calling watcher.ref() multiple times will have\nno effect.
By default, all FSWatcher objects are \"ref'ed\", making it normally\nunnecessary to call watcher.ref() unless watcher.unref() had been\ncalled previously.
When called, the active FSWatcher object will not require the Node.js\nevent loop to remain active. If there is no other activity keeping the\nevent loop running, the process may exit before the FSWatcher object's\ncallback is invoked. Calling watcher.unref() multiple times will have\nno effect.
A successful call to fs.watchFile() method will return a new fs.StatWatcher\nobject.
When called, requests that the Node.js event loop not exit so long as the\nStatWatcher is active. Calling watcher.ref() multiple times will have\nno effect.
By default, all StatWatcher objects are \"ref'ed\", making it normally\nunnecessary to call watcher.ref() unless watcher.unref() had been\ncalled previously.
When called, the active StatWatcher object will not require the Node.js\nevent loop to remain active. If there is no other activity keeping the\nevent loop running, the process may exit before the StatWatcher object's\ncallback is invoked. Calling watcher.unref() multiple times will have\nno effect.
Instances of fs.ReadStream are created and returned using the\nfs.createReadStream() function.
Emitted when the fs.ReadStream's underlying file descriptor has been closed.
Emitted when the fs.ReadStream's file descriptor has been opened.
Emitted when the fs.ReadStream is ready to be used.
Fires immediately after 'open'.
The number of bytes that have been read so far.
" }, { "textRaw": "`path` {string|Buffer}", "type": "string|Buffer", "name": "path", "meta": { "added": [ "v0.1.93" ], "changes": [] }, "desc": "The path to the file the stream is reading from as specified in the first\nargument to fs.createReadStream(). If path is passed as a string, then\nreadStream.path will be a string. If path is passed as a Buffer, then\nreadStream.path will be a Buffer.
This property is true if the underlying file has not been opened yet,\ni.e. before the 'ready' event is emitted.
A fs.Stats object provides information about a file.
Objects returned from fs.stat(), fs.lstat() and fs.fstat() and\ntheir synchronous counterparts are of this type.\nIf bigint in the options passed to those methods is true, the numeric values\nwill be bigint instead of number, and the object will contain additional\nnanosecond-precision properties suffixed with Ns.
Stats {\n dev: 2114,\n ino: 48064969,\n mode: 33188,\n nlink: 1,\n uid: 85,\n gid: 100,\n rdev: 0,\n size: 527,\n blksize: 4096,\n blocks: 8,\n atimeMs: 1318289051000.1,\n mtimeMs: 1318289051000.1,\n ctimeMs: 1318289051000.1,\n birthtimeMs: 1318289051000.1,\n atime: Mon, 10 Oct 2011 23:24:11 GMT,\n mtime: Mon, 10 Oct 2011 23:24:11 GMT,\n ctime: Mon, 10 Oct 2011 23:24:11 GMT,\n birthtime: Mon, 10 Oct 2011 23:24:11 GMT }\nbigint version:
BigIntStats {\n dev: 2114n,\n ino: 48064969n,\n mode: 33188n,\n nlink: 1n,\n uid: 85n,\n gid: 100n,\n rdev: 0n,\n size: 527n,\n blksize: 4096n,\n blocks: 8n,\n atimeMs: 1318289051000n,\n mtimeMs: 1318289051000n,\n ctimeMs: 1318289051000n,\n birthtimeMs: 1318289051000n,\n atimeNs: 1318289051000000000n,\n mtimeNs: 1318289051000000000n,\n ctimeNs: 1318289051000000000n,\n birthtimeNs: 1318289051000000000n,\n atime: Mon, 10 Oct 2011 23:24:11 GMT,\n mtime: Mon, 10 Oct 2011 23:24:11 GMT,\n ctime: Mon, 10 Oct 2011 23:24:11 GMT,\n birthtime: Mon, 10 Oct 2011 23:24:11 GMT }\nReturns true if the fs.Stats object describes a block device.
Returns true if the fs.Stats object describes a character device.
Returns true if the fs.Stats object describes a file system directory.
Returns true if the fs.Stats object describes a first-in-first-out (FIFO)\npipe.
Returns true if the fs.Stats object describes a regular file.
Returns true if the fs.Stats object describes a socket.
Returns true if the fs.Stats object describes a symbolic link.
This method is only valid when using fs.lstat().
The numeric identifier of the device containing the file.
" }, { "textRaw": "`ino` {number|bigint}", "type": "number|bigint", "name": "ino", "desc": "The file system specific \"Inode\" number for the file.
" }, { "textRaw": "`mode` {number|bigint}", "type": "number|bigint", "name": "mode", "desc": "A bit-field describing the file type and mode.
" }, { "textRaw": "`nlink` {number|bigint}", "type": "number|bigint", "name": "nlink", "desc": "The number of hard-links that exist for the file.
" }, { "textRaw": "`uid` {number|bigint}", "type": "number|bigint", "name": "uid", "desc": "The numeric user identifier of the user that owns the file (POSIX).
" }, { "textRaw": "`gid` {number|bigint}", "type": "number|bigint", "name": "gid", "desc": "The numeric group identifier of the group that owns the file (POSIX).
" }, { "textRaw": "`rdev` {number|bigint}", "type": "number|bigint", "name": "rdev", "desc": "A numeric device identifier if the file represents a device.
" }, { "textRaw": "`size` {number|bigint}", "type": "number|bigint", "name": "size", "desc": "The size of the file in bytes.
" }, { "textRaw": "`blksize` {number|bigint}", "type": "number|bigint", "name": "blksize", "desc": "The file system block size for i/o operations.
" }, { "textRaw": "`blocks` {number|bigint}", "type": "number|bigint", "name": "blocks", "desc": "The number of blocks allocated for this file.
" }, { "textRaw": "`atimeMs` {number|bigint}", "type": "number|bigint", "name": "atimeMs", "meta": { "added": [ "v8.1.0" ], "changes": [] }, "desc": "The timestamp indicating the last time this file was accessed expressed in\nmilliseconds since the POSIX Epoch.
" }, { "textRaw": "`mtimeMs` {number|bigint}", "type": "number|bigint", "name": "mtimeMs", "meta": { "added": [ "v8.1.0" ], "changes": [] }, "desc": "The timestamp indicating the last time this file was modified expressed in\nmilliseconds since the POSIX Epoch.
" }, { "textRaw": "`ctimeMs` {number|bigint}", "type": "number|bigint", "name": "ctimeMs", "meta": { "added": [ "v8.1.0" ], "changes": [] }, "desc": "The timestamp indicating the last time the file status was changed expressed\nin milliseconds since the POSIX Epoch.
" }, { "textRaw": "`birthtimeMs` {number|bigint}", "type": "number|bigint", "name": "birthtimeMs", "meta": { "added": [ "v8.1.0" ], "changes": [] }, "desc": "The timestamp indicating the creation time of this file expressed in\nmilliseconds since the POSIX Epoch.
" }, { "textRaw": "`atimeNs` {bigint}", "type": "bigint", "name": "atimeNs", "meta": { "added": [ "v12.10.0" ], "changes": [] }, "desc": "Only present when bigint: true is passed into the method that generates\nthe object.\nThe timestamp indicating the last time this file was accessed expressed in\nnanoseconds since the POSIX Epoch.
Only present when bigint: true is passed into the method that generates\nthe object.\nThe timestamp indicating the last time this file was modified expressed in\nnanoseconds since the POSIX Epoch.
Only present when bigint: true is passed into the method that generates\nthe object.\nThe timestamp indicating the last time the file status was changed expressed\nin nanoseconds since the POSIX Epoch.
Only present when bigint: true is passed into the method that generates\nthe object.\nThe timestamp indicating the creation time of this file expressed in\nnanoseconds since the POSIX Epoch.
The timestamp indicating the last time this file was accessed.
" }, { "textRaw": "`mtime` {Date}", "type": "Date", "name": "mtime", "meta": { "added": [ "v0.11.13" ], "changes": [] }, "desc": "The timestamp indicating the last time this file was modified.
" }, { "textRaw": "`ctime` {Date}", "type": "Date", "name": "ctime", "meta": { "added": [ "v0.11.13" ], "changes": [] }, "desc": "The timestamp indicating the last time the file status was changed.
" }, { "textRaw": "`birthtime` {Date}", "type": "Date", "name": "birthtime", "meta": { "added": [ "v0.11.13" ], "changes": [] }, "desc": "The timestamp indicating the creation time of this file.
" } ], "modules": [ { "textRaw": "Stat time values", "name": "stat_time_values", "desc": "The atimeMs, mtimeMs, ctimeMs, birthtimeMs properties are\nnumeric values that hold the corresponding times in milliseconds. Their\nprecision is platform specific. When bigint: true is passed into the\nmethod that generates the object, the properties will be bigints,\notherwise they will be numbers.
The atimeNs, mtimeNs, ctimeNs, birthtimeNs properties are\nbigints that hold the corresponding times in nanoseconds. They are\nonly present when bigint: true is passed into the method that generates\nthe object. Their precision is platform specific.
atime, mtime, ctime, and birthtime are\nDate object alternate representations of the various times. The\nDate and number values are not connected. Assigning a new number value, or\nmutating the Date value, will not be reflected in the corresponding alternate\nrepresentation.
The times in the stat object have the following semantics:
\natime \"Access Time\": Time when file data last accessed. Changed\nby the mknod(2), utimes(2), and read(2) system calls.mtime \"Modified Time\": Time when file data last modified.\nChanged by the mknod(2), utimes(2), and write(2) system calls.ctime \"Change Time\": Time when file status was last changed\n(inode data modification). Changed by the chmod(2), chown(2),\nlink(2), mknod(2), rename(2), unlink(2), utimes(2),\nread(2), and write(2) system calls.birthtime \"Birth Time\": Time of file creation. Set once when the\nfile is created. On filesystems where birthtime is not available,\nthis field may instead hold either the ctime or\n1970-01-01T00:00Z (ie, Unix epoch timestamp 0). This value may be greater\nthan atime or mtime in this case. On Darwin and other FreeBSD variants,\nalso set if the atime is explicitly set to an earlier value than the current\nbirthtime using the utimes(2) system call.Prior to Node.js 0.12, the ctime held the birthtime on Windows systems. As\nof 0.12, ctime is not \"creation time\", and on Unix systems, it never was.
Instances of fs.WriteStream are created and returned using the\nfs.createWriteStream() function.
Emitted when the WriteStream's underlying file descriptor has been closed.
Emitted when the WriteStream's file is opened.
Emitted when the fs.WriteStream is ready to be used.
Fires immediately after 'open'.
The number of bytes written so far. Does not include data that is still queued\nfor writing.
" }, { "textRaw": "`writeStream.path`", "name": "path", "meta": { "added": [ "v0.1.93" ], "changes": [] }, "desc": "The path to the file the stream is writing to as specified in the first\nargument to fs.createWriteStream(). If path is passed as a string, then\nwriteStream.path will be a string. If path is passed as a Buffer, then\nwriteStream.path will be a Buffer.
This property is true if the underlying file has not been opened yet,\ni.e. before the 'ready' event is emitted.
Tests a user's permissions for the file or directory specified by path.\nThe mode argument is an optional integer that specifies the accessibility\nchecks to be performed. Check File access constants for possible values\nof mode. It is possible to create a mask consisting of the bitwise OR of\ntwo or more values (e.g. fs.constants.W_OK | fs.constants.R_OK).
The final argument, callback, is a callback function that is invoked with\na possible error argument. If any of the accessibility checks fail, the error\nargument will be an Error object. The following examples check if\npackage.json exists, and if it is readable or writable.
const file = 'package.json';\n\n// Check if the file exists in the current directory.\nfs.access(file, fs.constants.F_OK, (err) => {\n console.log(`${file} ${err ? 'does not exist' : 'exists'}`);\n});\n\n// Check if the file is readable.\nfs.access(file, fs.constants.R_OK, (err) => {\n console.log(`${file} ${err ? 'is not readable' : 'is readable'}`);\n});\n\n// Check if the file is writable.\nfs.access(file, fs.constants.W_OK, (err) => {\n console.log(`${file} ${err ? 'is not writable' : 'is writable'}`);\n});\n\n// Check if the file exists in the current directory, and if it is writable.\nfs.access(file, fs.constants.F_OK | fs.constants.W_OK, (err) => {\n if (err) {\n console.error(\n `${file} ${err.code === 'ENOENT' ? 'does not exist' : 'is read-only'}`);\n } else {\n console.log(`${file} exists, and it is writable`);\n }\n});\nDo not use fs.access() to check for the accessibility of a file before calling\nfs.open(), fs.readFile() or fs.writeFile(). Doing\nso introduces a race condition, since other processes may change the file's\nstate between the two calls. Instead, user code should open/read/write the\nfile directly and handle the error raised if the file is not accessible.
write (NOT RECOMMENDED)
\nfs.access('myfile', (err) => {\n if (!err) {\n console.error('myfile already exists');\n return;\n }\n\n fs.open('myfile', 'wx', (err, fd) => {\n if (err) throw err;\n writeMyData(fd);\n });\n});\nwrite (RECOMMENDED)
\nfs.open('myfile', 'wx', (err, fd) => {\n if (err) {\n if (err.code === 'EEXIST') {\n console.error('myfile already exists');\n return;\n }\n\n throw err;\n }\n\n writeMyData(fd);\n});\nread (NOT RECOMMENDED)
\nfs.access('myfile', (err) => {\n if (err) {\n if (err.code === 'ENOENT') {\n console.error('myfile does not exist');\n return;\n }\n\n throw err;\n }\n\n fs.open('myfile', 'r', (err, fd) => {\n if (err) throw err;\n readMyData(fd);\n });\n});\nread (RECOMMENDED)
\nfs.open('myfile', 'r', (err, fd) => {\n if (err) {\n if (err.code === 'ENOENT') {\n console.error('myfile does not exist');\n return;\n }\n\n throw err;\n }\n\n readMyData(fd);\n});\nThe \"not recommended\" examples above check for accessibility and then use the\nfile; the \"recommended\" examples are better because they use the file directly\nand handle the error, if any.
\nIn general, check for the accessibility of a file only if the file will not be\nused directly, for example when its accessibility is a signal from another\nprocess.
\nOn Windows, access-control policies (ACLs) on a directory may limit access to\na file or directory. The fs.access() function, however, does not check the\nACL and therefore may report that a path is accessible even if the ACL restricts\nthe user from reading or writing to it.
Synchronously tests a user's permissions for the file or directory specified\nby path. The mode argument is an optional integer that specifies the\naccessibility checks to be performed. Check File access constants for\npossible values of mode. It is possible to create a mask consisting of\nthe bitwise OR of two or more values\n(e.g. fs.constants.W_OK | fs.constants.R_OK).
If any of the accessibility checks fail, an Error will be thrown. Otherwise,\nthe method will return undefined.
try {\n fs.accessSync('etc/passwd', fs.constants.R_OK | fs.constants.W_OK);\n console.log('can read/write');\n} catch (err) {\n console.error('no access!');\n}\nAsynchronously append data to a file, creating the file if it does not yet\nexist. data can be a string or a Buffer.
fs.appendFile('message.txt', 'data to append', (err) => {\n if (err) throw err;\n console.log('The \"data to append\" was appended to file!');\n});\nIf options is a string, then it specifies the encoding:
fs.appendFile('message.txt', 'data to append', 'utf8', callback);\nThe path may be specified as a numeric file descriptor that has been opened\nfor appending (using fs.open() or fs.openSync()). The file descriptor will\nnot be closed automatically.
fs.open('message.txt', 'a', (err, fd) => {\n if (err) throw err;\n fs.appendFile(fd, 'data to append', 'utf8', (err) => {\n fs.close(fd, (err) => {\n if (err) throw err;\n });\n if (err) throw err;\n });\n});\nSynchronously append data to a file, creating the file if it does not yet\nexist. data can be a string or a Buffer.
try {\n fs.appendFileSync('message.txt', 'data to append');\n console.log('The \"data to append\" was appended to file!');\n} catch (err) {\n /* Handle the error */\n}\nIf options is a string, then it specifies the encoding:
fs.appendFileSync('message.txt', 'data to append', 'utf8');\nThe path may be specified as a numeric file descriptor that has been opened\nfor appending (using fs.open() or fs.openSync()). The file descriptor will\nnot be closed automatically.
let fd;\n\ntry {\n fd = fs.openSync('message.txt', 'a');\n fs.appendFileSync(fd, 'data to append', 'utf8');\n} catch (err) {\n /* Handle the error */\n} finally {\n if (fd !== undefined)\n fs.closeSync(fd);\n}\nAsynchronously changes the permissions of a file. No arguments other than a\npossible exception are given to the completion callback.
\nSee also: chmod(2).
fs.chmod('my_file.txt', 0o775, (err) => {\n if (err) throw err;\n console.log('The permissions for file \"my_file.txt\" have been changed!');\n});\nThe mode argument used in both the fs.chmod() and fs.chmodSync()\nmethods is a numeric bitmask created using a logical OR of the following\nconstants:
| Constant | \nOctal | \nDescription | \n
|---|---|---|
fs.constants.S_IRUSR | \n0o400 | \nread by owner | \n
fs.constants.S_IWUSR | \n0o200 | \nwrite by owner | \n
fs.constants.S_IXUSR | \n0o100 | \nexecute/search by owner | \n
fs.constants.S_IRGRP | \n0o40 | \nread by group | \n
fs.constants.S_IWGRP | \n0o20 | \nwrite by group | \n
fs.constants.S_IXGRP | \n0o10 | \nexecute/search by group | \n
fs.constants.S_IROTH | \n0o4 | \nread by others | \n
fs.constants.S_IWOTH | \n0o2 | \nwrite by others | \n
fs.constants.S_IXOTH | \n0o1 | \nexecute/search by others | \n
An easier method of constructing the mode is to use a sequence of three\noctal digits (e.g. 765). The left-most digit (7 in the example), specifies\nthe permissions for the file owner. The middle digit (6 in the example),\nspecifies permissions for the group. The right-most digit (5 in the example),\nspecifies the permissions for others.
| Number | \nDescription | \n
|---|---|
7 | \nread, write, and execute | \n
6 | \nread and write | \n
5 | \nread and execute | \n
4 | \nread only | \n
3 | \nwrite and execute | \n
2 | \nwrite only | \n
1 | \nexecute only | \n
0 | \nno permission | \n
For example, the octal value 0o765 means:
When using raw numbers where file modes are expected, any value larger than\n0o777 may result in platform-specific behaviors that are not supported to work\nconsistently. Therefore constants like S_ISVTX, S_ISGID or S_ISUID are not\nexposed in fs.constants.
Caveats: on Windows only the write permission can be changed, and the\ndistinction among the permissions of group, owner or others is not\nimplemented.
", "type": "module", "displayName": "File modes" } ] }, { "textRaw": "`fs.chmodSync(path, mode)`", "type": "method", "name": "chmodSync", "meta": { "added": [ "v0.6.7" ], "changes": [ { "version": "v7.6.0", "pr-url": "https://github.com/nodejs/node/pull/10739", "description": "The `path` parameter can be a WHATWG `URL` object using `file:` protocol. Support is currently still *experimental*." } ] }, "signatures": [ { "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`mode` {string|integer}", "name": "mode", "type": "string|integer" } ] } ], "desc": "For detailed information, see the documentation of the asynchronous version of\nthis API: fs.chmod().
See also: chmod(2).
Asynchronously changes owner and group of a file. No arguments other than a\npossible exception are given to the completion callback.
\nSee also: chown(2).
Synchronously changes owner and group of a file. Returns undefined.\nThis is the synchronous version of fs.chown().
See also: chown(2).
Asynchronous close(2). No arguments other than a possible exception are given\nto the completion callback.
Calling fs.close() on any file descriptor (fd) that is currently in use\nthrough any other fs operation may lead to undefined behavior.
Synchronous close(2). Returns undefined.
Calling fs.closeSync() on any file descriptor (fd) that is currently in use\nthrough any other fs operation may lead to undefined behavior.
Asynchronously copies src to dest. By default, dest is overwritten if it\nalready exists. No arguments other than a possible exception are given to the\ncallback function. Node.js makes no guarantees about the atomicity of the copy\noperation. If an error occurs after the destination file has been opened for\nwriting, Node.js will attempt to remove the destination.
mode is an optional integer that specifies the behavior\nof the copy operation. It is possible to create a mask consisting of the bitwise\nOR of two or more values (e.g.\nfs.constants.COPYFILE_EXCL | fs.constants.COPYFILE_FICLONE).
fs.constants.COPYFILE_EXCL: The copy operation will fail if dest already\nexists.fs.constants.COPYFILE_FICLONE: The copy operation will attempt to create a\ncopy-on-write reflink. If the platform does not support copy-on-write, then a\nfallback copy mechanism is used.fs.constants.COPYFILE_FICLONE_FORCE: The copy operation will attempt to\ncreate a copy-on-write reflink. If the platform does not support copy-on-write,\nthen the operation will fail.const fs = require('fs');\nconst { COPYFILE_EXCL } = fs.constants;\n\nfunction callback(err) {\n if (err) throw err;\n console.log('source.txt was copied to destination.txt');\n}\n\n// destination.txt will be created or overwritten by default.\nfs.copyFile('source.txt', 'destination.txt', callback);\n\n// By using COPYFILE_EXCL, the operation will fail if destination.txt exists.\nfs.copyFile('source.txt', 'destination.txt', COPYFILE_EXCL, callback);\nSynchronously copies src to dest. By default, dest is overwritten if it\nalready exists. Returns undefined. Node.js makes no guarantees about the\natomicity of the copy operation. If an error occurs after the destination file\nhas been opened for writing, Node.js will attempt to remove the destination.
mode is an optional integer that specifies the behavior\nof the copy operation. It is possible to create a mask consisting of the bitwise\nOR of two or more values (e.g.\nfs.constants.COPYFILE_EXCL | fs.constants.COPYFILE_FICLONE).
fs.constants.COPYFILE_EXCL: The copy operation will fail if dest already\nexists.fs.constants.COPYFILE_FICLONE: The copy operation will attempt to create a\ncopy-on-write reflink. If the platform does not support copy-on-write, then a\nfallback copy mechanism is used.fs.constants.COPYFILE_FICLONE_FORCE: The copy operation will attempt to\ncreate a copy-on-write reflink. If the platform does not support copy-on-write,\nthen the operation will fail.const fs = require('fs');\nconst { COPYFILE_EXCL } = fs.constants;\n\n// destination.txt will be created or overwritten by default.\nfs.copyFileSync('source.txt', 'destination.txt');\nconsole.log('source.txt was copied to destination.txt');\n\n// By using COPYFILE_EXCL, the operation will fail if destination.txt exists.\nfs.copyFileSync('source.txt', 'destination.txt', COPYFILE_EXCL);\nUnlike the 16 kb default highWaterMark for a readable stream, the stream\nreturned by this method has a default highWaterMark of 64 kb.
options can include start and end values to read a range of bytes from\nthe file instead of the entire file. Both start and end are inclusive and\nstart counting at 0, allowed values are in the\n[0, Number.MAX_SAFE_INTEGER] range. If fd is specified and start is\nomitted or undefined, fs.createReadStream() reads sequentially from the\ncurrent file position. The encoding can be any one of those accepted by\nBuffer.
If fd is specified, ReadStream will ignore the path argument and will use\nthe specified file descriptor. This means that no 'open' event will be\nemitted. fd should be blocking; non-blocking fds should be passed to\nnet.Socket.
If fd points to a character device that only supports blocking reads\n(such as keyboard or sound card), read operations do not finish until data is\navailable. This can prevent the process from exiting and the stream from\nclosing naturally.
By default, the stream will not emit a 'close' event after it has been\ndestroyed. This is the opposite of the default for other Readable streams.\nSet the emitClose option to true to change this behavior.
By providing the fs option, it is possible to override the corresponding fs\nimplementations for open, read, and close. When providing the fs option,\noverrides for open, read, and close are required.
const fs = require('fs');\n// Create a stream from some character device.\nconst stream = fs.createReadStream('/dev/input/event0');\nsetTimeout(() => {\n stream.close(); // This may not close the stream.\n // Artificially marking end-of-stream, as if the underlying resource had\n // indicated end-of-file by itself, allows the stream to close.\n // This does not cancel pending read operations, and if there is such an\n // operation, the process may still not be able to exit successfully\n // until it finishes.\n stream.push(null);\n stream.read(0);\n}, 100);\nIf autoClose is false, then the file descriptor won't be closed, even if\nthere's an error. It is the application's responsibility to close it and make\nsure there's no file descriptor leak. If autoClose is set to true (default\nbehavior), on 'error' or 'end' the file descriptor will be closed\nautomatically.
mode sets the file mode (permission and sticky bits), but only if the\nfile was created.
An example to read the last 10 bytes of a file which is 100 bytes long:
\nfs.createReadStream('sample.txt', { start: 90, end: 99 });\nIf options is a string, then it specifies the encoding.
options may also include a start option to allow writing data at some\nposition past the beginning of the file, allowed values are in the\n[0, Number.MAX_SAFE_INTEGER] range. Modifying a file rather than replacing\nit may require the flags option to be set to r+ rather than the default w.\nThe encoding can be any one of those accepted by Buffer.
If autoClose is set to true (default behavior) on 'error' or 'finish'\nthe file descriptor will be closed automatically. If autoClose is false,\nthen the file descriptor won't be closed, even if there's an error.\nIt is the application's responsibility to close it and make sure there's no\nfile descriptor leak.
By default, the stream will not emit a 'close' event after it has been\ndestroyed. This is the opposite of the default for other Writable streams.\nSet the emitClose option to true to change this behavior.
By providing the fs option it is possible to override the corresponding fs\nimplementations for open, write, writev and close. Overriding write()\nwithout writev() can reduce performance as some optimizations (_writev())\nwill be disabled. When providing the fs option, overrides for open,\nclose, and at least one of write and writev are required.
Like ReadStream, if fd is specified, WriteStream will ignore the\npath argument and will use the specified file descriptor. This means that no\n'open' event will be emitted. fd should be blocking; non-blocking fds\nshould be passed to net.Socket.
If options is a string, then it specifies the encoding.
Test whether or not the given path exists by checking with the file system.\nThen call the callback argument with either true or false:
fs.exists('/etc/passwd', (exists) => {\n console.log(exists ? 'it\\'s there' : 'no passwd!');\n});\nThe parameters for this callback are not consistent with other Node.js\ncallbacks. Normally, the first parameter to a Node.js callback is an err\nparameter, optionally followed by other parameters. The fs.exists() callback\nhas only one boolean parameter. This is one reason fs.access() is recommended\ninstead of fs.exists().
Using fs.exists() to check for the existence of a file before calling\nfs.open(), fs.readFile() or fs.writeFile() is not recommended. Doing\nso introduces a race condition, since other processes may change the file's\nstate between the two calls. Instead, user code should open/read/write the\nfile directly and handle the error raised if the file does not exist.
write (NOT RECOMMENDED)
\nfs.exists('myfile', (exists) => {\n if (exists) {\n console.error('myfile already exists');\n } else {\n fs.open('myfile', 'wx', (err, fd) => {\n if (err) throw err;\n writeMyData(fd);\n });\n }\n});\nwrite (RECOMMENDED)
\nfs.open('myfile', 'wx', (err, fd) => {\n if (err) {\n if (err.code === 'EEXIST') {\n console.error('myfile already exists');\n return;\n }\n\n throw err;\n }\n\n writeMyData(fd);\n});\nread (NOT RECOMMENDED)
\nfs.exists('myfile', (exists) => {\n if (exists) {\n fs.open('myfile', 'r', (err, fd) => {\n if (err) throw err;\n readMyData(fd);\n });\n } else {\n console.error('myfile does not exist');\n }\n});\nread (RECOMMENDED)
\nfs.open('myfile', 'r', (err, fd) => {\n if (err) {\n if (err.code === 'ENOENT') {\n console.error('myfile does not exist');\n return;\n }\n\n throw err;\n }\n\n readMyData(fd);\n});\nThe \"not recommended\" examples above check for existence and then use the\nfile; the \"recommended\" examples are better because they use the file directly\nand handle the error, if any.
\nIn general, check for the existence of a file only if the file won’t be\nused directly, for example when its existence is a signal from another\nprocess.
" }, { "textRaw": "`fs.existsSync(path)`", "type": "method", "name": "existsSync", "meta": { "added": [ "v0.1.21" ], "changes": [ { "version": "v7.6.0", "pr-url": "https://github.com/nodejs/node/pull/10739", "description": "The `path` parameter can be a WHATWG `URL` object using `file:` protocol. Support is currently still *experimental*." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" } ] } ], "desc": "Returns true if the path exists, false otherwise.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.exists().
fs.exists() is deprecated, but fs.existsSync() is not. The callback\nparameter to fs.exists() accepts parameters that are inconsistent with other\nNode.js callbacks. fs.existsSync() does not use a callback.
if (fs.existsSync('/etc/passwd')) {\n console.log('The path exists.');\n}\nAsynchronous fchmod(2). No arguments other than a possible exception\nare given to the completion callback.
Synchronous fchmod(2). Returns undefined.
Asynchronous fchown(2). No arguments other than a possible exception are given\nto the completion callback.
Synchronous fchown(2). Returns undefined.
Asynchronous fdatasync(2). No arguments other than a possible exception are\ngiven to the completion callback.
Synchronous fdatasync(2). Returns undefined.
Asynchronous fstat(2). The callback gets two arguments (err, stats) where\nstats is an fs.Stats object. fstat() is identical to stat(),\nexcept that the file to be stat-ed is specified by the file descriptor fd.
Synchronous fstat(2).
Asynchronous fsync(2). No arguments other than a possible exception are given\nto the completion callback.
Synchronous fsync(2). Returns undefined.
Asynchronous ftruncate(2). No arguments other than a possible exception are\ngiven to the completion callback.
If the file referred to by the file descriptor was larger than len bytes, only\nthe first len bytes will be retained in the file.
For example, the following program retains only the first four bytes of the\nfile:
\nconsole.log(fs.readFileSync('temp.txt', 'utf8'));\n// Prints: Node.js\n\n// get the file descriptor of the file to be truncated\nconst fd = fs.openSync('temp.txt', 'r+');\n\n// Truncate the file to first four bytes\nfs.ftruncate(fd, 4, (err) => {\n assert.ifError(err);\n console.log(fs.readFileSync('temp.txt', 'utf8'));\n});\n// Prints: Node\nIf the file previously was shorter than len bytes, it is extended, and the\nextended part is filled with null bytes ('\\0'):
console.log(fs.readFileSync('temp.txt', 'utf8'));\n// Prints: Node.js\n\n// get the file descriptor of the file to be truncated\nconst fd = fs.openSync('temp.txt', 'r+');\n\n// Truncate the file to 10 bytes, whereas the actual size is 7 bytes\nfs.ftruncate(fd, 10, (err) => {\n assert.ifError(err);\n console.log(fs.readFileSync('temp.txt'));\n});\n// Prints: <Buffer 4e 6f 64 65 2e 6a 73 00 00 00>\n// ('Node.js\\0\\0\\0' in UTF8)\nThe last three bytes are null bytes ('\\0'), to compensate the over-truncation.
Returns undefined.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.ftruncate().
Change the file system timestamps of the object referenced by the supplied file\ndescriptor. See fs.utimes().
This function does not work on AIX versions before 7.1, it will return the\nerror UV_ENOSYS.
Synchronous version of fs.futimes(). Returns undefined.
Asynchronous lchmod(2). No arguments other than a possible exception\nare given to the completion callback.
Only available on macOS.
" }, { "textRaw": "`fs.lchmodSync(path, mode)`", "type": "method", "name": "lchmodSync", "meta": { "deprecated": [ "v0.4.7" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`mode` {integer}", "name": "mode", "type": "integer" } ] } ], "desc": "Synchronous lchmod(2). Returns undefined.
Asynchronous lchown(2). No arguments other than a possible exception are given\nto the completion callback.
Synchronous lchown(2). Returns undefined.
Changes the access and modification times of a file in the same way as\nfs.utimes(), with the difference that if the path refers to a symbolic\nlink, then the link is not dereferenced: instead, the timestamps of the\nsymbolic link itself are changed.
No arguments other than a possible exception are given to the completion\ncallback.
" }, { "textRaw": "`fs.lutimesSync(path, atime, mtime)`", "type": "method", "name": "lutimesSync", "meta": { "added": [ "v14.5.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`atime` {number|string|Date}", "name": "atime", "type": "number|string|Date" }, { "textRaw": "`mtime` {number|string|Date}", "name": "mtime", "type": "number|string|Date" } ] } ], "desc": "Change the file system timestamps of the symbolic link referenced by path.\nReturns undefined, or throws an exception when parameters are incorrect or\nthe operation fails. This is the synchronous version of fs.lutimes().
Asynchronous link(2). No arguments other than a possible exception are given to\nthe completion callback.
Synchronous link(2). Returns undefined.
Asynchronous lstat(2). The callback gets two arguments (err, stats) where\nstats is a fs.Stats object. lstat() is identical to stat(),\nexcept that if path is a symbolic link, then the link itself is stat-ed,\nnot the file that it refers to.
Synchronous lstat(2).
Asynchronously creates a directory.
\nThe callback is given a possible exception and, if recursive is true, the\nfirst directory path created, (err, [path]).
The optional options argument can be an integer specifying mode (permission\nand sticky bits), or an object with a mode property and a recursive\nproperty indicating whether parent directories should be created. Calling\nfs.mkdir() when path is a directory that exists results in an error only\nwhen recursive is false.
// Creates /tmp/a/apple, regardless of whether `/tmp` and /tmp/a exist.\nfs.mkdir('/tmp/a/apple', { recursive: true }, (err) => {\n if (err) throw err;\n});\nOn Windows, using fs.mkdir() on the root directory even with recursion will\nresult in an error:
fs.mkdir('/', { recursive: true }, (err) => {\n // => [Error: EPERM: operation not permitted, mkdir 'C:\\']\n});\nSee also: mkdir(2).
Synchronously creates a directory. Returns undefined, or if recursive is\ntrue, the first directory path created.\nThis is the synchronous version of fs.mkdir().
See also: mkdir(2).
Creates a unique temporary directory.
\nGenerates six random characters to be appended behind a required\nprefix to create a unique temporary directory. Due to platform\ninconsistencies, avoid trailing X characters in prefix. Some platforms,\nnotably the BSDs, can return more than six random characters, and replace\ntrailing X characters in prefix with random characters.
The created directory path is passed as a string to the callback's second\nparameter.
\nThe optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use.
fs.mkdtemp(path.join(os.tmpdir(), 'foo-'), (err, directory) => {\n if (err) throw err;\n console.log(directory);\n // Prints: /tmp/foo-itXde2 or C:\\Users\\...\\AppData\\Local\\Temp\\foo-itXde2\n});\nThe fs.mkdtemp() method will append the six randomly selected characters\ndirectly to the prefix string. For instance, given a directory /tmp, if the\nintention is to create a temporary directory within /tmp, the prefix\nmust end with a trailing platform-specific path separator\n(require('path').sep).
// The parent directory for the new temporary directory\nconst tmpDir = os.tmpdir();\n\n// This method is *INCORRECT*:\nfs.mkdtemp(tmpDir, (err, directory) => {\n if (err) throw err;\n console.log(directory);\n // Will print something similar to `/tmpabc123`.\n // A new temporary directory is created at the file system root\n // rather than *within* the /tmp directory.\n});\n\n// This method is *CORRECT*:\nconst { sep } = require('path');\nfs.mkdtemp(`${tmpDir}${sep}`, (err, directory) => {\n if (err) throw err;\n console.log(directory);\n // Will print something similar to `/tmp/abc123`.\n // A new temporary directory is created within\n // the /tmp directory.\n});\nReturns the created directory path.
\nFor detailed information, see the documentation of the asynchronous version of\nthis API: fs.mkdtemp().
The optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use.
Asynchronous file open. See open(2).
mode sets the file mode (permission and sticky bits), but only if the file was\ncreated. On Windows, only the write permission can be manipulated; see\nfs.chmod().
The callback gets two arguments (err, fd).
Some characters (< > : \" / \\ | ? *) are reserved under Windows as documented\nby Naming Files, Paths, and Namespaces. Under NTFS, if the filename contains\na colon, Node.js will open a file system stream, as described by\nthis MSDN page.
Functions based on fs.open() exhibit this behavior as well:\nfs.writeFile(), fs.readFile(), etc.
Asynchronously open a directory. See opendir(3).
Creates an fs.Dir, which contains all further functions for reading from\nand cleaning up the directory.
The encoding option sets the encoding for the path while opening the\ndirectory and subsequent read operations.
Synchronously open a directory. See opendir(3).
Creates an fs.Dir, which contains all further functions for reading from\nand cleaning up the directory.
The encoding option sets the encoding for the path while opening the\ndirectory and subsequent read operations.
Returns an integer representing the file descriptor.
\nFor detailed information, see the documentation of the asynchronous version of\nthis API: fs.open().
Read data from the file specified by fd.
buffer is the buffer that the data (read from the fd) will be written to.
offset is the offset in the buffer to start writing at.
length is an integer specifying the number of bytes to read.
position is an argument specifying where to begin reading from in the file.\nIf position is null, data will be read from the current file position,\nand the file position will be updated.\nIf position is an integer, the file position will remain unchanged.
The callback is given the three arguments, (err, bytesRead, buffer).
If this method is invoked as its util.promisify()ed version, it returns\na Promise for an Object with bytesRead and buffer properties.
Similar to the above fs.read function, this version takes an optional options object.\nIf no options object is specified, it will default with the above values.
Asynchronous readdir(3). Reads the contents of a directory.\nThe callback gets two arguments (err, files) where files is an array of\nthe names of the files in the directory excluding '.' and '..'.
The optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe filenames passed to the callback. If the encoding is set to 'buffer',\nthe filenames returned will be passed as Buffer objects.
If options.withFileTypes is set to true, the files array will contain\nfs.Dirent objects.
Synchronous readdir(3).
The optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe filenames returned. If the encoding is set to 'buffer',\nthe filenames returned will be passed as Buffer objects.
If options.withFileTypes is set to true, the result will contain\nfs.Dirent objects.
Asynchronously reads the entire contents of a file.
\nfs.readFile('/etc/passwd', (err, data) => {\n if (err) throw err;\n console.log(data);\n});\nThe callback is passed two arguments (err, data), where data is the\ncontents of the file.
If no encoding is specified, then the raw buffer is returned.
\nIf options is a string, then it specifies the encoding:
fs.readFile('/etc/passwd', 'utf8', callback);\nWhen the path is a directory, the behavior of fs.readFile() and\nfs.readFileSync() is platform-specific. On macOS, Linux, and Windows, an\nerror will be returned. On FreeBSD, a representation of the directory's contents\nwill be returned.
// macOS, Linux, and Windows\nfs.readFile('<directory>', (err, data) => {\n // => [Error: EISDIR: illegal operation on a directory, read <directory>]\n});\n\n// FreeBSD\nfs.readFile('<directory>', (err, data) => {\n // => null, <data>\n});\nThe fs.readFile() function buffers the entire file. To minimize memory costs,\nwhen possible prefer streaming via fs.createReadStream().
path, it will not be closed\nautomatically.'Hello World' and six bytes are read with the file descriptor,\nthe call to fs.readFile() with the same file descriptor, would give\n'World', rather than 'Hello World'.Returns the contents of the path.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.readFile().
If the encoding option is specified then this function returns a\nstring. Otherwise it returns a buffer.
Similar to fs.readFile(), when the path is a directory, the behavior of\nfs.readFileSync() is platform-specific.
// macOS, Linux, and Windows\nfs.readFileSync('<directory>');\n// => [Error: EISDIR: illegal operation on a directory, read <directory>]\n\n// FreeBSD\nfs.readFileSync('<directory>'); // => <data>\nAsynchronous readlink(2). The callback gets two arguments (err, linkString).
The optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe link path passed to the callback. If the encoding is set to 'buffer',\nthe link path returned will be passed as a Buffer object.
Synchronous readlink(2). Returns the symbolic link's string value.
The optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe link path returned. If the encoding is set to 'buffer',\nthe link path returned will be passed as a Buffer object.
Returns the number of bytesRead.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.read().
Returns the number of bytesRead.
Similar to the above fs.readSync function, this version takes an optional options object.\nIf no options object is specified, it will default with the above values.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.read().
Read from a file specified by fd and write to an array of ArrayBufferViews\nusing readv().
position is the offset from the beginning of the file from where data\nshould be read. If typeof position !== 'number', the data will be read\nfrom the current position.
The callback will be given three arguments: err, bytesRead, and\nbuffers. bytesRead is how many bytes were read from the file.
If this method is invoked as its util.promisify()ed version, it returns\na Promise for an Object with bytesRead and buffers properties.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.readv().
Asynchronously computes the canonical pathname by resolving ., .. and\nsymbolic links.
A canonical pathname is not necessarily unique. Hard links and bind mounts can\nexpose a file system entity through many pathnames.
\nThis function behaves like realpath(3), with some exceptions:
No case conversion is performed on case-insensitive file systems.
\nThe maximum number of symbolic links is platform-independent and generally\n(much) higher than what the native realpath(3) implementation supports.
The callback gets two arguments (err, resolvedPath). May use process.cwd\nto resolve relative paths.
Only paths that can be converted to UTF8 strings are supported.
\nThe optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe path passed to the callback. If the encoding is set to 'buffer',\nthe path returned will be passed as a Buffer object.
If path resolves to a socket or a pipe, the function will return a system\ndependent name for that object.
Asynchronous realpath(3).
The callback gets two arguments (err, resolvedPath).
Only paths that can be converted to UTF8 strings are supported.
\nThe optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe path passed to the callback. If the encoding is set to 'buffer',\nthe path returned will be passed as a Buffer object.
On Linux, when Node.js is linked against musl libc, the procfs file system must\nbe mounted on /proc in order for this function to work. Glibc does not have\nthis restriction.
Returns the resolved pathname.
\nFor detailed information, see the documentation of the asynchronous version of\nthis API: fs.realpath().
Synchronous realpath(3).
Only paths that can be converted to UTF8 strings are supported.
\nThe optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe path returned. If the encoding is set to 'buffer',\nthe path returned will be passed as a Buffer object.
On Linux, when Node.js is linked against musl libc, the procfs file system must\nbe mounted on /proc in order for this function to work. Glibc does not have\nthis restriction.
Asynchronously rename file at oldPath to the pathname provided\nas newPath. In the case that newPath already exists, it will\nbe overwritten. If there is a directory at newPath, an error will\nbe raised instead. No arguments other than a possible exception are\ngiven to the completion callback.
See also: rename(2).
fs.rename('oldFile.txt', 'newFile.txt', (err) => {\n if (err) throw err;\n console.log('Rename complete!');\n});\nSynchronous rename(2). Returns undefined.
Asynchronous rmdir(2). No arguments other than a possible exception are given\nto the completion callback.
Using fs.rmdir() on a file (not a directory) results in an ENOENT error on\nWindows and an ENOTDIR error on POSIX.
Synchronous rmdir(2). Returns undefined.
Using fs.rmdirSync() on a file (not a directory) results in an ENOENT error\non Windows and an ENOTDIR error on POSIX.
Asynchronous stat(2). The callback gets two arguments (err, stats) where\nstats is an fs.Stats object.
In case of an error, the err.code will be one of Common System Errors.
Using fs.stat() to check for the existence of a file before calling\nfs.open(), fs.readFile() or fs.writeFile() is not recommended.\nInstead, user code should open/read/write the file directly and handle the\nerror raised if the file is not available.
To check if a file exists without manipulating it afterwards, fs.access()\nis recommended.
For example, given the following directory structure:
\n- txtDir\n-- file.txt\n- app.js\nThe next program will check for the stats of the given paths:
\nconst fs = require('fs');\n\nconst pathsToCheck = ['./txtDir', './txtDir/file.txt'];\n\nfor (let i = 0; i < pathsToCheck.length; i++) {\n fs.stat(pathsToCheck[i], function(err, stats) {\n console.log(stats.isDirectory());\n console.log(stats);\n });\n}\nThe resulting output will resemble:
\ntrue\nStats {\n dev: 16777220,\n mode: 16877,\n nlink: 3,\n uid: 501,\n gid: 20,\n rdev: 0,\n blksize: 4096,\n ino: 14214262,\n size: 96,\n blocks: 0,\n atimeMs: 1561174653071.963,\n mtimeMs: 1561174614583.3518,\n ctimeMs: 1561174626623.5366,\n birthtimeMs: 1561174126937.2893,\n atime: 2019-06-22T03:37:33.072Z,\n mtime: 2019-06-22T03:36:54.583Z,\n ctime: 2019-06-22T03:37:06.624Z,\n birthtime: 2019-06-22T03:28:46.937Z\n}\nfalse\nStats {\n dev: 16777220,\n mode: 33188,\n nlink: 1,\n uid: 501,\n gid: 20,\n rdev: 0,\n blksize: 4096,\n ino: 14214074,\n size: 8,\n blocks: 8,\n atimeMs: 1561174616618.8555,\n mtimeMs: 1561174614584,\n ctimeMs: 1561174614583.8145,\n birthtimeMs: 1561174007710.7478,\n atime: 2019-06-22T03:36:56.619Z,\n mtime: 2019-06-22T03:36:54.584Z,\n ctime: 2019-06-22T03:36:54.584Z,\n birthtime: 2019-06-22T03:26:47.711Z\n}\nSynchronous stat(2).
Asynchronous symlink(2) which creates the link called path pointing to\ntarget. No arguments other than a possible exception are given to the\ncompletion callback.
The type argument is only available on Windows and ignored on other platforms.\nIt can be set to 'dir', 'file', or 'junction'. If the type argument is\nnot set, Node.js will autodetect target type and use 'file' or 'dir'. If\nthe target does not exist, 'file' will be used. Windows junction points\nrequire the destination path to be absolute. When using 'junction', the\ntarget argument will automatically be normalized to absolute path.
Relative targets are relative to the link’s parent directory.
\nfs.symlink('./mew', './example/mewtwo', callback);\nThe above example creates a symbolic link mewtwo in the example which points\nto mew in the same directory:
$ tree example/\nexample/\n├── mew\n└── mewtwo -> ./mew\nReturns undefined.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.symlink().
Asynchronous truncate(2). No arguments other than a possible exception are\ngiven to the completion callback. A file descriptor can also be passed as the\nfirst argument. In this case, fs.ftruncate() is called.
Passing a file descriptor is deprecated and may result in an error being thrown\nin the future.
" }, { "textRaw": "`fs.truncateSync(path[, len])`", "type": "method", "name": "truncateSync", "meta": { "added": [ "v0.8.6" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`len` {integer} **Default:** `0`", "name": "len", "type": "integer", "default": "`0`" } ] } ], "desc": "Synchronous truncate(2). Returns undefined. A file descriptor can also be\npassed as the first argument. In this case, fs.ftruncateSync() is called.
Passing a file descriptor is deprecated and may result in an error being thrown\nin the future.
" }, { "textRaw": "`fs.unlink(path, callback)`", "type": "method", "name": "unlink", "meta": { "added": [ "v0.0.2" ], "changes": [ { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/12562", "description": "The `callback` parameter is no longer optional. Not passing it will throw a `TypeError` at runtime." }, { "version": "v7.6.0", "pr-url": "https://github.com/nodejs/node/pull/10739", "description": "The `path` parameter can be a WHATWG `URL` object using `file:` protocol. Support is currently still *experimental*." }, { "version": "v7.0.0", "pr-url": "https://github.com/nodejs/node/pull/7897", "description": "The `callback` parameter is no longer optional. Not passing it will emit a deprecation warning with id DEP0013." } ] }, "signatures": [ { "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error}", "name": "err", "type": "Error" } ] } ] } ], "desc": "Asynchronously removes a file or symbolic link. No arguments other than a\npossible exception are given to the completion callback.
\n// Assuming that 'path/file.txt' is a regular file.\nfs.unlink('path/file.txt', (err) => {\n if (err) throw err;\n console.log('path/file.txt was deleted');\n});\nfs.unlink() will not work on a directory, empty or otherwise. To remove a\ndirectory, use fs.rmdir().
See also: unlink(2).
Synchronous unlink(2). Returns undefined.
Stop watching for changes on filename. If listener is specified, only that\nparticular listener is removed. Otherwise, all listeners are removed,\neffectively stopping watching of filename.
Calling fs.unwatchFile() with a filename that is not being watched is a\nno-op, not an error.
Using fs.watch() is more efficient than fs.watchFile() and\nfs.unwatchFile(). fs.watch() should be used instead of fs.watchFile()\nand fs.unwatchFile() when possible.
Change the file system timestamps of the object referenced by path.
The atime and mtime arguments follow these rules:
Dates, or a numeric string like '123456789.0'.NaN, Infinity or\n-Infinity, an Error will be thrown.Returns undefined.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.utimes().
Watch for changes on filename, where filename is either a file or a\ndirectory.
The second argument is optional. If options is provided as a string, it\nspecifies the encoding. Otherwise options should be passed as an object.
The listener callback gets two arguments (eventType, filename). eventType\nis either 'rename' or 'change', and filename is the name of the file\nwhich triggered the event.
On most platforms, 'rename' is emitted whenever a filename appears or\ndisappears in the directory.
The listener callback is attached to the 'change' event fired by\nfs.FSWatcher, but it is not the same thing as the 'change' value of\neventType.
The fs.watch API is not 100% consistent across platforms, and is\nunavailable in some situations.
The recursive option is only supported on macOS and Windows.\nAn ERR_FEATURE_UNAVAILABLE_ON_PLATFORM exception will be thrown\nwhen the option is used on a platform that does not support it.
On Windows, no events will be emitted if the watched directory is moved or\nrenamed. An EPERM error is reported when the watched directory is deleted.
This feature depends on the underlying operating system providing a way\nto be notified of filesystem changes.
\ninotify(7).kqueue(2).kqueue(2) for files and FSEvents for\ndirectories.event ports.ReadDirectoryChangesW.AHAFS, which must be enabled.If the underlying functionality is not available for some reason, then\nfs.watch() will not be able to function and may thrown an exception.\nFor example, watching files or directories can be unreliable, and in some\ncases impossible, on network file systems (NFS, SMB, etc) or host file systems\nwhen using virtualization software such as Vagrant or Docker.
It is still possible to use fs.watchFile(), which uses stat polling, but\nthis method is slower and less reliable.
On Linux and macOS systems, fs.watch() resolves the path to an inode and\nwatches the inode. If the watched path is deleted and recreated, it is assigned\na new inode. The watch will emit an event for the delete but will continue\nwatching the original inode. Events for the new inode will not be emitted.\nThis is expected behavior.
AIX files retain the same inode for the lifetime of a file. Saving and closing a\nwatched file on AIX will result in two notifications (one for adding new\ncontent, and one for truncation).
" }, { "textRaw": "Filename argument", "name": "Filename argument", "type": "misc", "desc": "Providing filename argument in the callback is only supported on Linux,\nmacOS, Windows, and AIX. Even on supported platforms, filename is not always\nguaranteed to be provided. Therefore, don't assume that filename argument is\nalways provided in the callback, and have some fallback logic if it is null.
fs.watch('somedir', (eventType, filename) => {\n console.log(`event type is: ${eventType}`);\n if (filename) {\n console.log(`filename provided: ${filename}`);\n } else {\n console.log('filename not provided');\n }\n});\nWatch for changes on filename. The callback listener will be called each\ntime the file is accessed.
The options argument may be omitted. If provided, it should be an object. The\noptions object may contain a boolean named persistent that indicates\nwhether the process should continue to run as long as files are being watched.\nThe options object may specify an interval property indicating how often the\ntarget should be polled in milliseconds.
The listener gets two arguments the current stat object and the previous\nstat object:
fs.watchFile('message.text', (curr, prev) => {\n console.log(`the current mtime is: ${curr.mtime}`);\n console.log(`the previous mtime was: ${prev.mtime}`);\n});\nThese stat objects are instances of fs.Stat. If the bigint option is true,\nthe numeric values in these objects are specified as BigInts.
To be notified when the file was modified, not just accessed, it is necessary\nto compare curr.mtime and prev.mtime.
When an fs.watchFile operation results in an ENOENT error, it\nwill invoke the listener once, with all the fields zeroed (or, for dates, the\nUnix Epoch). If the file is created later on, the listener will be called\nagain, with the latest stat objects. This is a change in functionality since\nv0.10.
Using fs.watch() is more efficient than fs.watchFile and\nfs.unwatchFile. fs.watch should be used instead of fs.watchFile and\nfs.unwatchFile when possible.
When a file being watched by fs.watchFile() disappears and reappears,\nthen the contents of previous in the second callback event (the file's\nreappearance) will be the same as the contents of previous in the first\ncallback event (its disappearance).
This happens when:
\nWrite buffer to the file specified by fd.
offset determines the part of the buffer to be written, and length is\nan integer specifying the number of bytes to write.
position refers to the offset from the beginning of the file where this data\nshould be written. If typeof position !== 'number', the data will be written\nat the current position. See pwrite(2).
The callback will be given three arguments (err, bytesWritten, buffer) where\nbytesWritten specifies how many bytes were written from buffer.
If this method is invoked as its util.promisify()ed version, it returns\na Promise for an Object with bytesWritten and buffer properties.
It is unsafe to use fs.write() multiple times on the same file without waiting\nfor the callback. For this scenario, fs.createWriteStream() is\nrecommended.
On Linux, positional writes don't work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
" }, { "textRaw": "`fs.write(fd, string[, position[, encoding]], callback)`", "type": "method", "name": "write", "meta": { "added": [ "v0.11.5" ], "changes": [ { "version": "v14.0.0", "pr-url": "https://github.com/nodejs/node/pull/31030", "description": "The `string` parameter won't coerce unsupported input to strings anymore." }, { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/12562", "description": "The `callback` parameter is no longer optional. Not passing it will throw a `TypeError` at runtime." }, { "version": "v7.2.0", "pr-url": "https://github.com/nodejs/node/pull/7856", "description": "The `position` parameter is optional now." }, { "version": "v7.0.0", "pr-url": "https://github.com/nodejs/node/pull/7897", "description": "The `callback` parameter is no longer optional. Not passing it will emit a deprecation warning with id DEP0013." } ] }, "signatures": [ { "params": [ { "textRaw": "`fd` {integer}", "name": "fd", "type": "integer" }, { "textRaw": "`string` {string}", "name": "string", "type": "string" }, { "textRaw": "`position` {integer}", "name": "position", "type": "integer" }, { "textRaw": "`encoding` {string} **Default:** `'utf8'`", "name": "encoding", "type": "string", "default": "`'utf8'`" }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error}", "name": "err", "type": "Error" }, { "textRaw": "`written` {integer}", "name": "written", "type": "integer" }, { "textRaw": "`string` {string}", "name": "string", "type": "string" } ] } ] } ], "desc": "Write string to the file specified by fd. If string is not a string, then\nan exception will be thrown.
position refers to the offset from the beginning of the file where this data\nshould be written. If typeof position !== 'number' the data will be written at\nthe current position. See pwrite(2).
encoding is the expected string encoding.
The callback will receive the arguments (err, written, string) where written\nspecifies how many bytes the passed string required to be written. Bytes\nwritten is not necessarily the same as string characters written. See\nBuffer.byteLength.
It is unsafe to use fs.write() multiple times on the same file without waiting\nfor the callback. For this scenario, fs.createWriteStream() is\nrecommended.
On Linux, positional writes don't work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
\nOn Windows, if the file descriptor is connected to the console (e.g. fd == 1\nor stdout) a string containing non-ASCII characters will not be rendered\nproperly by default, regardless of the encoding used.\nIt is possible to configure the console to render UTF-8 properly by changing the\nactive codepage with the chcp 65001 command. See the chcp docs for more\ndetails.
When file is a filename, asynchronously writes data to the file, replacing the\nfile if it already exists. data can be a string or a buffer.
When file is a file descriptor, the behavior is similar to calling\nfs.write() directly (which is recommended). See the notes below on using\na file descriptor.
The encoding option is ignored if data is a buffer.
const data = new Uint8Array(Buffer.from('Hello Node.js'));\nfs.writeFile('message.txt', data, (err) => {\n if (err) throw err;\n console.log('The file has been saved!');\n});\nIf options is a string, then it specifies the encoding:
fs.writeFile('message.txt', 'Hello Node.js', 'utf8', callback);\nIt is unsafe to use fs.writeFile() multiple times on the same file without\nwaiting for the callback. For this scenario, fs.createWriteStream() is\nrecommended.
When file is a file descriptor, the behavior is almost identical to directly\ncalling fs.write() like:
fs.write(fd, Buffer.from(data, options.encoding), callback);\nThe difference from directly calling fs.write() is that under some unusual\nconditions, fs.write() may write only part of the buffer and will need to be\nretried to write the remaining data, whereas fs.writeFile() will retry until\nthe data is entirely written (or an error occurs).
The implications of this are a common source of confusion. In\nthe file descriptor case, the file is not replaced! The data is not necessarily\nwritten to the beginning of the file, and the file's original data may remain\nbefore and/or after the newly written data.
\nFor example, if fs.writeFile() is called twice in a row, first to write the\nstring 'Hello', then to write the string ', World', the file would contain\n'Hello, World', and might contain some of the file's original data (depending\non the size of the original file, and the position of the file descriptor). If\na file name had been used instead of a descriptor, the file would be guaranteed\nto contain only ', World'.
Returns undefined.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.writeFile().
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.write(fd, buffer...).
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.write(fd, string...).
Write an array of ArrayBufferViews to the file specified by fd using\nwritev().
position is the offset from the beginning of the file where this data\nshould be written. If typeof position !== 'number', the data will be written\nat the current position.
The callback will be given three arguments: err, bytesWritten, and\nbuffers. bytesWritten is how many bytes were written from buffers.
If this method is util.promisify()ed, it returns a Promise for an\nObject with bytesWritten and buffers properties.
It is unsafe to use fs.writev() multiple times on the same file without\nwaiting for the callback. For this scenario, use fs.createWriteStream().
On Linux, positional writes don't work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
" }, { "textRaw": "`fs.writevSync(fd, buffers[, position])`", "type": "method", "name": "writevSync", "meta": { "added": [ "v12.9.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {number} The number of bytes written.", "name": "return", "type": "number", "desc": "The number of bytes written." }, "params": [ { "textRaw": "`fd` {integer}", "name": "fd", "type": "integer" }, { "textRaw": "`buffers` {ArrayBufferView[]}", "name": "buffers", "type": "ArrayBufferView[]" }, { "textRaw": "`position` {integer}", "name": "position", "type": "integer" } ] } ], "desc": "For detailed information, see the documentation of the asynchronous version of\nthis API: fs.writev().
Returns an object containing commonly used constants for file system\noperations. The specific constants currently defined are described in\nFS constants.
" } ], "type": "module", "displayName": "fs" } ] }