A fork of fs-ext that ships prebuilt binaries for all major platforms and adds Windows-specific file locking APIs.

The original fs-ext package requires compilation during npm install, which can fail in environments without build tools. This fork:

• Ships prebuilt binaries for macOS (x64, arm64), Linux (x64, arm64), and Windows (x64, arm64)
• Adds LockFileEx/UnlockFileEx Windows APIs for byte-range file locking
• Supports Node.js 20+ and Electron
• Falls back to local compilation if no prebuilt binary matches your platform

npm install fs-ext-extra-prebuilt

const { flock, flockSync } = require('fs-ext-extra-prebuilt');
const fs = require('fs');

const fd = fs.openSync('foo.txt', 'r');
flock(fd, 'ex', (err) => {
	if (err) {
		return console.error("Couldn't lock file");
	}
	// file is locked
});

Asynchronous flock(2). No arguments other than a possible error are passed to the callback. Flags can be 'sh', 'ex', 'shnb', 'exnb', 'un' and correspond to the various LOCK_SH, LOCK_EX, LOCK_SH|LOCK_NB, etc.

NOTE (from flock() man page): flock() does not lock files over NFS. Use fcntl(2) instead: that does work over NFS, given a sufficiently recent version of Linux and a server which supports locking.

Synchronous flock(2). Throws an exception on error.

Asynchronous fcntl(2).

callback will be given two arguments (err, result).

The supported commands are:

• 'getfd' ( F_GETFD )
• 'setfd' ( F_SETFD )
• 'setlk' ( F_SETLK )
• 'getlk' ( F_GETLK )
• 'setlkw' ( F_SETLKW )

For F_SETLK and F_SETLKW, the arg parameter specifies the lock type (F_RDLCK, F_WRLCK, or F_UNLCK). The optional start and len parameters specify the byte range to lock. If omitted, they default to 0, which locks the entire file.

Synchronous fcntl(2). Throws an exception on error.

Asynchronous lseek(2).

callback will be given two arguments (err, currFilePos).

whence can be 0 (SEEK_SET) to set the new position in bytes to offset, 1 (SEEK_CUR) to set the new position to the current position plus offset bytes (can be negative), or 2 (SEEK_END) to set to the end of the file plus offset bytes (usually negative or zero to seek to the end of the file).

Synchronous lseek(2). Throws an exception on error. Returns current file position.

Asynchronous LockFileEx. Locks a byte range in a file.

Flags:

• 0 - shared lock
• constants.LOCKFILE_EXCLUSIVE_LOCK - exclusive lock
• constants.LOCKFILE_FAIL_IMMEDIATELY - non-blocking (can be OR'd with above)

Synchronous LockFileEx. Throws an exception on error.

Asynchronous UnlockFileEx. Unlocks a byte range in a file.

Synchronous UnlockFileEx. Throws an exception on error.

Available via require('fs-ext-extra-prebuilt').constants:

• LOCK_SH, LOCK_EX, LOCK_NB, LOCK_UN - flock flags
• F_GETFD, F_SETFD, F_GETLK, F_SETLK, F_SETLKW - fcntl commands
• F_RDLCK, F_WRLCK, F_UNLCK - fcntl lock types
• FD_CLOEXEC - close-on-exec flag
• LOCKFILE_EXCLUSIVE_LOCK, LOCKFILE_FAIL_IMMEDIATELY - Windows LockFileEx flags

MIT