Native utilities for file manipulation, including locking and hole punching.
npm install fsctl
Write to a file using an exclusive lock:
const { open } = require('fs/promises')
const { lock, unlock } = require('fsctl')
const file = await open('file.txt', 'a+')
await waitForLock(file.fd, { exclusive: true })
try {
await file.write('hello world')
} finally {
unlock(file.fd)
}
Request a lock on a file, returning true
if the lock was granted or false
if another file descriptor currently holds the lock.
To lock only a portion of the file, offset
and length
may be passed. A length
of 0
will request a lock from offset
to the end of the file.
On macOS and Linux, BSD locks are used and so only locks on the whole file are supported.
Note that the lock is only advisory and there is nothing stopping another process from accessing the file by simply ignoring the lock.
Options include:
{
// If `true`, request a shared lock, i.e. a read lock, on the file. By
// default, an exclusive lock, i.e. a write lock, is requested.
// Be aware that an exclusive lock can only be granted to files that are
// writable!
shared: false
}
Request a lock on a file, resolving when the lock is granted. If another file descriptor holds the lock, the lock will not be granted until the other file descriptor releases the lock.
Options are the same as fsctl.lock()
.
Release a lock on a file.
Punch a hole in a file at offset
for length
bytes. On file systems that support sparse files, holes will take up no physical space.
On Windows, the file must first be marked sparse using fsctl.sparse(fd)
. Otherwise, zeros will be explicitly written to the hole.
On macOS, the hole must be aligned to block boundaries as the call will otherwise fail.
Mark a file as sparse. On Windows, this operation is required before holes can be punched in the file. On other systems, this operation has no effect.
MIT