graceful-fs functions as a drop-in replacement for the fs module, making various improvements.
The improvements are meant to normalize behavior across different platforms and environments, and to make filesystem access more resilient to errors.
readdircalls, and retries them once something closes if there is an EMFILE error from too many file descriptors.
lchmodfor Node versions prior to 0.6.2.
fs.lutimesif possible. Otherwise it becomes a noop.
lchownif the user isn't root.
lchownbecome noops, if not available.
readresults in EAGAIN error.
On Windows, it retries renaming a file for up to one second if
EPERM error occurs, likely because antivirus software has locked the directory.
// use just like fs var fs = require('graceful-fs') // now go and do stuff with it... fs.readFileSync('some-file-or-whatever')
If you want to patch the global fs module (or any other fs-like module) you can do this:
// Make sure to read the caveat below. var realFs = require('fs') var gracefulFs = require('graceful-fs') gracefulFs.gracefulify(realFs)
This should only ever be done at the top-level application layer, in order to delay on EMFILE errors from any fs-using dependencies. You should not do this in a library, because it can cause unexpected delays in other parts of the program.
This module is fairly stable at this point, and used by a lot of things. That being said, because it implements a subtle behavior change in a core part of the node API, even modest changes can be extremely breaking, and the versioning is thus biased towards bumping the major when in doubt.
The main change between major versions has been switching between providing a fully-patched
fs module vs monkey-patching the node core builtin, and the approach by which a non-monkey-patched
fs was created.
The goal is to trade
EMFILE errors for slower fs operations. So, if you try to open a zillion files, rather than crashing,
open operations will be queued up and wait for something else to
There are advantages to each approach. Monkey-patching the fs means that no
EMFILE errors can possibly occur anywhere in your application, because everything is using the same core
fs module, which is patched. However, it can also obviously cause undesirable side-effects, especially if the module is loaded multiple times.
Implementing a separate-but-identical patched
fs module is more surgical (and doesn't run the risk of patching multiple times), but also imposes the challenge of keeping in sync with the core module.
The current approach loads the
fs module, and then creates a lookalike object that has all the same methods, except a few that are patched. It is safe to use in all versions of Node from 0.8 through 7.0.