3 graceful-fs functions as a drop-in replacement for the fs module,
4 making various improvements.
6 The improvements are meant to normalize behavior across different
7 platforms and environments, and to make filesystem access more
10 ## Improvements over [fs module](https://nodejs.org/api/fs.html)
12 * Queues up `open` and `readdir` calls, and retries them once
13 something closes if there is an EMFILE error from too many file
15 * fixes `lchmod` for Node versions prior to 0.6.2.
16 * implements `fs.lutimes` if possible. Otherwise it becomes a noop.
17 * ignores `EINVAL` and `EPERM` errors in `chown`, `fchown` or
18 `lchown` if the user isn't root.
19 * makes `lchmod` and `lchown` become noops, if not available.
20 * retries reading a file if `read` results in EAGAIN error.
22 On Windows, it retries renaming a file for up to one second if `EACCESS`
23 or `EPERM` error occurs, likely because antivirus software has locked
30 var fs = require('graceful-fs')
32 // now go and do stuff with it...
33 fs.readFile('some-file-or-whatever', (err, data) => {
40 This module cannot intercept or handle `EMFILE` or `ENFILE` errors from sync
41 methods. If you use sync methods which open file descriptors then you are
42 responsible for dealing with any errors.
44 This is a known limitation, not a bug.
48 If you want to patch the global fs module (or any other fs-like
49 module) you can do this:
52 // Make sure to read the caveat below.
53 var realFs = require('fs')
54 var gracefulFs = require('graceful-fs')
55 gracefulFs.gracefulify(realFs)
58 This should only ever be done at the top-level application layer, in
59 order to delay on EMFILE errors from any fs-using dependencies. You
60 should **not** do this in a library, because it can cause unexpected
61 delays in other parts of the program.
65 This module is fairly stable at this point, and used by a lot of
66 things. That being said, because it implements a subtle behavior
67 change in a core part of the node API, even modest changes can be
68 extremely breaking, and the versioning is thus biased towards
69 bumping the major when in doubt.
71 The main change between major versions has been switching between
72 providing a fully-patched `fs` module vs monkey-patching the node core
73 builtin, and the approach by which a non-monkey-patched `fs` was
76 The goal is to trade `EMFILE` errors for slower fs operations. So, if
77 you try to open a zillion files, rather than crashing, `open`
78 operations will be queued up and wait for something else to `close`.
80 There are advantages to each approach. Monkey-patching the fs means
81 that no `EMFILE` errors can possibly occur anywhere in your
82 application, because everything is using the same core `fs` module,
83 which is patched. However, it can also obviously cause undesirable
84 side-effects, especially if the module is loaded multiple times.
86 Implementing a separate-but-identical patched `fs` module is more
87 surgical (and doesn't run the risk of patching multiple times), but
88 also imposes the challenge of keeping in sync with the core module.
90 The current approach loads the `fs` module, and then creates a
91 lookalike object that has all the same methods, except a few that are
92 patched. It is safe to use in all versions of Node from 0.8 through
97 * Do not monkey-patch the fs module. This module may now be used as a
98 drop-in dep, and users can opt into monkey-patching the fs builtin
99 if their app requires it.
103 * Monkey-patch fs, because the eval approach no longer works on recent
105 * fixed possible type-error throw if rename fails on windows
106 * verify that we *never* get EMFILE errors
107 * Ignore ENOSYS from chmod/chown
108 * clarify that graceful-fs must be used as a drop-in
112 * Use eval rather than monkey-patching fs.
113 * readdir: Always sort the results
114 * win32: requeue a file if error has an OK status
118 * A return to monkey patching
126 * Don't clobber the fs builtin
127 * Handle fs.read EAGAIN errors by trying again
128 * Expose the curOpen counter
129 * No-op lchown/lchmod if not implemented
130 * fs.rename patch only for win32
131 * Patch fs.rename to handle AV software on Windows
132 * Close #4 Chown should not fail on einval or eperm if non-root
133 * Fix isaacs/fstream#1 Only wrap fs one time
134 * Fix #3 Start at 1024 max files, then back off on EMFILE
135 * lutimes that doens't blow up on Linux
136 * A full on-rewrite using a queue instead of just swallowing the EMFILE error
137 * Wrap Read/Write streams as well
141 * Update engines for node 0.6
142 * Be lstat-graceful on Windows