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doc: improve fs.open() docs

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1 parent ccc4e54 commit 18b94ea838f834209c311005ac9cd3cc6d205bca @bnoordhuis bnoordhuis committed May 17, 2012
Showing with 10 additions and 8 deletions.
  1. +10 −8 doc/api/fs.markdown
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@@ -270,16 +270,18 @@ An exception occurs if the file does not exist.
* `'r+'` - Open file for reading and writing.
An exception occurs if the file does not exist.
-* `'rs'` - Open file for reading, telling the OS to open it synchronously
-(ie using the O_SYNC flag). Whilst rarely useful, when used with caution by
-those who know what they're doing it can be sometimes necessary. Note that
-this doesn't turn `fs.open()` into a synchronous blocking call, if that's what
-you want then you should be using `fs.openSync()`
-An exception occurs if the file does not exist.
+* `'rs'` - Open file for reading in synchronous mode. Instructs the operating
+ system to bypass the local file system cache.
+
+ This is primarily useful for opening files on NFS mounts as it allows you to
+ skip the potentially stale local cache. It has a very real impact on I/O
+ performance so don't use this mode unless you need it.
+
+ Note that this doesn't turn `fs.open()` into a synchronous blocking call.
+ If that's what you want then you should be using `fs.openSync()`
* `'rs+'` - Open file for reading and writing, telling the OS to open it
-synchronously.
-See notes for `'rs'` about using this with caution.
+ synchronously. See notes for `'rs'` about using this with caution.
* `'w'` - Open file for writing.
The file is created (if it does not exist) or truncated (if it exists).

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