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FileStream locking issues [message #35589]

Fri, 02 March 2012 14:04

mirek
Messages: 14285
Registered: November 2005

Ultimate Member

While working on problem with ide configuration file curruption (still unresolved), I have noticed that if two instances of same application do SaveFile at the same time, file can get corrupted.

Means there should be some sort of locking so that if some file is open with FileOut or FileAppend, next opening of the same file fails.

There already were some sharing flags, but they worked only in Win32 and IMO were never used.

Resolving situation: FileStream now supports NOWRITESHARE flag in Linux too (using flock system call), other sharing flags are deprecated (I think that for more complex situation, you cannot use FileStream anyway).

FileOut and FileAppend now specify NOWRITESHARE flag. Means second concurent try to FileOut the same file is gonna fail (file does not open).

Mirek

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Re: FileStream locking issues [message #35926 is a reply to message #35589]

Wed, 04 April 2012 21:59

Mindtraveller
Messages: 917
Registered: August 2007
Location: Russia, Moscow rgn.

Experienced Contributor

Great! Very handy indeed. Thanks.

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Re: FileStream locking issues [message #35935 is a reply to message #35589]

Thu, 05 April 2012 09:52

zsolt
Messages: 702
Registered: December 2005
Location: Budapest, Hungary

Contributor

In one of my previous projects, I had multiple processes writing into the same logfile (appending). It worked well with line buffered writes. I think, the OS resolves this.

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