Reading a file as long as it is open by another process
in [CSharp]
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From: Udi on 10 May 2010 10:15 Hi, I have two processes, one writres a text file and the other reads it. I'm looking for a way to pend the reader when it reaches to the end of the file, for as long as the writer holds the file open. i.e. if the reader reaches EOF, and then the writer adds a new row, i'd like the reader to be able to read the new rows until the writer releases the file. Is there an easy way to implement this? Thanks, Udi
From: RayLopez99 on 10 May 2010 17:48 On May 10, 10:15 am, Udi <udibensen...(a)gmail.com> wrote: > Hi, > I have two processes, one writres a text file and the other reads it. > I'm looking for a way to pend the reader when it reaches to the end of > the file, for as long as the writer holds the file open. > i.e. if the reader reaches EOF, and then the writer adds a new row, > i'd like the reader to be able to read the new rows until the writer > releases the file. > > Is there an easy way to implement this? > Thanks, > Udi Not sure what you mean--you mean 'read only'? I think that's doable even if you have several processes reading the same stream. Try it and see. RL
From: Arne Vajhøj on 10 May 2010 17:48 On 10-05-2010 10:15, Udi wrote: > I have two processes, one writres a text file and the other reads it. > I'm looking for a way to pend the reader when it reaches to the end of > the file, for as long as the writer holds the file open. > i.e. if the reader reaches EOF, and then the writer adds a new row, > i'd like the reader to be able to read the new rows until the writer > releases the file. If the file meta data is kept uptodate, then you may be able to do it by maintaining position and compare that with file length. In general that write-file-read-file approach is error-prone. Wny not use named pipe/TCP socket instead? Much easier! Arne
From: Bert Hyman on 10 May 2010 18:44 In news:552afb32-af94-4edf-9c52-0cd21b03d3cf(a)g21g2000yqk.googlegroups.com Udi <udibensenior(a)gmail.com> wrote: > i'd like the reader to be able to read the new rows until the writer > releases the file. You could try re-opening the file with OF_SHARE_EXCLUSIVE or OF_SHARE_DENY_WRITE. I'm sorry that I can't name the specific C# class/method for doing that, but it must be in there somewhere :-) So long as any other process has the file open for writing, your attempt will fail. Once you're able to open the file in either of those modes, you'll know that the writing process has closed the file. That would involve closing and opening the file each time you check, but that might not be too much trouble. -- Bert Hyman St. Paul, MN bert(a)iphouse.com
From: Arne Vajhøj on 10 May 2010 19:09
On 10-05-2010 18:44, Bert Hyman wrote: > In > news:552afb32-af94-4edf-9c52-0cd21b03d3cf(a)g21g2000yqk.googlegroups.com > Udi<udibensenior(a)gmail.com> wrote: >> i'd like the reader to be able to read the new rows until the writer >> releases the file. > > You could try re-opening the file with OF_SHARE_EXCLUSIVE or > OF_SHARE_DENY_WRITE. I'm sorry that I can't name the specific C# > class/method for doing that, but it must be in there somewhere :-) The FileStream class has constructors with all the options: http://msdn.microsoft.com/en-us/library/5h0z48dh.aspx Arne |