CODEWITHSUNDEEP
c#fileshare
gemini
gemini

Reputation: 31

File sharing for a separate writer and reader application in C#

I have 2 applications, one is writing to a file, and the other one reads the file. It's a log file, so the writer will be logging until the program stops, while the reader could be invoked any time to get the content of the file.

I thought that when the writer opens the file with FileShare.Read, the reader would be able to access the file, but it produces an error saying that the file is being used by another process.

Writer Application:

FileStream fs = new FileStream("file.log", FileMode.Open, FileAccess.Write, FileShare.Read); BinaryWriter writer = new BinaryWriter(fs);

Reader Application:

BinaryReader reader = new BinaryReader(File.OpenRead("file.log"));

How do I prevent this error?

Upvotes: 0

Views: 500

Answers (2)

Nico
Nico

Reputation: 12683

o read a locked file you are going to need to provide more flags for the FileStream.

Code such as below.

using (var reader = new FileStream("d:\\test.txt", FileMode.Open, FileAccess.Read,FileShare.ReadWrite))
{
            using (var binary = new BinaryReader(reader))
            {
                //todo: add your code
                binary.Close();
            }
            reader.Close();
}

This would open the file for reading only with the share mode of read write. This can be tested with a small app. (Using streamreader\write instead of binary)

    static Thread writer,
                  reader;

    static bool abort = false;

    static void Main(string[] args)
    {

        var fs = File.Create("D:\\test.txt");
        fs.Dispose();

        writer = new Thread(new ThreadStart(testWriteLoop));
        reader = new Thread(new ThreadStart(testReadLoop));
        writer.Start();
        reader.Start();

        Console.ReadKey();
        abort = true;
    }

    static void testWriteLoop()
    {
        using (FileStream fs = new FileStream("d:\\test.txt", FileMode.Open, FileAccess.Write, FileShare.Read))
        {
            using (var writer = new StreamWriter(fs))
            {
                while (!abort)
                {
                    writer.WriteLine(DateTime.Now.ToString());
                    writer.Flush();
                    Thread.Sleep(1000);
                }
            }
        }
    }

    static void testReadLoop()
    {
        while (!abort)
        {
            Thread.Sleep(1000);
            using (var reader = new FileStream("d:\\test.txt", FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
            {
                using (var stream = new StreamReader(reader))
                {
                    Console.WriteLine(stream.ReadToEnd());
                    stream.Close();

                }
                reader.Close();
            }
        }
    }

I realize the example above is pretty simple but the fact still remains that the "testWriteLoop" never releases the lock.

Hope this helps

Upvotes: 0

appcoder
appcoder

Reputation: 659

Can you try specifying FileShare.Read while reading the file also? Instead of directly using File.OpenRead use FileStream with this permission.

Also, for logging, you can use log4Net or any other free logging framework which manages logging so efficiently and we do not have to manage writing to files.

Upvotes: 0

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