I have a windows service writes its log in a text file in a simple format.
Now, I'm going to create a small application to read the service's log and shows both the existing log and the added one as live view.
The problem is that the service locks the text file for adding the new lines and at the same time the viewer application locks the file for reading.
The Service Code:
void WriteInLog(string logFilePath, data)
{
File.AppendAllText(logFilePath,
string.Format("{0} : {1}\r\n", DateTime.Now, data));
}
The viewer Code:
int index = 0;
private void Form1_Load(object sender, EventArgs e)
{
try
{
using (StreamReader sr = new StreamReader(logFilePath))
{
while (sr.Peek() >= 0) // reading the old data
{
AddLineToGrid(sr.ReadLine());
index++;
}
sr.Close();
}
timer1.Start();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
private void timer1_Tick(object sender, EventArgs e)
{
using (StreamReader sr = new StreamReader(logFilePath))
{
// skipping the old data, it has read in the Form1_Load event handler
for (int i = 0; i < index ; i++)
sr.ReadLine();
while (sr.Peek() >= 0) // reading the live data if exists
{
string str = sr.ReadLine();
if (str != null)
{
AddLineToGrid(str);
index++;
}
}
sr.Close();
}
}
Is there any problem in my code in reading and writing way?
How to solve the problem?
You need to make sure that both the service and the reader open the log file non-exclusively. Try this:
For the service - the writer in your example - use a FileStream instance created as follows:
var outStream = new FileStream(logfileName, FileMode.Open,
FileAccess.Write, FileShare.ReadWrite);
For the reader use the same but change the file access:
var inStream = new FileStream(logfileName, FileMode.Open,
FileAccess.Read, FileShare.ReadWrite);
Also, since FileStream implements IDisposable make sure that in both cases you consider using a using statement, for example for the writer:
using(var outStream = ...)
{
// using outStream here
...
}
Good luck!
Explicit set up the sharing mode while reading the text file.
using (FileStream fs = new FileStream(logFilePath,
FileMode.Open,
FileAccess.Read,
FileShare.ReadWrite))
{
using (StreamReader sr = new StreamReader(fs))
{
while (sr.Peek() >= 0) // reading the old data
{
AddLineToGrid(sr.ReadLine());
index++;
}
}
}
new StreamReader(File.Open(logFilePath,
FileMode.Open,
FileAccess.Read,
FileShare.ReadWrite))
-> this doesn't lock the file.
The problem is when you are writing to the log you are exclusively locking the file down so your StreamReader won't be allowed to open it at all.
You need to try open the file in readonly mode.
using (FileStream fs = new FileStream("myLogFile.txt", FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
{
using (StreamReader sr = new StreamReader(fs))
{
while (!fs.EndOfStream)
{
string line = fs.ReadLine();
// Your code here
}
}
}
I remember doing the same thing a couple of years ago. After some google queries i found this:
FileStream fs = new FileStream(#”c:\test.txt”,
FileMode.Open,
FileAccess.Read,
FileShare.ReadWrite);
i.e. use the FileShare.ReadWrite attribute on FileStream().
(found on Balaji Ramesh's blog)
Have you tried copying the file, then reading it?
Just update the copy whenever big changes are made.
This method will help you to fastest read a text file and without locking it.
private string ReadFileAndFetchStringInSingleLine(string file)
{
StringBuilder sb;
try
{
sb = new StringBuilder();
using (FileStream fs = File.Open(file, FileMode.Open))
{
using (BufferedStream bs = new BufferedStream(fs))
{
using (StreamReader sr = new StreamReader(bs))
{
string str;
while ((str = sr.ReadLine()) != null)
{
sb.Append(str);
}
}
}
}
return sb.ToString();
}
catch (Exception ex)
{
return "";
}
}
Hope this method will help you.
Related
I'm using a FileStream to lock the File to be not writeable for other processes and also read and write to it, I'm using following method for it:
public static void ChangeOrAddLine(string newLine, string oldLine = "")
{
string filePath = "C:\\test.txt";
FileMode fm = FileMode.Create;
//FileMode fm = FileMode.OpenOrCreate;
using (FileStream fs = new FileStream(filePath, FileMode.Create, FileAccess.ReadWrite, FileShare.Read))
using (StreamReader sr = new StreamReader(fs))
using (StreamWriter sw = new StreamWriter(fs))
{
List<string> lines = sr.ReadToEnd().Split(new string[] { "\r\n" }, StringSplitOptions.None).ToList();
bool lineFound = false;
if (oldLine != "")
for (int i = 0; i < lines.Count; i++)
if (lines[i] == oldLine)
{
lines[i] = newLine;
lineFound = true;
break;
}
if (!lineFound)
lines.Add(newLine);
sw.Write(string.Join("\r\n", lines));
}
}
I want to overwrite it with the new content but i don't find the right FileMode, using FileMode.OpenOrCreate just appends the new content to the old and FileMode.Create deletes the file-content at the time, the FileStream fm has been initialized, so the file is empty.
I need to just clear the old content at the moment, when i write the new content to it without losing the write-lock on it during the method is running.
OpenOrCreate just appends ...
Because you don't reposition after the reading.
That also shows the main problem with your approach: The FileStream only has one Position, and the Reader and the Writer heavily use caching.
However, as long as you want to replace everything and really need that locking scheme:
using (FileStream fs = new FileStream(filePath,
FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.Read))
{
using (StreamReader sr = new StreamReader(fs))
{
... // all the reading
}
fs.Position = 0;
using (StreamWriter sw = new StreamWriter(fs))
{
sw.Write(string.Join("\r\n", lines));
}
fs.SetLength(fs.Position); // untested, something along this line
}
and maybe you have to convince the sw and sr to leave their stream open.
But I have to note that the FileShare.Read flag doesn't make too much sense in this scenario. A reader could see al sorts of inconsistent data, including torn lines and broken UTF8 characters.
I have a C# app that tries to read a log file which is being written to by another app. When I try to read the file, I get IOException
"The process cannot access the file ... because it is being used by
another process."
What I tried using so far are the following, but none of them fix the problem
var log = File.ReadAllText(logPath);
var stream = new FileStream(logPath, FileMode.Open);
using (var stream = File.Open(logPath, FileMode.Open))
{
}
try this:
FileStream logFileStream = new FileStream("c:\test.txt", FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
StreamReader logFileReader = new StreamReader(logFileStream);
while (!logFileReader.EndOfStream)
{
string line = logFileReader.ReadLine();
// Your code here
}
// Clean up
logFileReader.Close();
logFileStream.Close();
edited with MethodMan's suggestions
using(FileStream logFileStream = new FileStream(#"c:\test.txt", FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
{
using(StreamReader logFileReader = new StreamReader(logFileStream))
{
string text = logFileReader.ReadToEnd();
// Your code..
}
}
You can do nothing, if the "another app" does not use Share.Read while creating/opening the file.
I'm using a filestream to access a file (making an md5 ComputeHash). If I attempt to rename the file during this time (which fails as the file is being accessed). So far so good, but when I then try to open the file anew after the original filestream is closed I get the info that the file is open in another process.
Code:
using (Stream fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)) {
MD5 md5 = MD5.Create();
byte[] mymd5computed = md5.ComputeHash(fileStream);
......
}
Thread.Sleep(50);
Thread a = new Thread (()=>{(FileStream sourceStream = File.Open(filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)){....} });
Like I said if while during the computation of the MD5 I try to rename the file I get the info that the file is still locked.
The lock on a file sometimes isn't released right away when you close your stream, so there are some other solutions you can use to wait until you can access the file again. One of them is explained here: http://www.codeproject.com/Tips/164428/C-FileStream-Lock-How-to-wait-for-a-file-to-get-re.
Recap:
public static void Lock(string path, Action<FileStream> action) {
var autoResetEvent = new AutoResetEvent(false);
while(true)
{
try
{
using (var file = File.Open(path,
FileMode.OpenOrCreate,
FileAccess.ReadWrite,
FileShare.Write))
{
action(file);
break;
}
}
catch (IOException)
{
var fileSystemWatcher =
new FileSystemWatcher(Path.GetDirectoryName(path))
{
EnableRaisingEvents = true
};
fileSystemWatcher.Changed +=
(o, e) =>
{
if(Path.GetFullPath(e.FullPath) == Path.GetFullPath(path))
{
autoResetEvent.Set();
}
};
autoResetEvent.WaitOne();
}
}
}
Sample use:
Lock(#"c:\file",
(f) =>
{
try
{
f.Write(buf, 0, buf.Length);
}
catch(IOException ioe)
{
// handle IOException
}
});
Hope it helps! :)
Plenty of information on StreamReader and not locking files on stackoverflow, but does a dialogue box somehow change that? I'd have to say no, but maybe I am not using it right, and it is locking the file? My code is:
private void read1()
{
TextReader tr = new StreamReader(#"T:\\testfile");
string input = null;
while ((input = tr.ReadLine()) != null)
{
if (input.Contains("test"))
{
MessageBox.Show(input);
}
}
}
I think you need to use a FileStream to do that.
Also, you're not closing your stream or calling Dispose() on it. You should use a using statement to make sure it happens. The following code should ensure the file isn't locked.
private void read1()
{
using (var fs = new FileStream(#"T:\testfile", FileMode.Open, FileAccess.Read, FileShare.ReadWrite)) {
using (var tr = new StreamReader(fs)) {
string input = null;
while ((input = tr.ReadLine()) != null)
{
if (input.Contains("test"))
{
MessageBox.Show(input);
}
}
}
}
}
I am working with IsolatedStorage in Windows Phone 7.5. I am trying to read some text from a file. But the debugger says the operation is not permitted on IsolatedStorageFileStream. Why?
//Read the file from the specified location.
fileReader = new StreamReader(new IsolatedStorageFileStream("info.dat", FileMode.Open, fileStorage));
//Read the contents of the file (the only line we created).
string textFile = fileReader.ReadLine();
//Write the contents of the file to the MEssageBlock on the page.
MessageBox.Show(textFile);
fileReader.Close();
UPD my new code
object _syncObject = new object();
lock (_syncObject)
{
using (var fileStorage = IsolatedStorageFile.GetUserStoreForApplication())
{
using (FileStream stream = new FileStream("/info.dat", FileMode.Open, FileAccess.Read, FileShare.Read))
{
using (var reader = new StreamReader(stream))
{
string textFile = reader.ReadLine();
MessageBox.Show(textFile);
}
}
}
}
}
Try this, it works for me: Hope it works for you too
String sb;
using (IsolatedStorageFile myIsolatedStorage = IsolatedStorageFile.GetUserStoreForApplication())
{
if (myIsolatedStorage.FileExists(fileName))
{
StreamReader reader = new StreamReader(new IsolatedStorageFileStream(fileName, FileMode.Open, myIsolatedStorage));
sb = reader.ReadToEnd();
reader.Close();
}
if(!String.IsNullOrEmpty(sb))
{
MessageBox.Show(sb);
}
}
If this doesn't work, then maybe your file doesn't exist.
Normally when I've used isolated storage, I've done something like:
using (var stream = fileStorage.OpenFile("info.dat", FileMode.Open))
{
using (var reader = new StreamReader(stream))
{
...
}
}
... rather than calling the constructor directly on IsolatedStorageFileStream. I can't say for sure whether that'll sort it out, but it's worth a try...
Just a guess:
WP emulator will reset all Isolatd Storage contents when it's closed
if you used FileMode.Open with a path to a non existing file you'll get Operation not permited exception.
You can use fileStorage.FileExists() to check if the file is there or use FileMode.OpenOrCreate.