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Introduction

The File Contents Watcher application allows you to load text-based files such as application or website log files and view them while they are being updated by your application or website. The application monitors the file for changes and automatically reloads the files if they are modified.

There are other applications available that display text-based files and automatically reload them when they are modified. An example of such a program is UltraEdit which I am currently using to write the first draft of this article. However, these programs are not written with the main purpose of monitoring a group of text files for changes and presenting them as a group. That's where the File Contents Watcher program comes in.

Below, I will present a few of features of this application and the concepts covered in developing this application.

Features

The File Contents Watcher application lets you:

1. Load one or more text-based files and view the contents in a textbox.
2. Automatically reload the file and scroll the view to the end when the file is modified.
3. List all the loaded files sorted by last modified time.
4. View basic file properties such as size and modified time.

The feature set is pretty simple and doesn't require much elaboration. There are two features the might not be immediate clear when you run the program. The first is that you can double click a file in the All Files tab and that will jump you to that file's contents view. The other feature is that the contents view of the file is limited to 250,000 characters. This is to prevent huge text files from bogging down the program. Text files of any size can be loaded, but only the last 250,000 characters will be displayed. The reasoning for this is that most of the time the files will be modified on the end by appending new data.

Developing The Application

Developing the File Contents Watcher application was fairly simple. Basically, the application is a set of composite Windows Forms User Controls wrapped around FileSystemWatcher objects.

User Controls

Warning: If you download the source code and want to view these user controls or the application's main form in the Windows Forms Designer, you must first compile the solution or the controls will not show up.

The application is made up of the following User Controls:

• All Files Control - Maintains the list of loaded files and provides file navigation.
• File Control - Displays information and contents of a file.
• File Contents Control - Used by the File Control to display the contents of a file.
• File Statistics Control - Used by the File Control to display the file properties.

This diagram shows how the controls are used in the application. Note that the lines between controls mean the top control "contains" or "is composed of" the lower control.

User Interface Control Composition Diagram

The User Controls are contained in a Magic Library TabControl. See the DotNetMagic User Controls section at the end of this article for details about this control library.

Watching The Files

The FileSystemWatcher class is central to the operation of this program. The following method is from the FileControl class and is called once when that control is created.

public void Initialize(string file)
{
   labelFileName.Text = file;
   fileSystemWatcher.Filter = System.IO.Path.GetFileName(file);
   fileSystemWatcher.Path = System.IO.Path.GetDirectoryName(file);

   fileContentsControl.UpdateFileInfo(file);
   fileStatisticsControl.UpdateFileInfo(file);
}

The method initializes the fileSystemWatcher object with the correct path and file name. Since the fileSystemWatcher object was added through the Windows Forms designer, this is all that it takes to start it watching the specified file. In the designer, the FileControl has signed up for the FileSystemWatcher.Changed event which will be fired when the specified file changes. The FileControl signals the other controls and sub-controls to update themselves when it receives a Changed event.

Future Work

This application is something I started for myself and I only wanted to spend a couple of hours making it. So the feature set isn't as polished as it could be. For example, the main form and controls could remember their location and state. There could be a recent file list.

I may implement one or more of these features if there is enough interest. For now, I'm releasing the application in a fairly bare-bones state. Hope you enjoy it.

DotNetMagic User Controls

The application uses the Magic Library TabControl for organizing the various controls in the user interface. The TabControl is one of the controls in the excellent Magic Library from Phil Wright [^]. I've used these in several applications, and they are very solid controls and I certainly recommend them.

The version used with this application is from the Magic Controls library Phil posted to Code Project with his article Magic TabControl - VS.NET Style [^].

He has since turned the Magic Library into a commercial User Controls library called DotNetMagic.

History

• December 29, 2004:
  • Changed the load log file dialog from single file mode to multiple file mode. You can now load many log files at once.
  • Removed "Save File Group" confirmation when program closes and only one file is loaded.
  • Removed "Save File Group" confirmation when program closes because Windows is exiting.
  • Added word-wrap support. This can be toggled using the View menu and applies to all loaded files.
  • Changed the display font to a fixed-length font (Courier New).
  • Changed hyperlinks to load using the default browser rather than hard coding Internet Explorer.
• April 7, 2004:
  • Added the ability to save and load file groups to more easily manage groups of files.
  • View is now scrolled to the end of files when the file is initially loaded.
  • Fixed broken link for Magic Controls in the article HTML.
• March 31, 2004:
  • This is the initial release of the article. No changes.

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Use FileStream.Seek() for big files Richard Redpay 16:11 13 Mar '07   I found it useful to add the following code to FileContentsControl.cs in the UpdateFileInfo() Method to avoid reading and processing initial text that will be discarded: sr = new System.IO.StreamReader(fs); // Inserted code to skip initial text in very long log files if (fs.Length > MAX_SIZE) { if (fs.CanSeek) { fs.Seek(-MAX_SIZE, SeekOrigin.End); // make sure we start on a new line string dummy = sr.ReadLine(); } } // End inserted code string contents = sr.ReadToEnd(); and then add the following to the class FileContentsControl public const long MAX_SIZE = 250000; Sign In·View Thread·PermaLink File Watcher for FAT File System [modified] albert214 22:27 26 Feb '07   hi.. any idea on how to create a file watcher for fat file system (win9x/me). thanks saint -- modified at 3:02 Monday 5th March, 2007 Sign In·View Thread·PermaLink Change location of docked window Shakeel Mumtaz 1:35 1 Oct '06   Dear i want to change the location of the window like 1-the dockable window show at location (x=0,y=100) 2-change the size of the window (width=250,height=300) plz reply me soon. Thanks in advance Ranjeet Singh Sign In·View Thread·PermaLink keyword search and email options JavaReb 8:23 16 Aug '06   How would one go about adding the ability to do a keyword search on the latest additions to a changed log file and then fire off an email for a keyword match ? BitShift Sign In·View Thread·PermaLink Good tool! Jim Wakeen 9:48 24 Apr '06   Here is an idea for an enhancement if you're interested: Since most log files are text based, a fixed point font might show better, even an option to choose your own font wouldn't be too difficult. Sign In·View Thread·PermaLink System Watcher fails when file copy takes long time darrenrhymer 11:11 6 Oct '05   Hi I've been using the FileSystemWatcher to check for new files in a folder and when found I load the contents into a database and move the file elsewhere. However, Ive just found out that if I copy the files from my machine to the server (where the service is running) via a VPN the service detects a new file and tries to process it, but the file hasnt fully copied yet so an error is eventually raised. Is there a way to tell the systemWatcher to wait until the file has fully copied or a way of checking if any locks excess on the file. Thanks for any help Darren Rhymer Sign In·View Thread·PermaLink 3.00/5 a question J.L 10:39 7 May '04   Very nice one! I added a static variable, say counter, and added counter++ inside the fileSystemWatcher_Changed event handler, I observed that whenever I modified one loaded file, the counter increased by 3 not 1. If I write an info to a log file using sw.WriteLine(strFileName + " " + "Changed at " + DateTime.Now); then 3 entries with same time stamp will be written. This is certainly not your bug, but I would like to know what's going on here, so I can log one entry per change. Hope you can give me some help. Thanks in advance, J.L Sign In·View Thread·PermaLink Re: a question Michael Kennedy 18:44 29 Jun '04   Hi J.L, Sorry for the slow reply. Have a look at this documentation: WatcherChangeTypes Enumeration[^] I think there is probably three changes for the following: The change of a file or folder. The types of changes include: changes to size, attributes, security settings, last write, and last access time. That's just a guess, but possibly they are being modified separately and result in 3 events? Also look at the remarks from this part of the documentation: FileSystemWatcher.Changed Event[^] They don't say explicitly how many events to expect, but that there may be more than one. Take care, Michael Michael Kennedy Partner, Software Engineer United Binary, LLC Index of my code project articles [^] Sign In·View Thread·PermaLink group feature? chenhuisheng 19:05 15 Apr '04   user can define groups that each group may hold as many files as they want. and when a group is loaded, all files within that group is being watched. Sign In·View Thread·PermaLink Re: group feature? Michael Kennedy 21:44 19 Apr '04   Hi Chenhuisheng, chenhuisheng wrote: user can define groups that each group may hold as many files as they want. and when a group is loaded, all files within that group is being watched. How is this different from the "Load Group" / "Save Group" feature I added in the latest version? Is it possible that you're referring to an older version which didn't have that feature? Thanks, Michael Michael Kennedy Partner, Software Engineer United Binary, LLC [^] Index of my code project articles Sign In·View Thread·PermaLink Frequently changed long files LiborV 7:20 8 Apr '04   Nice tool, helps me in my current work. I found one problem: when watching long files which change frequently, the program freezes and does not refresh. I suspect that's because refreshing the FileContents control (which includes opening the file, reading its whole contents and putting it into the window) takes longer than how fast the changes come, so the FileChanged events queue gets overloaded. To resolve this, I tried to update the FileContentsCotrol only if the file is really changed. I added private DateTime updateTime; to the FileControl member variables, initialized that in the Initialize method: updateTime = System.IO.File.GetLastWriteTime(file); and modified the fileSystemWatcher_Changed method: { //System.Threading.Thread.Sleep(250); DateTime upd = System.IO.File.GetLastWriteTime(filename); if(upd>updateTime) { updateTime = upd; fileStatisticsControl.UpdateFileInfo(filename); fileContentsControl.UpdateFileInfo(filename); Fire_FileChanged(filename); } } This works for me well. LiborV Sign In·View Thread·PermaLink Re: Frequently changed long files Michael Kennedy 21:48 19 Apr '04   Hi LiborV, Thanks for the tip. I was concerned about very large files and very frequently changing large files when I first wrote this application. But I didn't have time to address those issues and still get this article done. I'll try to get better support for large files in the next version. Your code will certainly be helpful for that. It's too bad that your message was posted just one day after I updated the application or I would have added better large file support to the current version. Thanks for the feedback. Regards, Michael Michael Kennedy Partner, Software Engineer United Binary, LLC [^] Index of my code project articles Sign In·View Thread·PermaLink IIS logs problem Yuri Gorobets 7:03 1 Apr '04   There is one problem - you cannot use your tool for IIS log files. Why? The reason is IIS log files change by chunks - it means by 64 KByte of spaces. IIS add 64KB of spaces to log file and when it writes data to log file it simple replace spaces by data characters. More, it changes file attributes only when add new 64 kbytes. This only your chance get Change event for this file. So, you should create feature for timer reload or something similar. Except it - very nice tool. Best Regards, Yuri Gorobets http://www.dotnetjunkies.com/weblog/removable thoughts Sign In·View Thread·PermaLink Re: IIS logs problem Michael Kennedy 16:28 1 Apr '04   Hi Yuri, Thanks. You can use this program for IIS log files. It's just that IIS buffers its output, so not every single request will generate a change in the log file. It's not that the program can't detect the changes in the file. It's just that IIS won't change the file every time. This is probably an important feature for sites that have very heavy load. I tried the utility out on an IIS log from IIS 5.0 and it took something like 10 requests for that log to update. I don't know how this varies from site to site. I imagine that it does somewhat though since you can change the logging contents and options in IIS. Take care, Michael Michael Kennedy Partner, Software Engineer United Binary, LLC [^] Sign In·View Thread·PermaLink Re: IIS logs problem BRI70 3:29 28 Jun '05   I was trying to use your program to monitor my IIS FTP server logs. I have an application that will tell a device to FTP firmware from my machine, and I need to see if the FTP was successful or not in real time. The simple FTP transactions that I am doing does not generate a whole lot of logging data, so it is not enough to push the buffer limit to write to the log file. Maybe IIS has a registry setting or something that I can force it to flush more often. I tried selecting more logging options in IIS to "pollute" the log file with verbose data, but that still does not fill the buffers enough. Needless to say, when your tool monitors a log file that gets flushed after each entry, it works great!!! Sign In·View Thread·PermaLink 2.00/5 Tracetool Thierry Parent 6:02 1 Apr '04   Nice program. Just notice that the tracetool project in codeproject does the same: http://www.codeproject.com/csharp/TraceTool.asp Tracetool can also display the outputdebugstring window and provide a framework (for dot net, delphi and java) for powerfull traces Thierry Sign In·View Thread·PermaLink Re: Tracetool Michael Kennedy 16:23 1 Apr '04   Hi Thierry, Thanks. That's an interesting program you have there. It looks to be on an entirely different scale than this simple utility. Take care, Michael Michael Kennedy Partner, Software Engineer United Binary, LLC [^] Sign In·View Thread·PermaLink Opening the file garythom_work 3:45 1 Apr '04   Hi there, very nice. I have one observation, when a file is initially opened, the view does not scroll to the end; as you correctly pointed out modifications are usually at the end of the file, hence the most recently added information is at the end too. It probably would be better to open and scroll to the end of the file. Sign In·View Thread·PermaLink Re: Opening the file Michael Kennedy 16:19 1 Apr '04   Hi, Thanks. That's a good idea. I guess that thinking does apply to the files you open up just the same as when they are updated. That's another one for the updates that I'll put in there when/if an update is released. Take care, Michael Michael Kennedy Partner, Software Engineer United Binary, LLC [^] Sign In·View Thread·PermaLink 1.00/5 Re: Opening the file Michael Kennedy 9:42 21 Apr '04   Hi, The current version now has this feature. Thanks for the suggestion. Regards, Michael Michael Kennedy Partner, Software Engineer United Binary, LLC [^] Index of my code project articles Sign In·View Thread·PermaLink Thanks nice one hotgib 2:56 1 Apr '04   Funny a few weeks ago I coded a log file viewer too. I think yours is cooler, I had only about an hour for mine... A few things which you could think about...in order to make this one just a little better. What about transparency (I put a little slider in the status bar...doesn't look nice but works gracefully),always on top and tray icon support. I found this very nice when logged websites and had no multi-monitor environment. I know it's a matter of minutes to put it into your source...just suggestions no criticism Anyway nice tool! cu Dennis Sign In·View Thread·PermaLink Re: Thanks nice one Michael Kennedy 16:13 1 Apr '04   Hi Dennis, Thanks, I'm glad you liked it. Those are some good suggestions. I especially like the tray icon support. Maybe it could use the notification balloons when a file changes. If I update the program I'll try to get that in there. Take care, Michael Michael Kennedy Partner, Software Engineer United Binary, LLC [^] Sign In·View Thread·PermaLink 2.00/5

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