Tail

On unix there are tons of little tools that are useful when working on a program. Tail shows the end of a file and tail -f will watch the file for changes and show them. This makes tail very yseful for watching file that are being written out to disk like logs files. I wanted a simple version of this tool for windows so I wrote one in VB.Net yesterday.


You can download the program from http://mysunfire.com/Downloads/tail.zip

The code for this program is very simple. It consists of a new win form project with a textbox set to dock fill.

   Private FilePath As String
   Private FileName As String
   Private WithEvents Watcher As IO.FileSystemWatcher

   Private Sub frmTail_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
       Try
           'Open Dialog to ask for file to tail
           Dim diag As New OpenFileDialog
           diag.InitialDirectory = "c:\"
           diag.ShowDialog()
           FilePath = diag.FileName

           'Show File
           ShowFile()

           'Set up file watcher
           Watcher = New IO.FileSystemWatcher(FilePath.Substring(0, FilePath.LastIndexOf("\") + 1))
           Watcher.EnableRaisingEvents = True

           'Sub string off file name
           Filename = FilePath.Substring(FilePath.LastIndexOf("\") + 1)

       Catch ex As Exception
           MessageBox.Show("Error Opening file!")
           Me.Close()
       End Try
   End Sub

   Private Sub Watcher_Changed(ByVal sender As Object, ByVal e As System.IO.FileSystemEventArgs) Handles Watcher.Changed, Watcher.Deleted, Watcher.Created
       'if file have changed then reload it
       If e.Name = Filename Then
           ShowFile()
       End If
   End Sub

   Private Sub ShowFile()
       Try
           'Wait for the file to finish being saved byh other program
           Threading.Thread.Sleep(10)

           'Open file reader and load the end of the file
           Dim rdr As New IO.StreamReader(FilePath)
           Dim text As String = rdr.ReadToEnd
           If text.Length > 10000000 Then
               text = text.Substring(text.Length - 10000000)
           End If

           'Store it to the text box
           txtFile.Text = text
           rdr.Close()

           'Scroll to the end so the bottom is always shown
           txtFile.Select(txtFile.Text.Length, 0)
           txtFile.ScrollToCaret()
       Catch ex As Exception
           'If the file was not accessable for what ever reason
       End Try
   End Sub