How do I check a text file for a certain string and notify when that string has been added?

Question

What I'm trying to do is monitor a chat log for a game that I play. I want to make a program that will notify me anytime my character name has been mentioned in the chat. If my name is mentioned in the chat it tells me. Then it tells me again after it scans the file again over and over again. Every time the file changes. I only want to be notified once of each instance of my name being mentioned. Can someone help me correct this code to do what I need?

Private Sub FileSystemWatcher1_Changed(sender As Object, e As IO.FileSystemEventArgs) Handles FileSystemWatcher1.Changed
    If e.FullPath = "C:\Games\Chat\Logs\chat.txt" Then
        Dim fileContents As String = My.Computer.FileSystem.ReadAllText(e.FullPath)

        ' Convert the text to lower case to provide for better trigger matching if case sensitivity
        ' isn't an issue.
        If fileContents.ToLower.Contains("palumbo") Then
            Dim strMessage As String
            strMessage = "Name Mentioned In Chat!" & vbNewLine
            txtMessage.SelectionColor = Color.Red
            txtMessage.SelectionFont = New Font("Arial", 18, FontStyle.Bold)
            txtMessage.AppendText(strMessage)
        End If
    End If

End Sub

The way this is working is it checks the file sees that it was mentioned then it tells me. Then if the file changes anything at all added to the file it scans it again and tells me again. Even if my name hasn't been mentioned again. I'm not sure what code I need to add to only tell me once each time its mentioned even if my name is mentioned 100 times. I only want it to tell me each time it's mentioned. Then wait for the next. Maybe by checking the line number when my name is mentioned and if the number is greater then the last time mentioned then tell me if not then skip it?

I'm not sure how to do that though.

Answer 1

You can keep a count of the number of occurrences of your character name and be notified when that changes. Also, if you read from a file that changes often, you're likely to get an IOException so one way around it is to make a copy and read that.

Private Sub FileSystemWatcher1_Changed(sender As Object, e As IO.FileSystemEventArgs) Handles FileSystemWatcher1.Changed
    If e.FullPath = "C:\Games\Chat\Logs\chat.txt" Then
        'temp file in different dir from the one being monitored
        Dim tmpfile As String = "C:\chat.txt"

        FileCopy(e.FullPath, tmpfile)

        Dim fileContents As String = My.Computer.FileSystem.ReadAllText(tmpfile)

        Static chatNameOccurences As Integer = 0
        Dim chatName As String = "palumbo"

        ' Convert the text to lower case to provide for better trigger matching if case sensitivity
        ' isn't an issue.
        If fileContents.ToLower.Contains(chatName) Then
            Dim occurrences As Integer = CountMatches(fileContents.ToLower, chatName)
            If Not occurrences.Equals(chatNameOccurences) Then
                chatNameOccurences = occurrences
                Dim strMessage As String
                strMessage = "Name Mentioned In Chat " & chatNameOccurences & " times!" & vbNewLine
                txtMessage.SelectionColor = Color.Red
                txtMessage.SelectionFont = New Font("Arial", 18, FontStyle.Bold)
                txtMessage.AppendText(strMessage)
            End If
        End If
    End If

End Sub

Public Function CountMatches(ByVal value As String, ByVal ch As String) As Integer
    Return New System.Text.RegularExpressions.Regex(ch).Matches(value).Count
End Function