Write Entries To a Log File

Category:

Files and Directories

Type:

Modules

Difficulty:

Beginning

Author:

Jan Nijboer

Version Compatibility: Visual Basic 6

More information:

Module to write entries to a logfile in the application's directory. If the existing logfile exceeds the size specified in MaxLogSize, the file is copied to [filename].old and a new logfile is created.

Just add it to your project and call the procedure WriteLog with a log-entry as a parameter. A reference to the scripting runtime is required.

Instructions: Copy the declarations and code below and paste directly into your VB project.

Declarations:
Option Explicit 'set the maximum logsize to 2 Mb Const MaxLogSize = 2000000

Code:

Public Sub WriteLog(sLogEntry As String)
   Const ForReading = 1, ForWriting = 2, ForAppending = 8
   Dim sLogFile As String, sLogPath As String, iLogSize As Long
   Dim fso, f
   
On Error GoTo ErrHandler

'Set the path and filename of the log
   sLogPath = App.Path & "\" & App.EXEName
   sLogFile = sLogPath & ".log"
   
   Set fso = CreateObject("Scripting.FileSystemObject")
   Set f = fso.OpenTextFile(sLogFile, ForAppending, True)
   
   'Get the size of the log to check if it's getting unwieldly
   iLogSize = GetLogSize(sLogFile)
   If iLogSize > MaxLogSize Then
   
        'If too big, back it up to to retain some sort of history
        fso.CopyFile sLogFile, (sLogPath & ".old"), True
        Set f = Nothing
        fso.DeleteFile sLogFile
        'And start with a clean log-file
        Set f = fso.OpenTextFile(sLogFile, ForAppending, True)
        
   End If
    
   'Append the log-entry to the file together with time and date
   f.WriteLine Now() & vbTab & sLogEntry
   
ErrHandler:
    Exit Sub
End Sub

Private Function GetLogSize(filespec As String) As Long
'Returns the size of a file in bytes. If the file does not
'exist, it returns -1.

Dim fso, f
   Set fso = CreateObject("Scripting.FileSystemObject")
   
   If (fso.FileExists(filespec)) Then
        Set f = fso.GetFile(filespec)
        GetLogSize = f.Size
   Else
        GetLogSize = -1
   End If
End Function