Visual Basic Programming Code Examples

Comparing the contents of two files The following function compares the contents of two files (of any type). Note, a demonstration routine can be found at the bottom of this post: 'Purpose : Compares the content of two files (compares any type of file) 'Inputs : sFile1 The path and file name of the first file to compare. ' sFile2 The path and file name of the second file to compare. 'Outputs : Returns 0 if the files are different. ' 1 if the files are identical. ' -1 if an error occurred. 'Notes : 'Revisions : Function FileCompare(sFile1 As String, sFile2 As String) As Long Const clChunkSize As Long = 1000 Dim iFile1 As Integer, iFile2 As Integer Dim lNumChunks As Long, lRemaining As Long, lThisChunk As Long Dim sBuffer1 As String * clChunkSize Dim sBuffer2 As String * clChunkSize If Len(Dir$(sFile1)) > 0 And Len(Dir$(sFile2)) > 0 Then On Error GoTo ErrFailed iFile1 = FreeFile Open sFile1 For Binary Access Read As iFile1 iFile2 = FreeFile Open sFile2 For Binary Access Read As iFile2 If LOF(iFile1) <> LOF(iFile2) Then 'Files are a different size FileCompare = 0 Else 'Files are same size lNumChunks = LOF(iFile1) \ clChunkSize lRemaining = LOF(iFile1) Mod clChunkSize 'Remaining number of bytes 'Loop over the files reading in chunks of data and compairing them For lThisChunk = 1 To lNumChunks Get iFile1, clChunkSize * (lThisChunk - 1) + 1, sBuffer1 Get iFile2, clChunkSize * (lThisChunk - 1) + 1, sBuffer2 If Not sBuffer1 = sBuffer2 Then 'Files are different FileCompare = 0 Exit For End If Next If lThisChunk = lNumChunks + 1 Then 'Check last chunk of data Get iFile1, (clChunkSize * lNumChunks) + 1, sBuffer1 'get the remaining bytes at the end Get iFile2, (clChunkSize * lNumChunks) + 1, sBuffer2 'get the remaining bytes at the end If Not Left$(sBuffer1, lRemaining) = Left$(sBuffer2, lRemaining) Then 'Files are different FileCompare = 0 Else 'File are identical FileCompare = 1 End If End If End If 'Close files Close iFile1 Close iFile2 Else 'Files don't exist FileCompare = -1 End If Exit Function ErrFailed: 'Err occurred FileCompare = -1 End Function 'Demonstration routine Sub Test() Dim lRet As Long lRet = FileCompare("C:\Copy of Test.txt", "C:\test.txt1") If lRet = 0 Then MsgBox "Files are different", vbInformation ElseIf lRet = 1 Then MsgBox "Files are identical", vbInformation Else MsgBox "Error Failed!", vbInformation End If End Sub