How to use Loc function in VBA?

In VBA (Visual Basic for Applications), the Loc function is used to obtain the current read/write position within an open file. This is most often used when you are working with files in a binary mode, as Loc will return the position as the number of bytes from the start of the file.

Basic syntax


position = Loc(fileNumber)

Where fileNumber is a required argument that represents the file number you want to get the position for. The file number is the number that is specified when you open the file using the Open statement. The result, position, is the current position in the file.



Sub FilePositionExample()
    Dim fileNum As Integer
    Dim filePath As String
    Dim filePos As Long

    ' Set the path to the file
    filePath = "C:\path\to\your\file.txt"

    ' Get the next available file number
    fileNum = FreeFile()

    ' Open the file for Binary Access
    Open filePath For Binary Access Read As #fileNum

    ' Do some file read or write operations here
    ' ...

    ' Get the current position in the file
    filePos = Loc(fileNum)

    ' Show the position
    MsgBox "The current file position is: " & filePos

    ' Close the file
    Close #fileNum
End Sub

When you run this code, it will open the specified file in binary mode, and then use the Loc function to find out the current position of the file pointer. Since there are no read or write operations in the example between the opening and the check, it would typically be at the beginning of the file when the MsgBox is shown.

Please remember that the Loc function is not frequently used for text files, as reading or writing operations with text files move the file pointer in variable-length increments, making Loc values for text files less meaningful.

Also, note that Loc function works with files opened for Binary, Random, and Input modes, but does not work with files opened for Output or Append.

Make sure that the file exists and you have appropriate permissions to read from the file if you are using the Loc function in conjunction with reading file operations.

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