FileLen Function

Returns a Long specifying the length of a file in bytes.

Syntax

FileLen(pathname)

Parameters

• pathname: Required. A String expression that specifies a file name. May include directory or folder, and drive. If the file is not found, an error occurs.

Return Value

Returns a Long representing the length of the file in bytes. For open files, the value returned is the size of the file immediately before it was opened.

Remarks

The FileLen function returns the size of a file in bytes. This is useful for determining file sizes before reading, checking disk space requirements, validating file downloads, and managing storage. Important Characteristics: - Returns file size in bytes - File does not need to be open - Error if file does not exist (Error 53) - Error if path is invalid (Error 76) - Works with full paths and relative paths - For open files, returns size before opening - Maximum file size: 2,147,483,647 bytes (2GB - 1) due to Long limit - Returns 0 for empty files - Does not include file system overhead - Can be used with wildcards via Dir function

Typical Uses

• Check available space before file operations
• Validate file downloads (compare expected vs actual size)
• Display file sizes to users
• Filter files by size
• Calculate total directory size
• Determine buffer sizes for file reading
• Progress bar calculations for file operations
• Detect truncated or corrupted files

Examples

Basic Usage

Dim fileSize As Long
' Get file size in bytes
fileSize = FileLen("C:\data.txt")
Debug.Print "File size: " & fileSize & " bytes"
' Convert to KB, MB, GB
Debug.Print "Size in KB: " & Format(fileSize / 1024, "0.00")
Debug.Print "Size in MB: " & Format(fileSize / 1048576, "0.00")

Format File Size for Display

Function FormatFileSize(bytes As Long) As String
    Const KB = 1024
    Const MB = 1048576         ' 1024 * 1024
    Const GB = 1073741824      ' 1024 * 1024 * 1024
    If bytes >= GB Then
        FormatFileSize = Format(bytes / GB, "0.00") & " GB"
    ElseIf bytes >= MB Then
        FormatFileSize = Format(bytes / MB, "0.00") & " MB"
    ElseIf bytes >= KB Then
        FormatFileSize = Format(bytes / KB, "0.00") & " KB"
    Else
        FormatFileSize = bytes & " bytes"
    End If
End Function
' Usage
Debug.Print FormatFileSize(FileLen("C:\data.txt"))

Check If File Exists and Get Size

Function GetFileSize(filePath As String) As Long
    On Error GoTo ErrorHandler
    GetFileSize = FileLen(filePath)
    Exit Function
ErrorHandler:
    GetFileSize = -1  ' Indicate error
End Function

Common Patterns

Calculate Directory Size

Function GetDirectorySize(folderPath As String) As Long
    Dim fileName As String
    Dim totalSize As Long
    Dim fileSize As Long
    If Right(folderPath, 1) <> "\" Then
        folderPath = folderPath & "\"
    End If
    fileName = Dir(folderPath & "*.*")
    totalSize = 0
    Do While fileName <> ""
        On Error Resume Next
        fileSize = FileLen(folderPath & fileName)
        If Err.Number = 0 Then
            totalSize = totalSize + fileSize
        End If
        Err.Clear
        fileName = Dir
    Loop
    GetDirectorySize = totalSize
End Function

Find Largest File

Function FindLargestFile(folderPath As String) As String
    Dim fileName As String
    Dim largestFile As String
    Dim largestSize As Long
    Dim currentSize As Long
    If Right(folderPath, 1) <> "\" Then
        folderPath = folderPath & "\"
    End If
    fileName = Dir(folderPath & "*.*")
    largestSize = 0
    Do While fileName <> ""
        On Error Resume Next
        currentSize = FileLen(folderPath & fileName)
        If Err.Number = 0 And currentSize > largestSize Then
            largestSize = currentSize
            largestFile = fileName
        End If
        Err.Clear
        fileName = Dir
    Loop
    FindLargestFile = largestFile
End Function

Filter Files by Size

Function GetFilesBySize(folderPath As String, minSize As Long, _
                        maxSize As Long) As Collection
    Dim files As New Collection
    Dim fileName As String
    Dim fullPath As String
    Dim fileSize As Long
    If Right(folderPath, 1) <> "\" Then
        folderPath = folderPath & "\"
    End If
    fileName = Dir(folderPath & "*.*")
    Do While fileName <> ""
        fullPath = folderPath & fileName
        On Error Resume Next
        fileSize = FileLen(fullPath)
        If Err.Number = 0 Then
            If fileSize >= minSize And fileSize <= maxSize Then
                files.Add fullPath
            End If
        End If
        Err.Clear
        fileName = Dir
    Loop
    Set GetFilesBySize = files
End Function

Validate File Download

Function ValidateDownload(filePath As String, expectedSize As Long) As Boolean
    On Error GoTo ErrorHandler
    Dim actualSize As Long
    actualSize = FileLen(filePath)
    ValidateDownload = (actualSize = expectedSize)
    If Not ValidateDownload Then
        Debug.Print "Size mismatch - Expected: " & expectedSize & _
                    ", Actual: " & actualSize
    End If
    Exit Function
ErrorHandler:
    ValidateDownload = False
End Function

Check Available Space

Function HasEnoughSpace(filePath As String, drive As String) As Boolean
    On Error GoTo ErrorHandler
    Dim fileSize As Long
    Dim freeSpace As Currency
    Dim fso As Object
    ' Get file size
    fileSize = FileLen(filePath)
    ' Get free space (using FileSystemObject)
    Set fso = CreateObject("Scripting.FileSystemObject")
    freeSpace = fso.GetDrive(drive).FreeSpace
    HasEnoughSpace = (freeSpace > fileSize)
    Exit Function
ErrorHandler:
    HasEnoughSpace = False
End Function

Progress Bar for File Copy

Sub CopyFileWithProgress(sourceFile As String, destFile As String)
    Dim fileSize As Long
    Dim buffer() As Byte
    Dim sourceNum As Integer
    Dim destNum As Integer
    Dim bytesRead As Long
    Dim chunkSize As Long
    On Error GoTo ErrorHandler
    ' Get total file size
    fileSize = FileLen(sourceFile)
    If fileSize = 0 Then Exit Sub
    chunkSize = 65536  ' 64KB chunks
    bytesRead = 0
    sourceNum = FreeFile
    Open sourceFile For Binary As #sourceNum
    destNum = FreeFile
    Open destFile For Binary As #destNum
    Do While bytesRead < fileSize
        If fileSize - bytesRead < chunkSize Then
            chunkSize = fileSize - bytesRead
        End If
        ReDim buffer(0 To chunkSize - 1)
        Get #sourceNum, , buffer
        Put #destNum, , buffer
        bytesRead = bytesRead + chunkSize
        ' Update progress bar
        ProgressBar.Value = (bytesRead / fileSize) * 100
        DoEvents
    Loop
    Close #sourceNum
    Close #destNum
    Exit Sub
ErrorHandler:
    If sourceNum > 0 Then Close #sourceNum
    If destNum > 0 Then Close #destNum
End Sub

List Files with Sizes

Sub ListFilesWithSizes(folderPath As String)
    Dim fileName As String
    Dim fullPath As String
    Dim fileSize As Long
    If Right(folderPath, 1) <> "\" Then
        folderPath = folderPath & "\"
    End If
    Debug.Print "Files in: " & folderPath
    Debug.Print String(60, "-")
    Debug.Print "Filename", "Size"
    Debug.Print String(60, "-")
    fileName = Dir(folderPath & "*.*")
    Do While fileName <> ""
        fullPath = folderPath & fileName
        On Error Resume Next
        fileSize = FileLen(fullPath)
        If Err.Number = 0 Then
            Debug.Print fileName, FormatFileSize(fileSize)
        End If
        Err.Clear
        fileName = Dir
    Loop
End Sub

Allocate Buffer Based on File Size

Function ReadFileToBuffer(filePath As String) As Byte()
    Dim fileSize As Long
    Dim buffer() As Byte
    Dim fileNum As Integer
    On Error GoTo ErrorHandler
    ' Get file size to allocate exact buffer
    fileSize = FileLen(filePath)
    If fileSize = 0 Then
        ReadFileToBuffer = buffer
        Exit Function
    End If
    ' Allocate buffer
    ReDim buffer(0 To fileSize - 1)
    ' Read file
    fileNum = FreeFile
    Open filePath For Binary As #fileNum
    Get #fileNum, , buffer
    Close #fileNum
    ReadFileToBuffer = buffer
    Exit Function
ErrorHandler:
    If fileNum > 0 Then Close #fileNum
    ReadFileToBuffer = buffer
End Function

Find Empty Files

Function FindEmptyFiles(folderPath As String) As Collection
    Dim emptyFiles As New Collection
    Dim fileName As String
    Dim fullPath As String
    Dim fileSize As Long
    If Right(folderPath, 1) <> "\" Then
        folderPath = folderPath & "\"
    End If
    fileName = Dir(folderPath & "*.*")
    Do While fileName <> ""
        fullPath = folderPath & fileName
        On Error Resume Next
        fileSize = FileLen(fullPath)
        If Err.Number = 0 And fileSize = 0 Then
            emptyFiles.Add fullPath
        End If
        Err.Clear
        fileName = Dir
    Loop
    Set FindEmptyFiles = emptyFiles
End Function

Compare File Sizes

Function CompareFileSizes(file1 As String, file2 As String) As Long
    ' Returns: -1 if file1 < file2, 0 if equal, 1 if file1 > file2
    On Error GoTo ErrorHandler
    Dim size1 As Long
    Dim size2 As Long
    size1 = FileLen(file1)
    size2 = FileLen(file2)
    If size1 < size2 Then
        CompareFileSizes = -1
    ElseIf size1 > size2 Then
        CompareFileSizes = 1
    Else
        CompareFileSizes = 0
    End If
    Exit Function
ErrorHandler:
    CompareFileSizes = 0
End Function

Advanced Usage

Disk Usage Report

Type DirectoryStats
    Path As String
    FileCount As Long
    TotalSize As Long
    LargestFile As String
    LargestSize As Long
    SmallestFile As String
    SmallestSize As Long
    AverageSize As Long
End Type
Function AnalyzeDirectory(folderPath As String) As DirectoryStats
    Dim stats As DirectoryStats
    Dim fileName As String
    Dim fullPath As String
    Dim fileSize As Long
    If Right(folderPath, 1) <> "\" Then
        folderPath = folderPath & "\"
    End If
    stats.Path = folderPath
    stats.FileCount = 0
    stats.TotalSize = 0
    stats.LargestSize = 0
    stats.SmallestSize = 2147483647  ' Max Long
    fileName = Dir(folderPath & "*.*")
    Do While fileName <> ""
        fullPath = folderPath & fileName
        On Error Resume Next
        fileSize = FileLen(fullPath)
        If Err.Number = 0 Then
            stats.FileCount = stats.FileCount + 1
            stats.TotalSize = stats.TotalSize + fileSize
            If fileSize > stats.LargestSize Then
                stats.LargestSize = fileSize
                stats.LargestFile = fileName
            End If
            If fileSize < stats.SmallestSize Then
                stats.SmallestSize = fileSize
                stats.SmallestFile = fileName
            End If
        End If
        Err.Clear
        fileName = Dir
    Loop
    If stats.FileCount > 0 Then
        stats.AverageSize = stats.TotalSize / stats.FileCount
    End If
    AnalyzeDirectory = stats
End Function

Sort Files by Size

Type FileSizeInfo
    Name As String
    Size As Long
End Type
Function GetFilesSortedBySize(folderPath As String) As Variant
    Dim files() As FileSizeInfo
    Dim fileName As String
    Dim fullPath As String
    Dim count As Long
    Dim i As Long, j As Long
    Dim temp As FileSizeInfo
    If Right(folderPath, 1) <> "\" Then
        folderPath = folderPath & "\"
    End If
    ReDim files(0 To 100)
    count = 0
    fileName = Dir(folderPath & "*.*")
    Do While fileName <> ""
        fullPath = folderPath & fileName
        On Error Resume Next
        files(count).Name = fileName
        files(count).Size = FileLen(fullPath)
        If Err.Number = 0 Then
            count = count + 1
            If count > UBound(files) Then
                ReDim Preserve files(0 To UBound(files) + 100)
            End If
        End If
        Err.Clear
        fileName = Dir
    Loop
    If count > 0 Then
        ReDim Preserve files(0 To count - 1)
        ' Bubble sort by size (largest first)
        For i = 0 To count - 2
            For j = i + 1 To count - 1
                If files(j).Size > files(i).Size Then
                    temp = files(i)
                    files(i) = files(j)
                    files(j) = temp
                End If
            Next j
        Next i
    End If
    GetFilesSortedBySize = files
End Function

File Size Distribution

Type SizeDistribution
    Range As String
    Count As Long
    TotalSize As Long
End Type
Function GetSizeDistribution(folderPath As String) As Variant
    Dim dist(0 To 5) As SizeDistribution
    Dim fileName As String
    Dim fullPath As String
    Dim fileSize As Long
    ' Define ranges
    dist(0).Range = "< 1 KB"
    dist(1).Range = "1 KB - 100 KB"
    dist(2).Range = "100 KB - 1 MB"
    dist(3).Range = "1 MB - 10 MB"
    dist(4).Range = "10 MB - 100 MB"
    dist(5).Range = "> 100 MB"
    If Right(folderPath, 1) <> "\" Then
        folderPath = folderPath & "\"
    End If
    fileName = Dir(folderPath & "*.*")
    Do While fileName <> ""
        fullPath = folderPath & fileName
        On Error Resume Next
        fileSize = FileLen(fullPath)
        If Err.Number = 0 Then
            If fileSize < 1024 Then
                dist(0).Count = dist(0).Count + 1
                dist(0).TotalSize = dist(0).TotalSize + fileSize
            ElseIf fileSize < 102400 Then
                dist(1).Count = dist(1).Count + 1
                dist(1).TotalSize = dist(1).TotalSize + fileSize
            ElseIf fileSize < 1048576 Then
                dist(2).Count = dist(2).Count + 1
                dist(2).TotalSize = dist(2).TotalSize + fileSize
            ElseIf fileSize < 10485760 Then
                dist(3).Count = dist(3).Count + 1
                dist(3).TotalSize = dist(3).TotalSize + fileSize
            ElseIf fileSize < 104857600 Then
                dist(4).Count = dist(4).Count + 1
                dist(4).TotalSize = dist(4).TotalSize + fileSize
            Else
                dist(5).Count = dist(5).Count + 1
                dist(5).TotalSize = dist(5).TotalSize + fileSize
            End If
        End If
        Err.Clear
        fileName = Dir
    Loop
    GetSizeDistribution = dist
End Function

Quota Management

Function CheckQuota(userFolder As String, quotaLimit As Long) As Boolean
    Dim totalSize As Long
    Dim fileName As String
    Dim fullPath As String
    Dim fileSize As Long
    If Right(userFolder, 1) <> "\" Then
        userFolder = userFolder & "\"
    End If
    totalSize = 0
    fileName = Dir(userFolder & "*.*")
    Do While fileName <> ""
        fullPath = userFolder & fileName
        On Error Resume Next
        fileSize = FileLen(fullPath)
        If Err.Number = 0 Then
            totalSize = totalSize + fileSize
        End If
        Err.Clear
        fileName = Dir
    Loop
    If totalSize > quotaLimit Then
        MsgBox "Quota exceeded!" & vbCrLf & _
               "Used: " & FormatFileSize(totalSize) & vbCrLf & _
               "Limit: " & FormatFileSize(quotaLimit), vbExclamation
        CheckQuota = False
    Else
        CheckQuota = True
    End If
End Function

Duplicate File Finder (by size)

Function FindPotentialDuplicates(folderPath As String) As Collection
    ' Files with same size are potential duplicates
    Dim sizeMap As New Collection
    Dim duplicates As New Collection
    Dim fileName As String
    Dim fullPath As String
    Dim fileSize As Long
    Dim sizeKey As String
    If Right(folderPath, 1) <> "\" Then
        folderPath = folderPath & "\"
    End If
    fileName = Dir(folderPath & "*.*")
    Do While fileName <> ""
        fullPath = folderPath & fileName
        On Error Resume Next
        fileSize = FileLen(fullPath)
        If Err.Number = 0 Then
            sizeKey = CStr(fileSize)
            ' Try to add to collection
            Err.Clear
            sizeMap.Add fullPath, sizeKey
            If Err.Number <> 0 Then
                ' Duplicate size found
                duplicates.Add fullPath
            End If
        End If
        Err.Clear
        fileName = Dir
    Loop
    Set FindPotentialDuplicates = duplicates
End Function

Error Handling

Function SafeFileLen(filePath As String) As Long
    On Error GoTo ErrorHandler
    SafeFileLen = FileLen(filePath)
    Exit Function
ErrorHandler:
    Select Case Err.Number
        Case 53  ' File not found
            Debug.Print "File not found: " & filePath
            SafeFileLen = -1
        Case 76  ' Path not found
            Debug.Print "Path not found: " & filePath
            SafeFileLen = -1
        Case Else
            Debug.Print "Error " & Err.Number & ": " & Err.Description
            SafeFileLen = -1
    End Select
End Function

Common Errors

• Error 53 (File not found): The specified file does not exist
• Error 76 (Path not found): The specified path is invalid
• Error 6 (Overflow): File larger than 2GB (Long limit exceeded)

Performance Considerations

• FileLen is very fast (reads file metadata only)
• Does not open the file or read contents
• Much faster than opening file to determine size
• Performance depends on file system and disk speed
• Network paths are slower than local paths
• Consider caching results if checking same file repeatedly

Best Practices

Check File Existence First

' Good - Check existence to avoid error
If Dir(filePath) <> "" Then
    fileSize = FileLen(filePath)
Else
    MsgBox "File not found"
End If
' Or use error handling
On Error Resume Next
fileSize = FileLen(filePath)
If Err.Number <> 0 Then
    MsgBox "Cannot get file size"
End If
On Error GoTo 0

Format for Display

' Good - Format sizes for readability
Dim size As Long
size = FileLen(filePath)
MsgBox "File size: " & FormatFileSize(size)
' Bad - Raw bytes for large files
MsgBox "File size: " & FileLen(filePath) & " bytes"

Comparison with Other Functions

FileLen vs LOF

' FileLen - For closed files, returns current size
fileSize = FileLen("C:\data.txt")
' LOF - For open files only, returns current size
Open "C:\data.txt" For Input As #1
fileSize = LOF(1)
Close #1

FileLen vs FileSystemObject.GetFile.Size

' FileLen - Built-in VB6 function
fileSize = FileLen("C:\data.txt")
' FSO - Requires reference to Scripting Runtime
Dim fso As Object
Set fso = CreateObject("Scripting.FileSystemObject")
fileSize = fso.GetFile("C:\data.txt").Size

Limitations

• Maximum file size: 2,147,483,647 bytes (2GB - 1) due to Long type
• For files > 2GB, use FileSystemObject or API calls
• File must exist (cannot get size of non-existent files)
• Cannot get size of directories
• Returns size before opening for open files
• No built-in wildcard support (must use with Dir)

Related Functions

• LOF: Returns length of open file
• Dir: Returns file names matching a pattern
• FileDateTime: Returns file modification date/time
• GetAttr: Returns file attributes
• FreeFile: Returns next available file number
• Open: Opens a file for reading or writing