EOF Function

Returns a Boolean value indicating whether the end of a file opened for Random or sequential Input has been reached.

Syntax

EOF(filenumber)

Parameters

• filenumber: Required. An Integer containing a valid file number.

Return Value

Returns a Boolean value. Returns True when the end of a file opened for Random or Input access has been reached; otherwise, returns False.

Remarks

The EOF function is used to detect when the end of a file has been reached during sequential or random file reading operations. It's essential for controlling loops that read through files.

Important Characteristics:

• Returns True when end of file is reached
• Returns False when more data is available
• Works with files opened for Input or Random access
• Does not work with files opened for Output or Append
• Does not work with binary mode files (use LOF instead)
• File must be open before calling EOF
• Error if file number is invalid or file is closed
• Position-dependent (affected by Get, Input, Line Input)
• Can be used to prevent "Input past end of file" error

File Access Modes

• Input: Sequential text file reading - EOF returns True after last character
• Random: Random access files - EOF returns True after last record
• Binary: Not supported (use LOF and Seek instead)
• Output/Append: Not applicable (write modes)

Examples

Basic Usage

' Read text file line by line
Dim fileNum As Integer
Dim line As String

fileNum = FreeFile
Open "C:\data.txt" For Input As #fileNum

Do Until EOF(fileNum)
Line Input #fileNum, line
Debug.Print line
Loop

Close #fileNum

Read All Lines into Array

Function ReadAllLines(filePath As String) As Variant
Dim fileNum As Integer
Dim lines() As String
Dim line As String
Dim count As Long

fileNum = FreeFile
Open filePath For Input As #fileNum

count = 0
ReDim lines(0 To 100)

Do Until EOF(fileNum)
Line Input #fileNum, line
lines(count) = line
count = count + 1

If count > UBound(lines) Then
ReDim Preserve lines(0 To UBound(lines) + 100)
End If
Loop

Close #fileNum

If count > 0 Then
ReDim Preserve lines(0 To count - 1)
ReadAllLines = lines
Else
ReadAllLines = Array()
End If
End Function

Random Access File

Type CustomerRecord
ID As Long
Name As String * 50
Balance As Double
End Type

Sub ReadAllCustomers()
Dim fileNum As Integer
Dim customer As CustomerRecord

fileNum = FreeFile
Open "customers.dat" For Random As #fileNum Len = Len(customer)

Do Until EOF(fileNum)
Get #fileNum, , customer
Debug.Print customer.ID, customer.Name, customer.Balance
Loop

Close #fileNum
End Sub

Common Patterns

Count Lines in File

Function CountLines(filePath As String) As Long
Dim fileNum As Integer
Dim line As String
Dim count As Long

fileNum = FreeFile
Open filePath For Input As #fileNum

count = 0
Do Until EOF(fileNum)
Line Input #fileNum, line
count = count + 1
Loop

Close #fileNum
CountLines = count
End Function

Search File for Text

Function FindInFile(filePath As String, searchText As String) As Boolean
Dim fileNum As Integer
Dim line As String

fileNum = FreeFile
Open filePath For Input As #fileNum

FindInFile = False
Do Until EOF(fileNum)
Line Input #fileNum, line
If InStr(1, line, searchText, vbTextCompare) > 0 Then
FindInFile = True
Exit Do
End If
Loop

Close #fileNum
End Function

Read CSV File

Function ReadCSV(filePath As String) As Variant
Dim fileNum As Integer
Dim line As String
Dim rows() As Variant
Dim rowCount As Long

fileNum = FreeFile
Open filePath For Input As #fileNum

rowCount = 0
ReDim rows(0 To 100)

Do Until EOF(fileNum)
Line Input #fileNum, line
rows(rowCount) = Split(line, ",")
rowCount = rowCount + 1

If rowCount > UBound(rows) Then
ReDim Preserve rows(0 To UBound(rows) + 100)
End If
Loop

Close #fileNum

If rowCount > 0 Then
ReDim Preserve rows(0 To rowCount - 1)
ReadCSV = rows
Else
ReadCSV = Array()
End If
End Function

Process File with Progress

Sub ProcessFileWithProgress(filePath As String)
Dim fileNum As Integer
Dim line As String
Dim lineCount As Long
Dim processedCount As Long

' Count total lines first
lineCount = CountLines(filePath)

fileNum = FreeFile
Open filePath For Input As #fileNum

processedCount = 0
Do Until EOF(fileNum)
Line Input #fileNum, line
ProcessLine line
processedCount = processedCount + 1

' Update progress
If processedCount Mod 100 = 0 Then
lblProgress.Caption = processedCount & " of " & lineCount
DoEvents
End If
Loop

Close #fileNum
End Sub

Read Until Marker

Function ReadUntilMarker(fileNum As Integer, marker As String) As String
Dim line As String
Dim content As String

content = ""
Do Until EOF(fileNum)
Line Input #fileNum, line

If line = marker Then
Exit Do
End If

content = content & line & vbCrLf
Loop

ReadUntilMarker = content
End Function

Skip Header Lines

Sub ProcessDataFile(filePath As String, headerLines As Integer)
Dim fileNum As Integer
Dim line As String
Dim i As Integer

fileNum = FreeFile
Open filePath For Input As #fileNum

' Skip header lines
For i = 1 To headerLines
If Not EOF(fileNum) Then
Line Input #fileNum, line
End If
Next i

' Process remaining data
Do Until EOF(fileNum)
Line Input #fileNum, line
ProcessDataLine line
Loop

Close #fileNum
End Sub

Read Fixed Number of Lines

Function ReadLines(filePath As String, maxLines As Long) As Variant
Dim fileNum As Integer
Dim lines() As String
Dim line As String
Dim count As Long

fileNum = FreeFile
Open filePath For Input As #fileNum

ReDim lines(0 To maxLines - 1)
count = 0

Do Until EOF(fileNum) Or count >= maxLines
Line Input #fileNum, line
lines(count) = line
count = count + 1
Loop

Close #fileNum

If count > 0 Then
ReDim Preserve lines(0 To count - 1)
ReadLines = lines
Else
ReadLines = Array()
End If
End Function

Merge Multiple Files

Sub MergeFiles(inputFiles As Variant, outputFile As String)
Dim outNum As Integer
Dim inNum As Integer
Dim i As Integer
Dim line As String

outNum = FreeFile
Open outputFile For Output As #outNum

For i = LBound(inputFiles) To UBound(inputFiles)
inNum = FreeFile
Open inputFiles(i) For Input As #inNum

Do Until EOF(inNum)
Line Input #inNum, line
Print #outNum, line
Loop

Close #inNum
Next i

Close #outNum
End Sub

Filter File Contents

Sub FilterFile(inputFile As String, outputFile As String, filterText As String)
Dim inNum As Integer
Dim outNum As Integer
Dim line As String

inNum = FreeFile
Open inputFile For Input As #inNum

outNum = FreeFile
Open outputFile For Output As #outNum

Do Until EOF(inNum)
Line Input #inNum, line

If InStr(1, line, filterText, vbTextCompare) > 0 Then
Print #outNum, line
End If
Loop

Close #inNum
Close #outNum
End Sub

Advanced Usage

Parse Configuration File

Function ParseConfigFile(filePath As String) As Collection
Dim fileNum As Integer
Dim line As String
Dim config As New Collection
Dim equalPos As Integer
Dim key As String
Dim value As String

fileNum = FreeFile
Open filePath For Input As #fileNum

Do Until EOF(fileNum)
Line Input #fileNum, line
line = Trim(line)

' Skip empty lines and comments
If Len(line) > 0 And Left(line, 1) <> "#" Then
equalPos = InStr(line, "=")
If equalPos > 0 Then
key = Trim(Left(line, equalPos - 1))
value = Trim(Mid(line, equalPos + 1))

On Error Resume Next
config.Add value, key
On Error GoTo 0
End If
End If
Loop

Close #fileNum
Set ParseConfigFile = config
End Function

Read Log File with Timestamp Filter

Function ReadLogsSince(logFile As String, sinceDate As Date) As Variant
Dim fileNum As Integer
Dim line As String
Dim logs() As String
Dim count As Long
Dim lineDate As Date

fileNum = FreeFile
Open logFile For Input As #fileNum

count = 0
ReDim logs(0 To 100)

Do Until EOF(fileNum)
Line Input #fileNum, line

' Assuming timestamp is first 19 chars: "2025-11-21 10:30:45"
If Len(line) >= 19 Then
On Error Resume Next
lineDate = CDate(Left(line, 19))

If Err.Number = 0 And lineDate >= sinceDate Then
logs(count) = line
count = count + 1

If count > UBound(logs) Then
ReDim Preserve logs(0 To UBound(logs) + 100)
End If
End If
On Error GoTo 0
End If
Loop

Close #fileNum

If count > 0 Then
ReDim Preserve logs(0 To count - 1)
ReadLogsSince = logs
Else
ReadLogsSince = Array()
End If
End Function

Batch Process Multiple Files

Sub BatchProcessFiles(filePattern As String)
Dim fileName As String
Dim fileNum As Integer
Dim line As String
Dim processedCount As Long

fileName = Dir(filePattern)
Do While fileName <> ""
fileNum = FreeFile
Open fileName For Input As #fileNum

Do Until EOF(fileNum)
Line Input #fileNum, line
ProcessLine line
Loop

Close #fileNum
processedCount = processedCount + 1

fileName = Dir
Loop

MsgBox processedCount & " files processed"
End Sub

Read File in Chunks

Function ReadFileChunk(fileNum As Integer, chunkSize As Long) As Variant
Dim lines() As String
Dim line As String
Dim count As Long

ReDim lines(0 To chunkSize - 1)
count = 0

Do Until EOF(fileNum) Or count >= chunkSize
Line Input #fileNum, line
lines(count) = line
count = count + 1
Loop

If count > 0 Then
ReDim Preserve lines(0 To count - 1)
ReadFileChunk = lines
Else
ReadFileChunk = Array()
End If
End Function

' Usage with pagination
Sub ProcessLargeFile(filePath As String)
Dim fileNum As Integer
Dim chunk As Variant
Dim pageNum As Long

fileNum = FreeFile
Open filePath For Input As #fileNum

pageNum = 1
Do Until EOF(fileNum)
chunk = ReadFileChunk(fileNum, 1000)
ProcessChunk chunk, pageNum
pageNum = pageNum + 1
Loop

Close #fileNum
End Sub

Database Import from Text File

Sub ImportDataFromFile(filePath As String, tableName As String)
Dim fileNum As Integer
Dim line As String
Dim fields() As String
Dim sql As String
Dim recordCount As Long

fileNum = FreeFile
Open filePath For Input As #fileNum

' Skip header
If Not EOF(fileNum) Then
Line Input #fileNum, line
End If

recordCount = 0
Do Until EOF(fileNum)
Line Input #fileNum, line
fields = Split(line, vbTab)

sql = "INSERT INTO " & tableName & " VALUES ('" & _
Join(fields, "','") & "')"

' Execute SQL (pseudo-code)
ExecuteSQL sql
recordCount = recordCount + 1
Loop

Close #fileNum
MsgBox recordCount & " records imported"
End Sub

Create File Index

Type FileIndex
LineNumber As Long
FilePosition As Long
Content As String
End Type

Function BuildFileIndex(filePath As String) As Variant
Dim fileNum As Integer
Dim index() As FileIndex
Dim line As String
Dim count As Long

fileNum = FreeFile
Open filePath For Input As #fileNum

count = 0
ReDim index(0 To 100)

Do Until EOF(fileNum)
index(count).LineNumber = count + 1
index(count).FilePosition = Seek(fileNum)
Line Input #fileNum, line
index(count).Content = Left(line, 100)  ' Store first 100 chars

count = count + 1
If count > UBound(index) Then
ReDim Preserve index(0 To UBound(index) + 100)
End If
Loop

Close #fileNum

If count > 0 Then
ReDim Preserve index(0 To count - 1)
BuildFileIndex = index
Else
BuildFileIndex = Array()
End If
End Function

Error Handling

Function SafeReadFile(filePath As String) As Variant
On Error GoTo ErrorHandler

Dim fileNum As Integer
Dim lines() As String
Dim line As String
Dim count As Long

fileNum = FreeFile
Open filePath For Input As #fileNum

count = 0
ReDim lines(0 To 100)

Do Until EOF(fileNum)
Line Input #fileNum, line
lines(count) = line
count = count + 1

If count > UBound(lines) Then
ReDim Preserve lines(0 To UBound(lines) + 100)
End If
Loop

Close #fileNum

If count > 0 Then
ReDim Preserve lines(0 To count - 1)
SafeReadFile = lines
Else
SafeReadFile = Array()
End If
Exit Function

ErrorHandler:
If fileNum > 0 Then Close #fileNum
SafeReadFile = Null
End Function

Common Errors

• Error 52 (Bad file name or number): File number is invalid or file is closed
• Error 62 (Input past end of file): Attempted to read beyond EOF without checking
• Error 54 (Bad file mode): File not opened for Input or Random access

Performance Considerations

• EOF is very fast (single status check)
• No performance penalty for frequent calls
• Use Do Until EOF rather than counting lines beforehand
• For large files, consider buffered reading
• Random access files: EOF checks record position
• Sequential files: EOF checks character position

Best Practices

Always Use EOF to Control File Reading

' Good - Use EOF to detect end
Do Until EOF(fileNum)
Line Input #fileNum, line
ProcessLine line
Loop

' Bad - May cause "Input past end of file" error
Do While True
Line Input #fileNum, line  ' Error if EOF reached
ProcessLine line
Loop

Always Close Files

' Good - Always close, even on error
On Error GoTo ErrorHandler
Open filePath For Input As #fileNum
Do Until EOF(fileNum)
' Process
Loop
Close #fileNum
Exit Sub

ErrorHandler:
If fileNum > 0 Then Close #fileNum

Check EOF Before Reading

' Good - Check before reading
If Not EOF(fileNum) Then
Line Input #fileNum, line
End If

' Or use in loop condition
Do Until EOF(fileNum)
Line Input #fileNum, line
Loop

Comparison with Other Methods

EOF vs LOF

' EOF - Detects end of file for Input/Random
Do Until EOF(fileNum)
Line Input #fileNum, line
Loop

' LOF - Gets file length (useful for Binary mode)
Open file For Binary As #fileNum
fileSize = LOF(fileNum)

EOF vs Seek

' EOF - Boolean end-of-file check
isAtEnd = EOF(fileNum)

' Seek - Get/set current position
currentPos = Seek(fileNum)

Limitations

• Only works with Input and Random access modes
• Not applicable to Binary mode (use LOF and Seek)
• Not applicable to Output or Append modes
• Does not indicate how much data remains
• File must be open
• Cannot detect EOF before opening file

Related Functions

• LOF: Returns length of file in bytes
• Seek: Returns or sets current position in file
• Open: Opens file for reading/writing
• Close: Closes open file
• Line Input: Reads line from file
• Input: Reads data from file
• Get: Reads data from random/binary file
• FreeFile: Returns next available file number