`Trim$` Function

The Trim$ function in Visual Basic 6 returns a string with both leading and trailing spaces removed. The dollar sign ($) suffix indicates that this function always returns a String type, never a Variant.

Syntax

Trim$(string)

Parameters

string - Required. Any valid string expression. If string contains Null, Null is returned.

Return Value

Returns a String with all leading and trailing space characters (ASCII 32) removed from string.

Behavior and Characteristics

Space Removal

Removes both leading (left-side) and trailing (right-side) spaces
Only removes space characters (ASCII character 32)
Does not remove tabs, newlines, or other whitespace characters
If the string contains only spaces, returns an empty string ("")
Preserves spaces in the middle of the string

Type Differences: `Trim$` vs `Trim`

Trim$: Always returns String type (never Variant)
Trim: Returns Variant (can propagate Null values)
Use Trim$ when you need guaranteed String return type
Use Trim when working with potentially Null values

Common Usage Patterns

1. Clean User Input

Function CleanInput(userInput As String) As String
CleanInput = Trim$(userInput)
End Function

Dim cleaned As String
cleaned = CleanInput("  Hello World  ")  ' Returns "Hello World"

2. Process Text File Lines

Function ReadCleanLine(fileNum As Integer) As String
Dim rawLine As String
Line Input #fileNum, rawLine
ReadCleanLine = Trim$(rawLine)
End Function

3. Validate Non-Empty Input

Function IsValidInput(input As String) As Boolean
IsValidInput = (Len(Trim$(input)) > 0)
End Function

If IsValidInput(txtName.Text) Then
' Process the input
Else
MsgBox "Please enter a value"
End If

4. String Comparison

Function CompareValues(value1 As String, value2 As String) As Boolean
' Compare strings ignoring leading/trailing spaces
CompareValues = (Trim$(value1) = Trim$(value2))
End Function

5. Database Field Cleaning

Function GetFieldValue(rs As Recordset, fieldName As String) As String
If Not IsNull(rs.Fields(fieldName).Value) Then
GetFieldValue = Trim$(rs.Fields(fieldName).Value & "")
Else
GetFieldValue = ""
End If
End Function

6. Configuration File Parsing

Function ParseConfigLine(configLine As String) As String
Dim equalPos As Integer
equalPos = InStr(configLine, "=")
If equalPos > 0 Then
ParseConfigLine = Trim$(Mid$(configLine, equalPos + 1))
Else
ParseConfigLine = ""
End If
End Function

7. Clean Array Elements

Sub CleanStringArray(arr() As String)
Dim i As Integer
For i = LBound(arr) To UBound(arr)
arr(i) = Trim$(arr(i))
Next i
End Sub

8. Form Input Processing

Sub ProcessForm()
Dim userName As String
Dim userEmail As String

userName = Trim$(txtName.Text)
userEmail = Trim$(txtEmail.Text)

If Len(userName) > 0 And Len(userEmail) > 0 Then
SaveUserData userName, userEmail
End If
End Sub

9. CSV Field Processing

Function ParseCSVField(field As String) As String
' Remove quotes and trim spaces
Dim cleaned As String
cleaned = field
If Left$(cleaned, 1) = """" Then cleaned = Mid$(cleaned, 2)
If Right$(cleaned, 1) = """" Then cleaned = Left$(cleaned, Len(cleaned) - 1)
ParseCSVField = Trim$(cleaned)
End Function

10. Search Query Preparation

Function PrepareSearchQuery(query As String) As String
Dim cleaned As String
cleaned = Trim$(query)
' Remove multiple spaces
While InStr(cleaned, "  ") > 0
cleaned = Replace$(cleaned, "  ", " ")
Wend
PrepareSearchQuery = cleaned
End Function

Trim() - Returns a Variant with leading and trailing spaces removed (can handle Null)
LTrim$() - Removes only leading (left-side) spaces from a string
RTrim$() - Removes only trailing (right-side) spaces from a string
Left$() - Returns a specified number of characters from the left side
Right$() - Returns a specified number of characters from the right side
Len() - Returns the length of a string
Space$() - Creates a string consisting of the specified number of spaces

Best Practices

When to Use `Trim$` vs `LTrim$` vs `RTrim$`

Dim text As String
text = "  Hello  "

Debug.Print Trim$(text)   ' "Hello" (both sides trimmed)
Debug.Print LTrim$(text)  ' "Hello  " (left side only)
Debug.Print RTrim$(text)  ' "  Hello" (right side only)

Use for User Input Validation

Function ValidateInput(input As String) As Boolean
' Check if input is meaningful after trimming
Dim cleaned As String
cleaned = Trim$(input)

If Len(cleaned) = 0 Then
MsgBox "Input cannot be empty or only spaces"
ValidateInput = False
Else
ValidateInput = True
End If
End Function

Combine with Other String Functions

Function NormalizeText(text As String) As String
Dim result As String
result = Trim$(text)
result = UCase$(result)  ' Convert to uppercase
NormalizeText = result
End Function

Handle Null Values Safely

Function SafeTrim(value As Variant) As String
If IsNull(value) Then
SafeTrim = ""
Else
SafeTrim = Trim$(CStr(value))
End If
End Function

Performance Considerations

Trim$ is very efficient and lightweight
Performs a single pass from both ends of the string
More efficient than calling LTrim$ and RTrim$ separately
No performance penalty for strings without leading/trailing spaces

' Efficient: single Trim$ call
Dim cleaned As String
cleaned = Trim$(input)

' Less efficient: two function calls
cleaned = LTrim$(RTrim$(input))

' Use Trim$ instead of the above

Common Pitfalls

1. Only Removes Spaces (ASCII 32)

Dim text As String
text = vbTab & "Hello" & vbTab  ' Tabs at both ends

' Trim$ does NOT remove tabs
Debug.Print Trim$(text)  ' Still has tabs!

' To remove all whitespace, use custom function
Function TrimAllWhitespace(s As String) As String
Dim i As Integer, j As Integer

' Trim from left
For i = 1 To Len(s)
Select Case Mid$(s, i, 1)
Case " ", vbTab, vbCr, vbLf
' Continue
Case Else
Exit For
End Select
Next i

' Trim from right
For j = Len(s) To 1 Step -1
Select Case Mid$(s, j, 1)
Case " ", vbTab, vbCr, vbLf
' Continue
Case Else
Exit For
End Select
Next j

If i <= j Then
TrimAllWhitespace = Mid$(s, i, j - i + 1)
Else
TrimAllWhitespace = ""
End If
End Function

2. Null Value Handling

' Trim$ with Null causes runtime error
Dim result As String
result = Trim$(nullValue)  ' ERROR if nullValue is Null

' Protect against Null
If Not IsNull(value) Then
result = Trim$(value)
Else
result = ""
End If

3. Empty String vs Spaces-Only String

Dim input As String
input = "     "  ' Only spaces

' Trim$ returns empty string
Debug.Print Len(Trim$(input))  ' 0

' Check for meaningful content
If Len(Trim$(input)) = 0 Then
Debug.Print "No content"
End If

4. Database Field Assumptions

' Wrong: not handling Null
value = Trim$(rs!TextField)  ' May error if field is Null

' Better: handle Null explicitly
If IsNull(rs!TextField) Then
value = ""
Else
value = Trim$(rs!TextField & "")
End If

5. Case Sensitivity

' Trim$ does not change case
Debug.Print Trim$("  HELLO  ")  ' "HELLO" (not "hello")

' Combine with case conversion if needed
Debug.Print UCase$(Trim$("  hello  "))  ' "HELLO"
Debug.Print LCase$(Trim$("  HELLO  "))  ' "hello"

6. Non-Breaking Spaces

' Trim$ only removes regular spaces (ASCII 32)
' Non-breaking spaces (Chr$(160)) are NOT removed
Dim text As String
text = Chr$(160) & "Hello" & Chr$(160)
Debug.Print Trim$(text)  ' Still has Chr$(160) at both ends

Practical Examples

Processing INI File Values

Function GetINIValue(section As String, key As String, fileName As String) As String
Dim fileNum As Integer
Dim currentLine As String
Dim inSection As Boolean
Dim equalPos As Integer
Dim lineKey As String

fileNum = FreeFile
Open fileName For Input As #fileNum

While Not EOF(fileNum)
Line Input #fileNum, currentLine
currentLine = Trim$(currentLine)

If currentLine = "[" & section & "]" Then
inSection = True
ElseIf Left$(currentLine, 1) = "[" Then
inSection = False
ElseIf inSection Then
equalPos = InStr(currentLine, "=")
If equalPos > 0 Then
lineKey = Trim$(Left$(currentLine, equalPos - 1))
If lineKey = key Then
GetINIValue = Trim$(Mid$(currentLine, equalPos + 1))
Close #fileNum
Exit Function
End If
End If
End If
Wend

Close #fileNum
GetINIValue = ""
End Function

Form Validation

Function ValidateForm() As Boolean
Dim errors As String

If Len(Trim$(txtName.Text)) = 0 Then
errors = errors & "Name is required" & vbCrLf
End If

If Len(Trim$(txtEmail.Text)) = 0 Then
errors = errors & "Email is required" & vbCrLf
End If

If Len(errors) > 0 Then
MsgBox errors, vbExclamation
ValidateForm = False
Else
ValidateForm = True
End If
End Function

Clean Data Import

Sub ImportCSVData(fileName As String)
Dim fileNum As Integer
Dim currentLine As String
Dim fields() As String
Dim i As Integer

fileNum = FreeFile
Open fileName For Input As #fileNum

While Not EOF(fileNum)
Line Input #fileNum, currentLine
fields = Split(currentLine, ",")

' Clean all fields
For i = LBound(fields) To UBound(fields)
fields(i) = Trim$(fields(i))
Next i

' Process cleaned fields
ProcessRecord fields
Wend

Close #fileNum
End Sub

Limitations

Only removes space characters (ASCII 32), not other whitespace
Cannot handle Null values (use Trim variant function instead)
Does not remove non-breaking spaces (character 160) or Unicode whitespace
No option to specify custom characters to remove
Works with strings only, not byte arrays
Does not change character case (use with UCase$ or LCase$ if needed)

Trim$ Function