Existence detection

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{{noref|date=February 2023}}

{{Notability|date=September 2024}}

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Existence checking or existence detection is an important aspect of many computer programs. An existence check before reading a file can catch and/or prevent a fatal error, for instance. For that reason, most programming language libraries contain a means of checking whether a file exists.

An existence check can sometimes involve a "brute force" approach of checking all records for a given identifier, as in this Microsoft Excel Visual Basic for Applications code for detecting whether a worksheet exists:

Function SheetExists(sheetName As String) As Boolean

Dim sheetCount As Integer

Dim t As Integer

SheetExists = False

sheetCount = ActiveWorkbook.Sheets.Count

For t = 1 To sheetCount

If Sheets(t).Name = sheetName Then

SheetExists = True

Exit Function

End If

Next t

End Function