Manipulate/copy .CSV data, without opening the file? - optimization

Question

I'm trying to optimize some code that takes some test data stored in CSV files does some analysis and copies their data into an excel sheet. This code is often run on hundreds of tests at a time, and its taking about 4.5 seconds per test so it can take hours to complete at times.
I looked up some optimization techniques and cut it down by about .25 seconds per test but I think the bulk of the time is being taken up by excel having to "open" the individual files before it can do anything with them. Is there a way to do this more efficiently?
I am open to answers that involve using another language to compile the files into one big file if that would make things quicker.

Answer 1

I would open them as text rather than workbooks:
Sub ReadCSV()
Dim MyString As String
Open "C:\path\text.csv" For Input As #1 ' Open file for input.
Do While Not EOF(1) ' Loop until end of file.
Line Input #1, MyString ' Read a line into variable
Debug.Print MyString ' Print data to the Immediate window.
Loop
Close #1 ' Close file.
End Sub
This will be much faster than opening as a workbook

Answer 2

I have this function working greate handling lot of CSV files. You need to indicate in cell "D11" the name of folder containing all the CSV files and will combine them into one single file. I handle over 200 files and make it quick. Hope it helps.
Sub CombineAllFilesInADirectory()
Dim Path As String 'string variable to hold the path to look through
Dim FileName As String 'temporary filename string variable
Dim tWB As Workbook 'temporary workbook (each in directory)
Dim tWS As Worksheet 'temporary worksheet variable
Dim aWS As Worksheet 'active sheet in master workbook
Dim RowCount As Long 'Rows used on master sheet
Dim uRange As Range 'usedrange for each temporary sheet
Dim mWB_comb As Workbook 'master workbook exclusivo de esta funcion
Path = Sheets("CombineFiles").Range("D11").Value
Application.EnableEvents = False 'turn off events
Application.ScreenUpdating = False 'turn off screen updating
Set mWB_comb = Workbooks.Add(1) 'create a new one-worksheet workbook
Set aWS = mWB_comb.ActiveSheet 'set active sheet variable to only sheet in mWB
If Right(Path, 1) <> Application.PathSeparator Then 'if path doesnt end in "\"
Path = Path & Application.PathSeparator 'add "\"
End If
FileName = Dir(Path & "*.csv", vbNormal) 'set first file's name to filename variable
Application.StatusBar = "reading files, please wait."
Do Until FileName = "" 'loop until all files have been parsed
If Path <> ThisWorkbook.Path Or FileName <> ThisWorkbook.Name Then
Set tWB = Workbooks.Open(FileName:=Path & FileName) 'open file, set to tWB variable
For Each tWS In tWB.Worksheets 'loop through each sheet
Set uRange = tWS.Range("A4", tWS.Cells(tWS.UsedRange.Row + tWS.UsedRange.Rows.count - 1, _
tWS.UsedRange.Column + tWS.UsedRange.Columns.count - 1)) 'set used range
If RowCount + uRange.Rows.count > 65536 Then 'if the used range wont fit on the sheet
aWS.Columns.AutoFit 'autofit mostly-used worksheet's columns
Set aWS = mWB_comb.Sheets.Add(After:=aWS) 'add a new sheet that will accommodate data
RowCount = 0 'reset RowCount variable
End If
If RowCount = 0 Then 'if working with a new sheet
aWS.Range("A1", aWS.Cells(3, uRange.Columns.count)).Value = tWS.Range("A1", _
tWS.Cells(3, uRange.Columns.count)).Value 'copy headers from tWS
RowCount = 3 'add one to rowcount
End If
aWS.Range("A" & RowCount + 1).Resize(uRange.Rows.count, _
uRange.Columns.count).Value = uRange.Value 'move data from temp sheet to data sheet
RowCount = RowCount + uRange.Rows.count 'increase rowcount accordingly
Next 'tWS
tWB.Close False 'close temporary workbook without saving
End If
FileName = Dir() 'set next file's name to FileName variable
Loop
Application.StatusBar = "Ready"
mWB_comb.Sheets(1).Select 'select first data sheet on master workbook
Application.EnableEvents = True 're-enable events
Application.ScreenUpdating = True 'turn screen updating back on
'Clear memory of the object variables
Set tWB = Nothing
Set tWS = Nothing
Set mWB_comb = Nothing
Set aWS = Nothing
Set uRange = Nothing
End Sub