Read file without opening and delete it - vba

Question

I'm trying to figure out a way to read the first line of text in a .txt through excel VBA without opening the file, something I've been having trouble finding since all the examples I've seen involve opening the .txt one way or another.
Aside from this, I was wondering if there was any way for me to get the VBA code to delete the mentioned .txt a set time after excel has been closed... which I'm not too sure is even remotely possible (with VBA at least).
EDIT:
The simplified code goes like this:
Option Explicit
Public g_strVar As String
Sub Test_Proc()
Dim row as Long
row = 2
Do While Cells(row, 1) <> ""
Cells(row, 2) = ImportVariable(Cells(row, 1))
row = row + 1
Loop
End Sub
Function ImportVariable(strFile As String) As String
Open strFile For Input As #1
Line Input #1, ImportVariable
Close #1
End Function
Column 1 contains the locations of each and every .txt file, and on the column next to it I have to detail what is the first line of text on each file. Problem is that the list has been in a couple occasions about 10K long, and the only place I can think of from where I can improve on the time this takes to execute is in the "Open / Close" since some of these .txt files are 12.000 KB in size and take a bit to open.

Answer 1

This might be faster than opening each file (reads first line from a 18.5 Mb file in 0.1953125 sec)
Option Explicit
Dim cmdLine As Object
Sub Test_Proc()
Dim i As Long, minRow As Long, maxRow As Long, rng1 As Range, rng2 As Range
Dim t As Double, ws As Worksheet, x As Variant, col1 As Variant, col2 As Variant
Set ws = ThisWorkbook.Worksheets(1)
minRow = 2
With ws
.Columns(2).Delete
maxRow = .UsedRange.Rows.Count
Set rng1 = .Range("A1:A" & maxRow)
Set rng2 = .Range("B1:B" & maxRow)
End With
col1 = rng1.Value2: col2 = rng2.Value2
Set cmdLine = CreateObject("WScript.Shell")
Application.ScreenUpdating = False
t = Timer
For i = minRow To maxRow
If Len(col1(i, 1)) > 0 Then
ws.Cells(i, 2).Value2 = Replace(ImportLine(col1(i, 1)), vbCrLf, vbNullString)
End If
Next
'rng2.Value2 = col2
Application.ScreenUpdating = True
InputBox "Duration: ", "Duration", Timer - t '18.5 Mb file in 0.1953125 sec
End Sub
Function ImportLine(ByVal strFile As String) As String
ImportLine = Replace(cmdLine.Exec( _
"%comspec% /C FindStr /N . " & strFile & " | FindStr ^1:" _
).STDOut.ReadAll, "1:", vbNullString)
End Function
A bit nested but it does the following:
CMD /C - opens a command line window, then closes it when completed
FindStr /N . C:\test.txt - Find any character, and output the line with line number in format "1:"
| FindStr ^1: - redirect to another FindStr that uses regex to find "1:" at start of line
When the command line is completed, return the output to the Replace function
Replace removes "1:" and returns the string
If your files might contain the string "1:" somewhere else within the first line
we can use the Right() function: return Right(output, Len(output)-2)
or we can use a different command line that numbers the lines with "[1]":
Find /N " " C:\test.txt | Find "[1]"