How can I use VBScript to insert a line into a text file?

A. VBScript has no built-in functionality that lets you insert a line into a file. The simplest way to do that is to open the file you want to insert a line into, write the file line by line to a new file, and insert the new line where you want it. I wrote the following script, which you can download at http://www.windowsitpro.com/content/content/47437/insertfile.zip, to insert a line into a sysprep.inf file in the \[Unattended\] section. (Some lines wrap because of space constraints.)

Option Explicit

Dim strFileSourcePath, strFileTargetPath, objFSOSource, objFSOTarget, fso, objFilesSource, objFilesTarget, strCurrentLine

Const ForReading = 1, ForWriting = 2

strFileSourcePath = "C:\sysprep\sysprep.inf"
strFileTargetPath = "C:\sysprep\sysprep.new"

Set objFSOSource = CreateObject("scripting.filesystemobject")
Set objFSOTarget = CreateObject("scripting.filesystemobject")

Set objFilesSource = objFSOSource.OpenTextFile(strFileSourcePath,ForReading,True,0) 
Set objFilesTarget = objFSOSource.OpenTextFile(strFileTargetPath,ForWriting,True,0) 
Set fso = CreateObject("Scripting.FileSystemObject")

Do While objFilesSource.AtEndOfStream  True
  strCurrentLine = objFilesSource.ReadLine

  if StrComp(Left(strCurrentLine,12),"\[Unattended\]") = 0 then
    objFilesTarget.WriteLine strCurrentLine
    objFilesTarget.WriteLine "OemPnPDriversPath = xpdrivers\network; xpdrivers\storage; xpdrivers\Video"
  else
    objFilesTarget.WriteLine strCurrentLine
  end if

Loop

objFilesSource.Close
objFilesTarget.Close

Set objFSOSource = Nothing
Set objFSOTarget = Nothing

fso.MoveFile "C:\sysprep\sysprep.inf", "C:\sysprep\sysprep.old"
fso.MoveFile "C:\sysprep\sysprep.new", "C:\sysprep\sysprep.inf"

Set fso = Nothing
 

The script reads each line from the existing sysprep.inf and writes it to sysprep.new. It checks the first 12 characters of each line looking for the characters "\[Unattended\]" (not including quotation marks\}. When the script finds a line in which the first 12 characters are "\[Unattended\]", it writes the current line, then writes the new content (in my case a OemPnPDriversPath entry). At the end of the execution, the script renames the existing file with an .old file extension (i.e., sysprep.old) and renames the newly created file with an .inf file extension (i.e., sysprep.inf).