Find the line & edit it

Question

I posted another one on this,, but i had to edit it really much...

What the thing bassicly is that a Batch (Maybe including VBScript) can find line 29 in a txtfile... it should edit this line.

If line 29 is like this: 'option=21' it should change it to 'option=22'

the problem is that this line is located more in the file. so it should just edit line 29...

How-to???

[please no custom programs;;; it should be done by every user without installing something OK.]

Answer 1

This isn't something you're usually doing in batch, but it's fairly straightforward:

@echo off
setlocal enableextensions enabledelayedexpansion

rem the input file
set inputfile=file.txt

rem temporary file for output, we can't just write into the
rem same file we're reading
set tempfile=%random%-%random%.tmp

rem delete the temporary file if it's already there
rem shouldn't really happen, but just in case ...
copy /y nul %tempfile%

rem line counter
set line=0

rem loop through the file
for /f "delims=" %%l in (%inputfile%) do (
    set /a line+=1
    if !line!==29 (
        rem hardcoded, at the moment, you might want to look
        rem here whether the line really starts with "options"
        rem and just put another number at the end.
        echo option=22>>%tempfile%
    ) else (
        echo %%l>>%tempfile%
    )
)

del %inputfile%
ren %tempfile% %inputfile%

endlocal

It should point you into the general direction if you want to adapt it.