Extract line below Findstr criteria in Batch file for cycle

Question

I'm trying to extract from a set of txt files the line placed 2 rows below the one matching search criteria and redirect output to a csv file.

I managed to do that for a specific txt file in the set, but I'm getting troubles in writing the For Cycle to batch-scan each txt in a given folder.

Through this, I wrote the following code to scan a specific file. It works fine:

setlocal EnableDelayedExpansion
cd "myFolder"
if exist myOutput.csv del myOutput.csv

for /F "delims=:" %%A in ('findstr /B /N /C:"myCriteria" "myFile.txt"') do (
set /A LineBelow=%%A+2
set "LineBelow=!LineBelow!: "
)
(for /F "tokens=1* delims=:" %%A in ('findstr /N "^" "myFile.txt" ^| findstr /B "%LineBelow%"') do ^
echo %%B>>myOutput.csv)

start myOutput.csv

ENDLOCAL

When I tried to generalize the code in a For Cycle to scan each txt in myFolder I got an error in Findstr: !LineBelow! happens to be an empty variable...

Here's the flawed For Cycle:

setlocal EnableDelayedExpansion
cd "myFolder"
if exist myOutput.csv del myOutput.csv

for %%F IN ("*.txt") do (
(
for /F "delims=:" %%A in ('findstr /B /N /C:"myCriteria" "%%F"') do (
set /A LineBelow=%%A+2
set "LineBelow=!LineBelow!: "
))
(for /F "tokens=1* delims=:" %%A in ('findstr /N "^" "%%F" ^| findstr /B "!LineBelow!"') do ^
echo %%B>>myOutput.csv))

start myOutput.csv

ENDLOCAL

Could anybody help me in correcting this code? Thanks

Answer 1

@echo off
    setlocal enableextensions enabledelayedexpansion

    cd "myFolder"

    > myOutput.csv (
        for /f "tokens=1,2 delims=:" %%a in ('
            findstr  /b /n /c:"myCriteria" *.txt
        ') do (
            set /a "line=%%b+2"
            for /f "tokens=1,* delims=:" %%c in ('
                findstr /n "^" "%%a" ^| findstr /b /c:"!line!:" 2^>nul
            ') do echo(%%d
        )
    )

This uses findstr to directly enumerate all the lines matching the myCriteria and include in the output the name of the file (%%a) and the number of the line (%%b). This information is used to retrieve the final line (%%d) from the matching files.