for loop - Extract Part of a text file in BAT -

i capturing m3u file on daily basis wish parse part of file few channels need.

for example have renamed m3u test.txt file has following fictional structure:

#extinf:0,abc   #live link 1 #extinf:0,xyz    #live link 2 #extinf:0,uvw   #live link 3 

i capture line staring "#extinf:0,xyz" , line beneath end output.txt follows:

#extinf:0,xyz    #live link 2 

i know 1 needs use loop bit of noob on area.

i this, supposing .m3u file not contain trailing white-spaces in lines preceded #extinf, sample data does:

@echo off setlocal enableextensions disabledelayedexpansion  rem // define constants here: set "file=%~1" set "header=#extm3u" set "prefix=#extinf" set "match=%~2"  set "flag=" /f usebackq^ delims^=^ eol^= %%l in ("%file%") (     if defined flag (         echo(%%l         set "flag="     )     /f "delims=:" %%p in ("%%l") (         if "%%p"=="%header%" (             echo(%%l         ) else if "%%p"=="%prefix%" (             set "line=%%l"             setlocal enabledelayedexpansion             if /i "!line:*,=!"=="!match!" (                 echo(!line!                 endlocal                 set "flag=#"             ) else endlocal         )     ) )  endlocal exit /b 

call script this, supposing saved extract-entry.bat:

extract-entry.bat "input_file.m3u" "xyz" > "output_file.m3u" 

the script walks through given .m3u file line line. returns current line unedited , resets variable flag, if variable flag set, not case @ beginning.

then looks #extinf. if found (e. g., #extinf:0,xyz), string after comma (xyz) compared against given search string. if matched, current line output , flag variable set in order following line too.

the header line #extm3u output.

toggling delayed expansion makes script robust against characters have special meaning command interpreter without losing them.