中国DOS联盟

@echo off

setlocal EnableDelayedExpansion

for /f "delims=" %%a in (test.txt) do (

  set str=%%a

  if /i "!str:~,2!" equ "c=" (echo c=90>>test_new.txt) else echo %%a>>test_new.txt

)

@echo off

change a.txt /from "C=*" /to "C=90"

@echo off

sed -i "s/C=.*/C=90/g" a.txt