wtuldn

@echo off
setlocal EnableDelayedExpansion
set m=0
for /f "delims=" %%a in (千字文.txt) do (
    set x=%%a
    call :next !x: =!
)
echo 千字文共有!m!字
pause

:next
set "var=%~1"
set n=0

:loop
call set str=%%var:~!n!,1%%
if "%str%"=="" goto :eof
set /a n+=1,m+=1
goto loop

wtuldn

第二题、第三题、第一题：
@echo off
setlocal EnableDelayedExpansion
for /f "delims=" %%a in (千字文.txt) do (
    for %%b in (%%a) do (
       set var=%%b
       for /l %%c in (0,1,3) do (
         set /a #!var:~%%c,1!+=1
        )   
     )
)
rem set #>>2.txt
  for /f "tokens=1,2 delims=#=" %%a in ('set #') do (
    if %%b gtr 1 echo 重复字：%%a 出现次数:%%b
)
echo:
echo:

for /f "tokens=1-6 delims= " %%a in (千字文.txt) do (
echo %%f
echo %%e
echo %%d
echo %%c
echo %%b
echo %%a
)
echo:
echo:
set m=0
for /f "delims=" %%a in (千字文.txt) do (
    set x=%%a
    call :next !x: =!
)
echo 千字文共有!m!字

:next
set "var=%~1"
set n=0

:loop
call set str=%%var:~!n!,1%%
if "%str%"=="" goto :eof
set /a n+=1,m+=1
goto loop

echo:
echo:

pause