::假设a.txt内容有50行。测试以下两个代码的速度
@echo off
for /f %%a in (a.txt) do (
   set var=%%a
   set /a n=2
   call echo %%var:~!n!,1%%
)
pause
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::假设a.txt内容有50行。
@echo off
for /f %%a in (a.txt) do (
   set var=%%a
   set /a n=2
   echo !var:~2,1!
)
pause
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::假设a.txt内容有50行。测试以下两个代码的速度
@echo off
for /f %%a in (a.txt) do (
   echo %%a|findstr a
)
pause
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::假设a.txt内容有50行
@echo off
for /f %%a in ('findstr "a" a.txt') do echo %%a
pause
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@echo off
::假设当前目录文件比较多。
for /f "delims=" %%a in ('dir/b/s/a-d') do (
   for /f "delims=" %%i in ('dir/b "%%a"') do (
      echo %%i
))
pause
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@echo off&setlocal enabledelayedexpansion
set "t=%time%"
for /l %%i in (1,1,10000) do (
    set "str=%%i"
    echo !str!
)
echo 开始时间%t%
echo 结束时间%time%
pause>nul
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@echo off
set "t=%time%"
for /l %%i in (1,1,10000) do (
    set "str=%%i"
    call,echo %%str%%
)
echo 开始时间%t%
echo 结束时间%time%
pause>nul
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@echo off&setlocal enabledelayedexpansion
set "t=%time%"
for /f "delims=" %%a in (a.txt) do (［
　　set /a n+=1,m=0
    for /f "delims=" %%i in (b.txt) do (
        set /a m+=1
        if !n! equ !m! echo %%a#%%i
    )
)
echo 开始时间%t%
echo 结束时间%time%
pause>nul
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@echo off
set "t=%time%"&set "n=-1"
:begin
set /a n+=1
if %n% equ 0 (
   set "sk="
   ) else (
   set "sk=skip=%n%"
)
for /f "%sk% delims=" %%i in (a.txt) do set /p=%%i#<NUL&GOTO next
:next
for /f "%sk% delims=" %%i in (b.txt) do set /p=%%i<NUL&ECHO.&GOTO begin
echo 开始时间%t%
echo 结束时间%time%
pause>nul
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@echo off
set "t=%time%"
:begin
set /a a=%random%%%10000+1
if not defined _%a% (
   set /p=%a% <NUL
   set /a n+=1&set "_%a%=a"
   ) else (
  goto begin
)
if %n% neq 9000 goto begin
echo.&echo 开始时间%t%
echo 结束时间%time%
pause>nul
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@echo off&setlocal enabledelayedexpansion
set "t=%time%"
for /l %%i in (0,1,10000) do set "_!random!!random!!random!!random!=%%i"
for /f "tokens=2 delims==" %%i in ('set _') do (
     set /p=%%i <NUL
     set /a n+=1
     if !n! equ 9000 goto end
)
:end
echo.&echo 开始时间%t%
echo 结束时间%time%
pause>nul
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@echo off
for /l %%a in (1 1 30) do findstr . a.txt
for /l %%a in (1 1 30) do type a.txt
pause
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