中国DOS联盟

@echo off FOR /F "usebackq tokens=3* delims= " %%i in (`find /C " " %2`) do set total1=%%i FOR /F "usebackq tokens=3* delims= " %%i in (`find /V /C " " %2`) do set total2=%%i set /A total=%total1%+%total2% IF "%1"=="-f" ( set /A pos=%total%-6 more +%pos% %2 goto begin ) set /A t=-%1 set /A pos=%total%-%t% IF %total% GEQ %t% ( more +%pos% %2 ) ELSE ( echo toltal line is: %total% echo press any key show %2 content. pause>nul more %2 ) IF "%1"=="-f" ( :begin set /A totalpre=total timeout /T 1 /NOBREAK >nul FOR /F "usebackq tokens=3* delims= " %%i in (`find /C " " %2`) do set total1=%%i FOR /F "usebackq tokens=3* delims= " %%i in (`find /V /C " " %2`) do set total2=%%i set /A total=%total1%+%total2% IF %totalpre% NEQ %total% ( set /A t=%total%-%totalpre% set /A pos=%total%-%t% more +%pos% %2 ) GOTO begin ) @echo on 程序如上 ： 该程序是用来仿unix环境tail命令，如果执行命令tail -f filename more +%pos% %2 中有pos取不到值，第二次运行时就正常了，是什么问题呢？

原因是你的%pos%变量处于if的复合语句体内，需要用到变量延迟。 可以在more +%pos% %2前面加上"Setlocal EnableDelayedExpansion"，然后再more +!pos! %2来显示。 具体的内容就请参考set命令的帮助及论坛关于“变量延迟”有关的讨论贴了。