字符串截取功能批处理

::code by lxmxn @ cn-dos.net .
::目的：帮助新手们更好的理解变量字符截取功能.
::date 2006-12-16 .
::说明：有的变量截取之后值为空，这是正常的.
::
@echo off&setlocal enabledelayedexpansion
::设置变量var的值：
set var=0123456789abcdef
call :begin
for /l %%a in (1,3,15) do (
for /l %%b in (1,4,15) do (
call :printf %%a %%b
)
)
call :begin
for /l %%a in (1,4,15) do (
for /l %%b in (-1,-3,-15) do (
call :printf %%a %%b
)
)
call :begin
for /l %%a in (-2,-3,-15) do (
for /l %%b in (1,4,15) do (
call :printf %%a %%b
)
)
call :begin
for /l %%a in (-1,-4,-15) do (
for /l %%b in (-2,-3,-15) do (
call :printf %%a %%b
)
)
pause
endlocal&cls&echo.
echo 演示结束了，任意键退出……
pause>nul
goto :eof

::输出结果：
:printf
echo %%var:~%1,%2%% 截取之后的字符为: !var:~%1,%2!
goto :eof

::清理屏幕：
:begin
echo\&pause&cls&echo.
echo 变量var的值为: %var%
echo.
goto :eof