WindowsBatch与LinuxShell比较[变量值来自文件或命令]

一 Windows Batch

1) 如果变量的值来自文件，则必须类似set /p num=<num.txt 。
2）如果变量的值想来自命令的结果，则一些命令可以使用%%，例如set bbb=%time%，set aaa=%date%。对于一般的命令只能先输出到临时文件，然后再读入，例如time /t > ddd.txt set /p ddd=<ddd.txt。
3) 在for中可以使用命令，例如·time /t·。

实例：


@echo off




echo get the value from one txt file


rem the num.txt file only contains one line "001".




echo work well


set /p num=<num.txt


echo %num%




echo doesn't work


set num=<num.txt


echo %num%


type num.txt | set num=


echo %num%


type num.txt | set /p num=


echo %num%


set num=(`print num.txt`)


echo %num%




echo get value from command


echo some command work well, such as %time%, %date%



set bbb=%time%


echo %bbb%


set aaa=%date%


echo %aaa%




echo general command doesn't work


set ccc=('time /t')


echo %ccc%




echo one solution is to output the result to txt and then input it


time /t > ddd.txt


set /p ddd=<ddd.txt


echo %ddd%




echo specially,in for clause, ('time /t') is as one command.


echo and if also use setlocal enabledelayedexpansion, the way also can implement get value from command.


setlocal enabledelayedexpansion


for /f %%i in ('time /t') do (


echo %%i


set ti=%%i


echo !ti!


)




pause
二 Linux Shell

1）超级简单，只需要使用·command parameters·。
实例：
#!/bin/sh

ddd=`cat ./ddd.txt`
echo $ddd

d=`date`
echo $d
完！