命令行获取参数 命令替换 函数返回值 实验

#!/bin/bash
# read-without-new-line.sh
# using \c to get input in the same line
echo -e "Input your operate system:\c"
read answer
function func
{
    echo "Function start ...."
    if [ $answer != `uname` ]
#    if [ $naswer != $(uanme) ]    #### is same as above
#    if [ "$answer" != "`uname`" ] #### is same as above
    then
        echo No-$answer
        echo "You don't knowe your operate system!"
#        exit 5
        return 100
    else
        echo OK-$answer
        echo "Hehe, you knowe your operate system!"
#        exit 4
        return 99
    fi
}
echo -----Out put ---
echo Your system is:
echo $(uname)

c=$(func)
echo \$c=func\(\);
echo The value of \$c is:
echo $c

echo ----------------1
echo "excu function func directly , and \$? get the return of functioin \"func\""
func
echo $?
echo ----------------2
echo "display the result of function func!"
echo `func`   ### is same as c=\$func\(\)

#####    end of script    #####

Result:
    $./read-without-new-line.sh
    Input your operate system:Linux
    -----Out put ---
    Your system is:
    Linux
    $c=func()                  # call of function func()
    The value of $c is:
    Function start .... OK-Linux Hehe, you knowe your operate
    ----------------1
    excu function func directly , and $? get the return of functioin "func"
    Function start ....
    OK-Linux
    Hehe, you knowe your operate
    99
    ----------------2
    display the result of function
    Function start .... OK-Linux Hehe, you knowe your operate

    $ ./read-without-new-line.sh
    Input your operate system:windows
    -----Out put ---
    Your system is:
    Linux
    $c=func()
    The value of $c is:
    Function start .... No-windows You don’t knowe your operate
    ----------------1
    excu function func directly , and $? get the return of functioin "func"
    Function start ....
    No-windows
    You don‘t knowe your operate
    100
    ----------------2
    display the result of function
    Function start .... No-windows You don‘t knowe your operate

脚本说明：
1、在同一行读取输入需要添加\c来指定。如脚本开始 #echo -e "Input your operate system:\c"
2、字符串匹配

2.1 # if [ $answer != `uname`]
2.2 # if [ "$answer" != "`uanme`" ]
2.3 # if [ $answer != $(uname) ]

3、函数返回值

3.1 $c=func(), 变量c得到的是func的所有输出，使用echo显示的时候没有换行。 使用 $c=func();echo $c的方式和 echo `func`的结果是一致的。
3.2 return 返回的值可以通过 $? 获取得到。
3.3 exit 调用和直接执行函数是不一样的。调用函数的时候，函数的输出会存到变量中。但是脚本继续执行。 如果是直接执行，脚本会终止。如果脚本中直接执行函数并且使用exit退出了脚本，那么在脚本外使用 $?  可以获得exit指定的数字。