shell脚本根据用户的输入调用不同的函数

1. 创建caculator.sh脚本，内容如下：

#!/bin/sh
usage="Usage: `basename $0` (add|sub|mul|div|all) parameter1 parameter2"
command=$1
first=$2
second=$3
function add(){
    ans=$(($first + $second))
    echo $ans
}
function sub(){
    ans=$(($first - $second))
    echo $ans
}
function mul(){
    ans=$(($first * $second))
    echo $ans
}
function div(){
    ans=$(($first / $second))
    echo $ans
}
case $command in
 (add)
        add
        ;;
    (sub)
        sub
        ;;
    (mul)
        mul
        ;;
    (div)
        div
        ;;
    (all)
        add
        sub
        mul
        div
        ;;
    (*)
        echo "Error command"
        echo "$usage"
        ;;
esac

2. 修改执行权限

chmod 777 caculator.sh

3. 测试

$ ./caculator.sh add 2 3
5

$ ./caculator.sh sub 2 3
-1