【shell 练习1】编写Shell条件句练习

实例一、比较两个整数大小

#!/bin/bash

while true

do

    read -p "Please input two int nums:" a b

    expr $a + $b +  >/dev/null >&1     #判断是否为整数

    if [ $? -eq  ];then                 #返回值是否为0

        if [ $a -gt $b ];then

           echo " $a > $b"

           exit

        elif [ $a -lt $b ];then

           echo " $a < $b "

           exit

        else [ $a -eq $b ]

           echo " $a = $b "

           exit

        fi

    fi

done

实例二 、测试语句和if条件句混合使用，通过目录安装lamp，lnmp

目录安装：

#!/bin/sh

path=/server/scrips

[ ! -d "$path" ] && mkdir $path -p

#menu

cat <<END

    .[install lamp]

    .[install lnmp]

    .[exit]

    pls input the num you wang:

END

read num

expr $num +  &>/dev/null

if [ $? -ne  ];then

   echo "the num you input must be {1|2|3}"

   exit

fi

[ $num -eq  ]&&{

    echo "start install lamp."

    sleep ;

    [ -x "$path/lamp.sh" ]||{

    echo " does not exist or can not be exec."

    exit

    }

    $path/lamp.sh

    #source $path/lamp.sh

    exit $?

}

if [ $num -eq  ];then

   echo "start install lnmp."

   sleep ;

   if [ -x "$path/lamp.sh" ];then

   $path/lnmp.sh

   #source $path/lamp.sh

   exit $?

   else

       echo " does not exist or can not be exec. "

       exit

   fi

fi

if [ $num -eq  ];then

    echo bye

    exit

fi

[[ ! $num =~[-] ]] &&{

    echo "the num you input must be {1|2|3}"

    echo "Input ERROR"

    exit

}