Linux Shell脚本编程case条件语句

1，判断一个数字是否则在1,2,3之中.

#!/bin/bash
read -p "pls input a number:" n
case "$n" in
    )
        echo "变量是1"
        ;;
    )
        echo "变量是2"
        ;;
    )
        echo "变量是3"
        ;;
    *)
        echo "pls input a number between 1 and 3"
        exit;
esac

2，多级if语句改写

#!/bin/bash
read -p "pls input a number:" n
if [ $n -eq  ]; then
    echo "$n是变量1"
elif [ $n -eq  ]; then
    echo "$n是变量2"
elif [ $n -eq  ]; then
    echo "$n是变量3"
else
    echo "pls input a number between 1 and 3"
fi

3，if..else嵌套，实现

#!/bin/bash
read -p "pls input a number:" n
if [ $n -eq  ]; then
    echo 
else
    if [ $n -eq  ]; then
        echo 
    elif [ $n -eq  ]; then
        echo 
    else
        echo "pls input a number [1-3]"
    fi
fi

4，判断 分数等级

#!/bin/bash

read -p "pls input score to test level:" score

if [ $score -ge  ]; then
    echo "优秀"
elif [ $score -ge  ]; then
    echo "良好"
elif [ $score -ge  ]; then
    echo "中等"
elif [ $score -ge  ]; then
    echo "及格"
else
    echo "不及格"
fi

5,给文字加颜色

#!/bin/bash
RED_COLOR='\e[1;31m'
GREEN_COLOR='\e[1;32m'
YELLOW_COLOR='\e[1;33m'
BLUE_COLOR='\e[1;34m'
RESET_COLOR='\e[0m'

echo '
    , 悟空
    , 八戒
    , 唐僧
    , 白龙马
'
read -p "pls input a number:" n

case $n in
    )
        echo -e  "${RED_COLOR}悟空${RESET_COLOR}"
        ;;
    )
        echo -e  "${GREEN_COLOR}八戒${RESET_COLOR}"
        ;;
    )
        echo -e  "${YELLOW_COLOR}唐僧${RESET_COLOR}"
        ;;
    )
        echo -e  "${BLUE_COLOR}白龙马${RESET_COLOR}"
        ;;
    *)
        echo "you need input a number in {1|2|3|4}"
esac

另一种写法：

#!/bin/bash
RED_COLOR='\e[1;31m'
GREEN_COLOR='\e[1;32m'
YELLOW_COLOR='\e[1;33m'
BLUE_COLOR='\e[1;34m'
RESET_COLOR='\e[0m'

function menu(){
    cat <<END
    , 悟空
    , 八戒
    , 唐僧
    , 白龙马
END
}

function select_type(){
        read -p "pls input a number:" n
        case $n in
            )
                echo -e  "${RED_COLOR}悟空${RESET_COLOR}"
                ;;
            )
                echo -e  "${GREEN_COLOR}八戒${RESET_COLOR}"
                ;;
            )
                echo -e  "${YELLOW_COLOR}唐僧${RESET_COLOR}"
                ;;
            )
                echo -e  "${BLUE_COLOR}白龙马${RESET_COLOR}"
                ;;
            *)
                echo "you need input a number in {1|2|3|4}"
        esac
}

function main(){
    menu
    select_type
}

main

读取命令行参数，给内容设置颜色

#!/bin/bash
RED_COLOR='\e[1;31m'
GREEN_COLOR='\e[1;32m'
YELLOW_COLOR='\e[1;33m'
BLUE_COLOR='\e[1;34m'
RESET_COLOR='\e[0m'

if [ $# -ne  ]; then
    echo "Usage $0 input {red|green|yellow|blue}"
    exit
fi

case $ in
    red)
        echo -e "${RED_COLOR}$1${RESET_COLOR}"
        ;;
    green)
        echo -e "${GREEN_COLOR}$1${RESET_COLOR}"
        ;;
    yellow)
        echo -e "${YELLOW_COLOR}$1${RESET_COLOR}"
        ;;
    blue)
        echo -e "${BLUE_COLOR}$1${RESET_COLOR}"
        ;;
    *)    
        echo "usage $0 input {red|green|yellow|blue}"
        exit
esac

修改成函数调用方式

#!/bin/bash
function toColor(){
        RED_COLOR='\e[1;31m'
        GREEN_COLOR='\e[1;32m'
        YELLOW_COLOR='\e[1;33m'
        BLUE_COLOR='\e[1;34m'
        RESET_COLOR='\e[0m'

        if [ $# -ne  ]; then
            echo "Usage $0 input {red|green|yellow|blue}"
            exit
        fi

        case $ in
            red)
                echo -e "${RED_COLOR}$1${RESET_COLOR}"
                ;;
            green)
                echo -e "${GREEN_COLOR}$1${RESET_COLOR}"
                ;;
            yellow)
                echo -e "${YELLOW_COLOR}$1${RESET_COLOR}"
                ;;
            blue)
                echo -e "${BLUE_COLOR}$1${RESET_COLOR}"
                ;;
            *)    
                echo "usage $0 input {red|green|yellow|blue}"
                exit
        esac
}

function main(){
    toColor $ $
}

main $*