Shell编程 之 if语句2

4. 多分支 if 语句

　　4.1 语句结构

　　　　

　　4.2 简易计算器

#!/bin/bash

read -t 30 -p "input number1: " num1
read -t 30 -p "input number2: " num2
read -t 30 -p "input an operator: " ope

if [ -n "$num1" -a -n "$num2" -a -n "$ope" ]
        then
                test1=$(echo $num1 | sed 's/[0-9]//g')
                test2=$(echo $num2 | sed 's/[0-9]//g')

        if [ -z "$test1" -a -z "$test2" ]
                then
                        if [ "$ope" == '+' ]
                                then
                                        res=$(( $num1 + $num2))
                        elif [ "$ope" == '-' ]
                                then
                                        res=$(( $num1 - $num2))
                        elif [ "$ope" == '*' ]
                                then
                                        res=$(( $num1 * $num2))
                        elif [ "$ope" == '/' ]
                                then
                                        res=$(( $num1 / $num2))
                        else
                                echo "invalid operator"
                                exit 10
                        fi
        else
                echo "invalid number"
                exit 11
        fi
else
        echo "no number inputed"
        exit 12
fi

echo "$num1 $ope $num2 = $res"

　　4.5 判断用户输入的是什么文件

　　　　tips：运行中输错内容，按 ctrl + backspace 进行删除

#!/bin/bash

read -t 30 -p "input a filename: " file

if [ -z "$file" ]
        then
                echo "no inputs"
                exit 11
elif [ ! -e "$file" ]
        then
                echo "$file is not a file"
                exit 22
elif [ -f "$file" ]
        then
                echo "$file is a regular file"
elif [ -d "$file" ]
        then
                echo "$file is a directory"
else
        echo "$file is a specific file"
fi
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"if6.sh" 21L, 331C