Shell 编程：流程控制

if 语句

if condition
then
    command1 
    command2
    ...
    commandN 
fi

if condition
then
    command1 
    command2
    ...
    commandN
else
    command
fi

if condition1
then
    command1
elif condition2
then
    command2
else
    commandN
fi

条件语句

1. test 命令
2. [...] 等价于 test 命令
3. ((...)) 用于整数运算
4. [[...]] Bash 提供的扩展关键字

for 循环

for var in item1 item2 ... itemN
do
    command1
    command2
    ...
    commandN
done

for 无限循环

for (( ; ; ))

while 循环

while condition
do
    command
done

while 无限循环

while :
do
    command
done

while true
do
    command
done

until 循环

until condition
do
    command
done

break 跳出循环

#!/bin/bash
while :
do
    echo -n "输入 1 到 5 之间的数字:"
    read aNum
    case $aNum in
        1|2|3|4|5) echo "你输入的数字为 $aNum!"
        ;;
        *) echo "你输入的数字不是 1 到 5 之间的! 游戏结束"
            break
        ;;
    esac
done

continue 跳过本次循环

#!/bin/bash
while :
do
    echo -n "输入 1 到 5 之间的数字: "
    read aNum
    case $aNum in
        1|2|3|4|5) echo "你输入的数字为 $aNum!"
        ;;
        *) echo "你输入的数字不是 1 到 5 之间的!"
            continue
            echo "游戏结束"
        ;;
    esac
done