shell程序设计之for while until

语法结构
for loop-index in argument-list
do
    commands
done
示例如下：

#!/bin/bash

for fruit in apples oranges pears bananas
do
        echo "$fruit"
done
echo "Task complete."

结果：
apples
oranges
pears
bananas
Task complete.

while控制结构
while test-command
do
    commands
done
示例如下：

#!/bin/bash

number=0
while [ "$number" -lt 10 ]
do
        echo -n "$number"
        ((number += 1))
done
echo

结果：
0123456789

until语法结构
until test-command
do
    commands
done
示例如下：

#!/bin/bash

secretname=jenny
name=noname

echo "Try to guess the secret name!"
echo

until [ "$name" == "$secretname" ]
do
        echo -n "Your guess: "
        read name
done
echo "Very good."

break 、continue

#!/bin/bash

for index in 1 2 3 4 5 6 7 8 9 10
do
        if [ $index -le 3 ]
        then
                echo "continue"
                continue
        fi

        echo $index

        if [ $index -ge 8 ]
        then
                echo "break"
                break
        fi
done

结果：
continue
continue
continue
4
5
6
7
8
break