控制循环语句： break 和 continue

beyes

break[n]
退出循环
如果是在一个嵌入循环里，可以指定 n 来跳出循环个数

continue
跳过循环步

注：continue 命令类似于 break 命令，只有一点重要差别，它不会跳出循环，只是跳过这个循环步

beyes

嵌套两个循环：

#!/bin/bash

for x in 1 2 3 4 5 6 7 8
do
echo $x

        for y in a b c d e f g
        do
echo -n $y
        done

echo -e "\\n------------------"
done

输出结果：

[beyes@localhost shell]$ sh for_test_4.sh
1
abcdefg
------------------
2
abcdefg
------------------
3
abcdefg
------------------
4
abcdefg
------------------
5
abcdefg
------------------
6
abcdefg
------------------
7
abcdefg
------------------
8
abcdefg
------------------

修改一下源码（添加一行 continue 2)：

#!/bin/bash

for x in 1 2 3 4 5 6 7 8
do
echo $x

        for y in a b c d e f g
        do
               echo -n $y
                continue 2      # continue 后，数字1表示在本层循环；2表示上一层循环；以此类推...
        done

echo -e "\\n------------------"
done

beyes

#!/bin/bash

rm -rf fred*
echo > fred1
echo > fred2

mkdir fred3
echo > fred4

for file in fred*
do
        if [ -d "$file" ]; then
break;
        fi
done

echo first directory starting fred was $file

rm -rf fred*

exit 0

beyes

break 举例：

#!/bin/bash
#breakout
while :        # : 号为永远为真，且 : 和 while 之间要有空格
do
echo -n "Enter any number[1...5]:"
        read ANS
        case $ANS in
        1|2|3|4|5)
                echo "You enter a number between 1 and 5."
                ;;
        *)
                echo "Wrong number,bye.."
                break
                ;;
        esac
done

continue 应用举例：

#!/bin/bash
#breakout
while :
do
echo -n "Enter any number[1...5]:"
        read ANS
        case $ANS in
        1|2|3|4|5)
                echo "You enter a number between 1 and 5."
                ;;
        *)
                echo -n "Wrong number, continue(y/n)?:"
                read IS_CONTINUE
                case $IS_CONTINUE in
                        y|Y|yes|Yes)
                                continue
                                ;;
                        *)
                                break
                                ;;
                esac

        esac
done