shell脚本for循环 鸟哥的linux私房菜(7)

case $1 in

"one")

printit; echo ${1} | tr 'a-z' 'A-Z' # 将参数做大小写转换！

;;

"two")

printit; echo $1 | tr 'a-z' 'A-Z'

;;

"three")

printit; echo $1 | tr 'a-z' 'A-Z'

;;

*)

echo "Usage $0 {one|two|three}"

;;

esac

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以上面的例子来说，鸟哥做了一个函数名称为 printit ，所以，当我在后续的程序段里面， 只要执行printit 的话，就表示我的 shell script 要去执行『 function printit .... 』 里面的那几个程序段落

13.5 循环（loop）

13.5.1 while do done ，until do done（不定循环）

语法

当 condition 条件成立时，就进行循环，直到condition 的条件不成立才停止：

while [ condition ]

do

程序段落

done

与 while 相反，它说的是『当 condition 条件成立时，就终止循环， 否则就持续进行循环的程序段。

until [ condition ] ]

do

程序段落

done

范例

[dmtsai@study bin]$ vim yes_to_stop.sh

#!/bin/bash

# Program:

# Repeat question until user input correct answer.

# History:

# 2015/07/17 VBird First release

PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin

export PATH

while [ "${yn}" != "yes" -a "${yn}" != "YES" ]

do

read -p "Please input yes/YES to stop this program: " yn

done

echo "OK! you input the correct answer."

[dmtsai@study bin]$ vim yes_to_stop- - 2.sh

#!/bin/bash

# Program:

# Repeat question until user input correct answer.

# History:

# 2015/07/17 VBird First release

PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin

export PATH

until [ "${yn}" == "yes" -o "${yn}" == "YES" ]

do

read -p "Please input yes/YES to stop this program: " yn

done

echo "OK! you input the correct answer."

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