shell编程 case语句

case语句格式
# vi test.sh
:
echo "input : "
read num
echo "the input data is $num"

case $num in
1) echo"January";;    双分号结束
2) echo "Feburary";;
5) echo"may"         每个case可以有多条命令      
   echo "sdfd"
   echo"sdf";;       但最后一条命令一定是双分号结束

*) echo "not correct input";;   *）是其他值、default的意思     

esac   # sh ./test.sh
input :
2
the input data is 2
Feburary

# sh ./test.sh
input :
ter
the input data is ter
not correctinput   
 
    case 语句如果某个选项没有任何语句，也要加;;否则会出下边错误
test: line 166: syntax error near unexpected token `)'
test: line 166: `"system hostname config")'


    为什么输入no,仍不匹配到[no]
原来[]是专门针对单字符的值,如果用[no],就是n和o之一
case $yn in  
 [no]) return 1;;
  * )  echo "only acceptY,y,N,n,YES,yes,NO,no">&2;;[macg@mac-home ~]$ sh test.sh
enter y/n :
no                          
only accept Y,y,N,n,YES,yes,NO,no改正
case $yn in  
  no) return 1;;
  NO) return 1;;
  * ) echo "only accept Y,y,N,n,YES,yes,NO,no">&2;;
 esac[macg@mac-home ~]$ sh test.sh
enter y/n :
no                            

    一个getyn()函数的例子
getyn( )
{
while echo "enter y/n:"
do
 read yn
 case $yn in
  [Yy]) return 0 ;;
  yes) return 0 ;;
  YES) return 0 ;;
  [Nn]) return 1 ;;
  no) return 1;;
  NO) return 1;;
  * ) echo "only accept Y,y,N,n,YES,yes,NO,no";;
 esac
done
}if
getyn 调用函数     以函数作为if条件,必须用if command法
then    注意0为真
echo " your answer is yes"
else
echo "your anser is no"
fi   

    if, case，匹配字符串最常见，但如何匹配一段很长的输出，一堆文字？最好方法，用“*”，如：*"command notfound"*
[macg@machome ~]$ vi test.sh

var=$(ls -l$1)     $()取命令输出，$1是命令行参数
echo "output is $var"

case $var in
"-rw-rw-r--"*) echo "thisis not a execute file";;
"-rwxrwxr-x"*) echo "thisis a execute file";
注意*在双引号外边
esac[macg@machome ~]$ sh test.sh 22.txt
output is -rw-rw-r--  1 macg macg 15Jun  9 19:00 22.txt
this is not a execute file

[macg@machome ~]$ chmod +x 22.txt
[macg@machome ~]$ sh test.sh 22.txt
output is -rwxrwxr-x  1 macg macg 15Jun  9 19:00 22.txt
this is a execute file   例2．匹配file命令输出的一堆文字,以获知文件类型
用’ ’ 取输出,然后用CASE+*对输出做修饰处理.
[macg@machome ~]$ vi test.sh

var=`file$1`       `  `和$()作用相同，是取命令输出
echo "output is $var"

case $var in
"$1: ASCII text"*) echo "this is a text file";;
"$1: directory"*) echo "this is a directory";;
注意*在双引号外边
esac    [macg@machome ~]$ sh test.sh22.txt
output is 22.txt: ASCII text
this is a text file

[macg@machome ~]$ sh test.sh test-dir
output is test-dir: directory
this is a directory

     最典型的shell case命令匹配命令行，用于sysv启动脚本的start|stop|restart|status处理
  case  "$@"  in    
($@ 字符串数组：以"参数1" "参数2" ...的字符串数组形式保存所有参数 
对于单个参数的情况，$@就是一个字符串)

 start)    
         echo  -n  "Starting  firewall..."    
         。。。  
         echo  "OK!"    
         exit  0    
         ;;    
 stop)    
         echo  -n  "Stopping   firewall..."
         。。。   
         exit  0    
         ;;   
restart)    
         $0  stop    $0即执行原始程序       
         $0  start    
         ;;    
status)    
         clear    
         echo  ">------------------------------------------"    
         iptables  -L    
         echo  ">------------------------------------------"    
         iptables  -t  nat  -L  POSTROUTING    
         exit  0   
    *)    
         echo  "Usage:  $0  {start|stop|restart|status}"    
         exit  1    
 esac