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 correct input

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 accept Y,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 not found"*

[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 "this is not a execute file";; "-rwxrwxr-x"*) echo "this is 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 15 Jun 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 15 Jun 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.sh 22.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sys v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