控制流结构——case

最新推荐文章于 2024-12-26 22:09:48 发布

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最新推荐文章于 2024-12-26 22:09:48 发布

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分类专栏： Shell 文章标签：脚本工作

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[size=medium][b]case语句[/b][/size]
case语句为多选择语句。可以用case语句匹配一个值与一个模式，如果匹配成功，执行相匹配的命令。case语句格式如下：

case 值 in
模式1 )
  命令1
  . . .
  ;;
模式2 )
  命令2
  . . .
  ;;
esac

/home/l/g/tomotoboy >cat caseselect
#!/bin/sh
#caseselect
echo - n "Enter a number from 1 to 5 :"
read ANS
 case $ANS in
1) echo "you select 1"
;;
2) echo "you select 2"
;;
3) echo "you select 3"
;;
4) echo "you select 4"
;;
5) echo "you select 5"
;;
*) echo "`basename $0`: This is not between 1 and 5" >&2
;;
esac

/home/l/g/tomotoboy >caseselect
- n Enter a number from 1 to 5 :
4
you select 4
/home/l/g/tomotoboy >caseselect
- n Enter a number from 1 to 5 :
7
caseselect: This is not between 1 and 5

[b]对匹配模式使用|[/b]

/home/l/g/tomotoboy >cat caseterm
#!/bin/sh
#caseterm
echo "choices are.. vt100, vt102, vt220"
echo -n "enter your terminal type :"
read TERMINAL
 case $TERMINAL in
 vt100|vt102) TERM=vt100
 ;;
 vt220) TERM=vt220
 ;;
 *) echo "`basename $0`: Unknown reponse" >&2
   echo "setting it to vt100 anyway,so there"
   TERM=vt100
 ;;
esac
export TERM
echo "Your terminal is set to $TERM'
"caseterm" 17 lines, 348 characters

/home/l/g/tomotoboy >caseterm
choices are.. vt100, vt102, vt220
-n enter your terminal type :
vt100
Your terminal is set to vt100'

[b]提示键入y或n[/b]
case的一个有效用法是提示用户响应以决定是否继续进程。这里提示输入y以继续处理n退出。如果用户输入Y、y或yes，处理继续执行case语句后面部分。如果用户输入N、n或no或其他响应，用户退出脚本。

/home/l/g/tomotoboy >cat caseans
#!/bin/sh
#caseans
echo -n "Do you wish to proceed [y..n]"
read ANS
 case $ANS in
 y|Y|yes|Yes) echo "yes is selected"
 ;;
 n|N|no|No) echo "no is selectd"
 ;;
 *) echo "`basename $0` : Unknown response" >&2
 ;;
 esac

/home/l/g/tomotoboy >caseans
-n Do you wish to proceed [y..n]
y
yes is selected

[b]case与命令参数传入[/b]

/home/l/g/tomotoboy >cat >> caseparam
#!/bin/sh
#caseparam
if [ $# != 1 ];then
   echo "Usage:`basename $0` [start|stop|help]" >&2
fi
OPT=$1
case $OPT in
 start) echo "starting..`basename $0`"
;;
 stop) echo "stopping..`basename $0`"
;;
 help) echo "stopping..`basename $0`"
 echo "Usage:`basename $0` [start|stop|help]"
;;
 *) echo "stopping..`basename $0`"
 echo "Usage:`basename $0` [start|stop|help]"
;;
esac
/home/l/g/tomotoboy >chmod u+x caseparam
/home/l/g/tomotoboy >caseparam help
stopping..caseparam
Usage:caseparam [start|stop|help]
/home/l/g/tomotoboy >caseparam start
starting..caseparam

[b]捕获输入并执行空命令[/b]
不一定要在匹配模式后加入命令，如果你原本不想做什么，只是在进一步处理前过滤出意外响应，这样做是一种好办法。如果要运行对应于一个会计部门的帐目报表，必须首先在决定运行报表的类型前确认用户输入一个有效的部门号，匹配所有可能值，其他值无效。用case可以很容易实现上述功能。下面的脚本中如果用户输入部门号不是234、453、655或454，用户退出并返回可用信息。一旦响应了用户的有效部门号，脚本应用同样的技术取得报表类型，在case语句末尾显示有效的部门号和报表类型。脚本如下：

#!/bin/sh
# casevalid
echo -n "enter the account dept No: "
read ACC
 case $ACC in
      234);;
      453);;
      655);;
      454);;
         *) echo "basename $01`: Unknon dept No"
              echo "try..234,453,655,454"
              exit 1
              ;;
esac
#if we are here, then we have a validdated the dept no
echo " 1 . post"
echo " 2 . prior"
echo -n "enter the type of report: "
read ACC_TYPE
   case $ACC_TYPE in
   1)TYPE=post;;
   2)TYPE=prior;;
   *) echo "`basename $0`: Unknown account type." >&2
"casevalid" 29 lines, 665 characters
/home/l/g/tomotoboy >casevalid
-n enter the account dept No:
454
 1 . post
 2 . prior
-n enter the type of report:
1
now running report for dept 454 for the type post