一、function介绍

函数function是由若干条shell命令组成的语句块，实现代码重用和模块化编程。

二、function简单应用的脚本

[root@192 scripts]# cat ittest.sh 
#!/bin/bash
########################################
#Author:jeven
#time:Mon 23 May 2022 05:39:10 PM CST
#filename:ittest.sh
#Script description:
########################################
function test () {
	echo -n  "your choice is"
}
echo "this program will print your selection!"
case $1 in 
 "one")
         test ; echo $1 |tr 'a-z' 'A-Z'
	 ;;
 "two")
         test ; echo $1 |tr 'a-z' 'A-Z'
	 ;;
 "three")
         test ; echo $1  |tr 'a-z' 'A-Z'
	 ;;
  *)
         echo "Usage $0 ,please inpute {one|two|three}"
	 ;;
esac

三、执行脚本

[root@192 scripts]# sh ittest.sh one
this program will print your selection!
your choice isONE
[root@192 scripts]# sh ittest.sh two
this program will print your selection!
your choice isTWO
[root@192 scripts]# sh ittest.sh three
this program will print your selection!
your choice isTHREE
[root@192 scripts]# sh ittest.sh ta1a1
this program will print your selection!
Usage ittest.sh ,please inpute {one|two|three}