LInux Shell基础

显示信息：

#!/bin/bash
echo "Hello World!"  #display one message

获取输入：

#!/bin/bash
echo $1
echo $2
echo $3

变量定义：

#!/bin/bash
A=b
All=all
echo "$A"ll
echo $All 

 条件判断：

#!/bin/bash
if [ "$1" == "normal" ]
then
	echo "this is normal case"
elif [ -z "$1" ]
then
	echo "no input..."
fi

 while循环：

#!/bin/bash
echo "please use add or delete or exit"
ACTION="default"
while [ -n $ACTION ]
do
	read ACTION
	case $ACTION in
		add)
			echo "add somebody"
			;;
		delete)
			echo "delete somebody"
			;;
		exit)
			echo "complete"
			break
			;;
		*)
			echo "invalide action, please re-enter"
			;;
	esac
done 

 for循环：

#!/bin/bash 
for x in 1 2 3 4 5 hello
do
	echo $x
done

for y in `ls /home/oss`
do
	echo "$y"
done

 函数：

#!/bin/bash

strcat() {
	OUT="$1"" ""$2"
	return 0
}

strcat2() {
	echo "$1"" ""$2"
	return 3
}

A="bird"
B="mouse"

OUT=""
strcat $A $B
echo $OUT

OUT2=`strcat2 $A $B`
echo $?
echo $OUT2

 常用内置符号常量：

符号值	意义
$@	代表全部参数，比如test a b c，此处“a”，“b”，“c”，展开后为三个字符串
$*	全部参数，比如test a b c，此处“a b c”，展开后为一个字符串
$#	参数个数
$?	上一个命令的返回结果
$$	当前命令所在的进程ID