shell要点

1、

for file in `ls /etc`
do
    echo $file
done

 

2、变量赋值单引号内变量不变换，转义字符无效

双引号可以变换

your_name='qinjx'
str="Hello, I know your are $your_name! \n"
字符串长度echo ${#str}
提取子字符串echo ${str:1:4} #输出ello

3、数组

array_name=(value0 value1 value2 value3)

array_name[0]=value0
array_name[1]=value1
array_name[n]=valuen
读取元素
valuen=${array_name[n]}
# 取得数组元素的个数
length=${#array_name[@]}
# 或者
length=${#array_name[*]}
# 取得数组单个元素的长度
lengthn=${#array_name[n]}

4、test　　数值测试

　　　　

exampe

num1=100
num2=100
if test $[num1] -eq $[num2]
then
    echo 'The two numbers are equal!'
else
    echo 'The two numbers are not equal!'
fi

字符串测试

　　　　

文件测试

　　　　

5、流程控制

if condition1
then
    command1
elif condition2
    command2
else
    commandN
fi

COUNTER=0
while [ $COUNTER -lt 5 ]
do
    COUNTER='expr $COUNTER+1'
    echo $COUNTER
done

echo 'Input a number between 1 to 4'
echo 'Your number is:\c'
read aNum
case $aNum in
    1)  echo 'You select 1'
    ;;
    2)  echo 'You select 2'
    ;;
    3)  echo 'You select 3'
    ;;
    4)  echo 'You select 4'
    ;;
    *)  echo 'You do not select a number between 1 to 4'
    ;;
esac

6、函数

#!/bin/bash
funWithParam(){
    echo "The value of the first parameter is $1 !"
    echo "The value of the second parameter is $2 !"
    echo "The value of the tenth parameter is $10 !"
    echo "The value of the tenth parameter is ${10} !"
    echo "The value of the eleventh parameter is ${11} !"
    echo "The amount of the parameters is $# !"
    echo "The string of the parameters is $* !"
}
funWithParam 1 2 3 4 5 6 7 8 9 34 73

输出为

The value of the first parameter is 1 !
The value of the second parameter is 2 !
The value of the tenth parameter is 10 !
The value of the tenth parameter is 34 !
The value of the eleventh parameter is 73 !
The amount of the parameters is 12 !
The string of the parameters is 1 2 3 4 5 6 7 8 9 34 73 !"

参数处理：

　　　　

 

6，shell算术表达式

declare 

不支持浮点数，需要bc,awk支持

$[ ]

$(( ))

let

$(expr  )

 

7、处理命令行参数

option = $(getopt -o    -l)