shell（7）----- 脚本demo

 

-------------------------case  用法------------------------------

 

 

[root@aliyun247 test]# cat cash.sh

#!/bin/bash

echo "hello hello cnamg"

read -p "please input a number 1 or 2 or 3 or 4" n

 

case $n in

 

  1)

          echo "nice"

        ;;

  2)   echo "very nice"

        ;;

  3)    echo "very nice nice"

        ;;

  4)    echo "very good bigger  nice"

        ;;

esac 

 

-------------------------case 循环体------------------------------

 

 

-----------------------for 循环 的失败体 可能因为系统版本原因-------------------

 

[root@aliyun247 test]# cat for.sh

#!/bin/bash

 

 

#seq  1 10;

#seq -1 -1 -10;

#seq  1  2 10;

 

 

sum=0

for i in seq 1 100

do

  sum=$(($i+$sum))

done

echo $sum

 

---------------------------for 循环 的失败体-------------------

 

------------------------判断字符是否为空-----------------

 

 

#!/bin/bash

read -p "请输入一个字符串" str

if [[ -z  $str ]]

then 

      echo "您输入的字符串为空"

else

  echo $str

fi

 

 

 

 

------------------------判断字符是否为空 结束----------------

 

 

 

---------------exec 用法------------------------

 

#!/bin/bash

d='date+%F'

exec> /tmp/$d.log 2>&1

echo "begin at 'date' "

ls /tmp/8jdjdh

cd /tem/ddd

echo "end at 'date' "

 

以上错误代码  ~  

 

                                                                                                                                                                                

#!/bin/bash

d=$(date +%F)

exec> /tmp/$d.log 2>&1

echo "begin at $(date) "

ls /tmp/8jdjdh

cd /tem/ddd

echo "end at $(date) "                          

 

$(）  执行体

 

 

-------------------------------exec 结束-------------------------------

 

 

---------------------if 用法----------------

#!/bin/bash

read -p "请输入一个数字" n

nl=$[$n%2]

if [[ $nl -eq 0 ]]

then

   echo "您输入的是偶数"

else

   echo "您输入的是奇数"

fi

 

~                                                                                                                                                                                  

~                                                                                                                                                                                  

~   

 if[[ 0 -eq 0 ]]: command not found     

  需要改为  if与[[ 符号之间需要空格       if  [[ 0 -eq 0 ]]        

 

 

 

 

---------------------if 结束----------------