数组

数组是一种特殊的数据结构，其中的每一项被称为一个元素，对于每个元素，都可以用索引方式取出元素的值。使用数组的典型场景是一次性要记录很多类型相同的数据时（但不是说一定要相同，因为Shell变量是弱类型性的，并不要求数组的每个元素都是相同类型）。

1. 创建数组

   • 直接创建数组

     ronie@ronie-virtual-machine:~/Desktop$ arr=(1 2 3 4 5)
     ronie@ronie-virtual-machine:~/Desktop$ echo ${arr[0]}
     1
     ronie@ronie-virtual-machine:~/Desktop$ echo ${arr}
     1
     ronie@ronie-virtual-machine:~/Desktop$ echo ${arr[2]}
     3
     ronie@ronie-virtual-machine:~/Desktop$ 

   • 使用数字下标来定义数组

     ronie@ronie-virtual-machine:~/Desktop$ arr[0]=0
     ronie@ronie-virtual-machine:~/Desktop$ arr[1]=2
     ronie@ronie-virtual-machine:~/Desktop$ arr[2]=1
     ronie@ronie-virtual-machine:~/Desktop$ arr[3]=4
     ronie@ronie-virtual-machine:~/Desktop$ arr[4]=6
     ronie@ronie-virtual-machine:~/Desktop$ echo ${arr[2]}
     1
     ronie@ronie-virtual-machine:~/Desktop$ echo ${arr[1]}
     2
     ronie@ronie-virtual-machine:~/Desktop$ 

2. 读取数组元素值：

   • ${array_name[index]}

     ronie@ronie-virtual-machine:~/Desktop$ arr[0]=0
     ronie@ronie-virtual-machine:~/Desktop$ arr[1]=2
     ronie@ronie-virtual-machine:~/Desktop$ arr[2]=1
     ronie@ronie-virtual-machine:~/Desktop$ arr[3]=4
     ronie@ronie-virtual-machine:~/Desktop$ arr[4]=6
     ronie@ronie-virtual-machine:~/Desktop$ echo ${arr[2]}
     1
     ronie@ronie-virtual-machine:~/Desktop$ echo ${arr[1]}
     2
     ronie@ronie-virtual-machine:~/Desktop$ 
     

   • 获取数组中的所有元素：使用@或*

     ronie@ronie-virtual-machine:~/Desktop$ arr=(1 2 3 4 5 6)
     ronie@ronie-virtual-machine:~/Desktop$ echo ${arr[@]}
      1 2 3 4 5 6
     ronie@ronie-virtual-machine:~/Desktop$ echo ${arr[*]}
      1 2 3 4 5 6
     ronie@ronie-virtual-machine:~/Desktop$ 
     

3. 关联数组：

   • declare -A array_name

     ronie@ronie-virtual-machine:~/Desktop$ declare -A arr=(["ronie"]="male" ["kelly"]="female")
     ronie@ronie-virtual-machine:~/Desktop$ echo ${arr[ronie]}
     male
     ronie@ronie-virtual-machine:~/Desktop$ 

   • 先声明一个关联数组，然后再设置键和值

     ronie@ronie-virtual-machine:~/Desktop$ declare -A arr
     ronie@ronie-virtual-machine:~/Desktop$ arr['ronie']='18'
     ronie@ronie-virtual-machine:~/Desktop$ arr['mike']='32'
     ronie@ronie-virtual-machine:~/Desktop$ echo ${arr['ronie']}
     18
     ronie@ronie-virtual-machine:~/Desktop$ 
     

   • 使用感叹号!获取数组的所有键

     ronie@ronie-virtual-machine:~/Desktop$ declare -A arr
     ronie@ronie-virtual-machine:~/Desktop$ arr['mike']='32'
     ronie@ronie-virtual-machine:~/Desktop$ arr['ronie']='18'
     ronie@ronie-virtual-machine:~/Desktop$ echo ${!arr[*]}
     ronie mike
     ronie@ronie-virtual-machine:~/Desktop$ 

   • 使用@或*获取数组中的所有元素

     ronie@ronie-virtual-machine:~/Desktop$ declare -A arr
     ronie@ronie-virtual-machine:~/Desktop$ arr['mike']='32'
     ronie@ronie-virtual-machine:~/Desktop$ arr['ronie']='18'
     ronie@ronie-virtual-machine:~/Desktop$ echo ${arr[@]}
      18 32
     ronie@ronie-virtual-machine:~/Desktop$ 
     

4. 获取数组的长度#

   ronie@ronie-virtual-machine:~/Desktop$ echo ${#arr[@]}
   2
   ronie@ronie-virtual-machine:~/Desktop$ echo ${#arr[*]}
   2
   ronie@ronie-virtual-machine:~/Desktop$