bash 数组

有2种数组：

• 索引数组
• 关联数组（java里的Hashmap），用key关联value

声明数组：

#声明索引数组
declare -a ary
#声明关联数组
declare -a ary

引用数组：${ary[idx]}

必须加大括号

直接访问数组名，就是访问第一个元素

[root@localhost ~]# ani[0]=dog
[root@localhost ~]# ani[1]=cat
[root@localhost ~]# echo ani
ani
[root@localhost ~]# echo ani[0]
ani[0]
[root@localhost ~]# echo $ani[0]
dog[0]
[root@localhost ~]# echo ${ani[0]}
dog
[root@localhost ~]# echo ${ani[1]}
cat

给数组赋值

• 单个赋值：ary[idx]=val

• 多个赋值：ary=(val1 val2...)

  [root@localhost ~]# ary=(1 2 3 4 )
  [root@localhost ~]# echo $ary
  1
  [root@localhost ~]# echo ${ary[0]}
  1
  [root@localhost ~]# echo ${ary[2]}
  3
  [root@localhost ~]# echo ${ary[1]}
  2
  [root@localhost ~]# echo ${ary[3]}
  4
  [root@localhost ~]# echo ${ary[4]}
  
  [root@localhost ~]#
  

• 跳跃赋值：ary=([0]="aa" [3]="dd")

  [root@localhost ~]# ary=([0]="aa" [3]="dd")
  [root@localhost ~]# echo ${ary[0]}
  aa
  [root@localhost ~]# echo ${ary[1]}
  
  [root@localhost ~]# echo ${ary[3]}
  dd
  

read读取数组

就选项-a就是读取数组

# read -a li
a b 1 d a2
[root@localhost ~]# echo $li
a
[root@localhost ~]# echo ${li[0]}
a
[root@localhost ~]# echo ${li[2]}
1
[root@localhost ~]# echo ${li[4]}
a2

取得数组元素的个数

• ${#ary[*]}
• ${#ary[@]}

取得数组中某个元素的长度

${#ary[indx/名字]}

得到数组的所以元素

• ${ary[*]}
• ${ary[@]}

关联数组

关联数组使用前最好先声明，使用-A选项声明。

[root@localhost scripts]# declare -A map
[root@localhost scripts]# map=([aa]=df12 [dd]=132432 [2]=12d)
[root@localhost scripts]# echo ${map[*]}
132432 df12 12d
[root@localhost scripts]# echo ${map[aa]}
df12
[root@localhost scripts]# echo ${map[2]}
12d

[root@localhost ~]# declare -A l3
[root@localhost ~]# l3[a]=aa
[root@localhost ~]# l3[b]=bb
[root@localhost ~]# echo ${l3[a]}
aa
[root@localhost ~]# echo ${l3[b]}
bb
[root@localhost ~]# echo ${#l3[*]}
2
[root@localhost ~]# echo ${#l3[@]}
2
[root@localhost ~]# echo ${#l3[a]}
2
[root@localhost ~]# echo ${#l3[b]}
2
[root@localhost ~]# l3[c]=1dsfs
[root@localhost ~]# echo ${#l3[c]}
5
[root@localhost ~]# echo ${l3[*]}
aa bb 1dsfs
[root@localhost ~]# echo ${l3[@]}
aa bb 1dsfs

数组的切片

${ary[@]:offset:length}

• offset：从第几个开始切
• length：切多长

[root@localhost scripts]# l1=(1 2 3 4 5 6)
[root@localhost scripts]# echo ${l1[@]:2:2}
3 4

删除数组里某个元素

# l1=(1 2 3 4 5 6)
[root@localhost scripts]# echo ${l1[@]:2:2}
3 4
[root@localhost scripts]# unset l1[1]
[root@localhost scripts]# echo ${l1[@]}
1 3 4 5 6

练习

1，生成10个随机整数，求最大值

$RANDOM是内置变量，能生成随机整数。

#!/bin/bash
#

declare -a rand
declare -i max=0

for i in {0..9}; do
    rand[$i]=$RANDOM
    echo ${rand[$i]}
    if [ $max -lt ${rand[$i]} ]; then
        max=${rand[$i]}
    fi

done
echo "max is $max"

2，统计/var/log/*.log文件的行数之和。

关键点：files=(/var/log/*.log)。括号里是globbing风格，会自动展开。

#!/bin/bash
#

declare -a files
declare -i lines

files=(/var/log/*.log)

for ((i=0;i<${#files[*]};i++)); do
    let lines+=`wc -l ${files[$i]} | cut -d" " -f1`
done
echo $lines

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