abstract

Array operation

Suppose you have two arrays

array1=(1 2 3 4 5 6)
array2=("James" "Colin" "Harry")

• Data variable name default output
  If a variable is output directly by default, its output value is the value of the first element by default, and the subscript starts from 0

root@pts/1 $ echo $array1
1
root@pts/1 $ echo $array2
James

• Get array elements
  Format: ${array name [subscript]}, subscript starts from 0, subscript * or @ represents the whole array content

root@pts/1 $ echo ${array1[2]}
3
root@pts/1 $ echo ${array2[1]}
Colin

## Get all elements
root@pts/1 $ echo ${array2[*]}
James Colin Harry
root@pts/1 $ echo ${array2[@]}
James Colin Harry

• Get array length
  Format: ${ා array name [* or @]}

root@pts/1 $ echo ${#array1[@]}
6
root@pts/1 $ echo ${#array2[*]}
3

• Array traversal

root@pts/1 $ for item in ${array2[@]}
> do
>     echo "The name is ${item}"
> done
The name is James
The name is Colin
The name is Harry

• Array element assignment

Format: array name [subscript] = value. If the subscript does not exist, the array element will be added; if the subscript already exists, the array element value will be overwritten

root@pts/1 $ array1[2]=18
root@pts/1 $ echo ${array1[*]}
1 2 18 4 5 6

root@pts/1 $ array2[4]="Betty"
root@pts/1 $ echo ${array2[*]}
James Colin Harry Betty

• Array slice

Format: ${array name [* or @]: start bit: length}, truncate part of array, return string, separated by spaces; use () to get new slice array

root@pts/1 $ echo ${array2[*]}
James Colin Harry Betty
root@pts/1 $ echo ${array2[*]:1:3}
Colin Harry Betty

root@pts/1 $ array3=(${array2[*]:1:2})
ks-devops [~] 2018-01-25 20:30:16
root@pts/1 $ echo ${array3[@]}
Colin Harry

• Array element replacement

Format: ${array name [* or @] / find character / replace character}, the original array will not be modified; if you want to modify the array, use "()" to assign the result to the new array

root@pts/1 $ echo ${array2[*]}
James Colin Harry Betty
root@pts/1 $ echo ${array2[*]/Colin/Colin.Liu}
James Colin.Liu Harry Betty

root@pts/1 $ array4=(${array2[*]/Colin/Colin.liu})
root@pts/1 $ echo ${array4[*]}
James Colin.liu Harry Betty

• Delete element

Format:
unset array, clear the whole array;
unset array [subscript], clear single element

root@pts/1 $ echo ${array2[*]}
James Colin Harry Betty
root@pts/1 $ echo ${array4[*]}
James Colin.liu Harry Betty

root@pts/1 $ unset array4
root@pts/1 $ unset ${array2[3]}

root@pts/1 $ echo ${array2[*]}
James Colin Harry Betty

root@pts/1 $ echo ${array4[*]}

root@pts/1 $