Outputting Contents #
* and @ can be used to access every element in an array.
[me@linuxbox ~]$ animals=("a dog" "a cat" "a fish")
[me@linuxbox ~]$ for i in ${animals[*]}; do echo $i; done
a
dog
a
cat
a
fish
[me@linuxbox ~]$ for i in ${animals[@]}; do echo $i; done
a
dog
a
cat
a
fish
[me@linuxbox ~]$ for i in "${animals[*]}"; do echo $i; done
a dog a cat a fish
[me@linuxbox ~]$ for i in "${animals[@]}"; do echo $i; done
a dog
a cat
a fish
Number of array elements #
[me@linuxbox ~]$ a[100]=foo
[me@linuxbox ~]$ echo ${#a[@]} # number of array elements
1
[me@linuxbox ~]$ echo ${#a[100]} # length of element 100
3
Finding subscripts (indexes) #
${!array[*]} ${!array[@]} both return indexes of the array
[me@linuxbox ~]$ foo=([2]=a [u]=b [6]=c)
[me@linuxbox ~]$ for i in "${foo[@]}"; do echo $i; done
a
b
c
[me@linuxbox ~]$ for i in "${!foo[@]}"; do echo $i; done
2
4
6
Adding elements to arrays #
Appending elements to arrays
[me@linuxbox ~]$ foo=(a b c)
[me@linuxbox ~]$ echo ${foo[@]}
a b c
[me@linuxbox ~]$ foo+=(d e f)
[me@linuxbox ~]$ echo ${foo[@]}
a b c d e f
Sorting arrays #
#!/bin/bash
# array-sort: Sort an array
a=(f e d c b a)
echo "Original array: ${a[@]}"
a_sorted=($(for i in "${a[@]}"; do echo $i; done | sort))
echo "Sorted array: ${a_sorted[@]}"
[me@linuxbox ~]$ array-sort
Original array: f e d c b a
Sorted array: a b c d e f
Deleting Arrays and Elements #
Use unset foo=(a b c d e f) unset foo echo ${foo[@]}
or unset ‘foo[2]’ echo ${foo[@]} a b d e f
Note: assigning an empty value to an array doesn’t empty it’s contents.