| Syntax | Description |
|---|---|
| ARRAY=() | Declares an indexed array ARRAY and initializes it to be empty. This can also be used to empty an existing array. |
| ARRAY[0]= | Generally sets the first element of an indexed array. If no array ARRAY existed before, it is created. |
| declare -a ARRAY | Declares an indexed array ARRAY. An existing array is not initialized. |
| declare -A ARRAY | Declares an associative array ARRAY. This is the one and only way to create associative arrays. |
- numerical array indexes start at 0
- Indexed arrays are always sparse, meaning indexes are not necessarily contiguous.
| Syntax | Description |
|---|---|
| ARRAY[N]=VALUE | Sets the element N of the indexed array ARRAY to VALUE. |
| ARRAY=(E1 E2 …) | Compound array assignment - sets the whole array ARRAY to the given list of elements indexed sequentially starting at zero. The array is unset before assignment unless the += operator is used. When the list is empty (ARRAY=()), the array will be set to an empty array. This method obviously does not use explicit indexes. An associative array can not be set like that! Clearing an associative array using ARRAY=() works. |
| ARRAY+=(E1 E2 …) | Append to ARRAY. |
| ARRAY=("${ANOTHER_ARRAY[@]}") | Copy ANOTHER_ARRAY to ARRAY, copying each element |
| Syntax | Description |
|---|---|
| ARRAY[STRING]=VALUE | Sets the element indexed by STRING of the associative array ARRAY. |
| ARRAY=([S1]=E1 [S2]=E2 …) | Individual mass-setting for associative arrays. The named indexes (here: S1 and S2) are strings |
| Syntax | Description |
|---|---|
| ${ARRAY[N]} | Expands to the value of the index N in the indexed array ARRAY. If N is a negative number, it's treated as the offset from the maximum assigned index (can't be used for assignment) - 1 |
| Syntax | Description |
|---|---|
| ${#ARRAY[N]} | Expands to the length of an individual array member at index N (stringlength) |
| ${#ARRAY[STRING]} | Expands to the length of an individual associative array member at index STRING (stringlength) |
| ${#ARRAY[@]} ${#ARRAY[*]} | Array Length; Expands to the number of elements in ARRAY |
| ${!ARRAY[@]} ${!ARRAY[*]} | KEYS; Expands to the indexes in ARRAY since BASH 3.0 |
| Syntax | Description |
|---|---|
| unset -v ARRAY | Destroys a complete array |
| unset -v ARRAY[@] | Same as above |
| unset -v ARRAY[*] | Same as above |
| unset -v ARRAY[N] | Destroys the array element at index N |
| unset -v ARRAY[STRING] | Destroys the array element of the associative array at index STRING |