Bash Arrays: Difference between revisions

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===Entire Array===
===Entire Array===
The (...) syntax can be used to initialize an entire array. The values must be separated by space:
a=("X" "Y" "Z")
If we want initialize only specific elements, we can use this syntax:
a=([0]="X" [4]="Y" [8]="Z")


==Reference==
==Reference==

Revision as of 21:55, 23 February 2018

Internal

Indexed Arrays

External

Overview

bash indexed arrays are 0-based and unidimensional. No explicit declaration is necessary if at least one element is initialized as described below:

Declaration

Arrays do not need explicit declarations, they will be automatically declared upon the first assignment of any of their elements.

my_array_var[0]="something"

They can be explicitly declared, though:

declare -a my_array_var

Previously declared arrays can be listed with:

declare -a

Assignment

Individual Elements

Individual elements are initialized by using ${var-name[index]}=value notation:

a[0]="something"

Entire Array

The (...) syntax can be used to initialize an entire array. The values must be separated by space:

a=("X" "Y" "Z")

If we want initialize only specific elements, we can use this syntax:

a=([0]="X" [4]="Y" [8]="Z")

Reference

Element arrays can be referenced with ${var-name[index]} notation:

echo ${a[0]}

If the array variable was not previously declared, or if the specific element was not initialized, a reference attempt will return the blank string.

Use Cases

Associative Arrays