Class 22 of 37 • Advance Shell Script \t\t\t\t

Arrays in Linux Shell Scripting - Indexed & Associative Arrays Guide

a shell variable is capable enough to hold single or multiple values.shell supports a different type of variable called "array variable" to store multiple values at the same time with giving a single name to variable.

Declare an Array

declare -a ARRAY_NAME
							

Defining Array Value

# Notice: no spaces around '=' in Bash variable assignment!
Array_Name[Index]=Value
# Or compound initialization:
Array_Name=( 'Val1' 'Val2' 'Val3' )
							

Example

declare -a myarray

# Correct syntax without spaces around '='
myarray[0]='Virtualhax Inc.'
myarray[1]='Veewom Technology'
myarray[2]='Quizer Studio'

echo ${myarray[0]}

# Output
# Virtualhax Inc.
							

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Array Operations Cheatsheet

Operation	Bash Syntax	Description
Print Single Element	echo "${myarray[1]}"	Prints item at index 1.
Print All Elements	echo "${myarray[@]}"	Expands all items as separate words.
Array Length	echo "${#myarray[@]}"	Returns total number of elements.
Print All Indices	echo "${!myarray[@]}"	Returns all active index numbers.
Append Element	myarray+=("New Item")	Adds a new value at the end of the array.
Delete Element	unset myarray[1]	Removes element at index 1.

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Iterating Through an Array in Bash

#!/bin/bash
# Loop through array elements

courses=('Linux' 'PHP' 'Python' 'C-Programming' 'HTML')

echo "Total Courses: ${#courses[@]}"
echo "----------------------------------------"

for course in "${courses[@]}"
do
    echo "Course: $course"
done
							

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Associative Arrays (Hashmaps / Dictionaries in Bash)

Starting in Bash 4+, you can store key-value pairs using associative arrays (declared via declare -A):

#!/bin/bash
# Associative array demonstration

declare -A capitals

capitals["India"]="New Delhi"
capitals["USA"]="Washington D.C."
capitals["Japan"]="Tokyo"

echo "Capital of India is: ${capitals["India"]}"

# Loop through keys
for country in "${!capitals[@]}"
do
    echo "The capital of $country is ${capitals[$country]}"
done
							

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Frequently Asked Questions (FAQ)