Linux Classroom Series – 07/Sept/2020

How to pass arrays to the functions

• Lets pass arguments to shell script which in turn passes array to the function

#!/bin/bash
display_array() {
    array=$@
    echo "The array inside the function is ${array[*]}" 
    for item in "$@"
    do
        echo "Argument is ${item}"
    done
}



test_input_1=(1 2 3 4 5)

for item in "${test_input_1[@]}"
do
    echo "External $item"
done

echo "The orginal array for test input 1 is ${test_input_1[*]}"
echo "Calling function"
display_array ${test_input_1[*]}

• Execute the following commands as shown below

Variable scope

• By default variables inside the function are global variables

#!/bin/bash

test_variable_1=10


testfunction() {
    test_variable_1=50
    test_variable_2=100
}

testfunction
echo "$test_variable_1"
echo "$test_variable_2"

• In shell if your variable has to be local inside function, you have to explicit

#!/bin/bash

test_variable_1=10


testfunction() {
    test_variable_1=50
    test_variable_2=100
    local test_variable_3=200
    echo "Inside function: $test_variable_3"
}

testfunction
echo "$test_variable_1"
echo "$test_variable_2"
echo "Outside function: $test_variable_3"

Returning values from functions

• Shell sample

#!/bin/bash
print_message() {
    input="$1"
    output="Message is ${input}"
    return $output
}

$reply=$print_message "1"}
echo $reply

• Try to fix the issue in above script to get the reply from function