#!/bin/bash
 
echo "<<< Load a file into an array"
echo "# Set the IFS (Internal Field Separator) to a newline
IFS='
'
# Load file.txt from the current directory
arr=( \$( < file.txt ) )
"
 
 
IFS='
'
arr=( $( < file.txt ) )
 
 
echo "<<< Addressing individual array elements"
echo "\${arr[0]} = ${arr[0]}" # the first line of the file
echo "\${arr[1]} = ${arr[1]}" # the second line of the file
 
 
echo ""
echo "<<< \${#VARNAME[@]} will always return the number of elements in an array"
echo "\$arr contains ${#arr[@]} (\${#arr[@]}) items"
 
echo ""
echo "<<< Loop through the array (\${arr[@]}), loading each item as \$foo."
num=1
for foo in "${arr[@]}" ; do
	echo "Loop iteration $num: $foo"
	num=$((num+1))
done
 
 
echo ""
echo "<<< Loop through the array, addressing each item with an index"
num=0
while [[ $num -lt ${#arr[@]} ]] ; do
	echo "Array index $num (\${arr[$num]}): ${arr[$num]}"
	num=$((num+1))
done

file line 1
file line 2
file line 3
file line 4

$./array.sh 
<<< Load a file into an array
# Set the IFS (Internal Field Separator) to a newline
IFS='
'
# Load file.txt from the current directory
arr=( $( < file.txt ) )
 
<<< Addressing individual array elements
${arr[0]} = file line 1
${arr[1]} = file line 2
 
<<< ${#VARNAME[@]} will always return the number of elements in an array
$arr contains 4 (${#arr[@]}) items
 
<<< Loop through the array (${arr[@]}), loading each item as $foo.
Loop iteration 1: file line 1
Loop iteration 2: file line 2
Loop iteration 3: file line 3
Loop iteration 4: file line 4
 
<<< Loop through the array, addressing each item with an index
Array index 0 (${arr[0]}): file line 1
Array index 1 (${arr[1]}): file line 2
Array index 2 (${arr[2]}): file line 3
Array index 3 (${arr[3]}): file line 4