Check out example codes for "ruby for loop". It will help you in understanding the concepts better.

Code Example 1

# You can use an each to mimic the functionality of a for loop

(0..5).each do |i|
  puts "Inside loop i = #{i}"
  # put your code for loop here
end

# outputs 
# Inside loop i = 0   
# Inside loop i = 1
# Inside loop i = 2
# Inside loop i = 3
# Inside loop i = 4
# Inside loop i = 5

Code Example 2

for element in array do
  element.do_stuff
end

Code Example 3

for i in 0..2 do 
  print(i)
end

# => 0
# => 1
# => 2

Code Example 4

while $i < $num  do
   puts("Inside the loop i = #$i" )
   $i +=1
end

Code Example 5

for element in array do
  element.do_stuff
end

Code Example 6

#!/usr/bin/ruby

$i = 0
$num = 5

while $i < $num  do
   puts("Inside the loop i = #$i" )
   $i +=1
end

# outputs
# Inside the loop i = 0
# Inside the loop i = 1
# Inside the loop i = 2
# Inside the loop i = 3
# Inside the loop i = 4

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