theshell

The second type of loops are for loops. They follow this syntax:

  for [variable] in [list] do
    [code]
  done

Their purpose is to iterate over a list. Also, while loops could do this, you might argue...
Of course, they could, but for loops are specifically meant to do this. Therefore, for instance, you don't have to declare your counter variable outside the loop. Most importantly, this variable can be accessed from inside the loop.
For loops take this form:

for VARIABLE in 1 2 3 4 5 .. N
do
    command1
    command2
    commandN
done

Here is a simple example:

for i in 1 2 3 4 5
do
   echo "Welcome $i times"
done

This first example of code simply displays a welcome message 5 times. The output of this piece of code is:

    Welcome 1 times
    Welcome 2 times
    Welcome 3 times
    Welcome 4 times
    Welcome 5 times

There are also other ways to specify the numerical range . For instance, if your numerical range is too big, you can simply write: {1..100} . This piece of code means every natural number between 1 and 100 (both included).
Ranges can also count backward like this: {10..1}. You can even increment the numerical value by steps of two: {0..10..2} . This piece of code means every natural number between 0 and 10 in steps of two; 0 2 4 6... 10.