For loops in bash

You can use for loops in bash just like in any other programing language. The basic syntax is like this:

for variable-name in 1 2 3
do
  list-of-commands
done

One line for loop in bash

To do a quick one-liner with for, we use a semicolon to separate each line. In this example, we will give for a list of 4 items to iterate through.

~$ for i in 1 2 3 4; do echo "This is line number $i"; done;
This is line number 1
This is line number 2
This is line number 3
This is line number 4

For loop in a bash script

When writing a script. We don’t need to use the semicolon as in the example above. This time we write each part of the command on a separate line. This example will print exactly the same output as the one-liner we just did.

for i in 1 2 3 4
do
        echo "This is line number $i"
done

Use a command to get a list of items

Instead of giving for a long list of items to iterate through, we can also wrap a command in $( ) to get the list. In this example we use the seq command to get a list of numbers 1 through 4. This will output exactly the same as above.

for i in $( seq 1 4 )
do
        echo "This is line number $i"
done