The Mighty For Loop in Bash

Are you tired of performing the same tedious tasks over and over again in your Bash scripts? Do you want to automate and streamline your workflow like a pro? If so, then it’s time to learn about the mighty for loop!

How the For Loop Works

The for loop is a fundamental control structure in Bash that allows you to repeat a set of commands for a given number of times or for each item in a list.

Here’s the basic syntax of a for loop:

for VARIABLE in list; do
    commands
done

The VARIABLE is a placeholder that takes on the value of each item in the list one by one. The commands are the actions that you want to perform for each iteration of the loop. The do keyword indicates the beginning of the loop body, and the done keyword indicates the end of the loop.

Here’s an example of a for loop that prints the numbers 1 through 10:

for i in {1..10}; do
    echo "$i"
done

The output of this loop would be:

1
2
3
4
5
6
7
8
9
10

You can also use the for loop to iterate over a list of items, such as the files in a directory. For example:

for file in /etc/*; do
    echo "$file"
done

This loop will print the names of all the files in the /etc directory.

Surprising Fact

Did you know that you can use the for loop to perform arithmetic operations? You can use the seq command to generate a sequence of numbers, and then use the for loop to perform calculations on each number.

For example, to calculate the squares of the numbers 1 through 10:

for i in $(seq 1 10); do
    echo "$((i * i))"
done

The output of this loop would be:

1
4
9
16
25
36
49
64
81
100

Key Takeaways

• The for loop is a control structure that allows you to repeat a set of commands for a given number of times or for each item in a list.
• The for loop has a simple syntax, with the VARIABLE taking on the value of each item in the list one by one and the commands being the actions to be performed for each iteration.
• You can use the for loop to perform arithmetic operations and other complex tasks in Bash.

5 Examples or Tips to Apply the For Loop for Increased Productivity

1. Use the for loop to automate repetitive tasks, such as renaming files or creating directories.
2. Use the seq command to generate a sequence of numbers and perform calculations on each number.
3. Use the for loop to iterate over a list of items, such as the files in a directory, and perform actions on each item.
4. Use the for loop in combination with the wget command to download a series of files from the internet.
5. Use the for loop to iterate over the lines of a file and perform actions on each line.

Challenge

Here’s a challenge to test your knowledge of the for loop: Write a Bash script that uses the for loop to iterate over the numbers 1 through 10, and for each number, print out the number and its square. The output should look like this:

1 1
2 4
3 9
4 16
5 25
6 36
7 49
8 64
9 81
10 100