For Loop

Sometimes you need to repeat an action multiple times. Instead of writing the same command over and over, you can use a for loop to iterate through a list of items and perform an action on each one.

Here's the basic structure of a for loop in Bash:

#!/bin/bash
for name in Alice Bob Charlie; do
    echo "Hello, $name!"
done

This script outputs a greeting for each name in the list. The variable name takes on each value in turn: first "Alice", then "Bob", then "Charlie". The do keyword marks the start of the loop body, and done ends it.

For loops are especially powerful when combined with wildcards. You can loop through all files in a directory:

#!/bin/bash
for file in *.txt; do
    echo "Processing $file"
done

This iterates through every .txt file in the current directory. Each iteration, the file variable holds the current filename, letting you perform operations on each file automatically.

You can also loop through a range of numbers using brace expansion:

#!/bin/bash
for i in {1..5}; do
    echo "Number: $i"
done

This prints the numbers 1 through 5. For loops turn repetitive tasks into just a few lines of code, making your scripts more efficient and easier to maintain.