Loops are an important part of any pragramming language, they offer a way to repeat commands or instruction witout repeating lines of code, the for loop comes in diffrent styles in bash scripting

Generally the for loop has the following syntax:

    for var in list
        do
            commands
    done

C style for loop:

for (( i= 0 ; i<=10; i++ )) ; do
    echo $i
done

for loop with basic range:

the following for loop will print numbers from 0 to 10:

for i in {0..10} ; do
    echo $i
done

for loop with range and step:

the following for loop will print the numbers : 0 5 10 15 20, since the step is 5

for i in {0..20..5} ; do
    echo $i
done

We can iterate through the results of a command

for w in $(echo "John Smith Sarah Ashly" ) ; do
    echo "my name is $w"
done

the next for loop will go through html files in a directory and change their extension to php

for f in $(ls dir/*.html) ; do
    mv "$f" "$( basename -s .html $f ).php"
done