BASH Loops

Bash supports both while and for loop. Each has some variants to help us do our work better!

Control statements

Besides loop condition, both while and for loop, undesrtands common control commands:

• break - finish loop execution immediately
• continue - jump to next iteration now

While loop

While loop with condition

foo=1
while [ $x -le 10 ]
do
  echo "Iteration ${foo}"
  foo=$(( $foo + 1 ))
done

Dead while loop

Loop without condition is a dead loop

while :
do
	echo "I' the DEAD LOOP!"
done

echo "Unreachable code"

Unless there is a break in it

while :
do
	break
    echo "Unreachable code"
done

echo "I'm free!"

For loop

With explicit list of items

for i in 1 2 3 4 5 6 7 8 9 10
do
   echo "Iteration ${i}"
done

For loop with range

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

every third element

for i in {1..10..3}
do
    echo "Iteration ${i}"
done

C style! 💃

for (( i=1; i<=10; i++ ))
do
   echo "Iteration ${i}"
done

Dead loop again!

for (( ; ; ))
do
	echo "I' the DEAD LOOP!"
done

echo "Unreachable code"

But we can use break just like in while loop