Infinite Loop trouble bash

Question

So, basically the code below is giving an infinite loop. However, if i change i+2 and f+2 to i++ and f++, they don't give an infinite loop. Can someone explain to me why this is? Thanks

#!/bin/bash
for ((i=0; i<5; i+2))
do
for ((f=0; f<5; f+2))
do
echo "$i $f"
done
done

Answer 1

You need to do += , not + (also, i+=2 should be f+=2 in your inner loop):

for ((i=0; i<5; i+=2))
do
    for ((f=0; f<5; f+=2))
    do
        echo "$i $f"
    done
done

Answer 2

i+2 does not change the value of i . It simply adds 2 to the current value of i and returns the result. i++ changes the value of i by incrementing it. Try this instead:

for ((i=0; i<5; i=i+2))

Note that i=i+2 can also be written shorthand as i+=2 . The meaning is the same: add 2 to the current value of i and assign the result to i .

Answer 3

+= syntax is short form so you could also represent i+=2 as i=i+2

for ((i=0; i<5; i+=2))
do
    for ((f=0; f<5; f+=2))
    do
        echo "$i $f"
    done
done