How to loop over the lines of a file?

Question

Say I have this file:

hello
world
hello world

This program

#!/bin/bash

for i in $(cat $1); do
    echo "tester: $i"
done

outputs

tester: hello
tester: world
tester: hello
tester: world

I'd like to have the for iterate over each line individually ignoring whitespaces though, i.e. the last two lines should be replaced by

tester: hello world

Using quotes for i in "$(cat $1)"; results in i being asigned the whole file at once. What should I change?

Answer 1

With for and IFS:

#!/bin/bash

IFS=$'\n'       # make newlines the only separator
set -f          # disable globbing
for i in $(cat "$1"); do
  echo "tester: $i"
done

Or with read (no more cat):

#!/bin/bash

while IFS= read -r line; do
  echo "tester: $line"
done < "$1"