how to loop over lines in file in bash code example

Example 1: bash iterate over lines of a file

while read p; do
  echo "$p"
done <peptides.txt

Example 2: bash for each line of file

while read p; do
  echo "$p"
done <peptides.txt

Example 3: bash loop lines in file

#!/bin/bash
filename='peptides.txt'
echo Start
while read p; do 
    echo $p
done < $filename