loop over lines in output bash code example

Example 1: bash loop lines in file

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

Example 2: for line in output bash

Use for in bash for iterating words in a string or values in an array as:
for value in {1, 2, 3}; do echo $value; done
for value in $(cat arguments_files.txt); do [some_command]; done
And use while for iterating lines from a pipe output as:
cat arguments_file.txt | while read line; do [some_command]; done