How to retrieve absolute path given relative

Try realpath.

~ $ sudo apt-get install realpath  # may already be installed
~ $ realpath .bashrc
/home/username/.bashrc

To avoid expanding symlinks, use realpath -s.

The answer comes from "bash/fish command to print absolute path to a file".

#! /bin/sh
echo "$(cd "$(dirname "$1")"; pwd)/$(basename "$1")"

UPD Some explanations

1. This script get relative path as argument "$1"
2. Then we get dirname part of that path (you can pass either dir or file to this script): dirname "$1"
3. Then we cd "$(dirname "$1") into this relative dir and get absolute path for it by running pwd shell command
4. After that we append basename to absolute path: $(basename "$1")
5. As final step we echo it

use:

find "$(pwd)"/ -type f

to get all files or

echo "$(pwd)/$line"

to display full path (if relative path matters to)

If you have the coreutils package installed you can generally use readlink -f relative_file_name in order to retrieve the absolute one (with all symlinks resolved)