#!/bin/bash

#
# Check that the data file exists
#
data="bash13_ex4.txt"
[ -e "$data" ] || { echo "File $data not found"; exit 1; }

#
# Email addresses can be:
#   1. local-part@domain
#   2. Name <local-part@domain>
#
part1='([a-zA-Z0-9_][a-zA-Z0-9_.]+@[a-zA-Z0-9.-]+)'
part2='([^<]+)<([a-zA-Z0-9_][a-zA-Z0-9_.]+@[a-zA-Z0-9.-]+)>'
re="^($part1|$part2)$"

#
# Read and check each line from the file
#
while read -r line; do
    #
    # Does it match the regular expression?
    #
    if [[ $line =~ $re ]]; then
        #declare -p BASH_REMATCH
        #
        # Decide which format it is depending on whether element 2 of
        # BASH_REMATCH is zero length
        #
        if [[ -z ${BASH_REMATCH[2]} ]]; then
            # Type 2
            name="${BASH_REMATCH[3]}"
            email="${BASH_REMATCH[4]}"
        else
            # Type 1
            name=
            email="${BASH_REMATCH[2]}"
        fi
        echo "Name: $name"
        echo "Email: $email"
    else
        echo "Not recognised: $line"
    fi
    echo
done < "$data"