#!/bin/sh -u
#   $0    (no arguments)
# Purpose: Display the full user@domain email address of the user.
#
# BUGS: Does not work unless there is a "domain" line in /etc/resolv.conf
#
# WARNING: Many of the comments in this file are "Instructor-Type"
#   comments and are *not* appropriate for real scripts.  Do not put
#   "Instructor-Type" comments into the scripts that you submit for marking.
#   I put them in my example files because I am teaching you how to
#   write scripts; do not submit my teaching comments back to me again.
# -IAN! idallen@ncf.ca

# Set the search path for the shell to be the standard places.
# Set the umask to be non-restrictive and friendly to others.
#  - nothing in this script now actually creates any files, so the umask
#    will not be needed; but, keep it here in case of future changes
#
export PATH=/bin:/usr/bin
umask 022

# Set variables to be each part of the email address.
#  - variable assignment is optional; it makes the code clearer
# Use shell "Command Substitution" to get the needed information.
#  - no need to quote here: wildcards do NOT expand in assignment statements
# The leading '^' in the pattern means "only at the beginning of the line".
#  - I quote the '^' character if I don't know how the shell might interpret it
# The awk code prints the second field in all lines coming from stdin.
#  - it works both for blank-delimted and/or tab-delimited fields
#  - the single argument to awk must be fully protected from the shell
#
whoami=$(whoami)
domain=$(grep -e '^domain' /etc/resolv.conf | awk '{print $2}')

# Quote the variables to prevent any possible glob/wildcard expansion.
# Note the difference between $whoami [a variable] and $(whoami) [a command].
# I quote the '@' character if I don't know how the shell might interpret it.
#
echo "$whoami@$domain"