#!/bin/bash -u
# Put two integers in ascending order.  Prompt for missing arguments.
#------------------------------------------------------------
# Syntax:
#    $0 [ integer1 [ integer2 ] ]
#------------------------------------------------------------
# Purpose:
#    Get two inputs from the command line or by prompting and reading.
#    Validate them as integers using a function given in class.
#    Output a line containing the smaller number followed by the larger.
#    Print an error message and exit non-zero on any errors.
#-------------------------------------------------------------
# Student Name:                  Ian! D. Allen
# Algonquin EMail Address:       alleni
# Student Number:                000-000-000
# Course Number:                 CST8129
# Lab Section Number:            010
# Professor Name:                Ian! D. Allen
# Assignment Name/Number/Date:   Exercise #6, script 6, due October 22
# Comment:                       This is a sample assignment label.
# see http://idallen.com/teaching/assignment_standards.html
#-------------------------------------------------------------

# Set standard search path and umask.
#
PATH=/bin:/usr/bin ; export PATH
umask 022

# Function definitions go here ------------------------------------

# The IsNumeric function tests its argument to see if it is a valid number.
# It sets the return/exit status to zero if it is a number, to 1 if not.
#
IsNumeric () {
    # Make sure this function is called with exactly one argument.
    #
    if [ $# -ne 1 ] ; then
        echo 1>&2 "$0: Function IsNumeric expects one argument; found $# ($*)"
        exit 2
    fi

    # The expr command sets a return code of 2 on a syntax error or
    # bad (non-numeric) input.  Throw away all the output and errors;
    # look at the return status only.
    #
    [ "$1" = '-' ] && return 1 # compensate for non-number bug in expr
    expr 0 + "$1" >/dev/null 2>&1  # expr sets return code
    test "$?" -ne 2   # set return code to 0 if expr return is not 2
}
# End of function definitions ---------------------------------------

# Pick up any missing arguments by prompting on stderr and reading
# them from standard input.  Accept only zero, one, or two arguments.
# If more than 2, echo the count and incorrect input on stderr and exit.
#
case "$#" in
0)  echo 1>&2 "Enter two integers:"
    read int1 int2
    ;;
1)  int1="$1"
    echo 1>&2 "Enter one integer:"
    read int2
    ;;
2)  int1="$1"
    int2="$2"
    ;;
*)  echo 1>&2 "$0: Expecting 0-2 integer arguments, found $# ($*)"
    exit 1
    ;;
esac

# Optional: Print a nice message if either input number was empty.
#
if [ -z "$int1" -o -z "$int2" ] ; then
    echo 1>&2 "$0: Empty integer input; nothing done.  Bye."
    exit 1
fi

# Validate each input integer to make sure it is numeric.
#
if ! IsNumeric "$int1" ; then
    echo 1>&2 "$0: First input number '$int1' is not numeric."
    exit 1
fi
if ! IsNumeric "$int2" ; then
    echo 1>&2 "$0: Second input number '$int2' is not numeric."
    exit 1
fi

# Copy the inputs and put the two numbers in order, so $big is biggest.
#
small=$int1
big=$int2
if [ $small -gt $big ] ; then
    tmp=$small
    small=$big
    big=$tmp
fi

echo "You entered: $int1 and $int2.  In order, they are: $small $big"

exit 0