#!/bin/sh -u
# simple shell script using an AWK script to sum a given column of numbers
#
#  $0 fieldno [filenames...]
#
# fieldno: the field number to sum in the input file(s)
#
# Sum a column of integers.  (May contain dollar signs.)
# Sum stdin if no files given.
#
# NOTE: This script fragment is incomplete - it does not follow all
# the script guidelines set out in "script_style.txt".  It also
# contains many "Instructor-Style" comments that you must not use in
# your own scripts.  See script_style.txt for details.
#
# -IAN! idallen@idallen.ca

# Assign fieldno and then shift it away, leaving only file names (if any).
# We will pass the file names to AWK, below.
# XXX This script fragment is missing input validation!
#
fieldno=$1
shift

# The AWK program is passed as one large multi-line single-quoted string.
# The program contains only three "lines" - a BEGIN, a middle, and and END.
# The middle line has a selector in front of it to select only lines
# where the given field contains only digits or dollar signs.
#
# Variables are passed into the AWK script using special syntax
# 'fieldno=$fieldno' immediately following the script string, below:
#
awk '
BEGIN   { sum=0; count=0 }

# Look for digits and dollar signs only.
#
$fieldno ~ /^[$0-9]+$/ {
            num = $fieldno

            print "DEBUG num before gsub is", num
            gsub("[$]","",num)
            print "DEBUG num after gsub is", num

            # make sure after gsub that there are digits left!
            if ( num ~ /^[0-9]+$/ ) {
                    sum = sum + num
                    count = count + 1
            }
            else {
                    print $fieldno, "is non numeric in", $0
		    next
            }
        }

END     { print "sum of", count, "numbers is", sum }
' fieldno=$fieldno "$@"