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##########################################################################
# Shellscript:	avg - calculate the average of a column
# Version    :	0.3 (beta)
# Author     :	Heiner Steven (heiner.steven@odn.de)
# Date       :	19.09.94
# Category   :	Text Utilities
# SCCS-Id.   :	$Id: avg,v 1.1.1.1 1999/06/15 19:29:05 heiner Exp $
##########################################################################
# Changes
# 22.06.95 hs	specify the column as argument (0.2)
# 19.05.96 hs	Allow multiple files, -f and -t option (0.3)
##########################################################################

PN=`basename $0`			# program name
VER='0.3 (beta)'

Col=1					# Column
Delim=					# Field delimiter

Usage () {
    echo >&2 "$PN - calculate the average, $VER (stv '94)
usage: $PN [-f column] [-t delim] [file ...]
    -f: specify column (default is $Col)
    -t: field delimiter (default is whitespace)"
    exit 1
}

Msg () {
    for i
    do echo "$PN: $i" >&2
    done
}

Fatal () { Msg "$@"; exit 1; }

#set -- `getopt hf: "$@"`
while [ $# -gt 0 ]
do
    case "$1" in
	-f)	Col="$2"; shift;;
	-t)	Delim="$2"; shift;;
	--)	shift; break;;
	-h)	Usage;;
	-*)	Usage;;
	*)	break;;			# First file name
    esac
    shift
done

case "$Col" in
    *[!0-9]*)	Fatal "no column number: $Col";;
esac

awk ${Delim:+-F "$Delim"} '
    (NF >= '$Col' && $'$Col' != "") { Sum += $'$Col'; n++; }
    END { if ( n ) printf "%g\n", Sum / n; }
' "$@"