#!/bin/sh
: '
: This script removes lines which are repeated later.  The text for
: equality is done by default on the first field, however if $1 is present,
: it is done only on awk-field $1.  Explicitly specifying field 1 sets NN
: to a lower value (for efficiency) than defaulting to field 1
:
: Author: Corey Satten, corey @ cac.washington.edu, 4/4/90
:         http://staff.washington.edu/corey
: '
PATH=/bin:/usr/bin:/usr/ucb:/usr/local/bin:.
AWK=/usr/local/bin/mawk			# mawk has longer line limit than awk

NN=200					# substr of $0 to split into fields
# is a field specified?
case "$1" in
    '')		FLD=1;;
    1)		FLD=1; NN=40;	shift;;
    -[0-9]*)	FLD="-($1)";	shift;;	# forgive negative field numbers
    *)		FLD=$1;		shift;;
esac

exec $AWK '				# now do the real work with awk
	{
	n = split(x=substr($0,1,'$NN'),f);# only split first NN chars to fields
	if (ln=lno[f['$FLD']]) {
	    val[ln] = $0		# new value replaces old one
	    }
	else {
	    val[lno[f['$FLD']]= ++ctr] = $0
	    }
	}
    END	{
	for (i=1; i<=ctr; ++i)
	    printf("%s\n", val[i])
	}
' ${1+"$@"}