#!/bin/sh -u
#
# Place argument 1 at the right place in a command line and then run
# the command. This is a tool to support filteredit et al.
#	- Cameron Simpson <cs@zip.com.au> 17jul2004
#

cmd=$0
usage="Usage: $cmd [-stdin] [-end] [-n] [--] arg command [command-args...]
	-stdin	Treat arg as a filename and attach stdin to the file.
		Implies -discard; add a -n or -end to also use the arg.
	-discard Discard the arg.
	-end	Put arg after all the command-args.
		This is the default.
	-n	Put arg after the first n command-args.
		-0 and -1 are the common examples.
	-x	trace execution of command."

badopts=

dostdin=
pos=end
trace=

while [ $# -gt 0 ]
do
  case "$1" in
    -stdin)	dostdin=1 pos= ;;
    -discard)	pos= ;;
    -end)	pos=end ;;
    -[0-9]*)	pos=`expr "x$1" : 'x-\([0-9]*\)'` ;;
    -x)		trace=set-x ;;
    --)		shift; break ;;
    -?*)	echo "$cmd: unrecognised argument: $1" >&2; badopts=1 ;;
    *)		break ;;
  esac
  shift
done

if [ $# = 0 ]
then
  echo "$cmd: missing arg" >&2
  badopts=1
else
  arg=$1; shift
  if [ $# = 0 ]
  then
    echo "$cmd: missing command" >&2
    badopts=1
  else
    command=$1
    shift
  fi
fi

[ $badopts ] && { echo "$usage" >&2; exit 2; }

case "$pos" in
  '')	;;
  end)	set -- ${1+"$@"} "$arg" ;;
  *)	first=1
	gotarg=1
	skipped=0
	for argv
	do
	  [ $first ] && { set --; first=; }
	  [ $skipped = $pos ] && { set -- ${1+"$@"} "$arg"; gotarg=; }
	  set -- ${1+"$@"} "$argv"
	  skipped=`expr $skipped + 1`
	done
	[ $gotarg ] && set -- ${1+"$@"} "$arg"
	;;
esac

[ $dostdin ] && exec <"$arg"

exec $trace "$command" ${1+"$@"}