tst	param / are we substituting for $n
	bne	2f/ yes
	mov	inbufp,r1 / no, move normal input pointer to r1
	cmp	r1,einbuf / end of input line?
	bne	1f / no
	jsr	pc,getbuf / yes, put next console line in buffer
	br	getc
1:
	movb	(r1)+,r0 / move byte from input buffer to r0
	mov	r1,inbufp / increment routine
	bis	escap,r0 / if last character was \ this adds
		         / 200 to current character
	clr	escap / clear, so escap normally zero
	cmp	r0,$'\\ / note that \\ is equal \ in as
	beq	1f
	cmp	r0,$'$ / is it $
	beq	3f / yes
	rts	pc / no
1:
	mov	$200,escap / mark presence of \ in command line
	br	getc / get next character
2:
	movb	*param,r0 / pick up substitution character put in
		          / r0
	beq	1f / if end of substitution arg, branch
	inc	param / if not end, set for next character
	rts	pc / return as though character in ro is normal
		   / input
1:
	clr	param / unset substitution pointer
	br	getc / get next char in normal input
3:
	jsr	pc,getc / get digit after $
	sub	$'0,r0 / strip off zone bits
	cmp	r0,$9. / compare with digit 9 
	blos	1f / less than or equal 9
	mov	$9.,r0 / if larger than 9, force 9
1:
	mov	shellarg,r1 / get pointer to stack for
		            / this call of shell
	inc	r0 / digit +1
	cmp	r0,(r1) / is it less than # of args in this call
	bge	getc / no, ignore it. so this $n is not replaced
	asl	r0 / yes, multiply by 2 (to skip words)
	add	r1,r0 / form pointer to arg pointer (-2)
	mov	2(r0),param / move arg pointer to param
	br	getc / go to get substitution arg for $n
getbuf:
	mov	$inbuf,r0 / move input buffer address
	mov	r0,inbufp / to input buffer pointer
	mov	r0,einbuf / and initialize pointer to end of
		          / character string
	dec	r0 / decrement pointer so can utilize normal
		   / 100p starting at 1f
	mov	r0,0f / initialize address for reading 1st char