V6/usr/source/s2/tty.s

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/ tty -- get tty number

.globl	ttyn

	clr	r0
	jsr	pc,ttyn
	movb	r0,nam
	mov	$1,r0
	sys	write; name; 5
	sys	exit

.data
name:
	<tty>
nam:
	<x\n>
.even