fork was present in v1 https://www.bell-labs.com/usr/dmr/www/man21.pdfdiff -r1.24 -r1.25 src/lib/libc/sys/fork.2
(sevan)
--- src/lib/libc/sys/fork.2 2016/07/12 12:24:40 1.24
+++ src/lib/libc/sys/fork.2 2019/09/01 19:40:07 1.25
@@ -1,4 +1,4 @@
-.\" $NetBSD: fork.2,v 1.24 2016/07/12 12:24:40 wiz Exp $
+.\" $NetBSD: fork.2,v 1.25 2019/09/01 19:40:07 sevan Exp $
.\"
.\" Copyright (c) 1980, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
@@ -29,7 +29,7 @@
.\"
.\" @(#)fork.2 8.1 (Berkeley) 6/4/93
.\"
-.Dd July 9, 2016
+.Dd September 1, 2019
.Dt FORK 2
.Os
.Sh NAME
@@ -136,4 +136,4 @@
A
.Fn fork
system call appeared in
-.At v6 .
+.At v1 .