For compatibility with the man(1) implementations of the man-1.6

and man-db packages, print the manpath if the -w option is given
without a following name argument.

This quirk has been in man-1.6 since at least man-1.5e (1998)
and in man-db since 2012.

Using this feature in portable software is a dubious idea because the
internal organization of manual page directories varies in about a
dozen respects among operating systems, so even if you get the answer,
there is no portable way to use it for looking up anything inside.
However, Matej Cepl <mcepl at suse dot cz> made me aware that some
software, for example the manual viewing functionality in the newest
editors/neovim code, unwisely relies on this feature anyway.

No objections were raised when this patch was shown on tech@.

1 files changed, 15 insertions, 3 deletions

diff --git a/usr.bin/mandoc/main.c b/usr.bin/mandoc/main.c
index bcf541409d1..694dc415e6d 100644
--- a/usr.bin/mandoc/main.c
+++ b/usr.bin/mandoc/main.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: main.c,v 1.245 2020/02/06 19:41:34 schwarze Exp $ */
+/*	$OpenBSD: main.c,v 1.246 2020/02/10 13:49:04 schwarze Exp $ */
 /*
  * Copyright (c) 2008-2012 Kristaps Dzonsons <kristaps@bsd.lv>
  * Copyright (c) 2010-2012, 2014-2020 Ingo Schwarze <schwarze@openbsd.org>
@@ -427,8 +427,20 @@ main(int argc, char *argv[])
 	/* man(1): Resolve each name individually. */
 
 	if (search.argmode == ARG_NAME) {
-		if (argc < 1)
-			usage(ARG_NAME);
+		if (argc < 1) {
+			if (outmode != OUTMODE_FLN)
+				usage(ARG_NAME);
+			if (conf.manpath.sz == 0) {
+				warnx("The manpath is empty.");
+				mandoc_msg_setrc(MANDOCLEVEL_BADARG);
+			} else {
+				for (i = 0; i + 1 < conf.manpath.sz; i++)
+					printf("%s:", conf.manpath.paths[i]);
+				printf("%s\n", conf.manpath.paths[i]);
+			}
+			manconf_free(&conf);
+			return (int)mandoc_msg_getrc();
+		}
 		for (res = NULL, ressz = 0; argc > 0; argc--, argv++) {
 			(void)mansearch(&search, &conf.manpath,
 			    1, argv, &resn, &resnsz);