From e07b0c12ba6435421ceb7dd028402d5cbfc1f1dd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fernando=20Apestegu=C3=ADa?= <fernape@FreeBSD.org>
Date: Mon, 11 Apr 2022 20:40:28 +0200
Subject: [PATCH] [patch][doc] Fix EXAMPLE in kqueue(2)

The error control was not properly implemented. "changelist" is const, hence
event.flags is never changed by the syscall.

PR:	196844
Reported by:	eugen@
Reviewed by:	PauAmma <pauamma@gundo.com>
Approved by:	eugen@
Fixes:	8c231786f01b9f8614e2fe5b47196db1caa7a772
---
 lib/libc/sys/kqueue.2 | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/lib/libc/sys/kqueue.2 b/lib/libc/sys/kqueue.2
index 8ba1779c5551..b4531b6cd02b 100644
--- a/lib/libc/sys/kqueue.2
+++ b/lib/libc/sys/kqueue.2
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd January 20, 2022
+.Dd April 13, 2022
 .Dt KQUEUE 2
 .Os
 .Sh NAME
@@ -742,8 +742,6 @@ main(int argc, char **argv)
     ret = kevent(kq, &event, 1, NULL, 0, NULL);
     if (ret == -1)
 	err(EXIT_FAILURE, "kevent register");
-    if (event.flags & EV_ERROR)
-	errx(EXIT_FAILURE, "Event error: %s", strerror(event.data));
 
     for (;;) {
 	/* Sleep until something happens. */
@@ -751,8 +749,12 @@ main(int argc, char **argv)
 	if (ret == -1) {
 	    err(EXIT_FAILURE, "kevent wait");
 	} else if (ret > 0) {
-	    printf("Something was written in '%s'\en", argv[1]);
-	}
+	    if (tevent.flags & EV_ERROR)
+		errx(EXIT_FAILURE, "Event error: %s", strerror(event.data));
+	    else
+		printf("Something was written in '%s'\en", argv[1]);
+}
+
     }
 }
 .Ed