Document the -N option in the usage message and the man page.

sbin/sysctl/sysctl.8

@@ -40,14 +40,14 @@
 .Nd get or set kernel state
 .Sh SYNOPSIS
 .Nm
-.Op Fl bn
+.Op Fl bNn
 .Ar name ...
 .Nm
-.Op Fl bn
+.Op Fl bNn
 .Fl w
 .Ar name=value ...
 .Nm
-.Op Fl bn
+.Op Fl bNn
 .Fl aAX
 .Sh DESCRIPTION
 The
@@ -73,6 +73,8 @@ few bytes is dumped in hex.
 Same as
 .Fl A
 except the entire value of opaque variables is hexdumped.
+.It Fl N
+Show only variable names, not their values.
 .It Fl n
 Specify that the printing of the field name should be
 suppressed and that only its value should be output.

sbin/sysctl/sysctl.c

@@ -71,11 +71,11 @@ usage(void)
 {
 
 	(void)fprintf(stderr, "%s\n%s\n%s\n%s\n%s\n",
-		"usage: sysctl [-bn] variable ...",
-		"       sysctl [-bn] -w variable=value ...",
-		"       sysctl [-bn] -a",
-		"       sysctl [-bn] -A",
-		"       sysctl [-bn] -X");
+		"usage: sysctl [-bNn] variable ...",
+		"       sysctl [-bNn] -w variable=value ...",
+		"       sysctl [-bNn] -a",
+		"       sysctl [-bNn] -A",
+		"       sysctl [-bNn] -X");
 	exit(1);
 }