getconf.1: Note that leading underscores in configuration

variable names are ignored by getconf(1).

While here, add a section with examples, and make the synopsis
more concise.

PR bin/57875

usr.bin/getconf/getconf.1

@@ -1,4 +1,4 @@
-.\"	$NetBSD: getconf.1,v 1.13 2014/04/13 01:45:34 snj Exp $
+.\"	$NetBSD: getconf.1,v 1.14 2024/02/18 19:35:38 jkoshy Exp $
 .\"
 .\" Copyright (c) 1996 The NetBSD Foundation, Inc.
 .\" All rights reserved.
@@ -27,7 +27,7 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd August 9, 2011
+.Dd February 18, 2024
 .Dt GETCONF 1
 .Os
 .Sh NAME
@@ -37,13 +37,10 @@
 .Nm
 .Ar system_var
 .Nm
-.Fl a
-.Nm
 .Ar path_var
 .Ar pathname
 .Nm
-.Fl a
-.Ar pathname
+.Fl a Op Ar pathname
 .Sh DESCRIPTION
 The
 .Nm
@@ -80,8 +77,28 @@ standard output, in the format
 =
 .Va value
 .Dc .
+.Pp
+For compatibility with other operating systems,
+.Nm
+will ignore leading underscores in the names specified in the
+.Ar system_var
+and
+.Ar path_var
+arguments.
 .Sh EXIT STATUS
 .Ex -std
+.Sh EXAMPLES
+To retrieve the number of configured processors, use:
+.Bd -literal -offset indent
+$ getconf NPROCESSORS_CONF
+.Ed
+.Pp
+To retrieve the maximum number of bytes (excluding the trailing
+.Dv NUL )
+for a filename in the current directory, use:
+.Bd -literal -offset indent
+$ getconf NAME_MAX .
+.Ed
 .Sh SEE ALSO
 .Xr pathconf 2 ,
 .Xr confstr 3 ,