- Add a simple example to uname(1) manual page to show how the hardware

platform (returned by -m) can be different from the machine's processor
  architecture (-p)
- Document that make(1) sets universal MACHINE and MACHINE_ARCH variables
  based on these values

Reviewed by:		imp, manpages (bjk)
Approved by:		bjk, imp (implied)
Differential Revision:	https://reviews.freebsd.org/D10489

usr.bin/uname/uname.1

@@ -28,7 +28,7 @@
 .\"	@(#)uname.1	8.3 (Berkeley) 4/8/94
 .\" $FreeBSD$
 .\"
-.Dd November 20, 2013
+.Dd May 31, 2017
 .Dt UNAME 1
 .Os
 .Sh NAME
@@ -61,6 +61,11 @@ Write the
 version of the kernel.
 .It Fl m
 Write the type of the current hardware platform to standard output.
+.Po Xr make 1
+uses it to set the
+.Va MACHINE
+variable.
+.Pc
 .It Fl n
 Write the name of the system to standard output.
 .It Fl o
@@ -69,6 +74,11 @@ This is a synonym for the
 option, for compatibility with other systems.
 .It Fl p
 Write the type of the machine processor architecture to standard output.
+.Po Xr make 1
+uses it to set the
+.Va MACHINE_ARCH
+variable.
+.Pc
 .It Fl r
 Write the current release level of the operating system
 to standard output.
@@ -106,6 +116,19 @@ will allow the corresponding data to be set to the contents
 of the environment variable.
 .Sh EXIT STATUS
 .Ex -std
+.Sh EXAMPLES
+The hardware platform
+.Pq Fl m
+can be different from the machine's processor architecture
+.Pq Fl p ,
+e.g., on 64-bit PowerPC,
+.Fl m
+would return
+.Va powerpc
+and
+.Fl p
+would return
+.Va powerpc64 .
 .Sh SEE ALSO
 .Xr feature_present 3 ,
 .Xr getosreldate 3 ,