sys-utils/README.hwclock

Hwclock is a program that runs under Linux and sets and queries the 
Hardware Clock, which is often called the Real Time Clock, RTC, or
CMOS clock.

Hwclock is shipped with an ELF executable built for ISA (Intel)
machines.  So there is nothing to build for those machines.  Just
install the executable file "hwclock" and the man page file
"hwclock.8" in suitable directories (like /sbin/hwclock and
/usr/man/man8/hwclock.8) and you're ready to go.

hwclock accesses platform-dependent hardware, so if you have something
other than an ISA machine, the shipped executable probably doesn't work,
and you have to compile hwclock yourself.

Sometimes, you need to install hwclock setuid root.  If you want users
other than the superuser to be able to display the clock value using the
direct ISA I/O method, install it setuid root.  If you have the /dev/rtc
interface on your system or are on a non-ISA system, there's no need for
users to use the direct ISA I/O method, so don't bother.

To install setuid root, do something like this:

  chmod a=rx,u=s /sbin/hwclock

In any case, hwclock will not allow you to set anything unless you have
the superuser _real_ uid.  (This is restriction is not necessary if you
haven't installed setuid root, but it's there for now).

You may want to preformat and/or compress the man page before installing.

If you want to build hwclock, just cd to the source directory and invoke
make with no parameters.

hwclock calls option processing routines in the libsshopt library,
which is part of Sverre H. Huseby's "shhopt" package.  An ELF
executable of this library is included in the package, but you can use
a copy that is already on your system by altering the make file.  You
can find a more authoritative copy of this library, and its source
code, on sunsite (ftp://sunsite.unc.edu/pub/Linux/libs/shhopt-X.Y).

As shipped, the routines are linked in statically, so you only need the
libsshopt.a file to build hwclock, not to run it.