NUT

Let's have a look at the manual entry for the command upsd of the NUT package :

NAME
       upsd - UPS information server

SYNOPSIS
       upsd -h

       upsd [OPTIONS]

...
OPTIONS
       -h
           Display the help text.

Ok, let's try it.

# upsd
# echo $?
1
# upsd -h
# echo $?
1

: after editing nut.conf
# upsd -h
Network UPS Tools upsd 2.7.4
Network server for UPS data.
...
# echo $?
0

I guess if there is a parse error in upsd.conf they call exit(1); directly.

Why not print ANY error message ?