Jun-ichiro itojun Hagino writes:
> use ${start_precmd} to check duplicate sendmail.cf.
> do not use "err" on failure, it is not that fatal (it's okay if we
> don't start sendmail)

i'd use `err', because you want the script to fail when you manually
run it. err (or any other non-zero-exit-condition causing behaviour)
won't cause the main /etc/rc to halt unless the script names ends in
`.sh', because except in that case, the script is run in a subshell
anyway.