[: argument expected with -v Option about zfs-backup

[cpzengel]

i also have this on on my high sierra mac

[adaugherity]

Without -v, there is no output in normal operation. (If called from cron, any output will be mailed to the user, so only errors should be displayed.) Likewise, the "same as local" message makes sense if source and target are in sync.

I am unable to reproduce the syntax errors. It would seem that somehow your shell is unhappy with lines like

[ "$DEBUG" -o "$VERBOSE" ] && echo "$msg $snap2"

but that makes no sense, because even if those variables were unset, being enclosed in quotes should handle that --
[ "" -o "" ] is valid syntax evaluating to false.

What shell are you using? Try a different one, e.g. bash (it should work in any POSIX-compatible sh though). If you can reproduce the error, run with

sh -x zfs-backup.sh ...

(or bash -x, etc.) and put that into a gist so we can see what's going wrong.