cron: add log suppression and mail suppression for successful runs

[freebsd_t.lastninja.net]

Summary

I would like to see FreeBSD provide the crontab extensions found in OpenBSD
that implement -n to suppress mail on successful run and -q to suppress
logging of command execution.

The -q option appears decades old, but -n is relatively new. The
original proposal by Job Snijder can be found here [1], and gives very
convincing reasons for inclusion in base.

This patch is a nearly identical port of OpenBSD cron for -q and -n
features. It is written to follow existing conventions and style of the
existing codebase. I'm also not good at writing manpages but gave it my best
shot.

[1]: https://marc.info/?l=openbsd-tech&m=152874866117948&w=2

PR: 237538

Test Plan

I tested each of the following crontab entries in isolation:

# should both log and send email
* * * * * date

# should log but not send email (check to preserve original behaviour)
* * * * * date >/dev/null

# should only send email, but won't show up in log
* * * * * -q date

# should not send email
* * * * * -n date

# should not send email or log
* * * * * -n -q date

# should send email because of ping failure
* * * * * -n -q ping -c 1 5.5.5.5

I also tested to ensure the command options work using the
/etc/crontab format which requires user to be specified.

Also, I tested the empty command entry, e.g.:

* * * * *

This will log but never send an email.

However, because of the way the parsing works, an empty command
is not supported in conjunction with command options. So:

* * * * * -q

will not parse as valid crontab syntax.

I suspect this is the same behaviour as OpenBSD crontab, and
frankly makes sense - since an empty command entry only purpose
is to provide a signal in the cron logs.

[freebsd_t.lastninja.net]

• crontab: add -n to not mail if run is successful

[freebsd_t.lastninja.net]

• crontab: add -n to not mail if run is successful

[bcr]

Can you run "mandoc -Tlint" and textproc/igor over the man page? Thanks!

[freebsd_t.lastninja.net]

• crontab: add -q option to suppress logging
• crontab: add -n to not mail if run is successful

[freebsd_t.lastninja.net]

In D20046#431547, @bcr wrote:

Can you run "mandoc -Tlint" and textproc/igor over the man page? Thanks!

Hi I have run both commands and rectified all warnings introduced by my change.

Thanks.

[bcr]

OK, thanks. Approved for the manpages part.

[kevans]

Sorry for the long delay... I think just these really minor style nits.

usr.sbin/cron/cron/do_command.c

99 ↗

(On Diff #56699)

Kill this blank line

539 ↗

(On Diff #56699)

Please move this comment to its own spacing after beginning and before end of comment markers

543 ↗

(On Diff #56699)

I'd lean towards moving the comment to the line before it, but the style here is all fairly broken (already, before this change) with respect to style(9)

usr.sbin/cron/lib/entry.c

440 ↗

(On Diff #56699)

Space after switch keyword

[danfe]

usr.sbin/cron/cron/do_command.c

101 ↗

(On Diff #56699)

Since you're changing these lines anyway, would it make sense to drop the register specifier?

546 ↗

(On Diff #56699)

This comment violates our style(9).

553 ↗

(On Diff #56699)

This one as well.

559 ↗

(On Diff #56699)

I'm not a native speaker, but shouldn't executed be followed by an adverb, not adjective?

[kevans]

usr.sbin/cron/cron/do_command.c

546 ↗

(On Diff #56699)

It matches the style of the rest of the file, which is more important and allowed by style(9) last time I read it.

553 ↗

(On Diff #56699)

Ditto above comment

559 ↗

(On Diff #56699)

Indeed, successfully