Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/653

Fixes:		fe590ffe40f49fe09d8275fbf29f0d46c5b99dc7
MFC after:	on demand
Sponsored by:	Dell EMC Isilon

Specifically, import the diff from commit e745bd4c10ab to
commit 83563783cc2 in https://github.com/vixie/cron.git

My sole motivation is changing to the common MIT license.
The old license, especially the "buildable source" clause,
is unfriendly for commercial users of this code.  Simply
changing the license without importing [most of] the code
accompanying that license seemed legally dubious.

The most regrettable change is losing Paul's uucp path.
I partially atone for this loss by restoring the upstream
$Id$ tags, since $FreeBSD$ is no longer useful.

This is [intended to be] a complete list of the functional
changes in this commit.  Some changes were made so that we
could consider vixie cron to be our upstream and reduce our
diffs against it, while others were simply a good idea.

- main() - use putenv instead of setenv for PATH
- open_pidfile no longer needs snprintf to build pidfile
- crontab main() - abort() on impossible errors
- check for truncation when building strings with snprintf
- getdtablesize() -> sysconf(_SC_OPEN_MAX)

These changes were not taken from upstream's 4.0 diff because
they [could] actually change behavior.  Some of them might be
beneficial, but should be taken separately.

- config.h - sendmail args: remove -oi and add -or0s
- call setlocale(LC_ALL, "") at the top of main()
- acquire_daemonlock - we already use pidfile
- cast getpid(), uid_t, and gid_t to long for printf
- remove unnecessary braces - I consider them beneficial
- BSDi support
- glue_strings() - use snprintf(), as we often already did

MFC after:	on demand
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D40260

Reviewed by:	zlei
Differential Revision:	https://reviews.freebsd.org/D39529

On system crontabs, multiple blanks are not being consumed after reading the
username. This change adds blank consumption before parsing any -[qn] options.
Without this change, an entry like:

  * * * * * username  -n true  # Two spaces between username and option.

will fail, as the shell will try to execute (' -n true'), while an entry like:

  * * * * * username -n true   # One space between username and option.

works as expected (executes 'true').

For user crontabs, this is not an issue as the preceding (day of week
or @shortcut) processing consumes any leading whitespace.

PR:		253699
Submitted by:	Eric A. Borisch <eborisch@gmail.com>
MFC after:	1 week

As a followup to the use of login.conf environment vars (other than PATH) in
cron, this patch adds PATH (and HOME) to the list of login.conf settings
respected.

The new logic is as follows:

1. SHELL is always _PATH_BSHELL unless explicitly overridden in the crontab
file itself; no other settings are respected. This is unchanged.

2. PATH is taken from the first of: crontab file, login.conf, _PATH_DEFPATH

3. HOME is taken from the first of: crontab file, login.conf, passwd entry,
unset

4. The current directory for invoking the command is taken from the crontab
file's value of HOME (existing behavior), or the passwd entry, but not
anywhere else (so it might not equal HOME if that was set in login.conf).

Submitted by:	Andrew Gierth <andrew_tao173.riddles.org.uk>
Reviewed by:	sigsys_gmail.com
Differential Revision:	https://reviews.freebsd.org/D23597

This commit adds two new extensions to crontab, ported from OpenBSD:
- -n: suppress mail on succesful run
- -q: 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.

Example usage:

# 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

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

PR:		237538
Submitted by:	Naveen Nathan <freebsd_t.lastninja.net>
Reviewed by:	bcr (manpages)
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D20046

given interval, which is counted in seconds since exit of the previous
invocation of the job. Example user crontab entry:

@25	sleep 10

The example will launch 'sleep 10' every 35 seconds. This is a rather
useless example above, but clearly explains the functionality.

The practical goal here is to avoid overlap of previous job invocation
to a new one, or to avoid too short interval(s) for jobs that last long
and doesn't have any point of immediate launch soon after previous run.

Another useful effect of interval jobs can be noticed when a cluster of
machines periodically communicates with a single node. Running the task
time based creates too much load on the node. Running interval based
spreads invocations across machines in cluster. Note that -j/-J won't
help in this case.

Sponsored by:	Netflix

requests, default to the previous 60-seconds scheduling method
unless there is any @every_second entries to conserve CPU cycles and
power.

This change also improves scheduling in the default mode by running
as close to the beginning of the minnute as possible by replacing
sleep(3) with nanosleep(2). Previously, the tasks would run anywhere
within the first second of the minute and that offset drifted back
and forth each time cron(8) was engaged.

MFC after:	1 month

Pointy hat to:	sobomax