Extending the expression to seconds about ncrontab HOT 27 CLOSED

[deleted comment]

Hi,
Do you have news about this issue ?
Indeed, I work on another open source project : Homidom, and I need to use 
second in Cron expression. I will continue to use ncrontab which works very 
well.
Thanks for your help,
Davidinfo

There are no new features planned at this time. However, if someone wishes to 
clone the repo and contribute a robust implementation together with unit tests 
then I'd be happy to review it and consider another release.

This project reflects the specification of cronjobs on *nix systems. Which does 
not have seconds.

See : http://en.wikipedia.org/wiki/Cron

If you need second precision job scheduling, then perhaps you need something 
else. For example, a background service executing periodically every n seconds.

[deleted comment]

I have cloned this repository and have created an implementation that handles 
both six-part cron expressions and the traditional five-part expressions.  It 
is on the "SixPartCronExpressions" branch of 
https://code.google.com/r/kfritz-ncrontab/source/browse/?name=SixPartCronExpress
ions.

azizatif, would you be interested in merging it in?

@kfritz Thanks for patch. Could you switch on code review in your clone through 
its admin UI?

Switched on, thanks.  I am not very familiar with Google Code.

@kfritz Thanks. Have NCrontabConsole and NCrontabViewer been updated and tested 
according? I built the solution and ran NCrontabViewer but could not get it to 
accept a 6-part expression with seconds. If I get the time to dig deeper, I 
drop in additional notes.

@kfritz Here is what I am seeing:

C:\NCrontab>src\NCrontabConsole\bin\Debug\NCrontabConsole.exe "0 12 1 * mon" 
2010-01-01 2011-01-01
01 February 2010 12:00
01 March 2010 12:00
01 November 2010 12:00

C:\NCrontab>src\NCrontabConsole\bin\Debug\NCrontabConsole.exe "30 0 12 1 * mon" 
2010-01-01 2011-01-01
'30 0 12 1 * mon' is not a valid crontab expression. It must contain at least 5 
components of a schedule (in the sequence of minutes, hours, days, months, days 
of week).

Ah, I was focused on updating the library and didn't take notice of the console 
and viewer apps.  It shouldn't be too hard, though; I'll take a look this 
afternoon.

@azizatif, I am unable to reproduce the issues you are seeing with 
NCrontabConsole.  The arguments you demonstrated are working for me.  I did, 
however, push an updated error message.  I also updated the Viewer app to show 
the seconds component when using a six-part expression.

OK, the WinForms and Console apps are working (and thanks), but the latter is 
not displaying the seconds component when a six-part expression is supplied:

C:\NCrontab>src\NCrontabConsole\bin\Debug\NCrontabConsole.exe "30 0 12 1 * mon" 
2010-01-01 2011-01-01
01 February 2010 12:00
01 March 2010 12:00
01 November 2010 12:00

Yeah, the console app accepts a format as an argument, so I figured we should 
just respect whatever format the user supplies.

The only trouble is that the following looks buggy (when it's not):

C:\NCrontab>src\NCrontabConsole\bin\Debug\NCrontabConsole.exe "15,30,45 0 12 1 
* mon" 2010-01-01 2011-01-01
01 February 2010 12:00
01 February 2010 12:00
01 February 2010 12:00
01 March 2010 12:00
01 March 2010 12:00
01 March 2010 12:00
01 November 2010 12:00
01 November 2010 12:00
01 November 2010 12:00

Should we just change the default format to "F" and always show seconds, then?  
Or, do you want the default to change based on what expression comes in?  I 
favor the former as it is probably best to avoid doing more parsing outside the 
core library.

Looks like that the console was designed to take a 4th argument that specifies 
the format of the output date/time occurrences. Unfortunately, due to a bug, 
supply the argument would cause an error. I've attached the fix. With it, the 
following now works:

C:\NCrontab>src\NCrontabConsole\bin\Debug\NCrontabConsole "15,30,45 0 12 1 * 
mon" 2010-01-01 2011-01-01 F
01 February 2010 12:00:15
01 February 2010 12:00:30
01 February 2010 12:00:45
01 March 2010 12:00:15
01 March 2010 12:00:30
01 March 2010 12:00:45
01 November 2010 12:00:15
01 November 2010 12:00:30
01 November 2010 12:00:45

C:\NCrontab>src\NCrontabConsole\bin\Debug\NCrontabConsole "15,30,45 0 12 1 * 
mon" 2010-01-01 2011-01-01 "yyyy-MM-dd HH:mm:ss"
2010-02-01 12:00:15
2010-02-01 12:00:30
2010-02-01 12:00:45
2010-03-01 12:00:15
2010-03-01 12:00:30
2010-03-01 12:00:45
2010-11-01 12:00:15
2010-11-01 12:00:30
2010-11-01 12:00:45

I don't think we need to make any further changes with regard to the console 
app.

Patch from comment 17 now applied in changeset 
1a62a629d1b93e1ddac2083b33718e0df432fe50

@kfritz I think the last decision that remains with respect to concluding this 
issue is whether seconds should be optional or mandatory. Beyond the 
traditional 5 field syntax, there are some implementations supporting 6 or 7 
with 6th including seconds and the 7th being the year. In the extended cases, 5 
fields are not allowed, making seconds mandatory. Yet another implementation 
allows fields of higher resolution to be omitted but seconds are always 
required. It's worth keeping these variations in mind so NCrontab does not 
introduce an ambiguity in the future. Suppose the year field is added in a 
future version. At that point, does 6 fields include second or year?

Perhaps there needs to be a classic vs extended mode distinction. In the 
extended mode, seconds must be required. In the classic mode, it should be 
illegal to specify anything but 5 fields. A user must choose between classic 
and extended mode for his/her app.

If you were to add the year component, I would side for making the seconds a 
required field.  Allowing both the lowest resolution fields and highest 
resolution fields to be optional would introduce a mess of problems.  I defer 
to your judgement as the project maintainer.

I'm not planning to add the year field but don't want to preclude the option in 
a future version. As a result, the seconds should be required in the 
non-classic mode so the patch still needs some work.

Closed by change set 7492e5d4f4cc5007f752160585b5ab3a7d302075

@azizatif, do you have plans to release the next version with this change?

@odinserj No promises but but I'll do my to make a release this week.

@odinserj NCrontab 2.0 has been released on NuGet:
http://www.nuget.org/packages/ncrontab/2.0.0

Hi I installed Crontab 2.0 and trying to use with Hangfire, but it still throws 
an error when I use the 6 part cron expression.