CronSandbox
For an offline exploration of crontab expressions
Processing . . .
This opening screen is a demonstration - predefined timing values and resulting schedule.
Enter YOUR timing operators for a crontab parameter string, and click 'Run'.
You will see a list of the dates and times that your cron job would execute.
'Run' an empty box to return to the start-up demonstration values.

Reminder of the format... mm hh D M DoW
mm - the minute, a value between 0 and 59
hh - the hour, a value between 0 and 23
D - day of the month, between 1 and 31
M - month, a value between 1 and 12
DoW - day-of-the-week, 0-6 (0 = Sunday)


Each of the five items can be more complex...

A '*' means use all values.

Multiples: e.g. every 20 mins would be '0,20,40'.

Range: e.g. hourly in the evening '19-23'.

Every nth '0-23/n', '*/2' would be every other.
'*/1' is generally acceptable elsewhere, but is flagged here as possibly an unintended entry.

Month can be just the first three letters of the name,
so 'mar,jun,sep,dec' or '3,6,9,12' or '3-12/3'
would all give you quarterly reports.


The DoW can also be e.g. 'mon,wed,fri'.
It is DoW OR DoM (rather than DoW AND DoM), so e.g.
'11th OR a Tuesday' rather than '11th AND a Tuesday'.


Five items, space separated (mm hh D M DoW):

MinsHrsDayMthDoW
0523**mon,wed,fri
This run time (UTC) Tue2016-Feb-091542
Forward ScheduleWed2016-Feb-102305
Fri2016-Feb-122305
Mon2016-Feb-152305
Wed2016-Feb-172305
Fri2016-Feb-192305
Mon2016-Feb-222305
Wed2016-Feb-242305
Fri2016-Feb-262305
Mon2016-Feb-292305
Wed2016-Mar-022305
Fri2016-Mar-042305
Mon2016-Mar-072305
Wed2016-Mar-092305
Fri2016-Mar-112305
Mon2016-Mar-142305
Wed2016-Mar-162305
Fri2016-Mar-182305
Mon2016-Mar-212305
Wed2016-Mar-232305
Fri2016-Mar-252305

CRON-job Application

We use CRON jobs to feed our embryonic Amazon Product Image Collager web widget, the books image shown here. Everyday, data is fetched from Amazon's 'Best Seller' lists for web development technologies (HTML, CSS, PHP, Python, Ruby,...).

The collage image is accompanied by an HTML Imagemap, with links to the individual product pages at Amazon.com. Optionally, Associate IDs can be embedded into the product links.
This image can be embedded into a webpage by adding an HTML '<div>' tag together with a line of Javascript. It is available as 1,2,3,4 or 5-item, vertical, staggered, white background.

You are welcome to take advantage of what we have so far, although this is not production-ready if you are maintaining a commercial site. Our reservations are about compatibility with any existing Javascript on the host page, and lack of multibrowser testing.

Even if you are not interested in being an Amazon Associate, a colourful graphic like this will add visitor interest to a personal site or blog. Once introduced to your HTML, it needs no further attention, and is refreshed regularly.

The two lines required to incorporate this collage into existing HTML are shown below.

The Javascript generates some HTML inside the '<div>' element, to fetch the image from our server (using an '<img>' tag), and associate it with a downloaded HTML Imagemap, using a '<map>' tag.

You can apply positioning and styling to the '<div>' as required. On this page we have that div as 'float:left'.

This is of course an exercise in a minimal facility to demonstrate "cross-domain data fetching" to overcome "same origin" browser restrictions. Related topics are "JSONP" and "Cross-Origin Resource Sharing (CORS)".

Changes will probably be reported here, so come back in a few weeks.
Or email me to register an interest and I'll let you know about progress.
LINE ONE. Ideally placed just before the closing HTML '</body>' tag:
<script type="text/javascript"
      src="http://www.dataphyx.com/apic/?S=AIDxxxxxx,IMG304">
         </script>
Optionally, 'AID' prefixes the the Amazon Associate ID 'xxxxxxx'.
Choose one of IMG301-IMG305 for 1-5 items in the collage.

LINE TWO: Positioned where the collage image is to appear. Note the same 'IMGnnn'.
<div id="DATAPHYX_APIC_IMG304"></div>