Cron Job-如何在特定日期两次执行脚本？

Question

I am new to php and database stuff, but have looked around and cannot find a solution.

What I'm trying to accomplish:

I have a slideshow of images. The images come from Flickr's API, stored in a database table, then the database data is generated into a JSON link.

My question is, is there a way to execute the php script that calls the flickr API everytime the slideshow circle through all the images in the JSON link? I could specify every 1 minutes, but that may be too long if there are only a few images in the slideshow.

If you can't do that,

is there a way to execute the script every 1 minute on only fridays from 9pm EST to 3am EST?

Answer 1

The answer is yes there is a way but how all depends on the slideshow you are using. If you didn't build it i would hunt for a function that's probably running at the end of the slideshow to trigger it to loop to the beginning. When you find that function you can alter it to run the script that connects to the API to get new images.

You might have to delay the loop in the slideshow long enough for the new images to load.

Answer 2

This is the cron specification for your last line:

# Friday from 9pm to 11:59pm
* 21-23 * * 5 php -q /path/to/script.php
# Saturday from midnight to 2:59am
* 0-2 * * 6 php -q /path/to/script.php

Answer 3

On your specific question of how to schedule it, would be something like

* 21-23 * * 5 /path/to/php /path/to/script
* 0-2 * * 6 /path/to/php /path/to/script

in your crontab file. Easiest to split into two, as you actully have commands running over two days. The first * means run it every minute.

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

The stuff with your gallery, is not particully clear, exactly what you doing.

Answer 4

You really have two aspects of this, which you likely need to do independently of one another.

First, you need a way to check the Flickr API for updates. I would suggest this could be a script which builds a cached representation of the data that is available for local consumption on the service. You can trigger this via cronjob (you already have good answers here on how to configure cron so I will skip that).

You don't the client to initiate the calls to the Flickr API as if you had 60 concurrent clients checking for updates all the way through to Flicker every minute, you would in essence be checking on average once a second for updates.

Your cached representation of the Flickr data can be in whatever format you consider easy to work with (JSON perhaps). You would expose the cached data to the frontend (ie javascript) on page load and via some server-side script that could be called via AJAX to get the cached data.

You could make the data update into javascipt independent of the scrolling behavior by having he call running every minute to the serverside script and populating the latest data into some javascript variable.

You could then either directly update the slideshow every minute, or as you suggest, have the slideshow rebuilt from the latest data (which is already in javascript) when the scrolling loops back to the beginning.

One thing you might also consider is, if possible keep data on when the slideshow information was last updated in Flickr, the last time it was cached on the server, and the last time javascript pulled the data from the server. By comparing these update times, you can save yourself a lot of hassle in rebuilding the cache, rebuilding the representation in javascript, etc. by simply determining if there is indeed an update to be had first.