I'm in charge of a printer, so I wrote a script which runs every 5 minutes and figures out if the printer has paper. If it doesn't, the script will text me. The problem is, if I'm busy, and can't fill the printer, I don't want the script to continue to text me every 5 minutes. Is there a way I can force it to only send me at most 1 text every 8 hours or so, to ensure that the script doesn't text me twice for the same out-of-paper situation? The only thing I can currently think of is to create a db of times that I get texts, then make sure that the most recent one wasn't too long ago, or to create a local file with the most recent time in it.
Thanks!
You need to store somewhere the fact that it has text you and when this last occurred. You could do this using a plain file and by reading the files modification date to see when the text was last sent or you can use a database.
Assuming that the script that sends the SMS is PHP, use something like this.
Can probably find a cleaner way of doing this, but this is just to show you the logic that is needed.
<?
/*
* Replace outOfPaper() / sendSms() with the actual logic of your script
*/
$statusFile = './lastsms';
if(outOfPaper() && (is_file($statusFile) && (filemtime($statusFile) < time()-((8*60)*60)))){
sendSms('+4412345678','Printer out of paper');
touch($statusFile);
}
?>
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I have been searching everywhere for a method of streaming a text file. By streaming I mean I want the page to remember its location, and everytime a new entry is added, it will add it to the bottom.
Example
(Displayed on page from txt file)
Jack
John
Ellis
(text file is updated to)
Jack
John
Ellis
Emma
Carly
I want the page to pick up the changes without having to refresh the whole page.
Im learning alot. I have figured out how to display the text files on the page via php (my knowledge base is stuck with php/html only self taught). I can get it to refresh, but im having to use javascript to auto scroll down the page to the bottom everytime, and have the page refreshing every few seconds.
Any ideas or tips?
Well, I would not do this the Shrek's Donkey way:
Are we there, yet?", 5 seconds later, "Are we there, yet?
What is the problem with this?
Bandwidth consumption, pure and simply.
What should I do?
The answer is: Server Push. Or something like Server Push, since is not possible to start things from the server with HTTP.
Instead of poll the server every 5 seconds if there is a new version of the file, why not let the server notify you just when it really has changed?
And how do I do this?
The answer is: with Ajax, but with a different approach.
The high level algorithm is:
Send an Ajax request to the server from the browser.
When the server receives the request, verify if the file has changed.
If it has changed, then return the new data.
If not, make the server sleep for a while and then go back to step 2.
If a long time has passed and there is no modification, the server could (or must) return a response, with no data bounded to it.
How can I check if the file has changed?
Instead of reading the file and comparing the data, a better approach is to send with the request the timestamp of when the file had it last change. You can do this with the filemtime funciton.
On the server, you verify if the file last modified time is bigger than the one coming from the request. If it is, then you read the file and send the response along with the new file modified time (step 2a). If not, go for step 2b and use the usleep function to make the server sleep for a while and save CPU.
To know if a long time has passed and there's no change, you can use the microtime function at the beginning of the script and make the difference of its value on every iteration. If there has been past much time, you'll send an empty response.
Making a draft, the server-side script would be like:
$startTime = microtime();
$filePath = '/path/to/file.txt';
$lastModifiedTime = $_GET['lastModifiedTyme']; // Supposing it comes from the query string
$currentModifiedTime = null;
while ($currentModifiedTime = filemtime($filePath) < $lastModifiedTime) {
usleep(1000); // dorme por 1 seg.
// If has passed more than 1 minute
if ((microtime() - $startTime) > 60000) {
header('HTTP/1.1 304 Not Modified'); // Or simply http_response_code(304) for PHP 5.4+
exit;
}
}
$data = file_get_contents($file);
$jsonResponse = json_encode(array(
'data' => $data,
'modifiedTime' => $currentModifiedTime
);
echo $jsonResponse;
On the client side, you'll have to re-run the request every time you receive a response. This could (and should) have a litte delay.
It sounds like a kind of an overhead, I know, but just for you to know that there are another ways of doing this.
What I'd recommend you do is use AJAX to periodically call a PHP file which loads the text file and update your web content to display the new content.
It will be similar to this: Refresh a table with jQuery/Ajax every 5 seconds
I have a file (usernames.txt) that has every username of my website members, when they submit their usernames, it will be saved in "usernames.txt", the problem is that there are a lot of users submitting there usernames every day, I want a php code or something that will delete the first (at the top) username every 30 seconds automatically (Even though more than 20 usernames are submitted every minute, the script I need will make the "usernames.txt" file smaller and that will make my server a bit faster. :)
It would be really great if someone has or knows the script I am talking about. :)
Thanks
I would also really, really encourage you to look at http://php.net/manual/en/refs.database.php as #elclanrs suggested. Really encourage you.
Failing that, and a very far second place suggestion, I'd even recommend trying to use serialize and unserialize, so you can read the data in and out of the file quicker. You can then read the data in as an array/object using unserialize, manipulate it, and put it back in the file using serialize.
Further failing that, you would have to read the file into memory (file_get_contents), loop through the lines, and remove the first line, and then write the entire file back out. Alternativly, read it in one line at a time (fopen), skip the first line, write the rest of the file back to a temporary file (fputs), and then swap the files around (rename).
Lastly, assuming you're on a *nix system, you could use something like:
exec("sed '1d' {$my_file_name}", $result);
file_put_contents($my_file_name, $result);
That all being said, you should really look at using a DB. If you don't want a standalone database, you can use sqlite, which will write the database to a local file:
$dbhandle = sqlite_open('db/test.db', 0666, $error);
I am using PHP and AJAX requests to get the output of a program that is always running and print it on a webpage at 5 second intervals. Sometimes this log file can get up to 2mb in size. It doesn't seem practical to me for the AJAX request to fetch the whole contents of this file every 5 seconds if the user has already gotten the full contents at least once. The request just needs to get whatever contents the user hasn't gotten in a previous request.
Problem is, I have no clue on where to begin to find what contents the user hasn't received. Any hints, tips, or suggestions?
Edit: The output from the program starts off with a time (HH:MM:SS AM/PM), everything after has no pattern. The log file may span over days, so there might not be just one "02:00:00 PM" in the file, for example. I didn't write the program that is being logged, so there isn't a way for me to modify the format in which it prints it's output.
I think using a head request might get you started along the right path.
check this thread:
HTTP HEAD Request in Javascript/Ajax?
if you're using jquery, it's a simple type change in the ajax call:
$.ajax({url: "some url", type: "HEAD".....});
personally, I would check the file size & date modified against the previous response, and fetch the new data if it has been updated. I'm not sure if you can fetch only parts of a file via ajax, but I'm sure this can be accomplished via php pretty easily, possibly this thread may help:
How to read only 5 last line of the text file in PHP?
It depends how your program is made and how does it print your data, but you can use timestamps to reduce the amount of data. If you have some kind of IDs, you should probably use them insteam of timestamps.
I want to create a very simple site, but unfortunately my php skills are weak. Basically, when a user shows up, I want to have a page with text and a blinking cursor (I can probably figure the cursor part out myself, but feel free to suggest). When a user types, I want it to show the text as they type, and when they hit enter (or click something/whatever), the text just typed will be sent to a database and then the page will update with that new text, for anybody else to see. The cursor will then be blinking on the next line down. So basically it's like a really simple wiki, where anyone can add anything, but nobody can ever remove what has been typed before. No logging in or anything. Can someone suggest the best way to go about this? I assume it will require a php call to the database to display the initial page, then another php request to send data, then another php request to display the new page. I just don't know the details. Thanks so much!
Bonus question 1: How can the page be updated dynamically, so if A sends text while B is typing, B sees the text A sent on B's page immediately?
Bonus question 2: What sorts of issues might arise if this database grows extremely large (say, millions of words), and how might I address these up front? If necessary, I could show only a small chunk of the (text-only) database on any given page, then have pagination.
If you only have one page, you don't need a database. All you need to do is save a text file on the server (use fopen() and related functions) that only gets appended to. If you have multiple pages, then a simple id (INTEGER), filetext (LARGEBLOB). (Note largeblob has a limit of 2^32 bytes).
For the user's browser part, you'll need to use Javascript and AJAX to inform the server of any updates. Just get in touch with a PHP script that (1) accepts the input and (2) appends it to a file.
Bonus question 1: How can the page be updated dynamically, so if A sends text while B is typing, B sees the text A sent on B's page immediately?
Also use the AJAX call to fetch new content (e.g. if you assign line numbers, then the browser just tells the script the last line it read, and the script returns all new lines past that point).
I assume it will require a php call to the database to display the initial page, then another php request to send data, then another php request to display the new page.
Pretty much. But only send the last 50 lines or so of the file when the browser visits it. You don't want to crash the browser.
Bonus question 2: What sorts of issues might arise if this database grows extremely large (say, millions of words), and how might I address these up front? If necessary, I could show only a small chunk of the (text-only) database on any given page, then have pagination.
Think in terms of bytes, not words, and you'll likely run into performance issues. You could cap file sizes or split up the storage into multiple files at a certain size so you don't have to scan pass content that will rarely be fetched.
I've got a script in php that continually grows an array as it's results are updated. It executes for a very long time on purpose as it needs to filter a few million strings.
As it loops through results it prints out strings and fills up the page until the scroll bar is super tiny. Instead of printing out the strings, I want to just show the number of successful results dynamically as the php script continues. I did echo(count($array)); and found the number at 1,232,907... 1,233,192 ... 1,234,874 and so forth printed out on many lines.
So, how do I display this increasing php variable as a single growing number on my webpage with Javascript?
Have your PHP script store that number somewhere, then use AJAX to retrieve it every so often.
You need to find a way to interface with the process, to get the current state out of it. Your script needs to export the status periodically, e.g. by writing it to a database.
The easiest way is to write the status to a text file every so often and poll this text file periodically using AJAX.
You can use the Forever Frame technique. Basically, you have a main page containing an iframe. The iframe loads gradually, intermittently adding an additional script tag. Each script tag modifies the content of the parent page.
There is a complete guide available.
That said, there are many good reasons to consider doing more pre-computation (e.g. in a cron job) to avoid doing the actual work during the request.
This isn't what you're looking for (I'm as interested in an answer to this..), but a solution that I've found works is to keep track of the count server-side, and only print every 1000/5000/whatever number works best, rather than one-by-one.
I'd suggest that you have a PHP script that returns the value in JSON format. Then in another php page you can do an AJAX call to the page and fetch the JSON value and display it. Your AJAX call can be programmed to run perhaps every 5 seconds or so depending on how fast your numbers output. Iframe though easier, is a bit outdated.