Reading only the last 10 lines of a text file "tail" (Jquery/Ajax/javascript or whatever)

Question

I've been searching for solutions here for a long time now, and i haven't been able to find any so far

what i need is a way to read the last 10 or so lines of a text file, which continually updates every second

i've found some possible codes in php, but then i wont be able to update the file every second.

how do i get only the last 10 lines of a text file using some sort of javascript?

In PHP, you can spawn a "tail" process and capture its output instead of rolling out your own. — techfoobar, Mar 16 '13 at 10:07
but will a tail process update the file without updating the page — Daniel Holst, Mar 16 '13 at 10:20
@techfoobar it should be possible, but at least I couldn't make it work. any examples? — eis, Mar 16 '13 at 10:25
Well can't really show an example as this involves server and client side technologies. The basic idea is to have a PHP script spawn tail (lookup exec(), passthru(), system() and related on PHP docs) and then have a JS AJAX poller that calls this periodically form the client. — techfoobar, Mar 16 '13 at 10:33
http://stackoverflow.com/questions/9201974/tail-f-realtime-log-via-javascript-jquery — mplungjan, Mar 16 '13 at 10:34

score 0 · Answer 1 · answered Mar 16 '13 at 10:09

0

Try using array_slice, which will return a part of an array. In this case you want it to return the last 15 lines of the array,

$filearr = file("filename");
$lastlines = array_slice($filearr,-10);

You can change -10 (-10,-15 any value you want).

Hope it works!

answered Mar 16 '13 at 10:09

Kautil

1,321
9
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wouldn't that method result in slow load times, since it's a really big text file? – Daniel Holst Mar 16 '13 at 10:21
im looking for a way to load only the necessary lines, instead of loading the whole file on every loop. – Daniel Holst Mar 16 '13 at 10:23
it will not result in slow load time. – Kautil Mar 16 '13 at 10:25
@Kautil - Of course it will affect performance if the file is huge. – techfoobar Mar 16 '13 at 10:31
@Kautil file() loads whole file in memory and converts it to an array, that's very uneffective to do every time – eis Mar 16 '13 at 10:34
that was what i was thinking – Daniel Holst Mar 16 '13 at 10:39

score 0 · Answer 2 · answered Mar 16 '13 at 10:34

0

Hmmm... maybe so, for large files:

$fileName = '[path_to_file]';
$file = new \SplFileObject($fileName);
$file->seek($file->getSize());

$lines = $file->key() - 1;

$file->setFlags(\SplFileObject::READ_CSV);

$counter = 0;
$records = 100;
$seek = $lines - $records;

$file->seek($seek);

$return = array();
while ($counter++ < $records) {
    try {
        $line = $file->fgets();
        $return[] = $line;
    } catch (\Exception $e) {
    }
}

answered Mar 16 '13 at 10:34

mkjasinski

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2
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that's php thou, how do i get it to update the page dynamically – Daniel Holst Mar 16 '13 at 10:38
i've seen the while loop, but do i have to put it after them
to keep the page loading, or would an iframe be the solution?
– Daniel Holst Mar 16 '13 at 10:41
$(document).ready(function() { // use ajax here with this solution }); – mkjasinski Mar 16 '13 at 10:46
I'm not that familiar with ajax, but isn't this php? – Daniel Holst Mar 16 '13 at 10:53
Ajax in jQuery is very simple, look for example: $.ajax({ type:'GET', url:'[path_to_your_script]', dataType:'text', data:{ // params }, success:function (msg) { // on success }, complete:function (r) { // on complete }, error:function (error) { // on error } }); – mkjasinski Mar 16 '13 at 10:57
so ajax calls a php file, which then returns the data to the ajax/jquery which then puts the retrieved data into the div? – Daniel Holst Mar 16 '13 at 11:00
yes, return array and add id for div and than $('#[id_value]').html('your html here'); after processing data from your array look here: http://api.jquery.com/html/ – mkjasinski Mar 16 '13 at 11:04
is there anyway to send an attribute like for example the file name when calling the script? – Daniel Holst Mar 16 '13 at 15:33
Yes, but better practice is set the filename in PHP script, enybody can set the filename in JS and get for example /etc/passwd file content, set this in script. – mkjasinski Mar 16 '13 at 16:01
the thing is that i need to show a different text for depending on the user id but i guess that's easily done in php using sessions :) – Daniel Holst Mar 16 '13 at 16:31
Yes, but data will be not actual. – mkjasinski Mar 16 '13 at 17:01
how do i handle the returned data? – Daniel Holst Mar 16 '13 at 17:39
Everything is in jQuery documentation. – mkjasinski Mar 16 '13 at 17:57
this code just returns [object Object] : `var jqxhr = $.get("/user/server/load_file_part.php", function() { alert("data retrieved: "+jqxhr+"");` – Daniel Holst Mar 17 '13 at 09:58

score 0 · Answer 3 · edited May 23 '17 at 10:25

0

Didn't find the correct answer here, so i started a new question where i'm more specific with what i want

Reading ONLY the last 50 lines of a large text file

edited May 23 '17 at 10:25

Community

1
1

answered Mar 17 '13 at 20:34

Daniel Holst

139
10

You should not have reposted. Instead, you should have edited the question to 1) make more clear what you want and 2) generate some activity (the editing) so it will reappear on the front page. If you would have done that you wouldn't have to post another duplicate. – 11684 Mar 17 '13 at 20:50

Reading only the last 10 lines of a text file "tail" (Jquery/Ajax/javascript or whatever)

3 Answers3