reading file as it changes ?

[TomT]

Hi

I'm trying to watch a plain text file for any changes.

I want to use PHP and read the file line by line as new lines are added.

Some times 1 line may be added, other times dozens of lines could be added. I want to read each line and check if it matches any keywords..

This is what I've got so far, but it's not line by line... it's buffer size based.

<?php
$file='log.txt';
$line = $lastpos = 0;
while (true) {
    usleep(500000);
    clearstatcache(false, $file);
    $len = filesize($file);
    if ($len < $lastpos) {
        $lastpos = $len;
    }
    elseif ($len > $lastpos) {
        $f = fopen($file, "rb");
        if ($f === false) die();
        fseek($f, $lastpos);
        while (!feof($f)) {
$buffer = fread($f, 4096);
if ($lastpos > 0) {
if (strpos($buffer, 'MATCH') !== false) echo "$line\r\n";
}
            flush();
$line++;
        }
        $lastpos = ftell($f);
        fclose($f);
    }
}
?>

 

Can anyone help point me in the right direction. Ideally I don't want to keep the log in memory as it could grow to a reasonable size.

Thanks

[Jacques1]

Why do you want a PHP script? Unix has tail or tailf to do exactly that:

tail -f log.txt | grep MATCH

The Windows PowerShell has Get-Content with similar features.

[TomT]

Ideally I'd like to do this as a self contained script, not calling any external applications.

The code I've got works, but does't display the results one by one..

[Jacques1]

tail and grep are fundamental Unix commands. They're far more basic and efficient than your PHP script.

 

If you insist on reinventing the wheel: fgets()

[TomT]

Thanks using fgets has helped and looks like it could work in this scenario.