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<?php
/**
* Slightly modified version of http://www.geekality.net/2011/05/28/php-tail-tackling-large-files/
* @author Torleif Berger, Lorenzo Stanco
* @link http://stackoverflow.com/a/15025877/995958
* @license http://creativecommons.org/licenses/by/3.0/
*/
function tailCustom($filepath, $lines = 1, $adaptive = true) {
// Open file
$f = @fopen($filepath, "rb");
if ($f === false) return false;
// Sets buffer size, according to the number of lines to retrieve.
// This gives a performance boost when reading a few lines from the file.
if (!$adaptive) $buffer = 4096;
else $buffer = ($lines < 2 ? 64 : ($lines < 10 ? 512 : 4096));
// Jump to last character
fseek($f, -1, SEEK_END);
// Read it and adjust line number if necessary
// (Otherwise the result would be wrong if file doesn't end with a blank line)
if (fread($f, 1) != "\n") $lines -= 1;
// Start reading
$output = '';
$chunk = '';
// While we would like more
while (ftell($f) > 0 && $lines >= 0) {
// Figure out how far back we should jump
$seek = min(ftell($f), $buffer);
// Do the jump (backwards, relative to where we are)
fseek($f, -$seek, SEEK_CUR);
// Read a chunk and prepend it to our output
$output = ($chunk = fread($f, $seek)) . $output;
// Jump back to where we started reading
fseek($f, -mb_strlen($chunk, '8bit'), SEEK_CUR);
// Decrease our line counter
$lines -= substr_count($chunk, "\n");
}
// While we have too many lines
// (Because of buffer size we might have read too many)
while ($lines++ < 0) {
// Find first newline and remove all text before that
$output = substr($output, strpos($output, "\n") + 1);
}
// Close file and return
fclose($f);
return trim($output);
}
?>
@gaspaonrocks
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gaspaonrocks commented Mar 21, 2018

Well... I added it to a project for a client of mine and it works wonderfully. Thank you very much @lorenzos

@modExpert
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modExpert commented Jun 23, 2019

Sorry for naive question...
What happens when, during the execution of this code, an attempt is made to write to the log?

@mxdpeep
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mxdpeep commented Oct 3, 2019

Sorry for naive question...
What happens when, during the execution of this code, an attempt is made to write to the log?

you must open the file in LOCK exclusive mode then or make a copy (if it's possible)

https://www.w3schools.com/php/func_filesystem_flock.asp

@consatan
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consatan commented Sep 29, 2020

// Jump back to where we started reading
fseek($f, -mb_strlen($chunk, '8bit'), SEEK_CUR);

Why not use fseek($f, -$seek, SEEK_CUR);

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