View last 5 lines of a PHP file?

Question

Through the Shell, I can display the last 5 lines of a file through the command tail.

Thus:

> tail -n 5 public/index.php 

I would like to do the same thing in PHP. But I didn’t want to load the whole file, but really only display the last 5 lines.

I know it’s possible to display the first five like this:

$f = new SplFileObject('public/index.php');

$f->rewind();

for ($i = 0; $i < 5; $i++) {
    echo $f->fgets();
}

But how can I display the last 5 lines of a file while maintaining good performance?

Observing: I don’t want a solution where you have to open the command line via PHP.

Answer 1

The best performance solution I could come up with was this:

$file = new SplFileObject('text.txt');
$file->seek(PHP_INT_MAX);

$linesTotal = $file->key();
$startLine = $linesTotal - 5;

for ($x = $startLine; $x <= $linesTotal; $x++) {
    $file->seek($x);
    echo $file->current().'<br>';
}

Some data from the test:

Tamanho do arquivo: 197 MB
Média de tempo de execução: 2.4412620067596 seconds

Answer 2

And why not use the tail?

$file = escapeshellarg('tmp.txt');
$rs = `tail -n 5 $file`;
echo $rs;

The test was done in a 2mb file, 92442 lines.

Execution time: 0.107839 (1 millionth of a second)

To confirm performance integrity, the same file has been increased by 8 times, 16mb.

The running time was the same.

Windows 10 Pro 64bit
PHP 5.6.9
Apache 2.4.10

Answer 3

Based on @Daltonmenezes' wonderful solution, I developed a class with the method tail, to perform such an operation.

Let’s see:

class FileObject extends SplFileObject {

    public function tail($amount)
    {
        $lastKey = $this->key();

        $this->seek(PHP_INT_MAX);

        $end = $this->key();

        $start = $end - $amount;

        // Set as last Line of iterations 

        $this->seek($lastKey);

        return new LimitIterator($this, $start, $end);
    }
}

The use of this would be:

$f = new FileObject('text.txt');

foreach ($f->tail(5) as $key => $value) {
    echo $value;
}

This results in:

Essa é a linha 9995
Essa é a linha 9996
Essa é a linha 9997
Essa é a linha 9998
Essa é a linha 9999

Answer 4

Open the file with the function file and use the function array_slice to catch the last 5 lines:

$linhas = file('arquivo.txt');
$linhas = array_slice($linhas, -5);

print_r(implode(PHP_EOL, $linhas));