journal-follow.php

<?php
/* © 2013 Mantas Mikulėnas <grawity@gmail.com>
 * Released under WTFPL v2 <http://sam.zoy.org/wtfpl/>
 */

class Journal implements Iterator
{
    protected $filter;
    protected $startpos;
    protected $proc;
    protected $stdout;
    protected $entry;

    public static function _join_argv($argv)
    {
        return implode(" ",
            array_map(function($a) {
                return strlen($a) ? escapeshellarg($a) : "''";
            }, $argv));
    }

    public function __construct($filter = [], $cursor = null)
    {
        $this->filter = $filter;
        $this->startpos = $cursor;
    }

    protected function _close_journal()
    {
        if ($this->stdout) {
            fclose($this->stdout);
            $this->stdout = null;
        }
        if ($this->proc) {
            proc_close($this->proc);
            $this->proc = null;
        }
        $this->entry = null;
    }

    protected function _open_journal($filter = [], $cursor = null)
    {
        if ($this->proc) {
            $this->_close_journal();
        }

        $this->filter = $filter;
        $this->startpos = $cursor;

        $cmd = ["journalctl", "-f", "-o", "json"];
        if ($cursor) {
            $cmd[] = "-c";
            $cmd[] = $cursor;
        }
        $cmd = array_merge($cmd, $filter);
        $cmd = self::_join_argv($cmd);

        $fdspec = array(
            0 => array("file", "/dev/null", "r"),
            1 => array("pipe", "w"),
            2 => array("file", "/dev/null", "w"),
        );

        $this->proc = proc_open($cmd, $fdspec, $fds);
        if (!$this->proc) {
            return false;
        }
        $this->stdout = $fds[1];
    }

    public function seek($cursor)
    {
        $this->_open_journal($this->filter, $cursor);
    }

    public function rewind()
    {
        $this->seek($this->startpos);
    }

    public function next()
    {
        $line = fgets($this->stdout);
        if ($line === false) {
            $this->entry = false;
        } else {
            $this->entry = json_decode($line);
        }
    }

    function valid()
    {
        /* null is valid, it just means next() hasn't been called yet */
        return ($this->entry !== false);
    }

    function current()
    {
        if (!$this->entry) {
            $this->next();
        }
        return $this->entry;
    }

    function key()
    {
        if (!$this->entry) {
            $this->next();
        }
        return $this->entry->__CURSOR;
    }
}

$a = new Journal();

foreach ($a as $cursor => $item) {
    echo "================\n";
    var_dump($cursor);
    //print_r($item);
    if ($item) {
        var_dump($item->MESSAGE);
    }
}