inotify_init

(PECL inotify >= 0.1.2)

inotify_init — Initialize an inotify instance

Description

inotify_init(): resource|false

Initialize an inotify instance for use with inotify_add_watch()

Parameters

This function has no parameters.

Return Values

A stream resource or false on error.

Examples

Example #1 Example usage of inotify

<?php
/ Open an inotify instance
$fd = inotify_init();

/ Watch __FILE__ for metadata changes (e.g. mtime)
$watch_descriptor = inotify_add_watch($fd, __FILE__, IN_ATTRIB);

/ generate an event
touch(__FILE__);

/ Read events
$events = inotify_read($fd);
print_r($events);

/ The following methods allows to use inotify functions without blocking on inotify_read():

/ - Using stream_select() on $fd:
$read = array($fd);
$write = null;
$except = null;
stream_select($read,$write,$except,0);

/ - Using stream_set_blocking() on $fd
stream_set_blocking($fd, 0);
inotify_read($fd); / Does no block, and return false if no events are pending

/ - Using inotify_queue_len() to check if event queue is not empty
$queue_len = inotify_queue_len($fd); / If > 0, inotify_read() will not block

/ Stop watching __FILE__ for metadata changes
inotify_rm_watch($fd, $watch_descriptor);

/ Close the inotify instance
/ This may have closed all watches if this was not already done
fclose($fd);

?>

The above example will output something similar to:

array(
  array(
    'wd' => 1,     / Equals $watch_descriptor
    'mask' => 4,   / IN_ATTRIB bit is set
    'cookie' => 0, / unique id to connect related events (e.g. 
                   / IN_MOVE_FROM and IN_MOVE_TO events)
    'name' => '',  / the name of a file (e.g. if we monitored changes
                   / in a directory)
  ),
);

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User Contributed Notes 1 note

down

david dot schueler at tel-billig dot de ¶

15 years ago

Example for tailing a file (like tail -f) using inotify.
<?php
/**
 * Tail a file (UNIX only!)
 * Watch a file for changes using inotify and return the changed data
 *
 * @param string $file - filename of the file to be watched
 * @param integer $pos - actual position in the file
 * @return string
 */
function tail($file,&$pos) {
    / get the size of the file
    if(!$pos) $pos = filesize($file);
    / Open an inotify instance
    $fd = inotify_init();
    / Watch $file for changes.
    $watch_descriptor = inotify_add_watch($fd, $file, IN_ALL_EVENTS);
    / Loop forever (breaks are below)
    while (true) {
        / Read events (inotify_read is blocking!)
        $events = inotify_read($fd);
        / Loop though the events which occured
        foreach ($events as $event=>$evdetails) {
            / React on the event type
            switch (true) {
                / File was modified
                case ($evdetails['mask'] & IN_MODIFY):
                    / Stop watching $file for changes
                    inotify_rm_watch($fd, $watch_descriptor);
                    / Close the inotify instance
                    fclose($fd);
                    / open the file
                    $fp = fopen($file,'r');
                    if (!$fp) return false;
                    / seek to the last EOF position
                    fseek($fp,$pos);
                    / read until EOF
                    while (!feof($fp)) {
                        $buf .= fread($fp,8192);
                    }
                    / save the new EOF to $pos
                    $pos = ftell($fp); / (remember: $pos is called by reference)
                    / close the file pointer
                    fclose($fp);
                    / return the new data and leave the function
                    return $buf;
                    / be a nice guy and program good code ;-)
                    break;

                    / File was moved or deleted
                case ($evdetails['mask'] & IN_MOVE):
                case ($evdetails['mask'] & IN_MOVE_SELF):
                case ($evdetails['mask'] & IN_DELETE):
                case ($evdetails['mask'] & IN_DELETE_SELF):
                    / Stop watching $file for changes
                    inotify_rm_watch($fd, $watch_descriptor);
                    / Close the inotify instance
                    fclose($fd);
                    / Return a failure
                    return false;
                    break;
            }
        }
    }
}

/ Use it like that:
$lastpos = 0;
while (true) {
    echo tail($file,$lastpos);
}
?>