从php中的.txt文件中获取特定文本

Question

I am having a log file like this :

2013-04-08-03-17-52: Cleaning Up all data for restart operation
2013-04-08-03-18-02: Creating new instance of app before closing
2013-04-08-03-18-03: New instance created and running
2013-04-08-03-18-03: Application started

Currently, i am loading full log file every second to show it to the user using jquery ajax, As this being soo inefficient i am trying to figure out some way to load only the updated lines from log file.

Is their any way to get lines only after a particular time stamp 2013-04-08-03-18-03 , For this i will be managing a variable with last timestamp and will be updating it every time i get new lines.

I am kind of New to Php and know only the basics of reading and writing files.

Answer 1

You might want to check the file modification time first to see whether or not you need to reload the log file. You can use the filemtime-function for that.

Furthermore, you can use the file_get_contents-function using an offset to read the file from a certain point.

Edit: So, how does it work?

Suppose you have stored the last modification time in a session variable $_SESSION['log_lastmod'] and the most recent offset in $_SESSION['log_offset'].

session_start();

// First, check if the variables exist. If not, create them so that the entire log is read.
if (!isset($_SESSION['log_lastmod']) && !isset($_SESSION['log_offset'])) {
    $_SESSION['log_lastmod'] = 0;
    $_SESSION['log_offset'] = 0;
}

if (filemtime('log.txt') > $_SESSION['log_lastmod']) {
    // read file from offset
    $newcontent = file_get_contents('log.txt', NULL, NULL, $_SESSION['log_offset']);
    // set new offset (add newly read characters to last offset)
    $_SESSION['log_offset'] += strlen($newcontent);
    // set new lastmod-time
    $_SESSION['log_lastmod'] = filemtime('log.txt');

    // manipulate $newcontent here to what you want it to show
} else {
    // put whatever should be returned to the client if there are no updates here
}