从php中的.txt文件中获取特定文本

问题描述：

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.

我有一个这样的日志文件： p>

  2013  -04-08-03-17-52：清理重启操作的所有数据
2013-04-08-03-18-02：关闭前创建新的app实例
2013-04-08-03-18-03  ：新实例已创建并正在运行
2013-04-08-03-18-03：应用程序已启动
  code>  pre> 
 
 目前，我每秒都要加载完整的日志文件以显示 它使用jquery ajax给用户，因为这样效率太低我试图想办法从日志文件中只加载更新的行。 p> 
 
 
他们是否只能获取行 在特定的时间戳之后 2013-04-08-03-18-03  code> 
，为此，我将管理一个带有上一个时间戳的变量，并且每次获得新行时都会更新它。 
 
 
我是Php的新手，只知道读写文件的基础知识。 p> 
  div>

答

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
}

答

Try something like this:

<?php
    session_start();
    $lines = file(/*Insert logfile path here*/);
    if(isset($_SESSION["last_date_stamp"])){
        $new_lines = array();
        foreach($lines as $line){
            // If the date stamp is newer than the session variable, add it to $new_lines
        }
        $returnLines = array_reverse($newLines); // the reverse is to put the lines in the right order
    } else {
        $returnLines = $lines;
    }
    $_SESSION['last_date_stamp'] = /* Insert the most recent date stamp here */;
    // return the $returnLines variable
?>

What this does is reads a file line by line and, if a session variable already exists, add all of the lines where the date stamp is newer than the one in the session variable to a return variable $returnLines, if no session variable exists it will put all of the lines in the file in $returnLines.

After this, it create.updates the session variable for use the next time the code is executed. Finally it returns the log file data by using the $returnLines variable.

Hope this helps.

答

You can try

session_start();
if (! isset($_SESSION['log'])) {
    $log = new stdClass();
    $log->timestamp = "2013-04-08-03-18-03";
    $log->position = 0;
    $log->max = 2;
    $_SESSION['log'] = &$log;
} else {
    $log = &$_SESSION['log'];
}

$format = "Y-m-d-:g:i:s";
$filename = "log.txt";

// Get last date
$dateLast = DateTime::createFromFormat($format, $log->timestamp);

$fp = fopen($filename, "r");
fseek($fp, $log->position); // prevent loading all file to memory

$output = array();
$i = 0;
while ( $i < $log->max && ! feof($fp) ) {
    $content = fgets($fp);

    // Check if date is current
    if (DateTime::createFromFormat($format, $log->timestamp) < $dateLast)
        continue;

    $log->position = ftell($fp); // save current position
    $log->timestamp = strstr($content, ":", true); // save curren time;
    $output[] = $content;
    $i ++;
}

fclose($fp);
echo json_encode($output); // send to ajax

从php中的.txt文件中获取特定文本

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