Read last line from file

Question

I\'ve been bumping into a problem. I have a log on a Linux box in which is written the output from several running processes. This file can get really big sometimes and I ne

Answer 1

If you know the upper bound of line length you could do something like this.

$maxLength = 1024;
$fp = fopen('somefile.txt', 'r');
fseek($fp, -$maxLength , SEEK_END); 
$fewLines = explode("\n", fgets($fp, $maxLength));
$lastLine = $fewLines[count($fewLines) - 1];

In response to the edit: fopen just acquires a handle to the file (i.e. make sure it exists, process has permission, lets os know a process is using the file, etc...). In this example only 1024 characters from the file will be read into memory.

Answer 2

This function will let you read last line or (optionally) entire file line-by-line from end, by passing $initial_pos which will tell from where to start reading a file from end (negative integer).

function file_read_last_line($file, $initial_pos = -1) {
  $fp = is_string($file) ? fopen($file, 'r') : $file;
  $pos = $initial_pos;
  $line = '';
  do {
    fseek($fp, $pos, SEEK_END);
    $char = fgetc($fp);
    if ($char === false) {
      if ($pos === $initial_pos) return false;
      break;
    }
    $pos = $pos - 1;
    if ($char === "\r" || $char === "\n") continue;
    $line = $char . $line;
  } while ($char !== "\n");
  if (is_string($file)) fclose($file);
  return $line;
}

Then, to read last line:

$last_line = file_read_last_line('/path/to/file');

To read entire file line-by-line from end:

$fp = fopen('/path/to/file', 'r');
$pos = -1;
while (($line = file_read_last_line($fp, $pos)) !== false) {
  $pos += -(strlen($line) + 1);
  echo 'LINE: ' . $line . "\n";
}
fclose($fp);

Answer 3

You're looking for the fseek function. There are working examples of how to read the last line of a file in the comments section there.

Answer 4

function readlastline() 
{ 
       $fp = @fopen("/dosmnt/LOGFILE.DAT", "r"); 
       $pos = -1; 
       $t = " "; 
       while ($t != "\n") { 
             fseek($fp, $pos, SEEK_END); 
             $t = fgetc($fp); 
             $pos = $pos - 1; 
       } 
       $t = fgets($fp); 
       fclose($fp); 
       return $t; 
} 

Source: http://forums.devshed.com/php-development-5/php-quick-way-to-read-last-line-156010.html

Answer 5

this the code of Ionuț G. Stan

i modified your code a little and made it a function for reuseability

function read_last_line ($file_path){



$line = '';

$f = fopen($file_path, 'r');
$cursor = -1;

fseek($f, $cursor, SEEK_END);
$char = fgetc($f);

/**
* Trim trailing newline chars of the file
*/
while ($char === "\n" || $char === "\r") {
    fseek($f, $cursor--, SEEK_END);
    $char = fgetc($f);
}

/**
* Read until the start of file or first newline char
*/
while ($char !== false && $char !== "\n" && $char !== "\r") {
    /**
     * Prepend the new char
     */
    $line = $char . $line;
    fseek($f, $cursor--, SEEK_END);
    $char = fgetc($f);
}

return $line;
}

echo read_last_line('log.txt');

you will get that last line

Answer 6

This should work:

$line = '';

$f = fopen('data.txt', 'r');
$cursor = -1;

fseek($f, $cursor, SEEK_END);
$char = fgetc($f);

/**
 * Trim trailing newline chars of the file
 */
while ($char === "\n" || $char === "\r") {
    fseek($f, $cursor--, SEEK_END);
    $char = fgetc($f);
}

/**
 * Read until the start of file or first newline char
 */
while ($char !== false && $char !== "\n" && $char !== "\r") {
    /**
     * Prepend the new char
     */
    $line = $char . $line;
    fseek($f, $cursor--, SEEK_END);
    $char = fgetc($f);
}

echo $line;