Is this the most efficient way to get and remove first line in file?

Question

I have a script which, each time is called, gets the first line of a file. Each line is known to be exactly of the same length (32 alphanumeric chars) and terminates with \"

Answer 1

you can iterate the file , instead of putting them all in memory

$handle = fopen("file", "r");
$first = fgets($handle,2048); #get first line.
$outfile="temp";
$o = fopen($outfile,"w");
while (!feof($handle)) {
    $buffer = fgets($handle,2048);
    fwrite($o,$buffer);
}
fclose($handle);
fclose($o);
rename($outfile,$file);

Answer 2

I think this is best for any file size

$myfile = fopen("yourfile.txt", "r") or die("Unable to open file!");
$ch=1;

while(!feof($myfile)) {
  $dataline= fgets($myfile) . "<br>";
  if($ch == 2){
  echo str_replace(' ', '&nbsp;', $dataline)."\n";
  }
  $ch = 2;
} 
fclose($myfile);

Answer 3

No need to create a second temporary file, nor put the whole file in memory:

if ($handle = fopen("file", "c+")) {             // open the file in reading and editing mode
    if (flock($handle, LOCK_EX)) {               // lock the file, so no one can read or edit this file 
        while (($line = fgets($handle, 4096)) !== FALSE) { 
            if (!isset($write_position)) {        // move the line to previous position, except the first line
                $write_position = 0;
            } else {
                $read_position = ftell($handle); // get actual line
                fseek($handle, $write_position); // move to previous position
                fputs($handle, $line);           // put actual line in previous position
                fseek($handle, $read_position);  // return to actual position
                $write_position += strlen($line);    // set write position to the next loop
            }
        }
        fflush($handle);                         // write any pending change to file
        ftruncate($handle, $write_position);     // drop the repeated last line
        flock($handle, LOCK_UN);                 // unlock the file
    }
    fclose($handle);
}

Answer 4

You could use file() method.

Gets the first line

$content = file('myfile.txt');
echo $content[0];  

Answer 5

The solutions here didn't work performantly for me. My solution grabs the last line (not the first line, in my case it was not relevant to get the first or last line) from the file and removes that from that file. This is very quickly even with very large files (>150000000 lines).

function file_pop($file)
{
    if ($fp = @fopen($file, "c+")) {
        if (!flock($fp, LOCK_EX)) {
            fclose($fp);
        }
        $pos = -1;
        $found = 0;
        while ($found < 2) {
            if (fseek($fp, $pos--, SEEK_END) < 0) { // can not seek to position
                rewind($fp); // rewind to the beginnung of the file
                break;
            };
            if (ord(fgetc($fp)) == 10) { // newline
                $found++;
            }
        }
        $lastpos = ftell($fp); // get current position of file
        $lastline = fgets($fp); // get current line

        ftruncate($fp, $lastpos); // truncate file to last position
        flock($fp, LOCK_UN); // unlock
        fclose($fp); // close the file

        return trim($lastline);
    }
}

Answer 6

This will shift the first line of a file, you dont need to load the entire file in memory like you do using the 'file' function. Maybe for small files is a bit more slow than with 'file' (maybe but i bet is not) but is able to manage largest files without problems.

$firstline = false;
if($handle = fopen($logFile,'c+')){
    if(!flock($handle,LOCK_EX)){fclose($handle);}
    $offset = 0;
    $len = filesize($logFile);
    while(($line = fgets($handle,4096)) !== false){
        if(!$firstline){$firstline = $line;$offset = strlen($firstline);continue;}
        $pos = ftell($handle);
        fseek($handle,$pos-strlen($line)-$offset);
        fputs($handle,$line);
        fseek($handle,$pos);
    }
    fflush($handle);
    ftruncate($handle,($len-$offset));
    flock($handle,LOCK_UN);
    fclose($handle);
}