Efficiently counting the number of lines of a text file. (200mb+)

This will use less memory, since it doesn't load the whole file into memory:

$file="largefile.txt";
$linecount = 0;
$handle = fopen($file, "r");
while(!feof($handle)){
  $line = fgets($handle);
  $linecount++;
}

fclose($handle);

echo $linecount;

fgets loads a single line into memory (if the second argument $length is omitted it will keep reading from the stream until it reaches the end of the line, which is what we want). This is still unlikely to be as quick as using something other than PHP, if you care about wall time as well as memory usage.

The only danger with this is if any lines are particularly long (what if you encounter a 2GB file without line breaks?). In which case you're better off doing slurping it in in chunks, and counting end-of-line characters:

$file="largefile.txt";
$linecount = 0;
$handle = fopen($file, "r");
while(!feof($handle)){
  $line = fgets($handle, 4096);
  $linecount = $linecount + substr_count($line, PHP_EOL);
}

fclose($handle);

echo $linecount;

If you're running this on a Linux/Unix host, the easiest solution would be to use exec() or similar to run the command wc -l $path. Just make sure you've sanitized $path first to be sure that it isn't something like "/path/to/file ; rm -rf /".

If you're under linux you can simply do:

number_of_lines = intval(trim(shell_exec("wc -l ".$file_name." | awk '{print $1}'")));

You just have to find the right command if you're using another OS

Regards

The most succinct cross-platform solution that only buffers one line at a time.

$file = new \SplFileObject(__FILE__);
$file->setFlags($file::READ_AHEAD);
$lines = iterator_count($file);

Unfortunately, we have to set the READ_AHEAD flag otherwise iterator_count blocks indefinitely. Otherwise, this would be a one-liner.

You have several options. The first is to increase the availble memory allowed, which is probably not the best way to do things given that you state the file can get very large. The other way is to use fgets to read the file line by line and increment a counter, which should not cause any memory issues at all as only the current line is in memory at any one time.

I use this method for purely counting how many lines in a file. What is the downside of doing this verses the other answers. I'm seeing many lines as opposed to my two line solution. I'm guessing there's a reason nobody does this.

$lines = count(file('your.file'));
echo $lines;

this is a bit late but...

Here is my solution for a text log file I have which uses \n to separate each line.

$data = file_get_contents("myfile.txt");
$numlines = strlen($data) - strlen(str_replace("\n","",$data));

It does load the file into memory but doesn't need to cycle through an unknown number of lines. It may be unsuitable if the file is GB in size but for smaller files with short lines of data it works a treat for me.

It just removes the "\n" from the file and compares how many have been removed by comparing the length of the data in the file to the length after removing all the line breaks ("\n" chars n my case). If your line delineator is a different char, replace the "\n" with whatever is your line delineation character.

I know it is not the best answer for all occasions but is something I have found quick and simple for my purposes where each line of the log is only a few hundred chars and total log file is not too large.