How to rewrite same file

Question

Currently I'm doing it like this:

$f = fopen('test', 'w');
fwrite($f, 'Hi');
fclose($f);

But I have a loop that does some expensive stuff (with files), and I'd like to avoid opening and closing the file handle every time I want to overwrite "test"

It should be something like this:

$f = fopen('test', 'w');

$i = 0;
while($ < 50000){

  $i++;
  foverwrite($f, 'i = ' . $i);

  sleep(5); // just a example

}

fclose($f);

Is this possible?

This script runs in the background in CLI mode and I'm reading the test file from the web with ajax like every 2 seconds. Basically I'm trying to display a progress bar lol

Answer 1

You can update the content of a file by rewinding the file pointer, see fseek(). Be careful, once you set file lenght to N by writing N bytes to it, next time, if you rewind and write X < N bytes, the file will remain N bytes long, containing X bytes of new data and N-X bytes of old stuff.

Anyway, don't worry about opening and closing files several times, they will be cached. Or you can open it on a ramdisk partition.