如何重写同一个文件

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

To go along with your example, you could implement your foverwrite() function using frewind() like this:

function foverwrite($handle,$content)
  {
  frewind($handle);
  return fwrite($handle,$content);
  }

This function will return fwrite()'s return value, so it can readily replace fwrite() where needed. Also, in case of opening the file in append mode (a or a+) it will just append contens, as frewind() will make no difference.

However, concerning the purpose of your script, which clearly is interprocess communication, you should take a look at more efficient techniques, like shared memory.