Question

I this piece of code:

$file = fopen($path, 'r+');
flock($file, LOCK_EX);
// reading the file into an array and doing some stuff to it
for ($i=0; $i<count($array); $i++)
  {
  fwrite($file, $array[$i]);
  }
flock($file, LOCK_UN);
fclose($file);

Basically what I want to do is: open a file > lock it > read it > do some stuff > clear the file > write to file > unlock it > close it.

The problem is the clearing part. I know I could do it with fopen($file, 'w+') but then reading would be a problem. Maybe I can change the mode somehow?

Any help would be appreciated, Paul

Answer 1

If you set the pointer to 0 using fseek you can then run ftruncate like so:

// reading the file into an array and doing some stuff to it

//1
fseek($handle,0); //Set the pointer to the first byte

//2
ftruncate($handle,filesize("yourfile.ext")); //from the first byte to the last truncate

//3 - File should be empty and still in writing mode.

for ($i=0; $i<count($array); $i++)
{
    fwrite($file, $array[$i]);
}

With ftruncate be aware of these issues regard the second param:

• If size is larger than the file then the file is extended with null bytes.

• If size is smaller than the file then the file is truncated to that size.

• http://www.php.net/manual/en/function.ftruncate.php

• http://www.php.net/manual/en/function.fseek.php