PHP, file exists: 'con'?

Question

I made 2 checks of file name validness (for uploading):

1. Is there another file with the same name?
2. Can a file with this name be created at all?

For (1) I use file_exists, for (2) — fopen for creating.

$dir = '../../images/';
if (file_exists($dir.$name))
{
    ok('alreadyexists', 'true');
}
else
{
    $file = fopen($dir.$name, 'x');
    if (FALSE == $file)
    {
        ok('invalid', 'true');
    }
    else
    {
        fclose($file);
        ok();
    }
}

Testing the code above, I tried the name 'con' (AFAIK, under Windows you can't create such files). I supposed it would fail at the second test, but file_exists returns true for '../../images/con'! Why?

Answer 1

I suggest to use is_writable($dir.$name) after the file has been touched / created (files get saved AFTER fclose). touch() is also a good approach for initially creating a file and test wether it can be written.

Could try:

touch($dir.$name);

is_writable($dir.$name);

//parse the output of
shell_exec('touch ' . $dir . $name);
// or
exec('touch ' . $dir . $name);

Would also be interesting what this prints:

filetype($dir.$name);

From http://www.php.net/manual/en/function.filetype.php

There are 7 values that can be returned. Here is a list of them and what each one means block: block special device char: character special device dir: directory fifo: FIFO (named pipe) file: regular file link: symbolic link unknown: unknown file type

// also interesting:
stat($dir.$name);

Answer 2

Yes, it is. con is historically name of IO-pseudo-device in Windows. You can't create file with such name and system will treat this as already existing file. Think of it as a bit of magic that makes our days beautiful.

Other devices (so, reserved file names) with such property are:

• AUX (console connection)
• NUL (null-device)
• COM1 .. COM9 (serial ports)
• PRN (printer)
• LPT1 .. LPT9 (parallel ports)