Is there any photoshop API functions can let me open a file with photoshop in my plugin?

I used  the function system("open file"), it works well in any other program.

For example, system("open 1.psd"), this code can use photoshop open the file 1.psd .

But it just don't work in my plugin program.

How can I use photoshop to open a file in filter plugin at Mac OS X?

Is there any photoshop API functions can let me open a file with photoshop in my plugin?