there is a page that i need to post a password to it and then i get a file to download. the post goes to the same page address its loads again and pop up the download manager (download starts automatically). now i want to do the same but in curl, i posted the data to the url and then its sends me the file back but i don't want my script to download the whole file i want only to get a link to download it by myself. how can i do that?
Actually, you most probably can't. Such password protected download system usually checks either cookies or browser / environment based variables. Getting the link itself shouldn't be problem, however you could not use it outside this generator's scope anyway.
firstly you need to post that password with curl assuming "on specific form. the form will take you to the downloading page" now you need to use regex (regular expressions). filter the data you want then save it on other variable to re-use it.
There is for sure a redirection after you hit 1st page with POST. Look for that redirection with curl and read http response headers: Content-Location or Location or even Refresh
To prevent the automatic download you have to set the curl opt to not follow redirects. I can't remember the exact command but curl by default will follow auto refreshes and URL redirects, which happen in split seconds so humans don't actually see it happening.
I kinda don't understand what you really want to do, but if you just want a link then have the php script perform the entire curl post and everything when they click it. Doesn't matter what the web server will require a password before access to a file, you can't skip that step.