curl -L -v -F "value=@myfile" "http://domain.tld/whatever.php"
curl
read "man curl" if you need to info like using cookies,etc. you can also use wget-L
follow redirects-v
be verbose-F
an input field value=
the name of the input field @myfile
the file you want uploaded"http://domain.tld/whatever.php"
the url that will take the file