the original code you posted compiles fine with just
Code:
g++ file.cpp
i suggest you read the man page on g++ to check out all the options you can use

>> oooah ok. what would I put there for linux app?
you dont have to put anything specific for a linux app. linux does not see files in terms of extensions, but rather permissions. so if you have a file named

foo

it will execute the same as foo as it would as

foo.bar
foobar
foo.exe
a.out

names dont matter.

so just put somthing descriptive for the '-o' option or leave it blank