Re: Basic question on streams
On Jul 23, 3:54 am, Robert Bauck Hamar <roberth+n...@ifi.uio.no>
wrote:
John Simeon wrote:
Wait, are you basically saying that ofstream inherits from ostream and
that, therefore, it should be possible to output to the screen with fou=
t?
No, he's saying that a std::ostream and a std::ofstream has
the same functions for output, and a std::ofstream can be used
in situations where a std::ostream is expected.
More generally, except when actually opening or closing the
file, you should use std::ostream&, and not std::ofstream&.
How would I do that if so?
Your first problem is: define screen. C++ has no concept of screens. C++
guarantees that there exists a standard out, but does not say where it en=
ds
and how. On many computers, the screen is a buffer in memory, and writing
to special addresses will make characters appear on the screen. On other
systems, the screen can only be reached with special system calls. How it
works on your system, however is not the topic of this group. But here is
something that works on my system:
std::ofstream out("/dev/stdout");
out << "Hello, world\n";
That's not standard Unix (which only requires "/dev/tty",
"/dev/null" and "/dev/console"), just a common extension. And
even on systems where it's implemented (e.g. Solaris or Linux),
it doesn't write to the screen; it writes to where ever standard
out happens to be redirected.
In general, to write to the screen, you need to use the X
Windows interfaces. "/dev/tty" will output to the terminal
window your process is connected to, IF it is connected to a
terminal window, and "/dev/console" will output to the console
window(s), if there are any.
This works on UNIX systems, where /dev/stdout is a special file. I don't
know if it works, but somethings tell me that the special file name CON h=
as
similar meanings on WinDOS.
I'm not sure about the name, but there is something similar to
"/dev/tty" under Windows, I think.
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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