carriage return with stdout and stderr

[Jilles Tjoelker]

On Sun, Jul 05, 2009 at 01:42:01PM +0200, Alexander Best wrote:
> i'm running something similar to this pseudo-code in an app of mine:

> for (i=0 ....)
>     fprintf(stdout,"TEXT %d\r", int);

> what's really strange is that if i print to stdout the output isn't very
> clean. the cursor jumps randomly within the output (being 1 line). if i print
> to stderr however the output looks really nice. the cursor says right at the
> front of the output all the time. just like in burncd e.g.

> what's causing this? because i'd rather print to stdout.

If you are writing to a terminal, stdout is line-buffered. This means
that output is flushed when the buffer is full or a '\n' is written. A
'\r' is not good enough. You can force a write using fflush(stdout).

stderr is always unbuffered, so everything is written immediately.

-- 
Jilles Tjoelker