RE: tools/gputop: Fix zero output when stdout is not a terminal

Srinivas, Vidya
2026-04-06T05:41:23Z

> -----Original Message-----
> From: Purkait, Soham <soham.purkait@intel.com>
> Sent: 06 April 2026 10:27
> To: Srinivas, Vidya <vidya.srinivas@intel.com>; igt-dev@lists.freedesktop.org;
> Konieczny, Kamil <kamil.konieczny@intel.com>
> Subject: Re: tools/gputop: Fix zero output when stdout is not a terminal
>
> Hi Vidya,
>
> On 02-04-2026 19:15, Vidya Srinivas wrote:
> > When gputop output is redirected to a file or pipe, such as:
> >
> > gputop -n 5 -d 1 > results.txt
>
> Isn’t only stdout (fd 1) redirected to the file here?
>
> I guess some thing like "echo test | ./gputop" would be returning the default
> value (-1 in this case) for con_h.

Hello,

Many thanks for the review.
I will update the patch like this. Should be okay?

if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) == -1 &&
ioctl(STDIN_FILENO, TIOCGWINSZ, &ws) == -1 &&
ioctl(STDERR_FILENO, TIOCGWINSZ, &ws) == -1) {
ws.ws_col = 80;
ws.ws_row = 50;
}

Regards
Vidya

>
> > gputop -n 3 -d 2 | grep rcs
> >
> > ioctl(0, TIOCGWINSZ) fails with -1 since stdin is not a terminal.
> > update_console_size() then returns without setting *w and *h, leaving
> > con_w and con_h at their initial value of -1.
> >
> > The main display loop uses 'if (lines >= con_h) break' to limit output
> > to the terminal height. With con_h = -1, the condition (0 >= -1) is
> > immediately true on the very first line, causing all client output to
> > be silently suppressed. The result is that gputop produces only ANSI
> > clear- screen escape sequences and zero actual data.
> >
> > This affects anyone using gputop in automation, CI pipelines, or any
> > non-interactive context on Linux or Android where output is redirected
> > or piped.
> >
> > Fix this by falling back to a default console size of 80x50 when the
> > ioctl fails, consistent with the existing fallback for serial consoles
> > (where ws_col and ws_row are both 0).
> >
> > Signed-off-by: Vidya Srinivas <vidya.srinivas@intel.com>
> > Reviewed-by: Kamil Konieczny <kamil.konieczny@linux.intel.com>
> > ---
> > tools/gputop.c | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/gputop.c b/tools/gputop.c index
> > 9b2e8cb6f..112ec5ddb 100644
> > --- a/tools/gputop.c
> > +++ b/tools/gputop.c
> > @@ -505,8 +505,11 @@ static void update_console_size(int *w, int *h)
> > {
> > struct winsize ws = {};
> >
> > - if (ioctl(0, TIOCGWINSZ, &ws) == -1)
> > + if (ioctl(0, TIOCGWINSZ, &ws) == -1) {
> > + *w = 80;
> > + *h = 50;
> How about assigning the values during initialization in the main function ?
>
> eg : int con_w = 80, con_h = 50;
>
> Thanks,
> Soham
>
> > return;
> > + }
> >
> > *w = ws.ws_col;
> > *h = ws.ws_row;