Re: [Crash-utility] [PATCH] Output prompt when stdin is not a TTY.
On Wed, May 31, 2023 at 11:05 AM Hsin-Yi Wang <hsinyi(a)chromium.org> wrote:
On Wed, May 31, 2023 at 10:54 AM HAGIO KAZUHITO(萩尾 一仁)
<k-hagio-ab(a)nec.com> wrote:
>
> On 2023/05/31 3:13, Hsin-Yi Wang wrote:
> > When stdin is not a TTY, prompt ("crash> ") won't be
displayed. If
> > another process interact with crash with piped stdin/stdout, it will not
> > get the prompt as a delimiter.
> >
> > Compared to other debugger like gdb, crash seems intended to give a
> > prompt in this case in the beginning of process_command_line(). It
> > checks if pc->flags does NOT have any of
> > READLINE|SILENT|CMDLINE_IFILE|RCHOME_IFILE|RCLOCAL_IFILE, a
> > prompt should be printed. The check will never be true since READLINE is
> > set in setup_environment() unconditionally. It makes more sense to
> > change the READLINE flag in the check to TTY instead.
> >
> > Additionally, when stdin is not TTY, repeat the command line from user
> > after prompt, which can give more context.
> >
> > The prompt and command line can be opt out by using the silent (-s) flag.
> >
> > Signed-off-by: Hsin-Yi Wang <hsinyi(a)chromium.org>
>
> Thanks, but I found a case that prints two prompts, after a fatal error:
>
> # cat ~/.crashrc
> sys config <<-- any command that fails with error(FATAL)
> sys
> # echo quit | crash
> ...
> 2 crash> sys config
> sys: kernel_config_data does not exist in this kernel
> 1 crash> 2 crash> sys
> KERNEL: /usr/lib/debug/lib/modules/4.18.0-305.el8.x86_64/vmlinux
> ...
>
> where the crash has this:
>
> --- a/cmdline.c
> +++ b/cmdline.c
> @@ -66,7 +66,7 @@ process_command_line(void)
>
> if (!(pc->flags &
> (TTY|SILENT|CMDLINE_IFILE|RCHOME_IFILE|RCLOCAL_IFILE)))
> - fprintf(fp, "%s", pc->prompt);
> + fprintf(fp, "1 %s", pc->prompt);
> fflush(fp);
>
> /*
> @@ -1487,7 +1487,7 @@ exec_input_file(void)
> continue;
>
> if (!(pc->flags & SILENT)) {
> - fprintf(fp, "%s%s", pc->prompt, buf);
> + fprintf(fp, "2 %s%s", pc->prompt, buf);
Ah, I misread this as the fprintf in process_command_line. I'll take a
look at this issue to see how to avoid it. Sorry for the confusion.
I don't think we need to print a prompt again here. It can be used as
a delimiter when all the previous output are done and waiting for user
input. If we print the prompt again. what it will read:
crash 8.0.3++
1 crash>
// suppose stdin has cmd1 after here.
2 crash> cmd1
cmd1_output
1 crash>
// supposes stdin has cmd2 after here.
2 crash> cmd2
cmd2_output
Without the 2nd prompt:
crash 8.0.3++
1 crash>
// suppose stdin has cmd1 after here.
cmd1
cmd1_output
1 crash>
// suppose stdin has cmd2 after here.
cmd2
cmd2_output
> fflush(fp);
> }
>
> Can we avoid this?
>
> Thanks,
> Kazu
>
> > ---
> > v1:
> > - The original discussion:
https://listman.redhat.com/archives/crash-utility/2023-May/010710.html
> > - Kazu: provide the idea to print the command line as well.
> > ---
> > cmdline.c | 6 +++++-
> > 1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/cmdline.c b/cmdline.c
> > index ded6551..9821d86 100644
> > --- a/cmdline.c
> > +++ b/cmdline.c
> > @@ -65,7 +65,7 @@ process_command_line(void)
> > BZERO(pc->command_line, BUFSIZE);
> >
> > if (!(pc->flags &
> > - (READLINE|SILENT|CMDLINE_IFILE|RCHOME_IFILE|RCLOCAL_IFILE)))
> > + (TTY|SILENT|CMDLINE_IFILE|RCHOME_IFILE|RCLOCAL_IFILE)))
> > fprintf(fp, "%s", pc->prompt);
> > fflush(fp);
> >
> > @@ -139,6 +139,10 @@ process_command_line(void)
> > } else {
> > if (fgets(pc->command_line, BUFSIZE-1, stdin) == NULL)
> > clean_exit(1);
> > + if (!(pc->flags & SILENT)) {
> > + fprintf(fp, "%s", pc->command_line);
> > + fflush(fp);
> > + }
> > clean_line(pc->command_line);
> > strcpy(pc->orig_line, pc->command_line);
> > }