Re: [PATCH] Output prompt when stdin is not a TTY.

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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@xxxxxxxxxxxx>

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);
                          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);
>           }
--
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