[Crash-utility] Usage Advice

[Dave Anderson]

----- "CAI Qian" <caiqian at redhat.com> wrote:

> Hallo!
> 
> There are a few things that bother me the most regards the crash utility
> usages.
> 
> 1) Pointer remains at the beginning after the UP array key. When
>    entering the UP array key, it repeats the last command like,
> 
>    crash> struct struct_tss
> 
>    However, then the current position remains at the beginning. It is
>    usually unlike in bash that the current position remains at the end,
>    so it is easier to update the command like,
> 
>    crash> struct struct_tss ffffffff819f1764

I believe that's a function of the readline library, and there may be
a setting/binding that could be used to make that happen.  Since the
beginning, readline has been set up by crash like this:

        if (STREQ(pc->editing_mode, "vi")) {
                rl_editing_mode = vi_mode;

                rl_bind_key(CTRL('N'), rl_get_next_history);
                rl_bind_key(CTRL('P'), rl_get_previous_history);

                rl_bind_key_in_map(CTRL('P'), rl_get_previous_history,
                        vi_insertion_keymap);
                rl_bind_key_in_map(CTRL('N'), rl_get_next_history,
                        vi_insertion_keymap);

                rl_generic_bind(ISFUNC, "[A", (char *)rl_get_previous_history,
                        vi_movement_keymap);
                rl_generic_bind(ISFUNC, "[B", (char *)rl_get_next_history,
                        vi_movement_keymap);
        }

        if (STREQ(pc->editing_mode, "emacs")) {
                rl_editing_mode = emacs_mode;
        }

I don't recall where those bindings came from -- I copied them from some
other program.  I'm guessing that there's a binding that would put the cursor
at the end of the recalled string, but I don't know what it is off-hand.

If anybody knows what the binding sequence is, please post it here...

On the other hand, when updating a command string, I guess it depends
whether the location you want to change is at the beginning or the end
of the string would be a cause to be bothered by it?
  
> 
> 2) Pressing PgUp/PgDn when input leads nothing can be input. This
> happens like,
> 
>    crash> log
> 
>    In order to see the full log output, I may press PgDn several
>    times. However, if continue pressing the key after the output has
>    already finished like,

In the case of the "log" command, the PageUp and PageDown keys are being
captured by the scrolling routine, which is /usr/bin/less by default.

> 
>    crash>
> 
>    there seems no way to input anything unless pressing Enter several
>    times until reach the next prompt.

Right -- PageUp and PageDown don't make sense once you are back to
the "crash> " command prompt.  

> 3) Ctrl-C is not working to cancel the current input. GDB has the same
>    problem. It needs to press Ctrl-C several times to get it to a new
>    prompt.

That's also done on purpose -- in certain circumstances it requires 
that Ctrl-C be hit 3 times (MAX_SIGINTS_ACCEPTED).  There was a good
reason that was put in place, but I'm afraid I don't recall why...

Dave