Re: ^L showing up in Emacs M-x shell-mode, with ksh but not bash

[Nicholas Papadonis <nick.papadonis.ml@gmail.com>]

This is what the child ksh M-x shell process is doing when I resize the
window.  As you can see the write of ">  " near the end.  Hopefully some
folks have more insight into this.

select(1, [0], NULL, NULL, NULL)        = ? ERESTARTNOHAND (To be restarted
if no handler)
--- SIGWINCH {si_signo=SIGWINCH, si_code=SI_KERNEL} ---
rt_sigaction(SIGWINCH, {sa_handler=0x55e35c5a23b0, sa_mask=[],
sa_flags=SA_RESTORER|SA_INTERRUPT, sa_restorer=0x7ffb3cb91060},
{sa_handler=0x55e35c5a23b0, sa_mask=[], sa_flags=SA_RESTORER|SA_INTERRUPT,
sa_restorer=0x7ffb3cb91060}, 8) = 0
ioctl(2, TIOCGWINSZ, {ws_row=9, ws_col=102, ws_xpixel=0, ws_ypixel=0}) = 0
rt_sigprocmask(SIG_UNBLOCK, [WINCH], NULL, 8) = 0
rt_sigreturn({mask=[]})                 = -1 EINTR (Interrupted system call)
ioctl(2, TIOCGWINSZ, {ws_row=9, ws_col=102, ws_xpixel=0, ws_ypixel=0}) = 0
poll([], 0, 50)                         = 0 (Timeout)
ioctl(2, TIOCGWINSZ, {ws_row=9, ws_col=102, ws_xpixel=0, ws_ypixel=0}) = 0
lseek(3, 0, SEEK_END)                   = 2
lseek(3, 0, SEEK_CUR)                   = 2
lseek(3, 2, SEEK_SET)                   = 2
read(3, "", 65536)                      = 0
lseek(3, 2, SEEK_SET)                   = 2
read(3, "", 65536)                      = 0
select(1, [0], NULL, NULL, {tv_sec=0, tv_usec=0}) = 0 (Timeout)
write(2, ">  ", 3)                      = 3
select(1, [0], NULL, NULL, NULL


On Mon, Nov 4, 2019 at 8:57 PM Kurtis Rader <krader@skepticism.us> wrote:

> On Mon, Nov 4, 2019 at 4:19 PM Nicholas Papadonis <
> nick.papadonis.ml@gmail.com> wrote:
>
>> When Emacs is invoked in an X-session and when I resize a M-x shell-mode
>> *shell* window by more then a single line of text, $PS2 is being output in
>> the shell mode window.  When I type <return> then a number of "^L"s are
>> also output in the shell mode window.
>>
>> I'm using /bin/ksh93 in Debian.
>>
>> This behavior does not occur with bash.
>>
>> Does anyone know why this is happening?  Also, more ways to debug it?
>>
>
> No idea what's happening, but I wouldn't leap to the conclusion that $PS2
> is being displayed. Given the presence of the [ctrl-L] chars it's just as
> likely that both chars are being sent to the shell. Possibly
> bracketed-paste mode is enabled by the emacs shell mode. If you start the
> shell, then in a different window strace it what appears in the trace when
> you resize the window? Also, you might want to try the current development
> version that you'll find at https://github.com/att/ast/
> <https://github.com/att/ast/pull/1427>. It's easy to build if you're
> willing to install Meson.
>
> P.S., You might want to take a look at https://asciinema.org for
> capturing terminal sessions for playback.
>
> --
> Kurtis Rader
> Caretaker of the exceptional canines Junior and Hank
>