I use emacs tramp mode, which opens an ssh connection to a remote machine for file access. It works to Linux and FreeBSD 12.1, but not to CURRENT. There has been a change in the way characters are echoed by the shell, with 12.1 treating a consecutive run of backspace as an atomic unit and CURRENT processing them one at a time. This is not necessarily a bug, but it is a nuisance and independently it is suboptimal.
I would like to blame libedit, which changed since 12.1. I didn't see any changes in pty code and the problem happens with at least two different shells. It could also be caused by a change to sshd or something I haven't through of. Here is a longer explanation. Emacs tramp mode opens an ssh connection to a remote machine. It doesn't want to see input echoed back so it runs stty -inlcr -onlcr -echo kill '^U' erase '^H' This doesn't do anything useful if a shell is running in line editing mode (raw) instead of using the tty (cooked). So tramp falls back to a hack to detect echoed input. It sends "_echo" followed by a string of backspace characters. "_echo" is unlikely to appear in program output. Here is the next command after the initial stty: _echo^H^H^H^H^Hstty icanon erase ^H cols 32767_echo^H^H^H^H^H The groups of 5 ^H represent 5 backspace characters and the lone ^H in the middle is a two character sequence for stty. The terminal output from a 12.1 system is _echo^H ^H^H ^H^H ^H^H ^H^H ^Hstty icanon erase ^H cols 32767_echo^H ^H^H ^H^H ^H^H ^H^H ^H #$ where again the middle ^H is a two character sequence and the others are backspace characters. There is a carriage return between the two lines. "#$ " is the shell prompt set by tramp. The terminal output from a CURRENT system is _echo #$ _ech ^H #$ _ec ^H #$ _e ^H #$ _ ^H #$ ^Hstty icanon erase ^H cols 32767_echo #$ stty icanon erase ^H cols 32767_ech ^H #$ stty icanon erase ^H cols 32767_ec ^H #$ stty icanon erase ^H cols 32767_e ^H #$ stty icanon erase ^H cols 32767_ ^H #$ stty icanon erase ^H cols 32767 ^H #$ with carriage returns between lines. This does not make sense to emacs. I tried both /bin/sh and /bin/csh as shells and tramp didn't work with either. I put set +V and set +E in my .profile thinking that would turn off line editing but there was no change. Probably the shell still takes raw input. A possible complicating factor is the CURRENT machines are both 64 bit ARM and the 12.1 machine is amd64. One has unsigned characters, the other signed. Shouldn't matter, but I haven't tried 12.1 on ARM so I can't swear it works. _______________________________________________ freebsd-current@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
