Inconsistent output in terminal emulator

[nico raffo]

Hi,

I'm writing a simple terminal emulator (on linux using standard pty
libraries) and have run across some behavior in bash that I cannot
explain after several weeks of reading documentation.

When I run a different shell, say zsh, it behaves the way I expect an
interactive shell would. As characters are sent to the shell to build
the command, the shell sends the characters back to the terminal to
display. However with bash, the shell doesn't respond at all until a
<CR> is sent, and then bash only sends the output of the command, not
the command itself. If my terminal emulator is expecting the shell to
provide all display text, it wouldn't show the commands at all.

In all other ways, bash behaves like an interactive shell. My ...rc
files are used correctly, and I can effectively launch and interact
with other programs.

The oddest part of all is that bash will start behaving like zsh if I
run zsh, then exit back to bash, even though it's still the same
process with the same environment.

Can anyone explain why bash is operating in one mode or the other, and
how I can explicitly set this behavior one way or the other?

Thanks!

Nico

Here is log showing this.

------------------------------------------------
bash: no job control in this shell
[BASH nraffo@sofia:~]$             <- <CR>
[BASH nraffo@sofia:~]$ pwd         <- pwd<CR>
/home/nraffo                       <- # bash only sends back pwd
output
[BASH nraffo@sofia:~]$ zsh         <- zsh<CR>
[ZSH nraffo@sofia:~]$              <- <CR>
                                   <- # zsh repeats the command
[ZSH nraffo@sofia:~]$ pwd          <- pwd<CR>
pwd                                <- # zsh repeats the command
/home/nraffo
[ZSH nraffo@sofia:~]$ exit         <- exit<CR>
exit                               <- # zsh repeats the command
[BASH nraffo@sofia:~]$             <- <CR>
                                   <- # now bash also repeats the
command
[BASH nraffo@sofia:~]$ pwd         <- pwd<CR>
pwd                                <- # bash repeating command
/home/nraffo
[BASH nraffo@sofia:~]$
-----------------------------------------------

Restarting in no-repeat mode:
(These don't change after going in and out of zsh)

-----------------------------------------------
bash: no job control in this shell
[BASH nraffo@sofia:~]$
[BASH nraffo@sofia:~]$ set
BASH=/bin/bash
BASH_ARGC=()
BASH_ARGV=()
BASH_LINENO=()
BASH_SOURCE=()
BASH_VERSINFO=([0]="3" [1]="00" [2]="15" [3]="1" [4]="release" [5]
="x86_64-redhat-linux-gnu")
BASH_VERSION='3.00.15(1)-release'
COLORS=/etc/DIR_COLORS
COLUMNS=168
DIRSTACK=()
EDITOR=vi
EUID=455
GROUPS=()
G_BROKEN_FILENAMES=1
HISTFILE=/home/nraffo/.bash_history
HISTFILESIZE=1000
HISTSIZE=1000
HOME=/home/nraffo
HOSTNAME=sofia.XXXXXXX.com
HOSTTYPE=x86_64
IFS=$' \t\n'
INPUTRC=/etc/inputrc
LANG=en_US.UTF-8
LESSOPEN='|/usr/bin/lesspipe.sh %s'
LINES=44
LOGNAME=nraffo
LS_COLORS=
MACHTYPE=x86_64-redhat-linux-gnu
MAIL=/var/spool/mail/nraffo
MAILCHECK=60
MYVIMRC=/home/nraffo/.vimrc
OPTERR=1
OPTIND=1
OSTYPE=linux-gnu
PATH=/usr/kerberos/bin:/usr/local/bin:/bin:/usr/bin:/usr/X11R6/bin:/
home/nraffo/bin
PIPESTATUS=([0]="0")
PPID=31674
PS1='[BASH \u@\h:\w]$ '
PS2='> '
PS4='+ '
PWD=/home/nraffo
SHELL=/bin/bash
SHELLOPTS=braceexpand:emacs:hashall:histexpand:history:interactive-
comments
SHLVL=3
SSH_CLIENT='10.10.0.64 50457 22'
SSH_CONNECTION='10.10.0.64 50457 10.10.1.14 22'
SSH_TTY=/dev/pts/1
SUPPORTED=en_US.UTF-8:en_US:en
TERM=dumb
TERMCAP=COLUMNS=168
UID=455
USER=nraffo
VIM=/home/nraffo/.mybin/vim72/share/vim
VIMRUNTIME=/home/nraffo/.mybin/vim72/share/vim/vim72
VIMSHELL=1
_=env
[BASH nraffo@sofia:~]$