Depends on your shell, but you can try this yourself -- for instance: $ ssh localhost -o ProxyCommand="ssh localhost 'pstree -a \$PPID >&2 ; nc %h %p'"

Depends on your shell, but you can try this yourself -- for instance: $ ssh localhost -o ProxyCommand="ssh localhost 'pstree -a \$PPID >&2 ; nc %h %p'" sshd `-bash -c pstree -a $PPID >&2 ; nc localhost 22 `-pstree -a 6703 Bash invoked this way will be non-interactive. Often bashrc will test "$PS1" to bail early in this case, but the point remains that it does run. I also tried my command with echos before and after that test in my bashrc to confirm what happens.