bin/oils-for-unix is an executable that contains OSH, YSH, and more.

Usage: oils-for-unix MAIN_NAME ARG*
       MAIN_NAME ARG*

It behaves like busybox.  The command name can be passed as the first argument:

    oils-for-unix ysh -c 'echo hi'

More commonly, it's invoked through a symlink like 'ysh', which causes it to
behave like that command:

    ysh -c 'echo hi'
