def usage_hint(command, shell):
    """
    Returns the usage hint and comment, for the given shell.
    """
    if shell == 'fish':
        return 'eval ({command})'.format(command=command), '#'
    elif shell == 'powershell':
        return (
            '{command} | ForEach-Object {{If (-Not[string]::IsNullOrEmpty($_)) {{ $_ | Invoke-Expression }}}}'
            .format(command=command), '#')
    elif shell == 'cmd':
        return '\t@FOR /f "tokens=*" %i IN ({command}) DO @%i'.format(command
            =command), 'REM'
    elif shell == 'emacs':
        return (
            '(with-temp-buffer (shell-command {command} (current-buffer))(eval-buffer))'
            .format(command=command), ';;')
    elif shell == 'tcsh':
        return 'eval `{command}`'.format(command=command), ':'
    else:
        return 'eval $({command})'.format(command=command), '#'
