Boost::process hide console on windows

Question

Recently boost 1.64 released, including boost::process. This provides an easy interface for starting processes. Previously I used the stand-alone version of the boost::proce

Answer 1

child constructor accepts a list of types that will be later converted using fancy ::boost::fusion methods into chain of calls performing actual initializations. So you can just push arguments of supported kind in any order:

#include <boost/process.hpp>
#include <boost/process/windows.hpp> // for windows::hide that can only be used on Windows

...

::boost::process::environment env = ::boost::this_process::environment();
::boost::process::child ch1("cmd", env, ::boost::process::windows::hide); // ok
::boost::process::child ch2(::boost::filesystem::path("C:\\Windows\\System32\\cmd.exe"), ::boost::process::windows::hide, env); // fine too

Hiding window conditionally is not that straightforward though because windows::hide and windows::show are of different types and can not be passed at the same function parameter. In this case it is required to write custom setup handler:

struct show_window
:   ::boost::process::detail::handler_base
{
    private: ::boost::detail::winapi::WORD_ const m_flag;

    public: explicit
    show_window(bool const show) noexcept
    :   m_flag{show ? ::boost::detail::winapi::SW_SHOWNORMAL_ : ::boost::detail::winapi::SW_HIDE_}
    {}

    // this function will be invoked at child process constructor before spawning process
    template <class WindowsExecutor>
    void on_setup(WindowsExecutor &e) const
    {
        // we have a chance to adjust startup info
        e.startup_info.dwFlags |= ::boost::detail::winapi::STARTF_USESHOWWINDOW_;
        e.startup_info.wShowWindow |= m_flag;
    }
};

auto const need_to_show{false};
auto env{::boost::this_process::environment()};
::boost::process::child ch("cmd", env, show_window{need_to_show});