Question

在Boost.Process 0.5（http://www.highscore.de/boost/process0.5/index.html）的这个简单示例中，程序（ls）的输出正在为流提供数据。流工作正常但与预期相反，流程在程序完成后不会变为无效（例如，流末尾）（类似于以前版本的Boost.Process，例如http://www.highscore.de/boost/process/index.html）

在子程序退出后，为了使流（示例中的is）自动无效，我缺少什么？

也许我必须在stream的Boost.Streams file_descriptor中设置这个选项？

#include <boost/process.hpp> // version 0.5 from http://www.highscore.de/boost/process0.5/process.zip
#include <boost/iostreams/device/file_descriptor.hpp>
#include <boost/iostreams/stream.hpp>
#include <string>
using namespace boost::process;
using namespace boost::process::initializers;
using namespace boost::iostreams;
int main(){
    boost::process::pipe p = create_pipe();
    file_descriptor_sink sink(p.sink, close_handle);
    child c = execute(run_exe("/usr/bin/ls"), bind_stdout(sink));
    file_descriptor_source source(p.source,  close_handle);
    stream<file_descriptor_source> is(source);
    std::string s;
    while(std::getline(is, s)){
        std::cout << "read: " << s << std::endl;
    }
    std::clog << "end" << std::endl; // never reach
}

Answer 1

我与图书馆的作者Boris Schaeling进行了私人（实际上是通过Nabble）的沟通。抛弃了几种可能性，比如posix / boost.iostreams中的bug，他给了我一些有效的代码修改。基本上，我可以推断出file_descriptor sink必须超出范围（已销毁）才能使流返回EOF。工作代码只是为sink添加了一个特定的范围（最后列出）。我认为这很容易将所有类型封装在pistream类中。（我的列表中的下一步是允许输出到流程。）

适用于Boost 1.48（Fedora 17）。

#include <boost/process.hpp> // version 0.5
#include <boost/iostreams/device/file_descriptor.hpp>
#include <boost/iostreams/stream.hpp>
#include <string>

using namespace boost::process;
using namespace boost::process::initializers;
using namespace boost::iostreams;

int main() {
    pipe p = create_pipe();
    {
        // note the scope for sink
        file_descriptor_sink sink(p.sink, close_handle);
        /*  child c = */ // not necessary to hold a child object, it seems.
        execute(run_exe("/usr/bin/ls"), bind_stdout(sink));
    }   // note the scope for sink

    file_descriptor_source source(p.source,  close_handle);
    stream<file_descriptor_source> is(source);
    std::string s;
    while(std::getline(is, s)) {
        std::cout << "read: " << s << std::endl;
    }
    std::clog << "end" << std::endl; // never reach
}

使用c(lang)++ -lboost_system -lboost_iostreams

进行编译

编辑：这似乎也有效，避免了人为的范围，但可能会让人感到困惑，因为接收器必须是临时的：

    ...
    pipe p = create_pipe();
    execute(run_exe("/usr/bin/ls"), bind_stdout(        
        file_descriptor_sink(p.sink, close_handle)
    ));
    file_descriptor_source source(p.source,  close_handle);
    ...

Answer 2

这适用于类似POSIX的系统：

#include <boost/process.hpp> // version 0.5 from http://www.highscore.de/boost/process0.5/process.zip
#include <boost/iostreams/device/file_descriptor.hpp>
#include <boost/iostreams/stream.hpp>
#include <boost/asio.hpp>
#include <string>

using namespace boost::process;
using namespace boost::process::initializers;
using namespace boost::iostreams;

int main()
{
    boost::asio::io_service io_service;
    int status = 1;
    boost::asio::signal_set set(io_service, SIGCHLD);
    set.async_wait(
        [&status](const boost::system::error_code&, int) { ::wait(&status); }
    );

    boost::process::pipe p = create_pipe();
    file_descriptor_sink sink(p.sink, close_handle);
    child c = execute(run_exe("/bin/ls"), bind_stdout(sink));
    file_descriptor_source source(p.source,  close_handle);
    stream<file_descriptor_source> is(source);
    std::string s;
    while(status && std::getline(is, s))
    {
        std::cout << "read: " << s << std::endl;
    }
    std::clog << "end" << std::endl; // never reach
}

请注意，它将SIGCHLD处理为异步设置status。它取自http://www.highscore.de/boost/process0.5/boost_process/tutorial.html#boost_process.tutorial.starting_a_program。此页面还显示了执行相同操作的Windows样式：

#if defined(BOOST_WINDOWS_API)
    DWORD exit_code;
    boost::asio::windows::object_handle handle(io_service, c.process_handle());
    handle.async_wait(
        [&handle, &exit_code](const boost::system::error_code&)
            { ::GetExitCodeProcess(handle.native(), &exit_code); }
    );
#endif

    io_service.run();

如何在Boost.Process 0.5中将程序终止与流结束绑定？

2 个答案: