2

如何在 on_exit 函数中获取 child.id() ？

bp::child c(args, ios, bp::on_exit([&](int e, std::error_code ec) {
            result = e;
            ios.stop();
            //need c.id();    

        }));

或者如果孩子按 id 运行，我如何检查其他功能？

        boost::process::child c(data->id); // doesn't work
        if (!c.running()) {
}
4

1 回答 1

2

您可以将任何您想要的额外信息绑定到您的处理程序。例如，您可以声明您的处理程序以引用child实例：

static void exit_handler(bp::child& process, int e, std::error_code ec) {
    std::cout << "Process " << process.id() << " exited with " << e << " (" << ec.message() << ")\n";
}

现在，您可以使用以下方法将其绑定到on_exit处理程序std::bind（当然您可以使用 lambda 来完成这项工作）：

p = bp::child(
        sv{"/bin/bash", "-c", command.str()},
        bp::on_exit(std::bind(exit_handler, std::ref(p), _1, _2)),
        io);

// Or, using a lambda to capture the reference:
p = bp::child(
        sv{"/bin/bash", "-c", command.str()},
        bp::on_exit([&p](int e, std::error_code ec) { exit_handler(p, e, ec); }),
        io);

生成 11 个子进程的完整示例，这些子进程需要不同的时间 < 1 秒才能完成并且都绑定到同一个处理程序：

住在科利鲁

#include <boost/process.hpp>
#include <boost/process/async.hpp>
#include <iostream>
#include <functional> // std::bind & placeholders
#include <sstream>    // ostringstream

namespace bp = boost::process;
using namespace std::placeholders;
using sv = std::vector<std::string>;

static void exit_handler(bp::child& process, int e, std::error_code ec) {
    std::cout << "Process " << process.id() << " exited with " << e << " (" << ec.message() << ")\n";
}

int main() {
    boost::asio::io_context io;
    auto work = make_work_guard(io);

    std::list<bp::child> children;

    for (auto ch = 'a'; ch < 'k'; ++ch) {
        auto& p = children.emplace_back();
        std::ostringstream command;
        command << "echo 'hello from " << ch << "';";
        command << "sleep 0.$RANDOM;";
        command << "echo 'bye from " << ch << "';";
        command << "exit " << (rand()%42) << ";";

        p = bp::child(
                sv{"/bin/bash", "-c", command.str()},
                bp::on_exit(std::bind(exit_handler, std::ref(p), _1, _2)),
                io);
    }

    work.reset(); // allow io to be finished
    io.run();     // wait for that

    std::cout << "Bye\n";
}

印刷：

hello from b
hello from a
hello from c
hello from d
hello from e
hello from f
hello from g
hello from i
hello from h
hello from j
bye from g
bye from a
bye from h
bye from b
bye from d
bye from f
bye from j
bye from e
bye from i
bye from c
Process 12044 exited with 10 (Success)
Process 12034 exited with 1 (Success)
Process 12047 exited with 30 (Success)
Process 12035 exited with 4 (Success)
Process 12038 exited with 19 (Success)
Process 12043 exited with 31 (Success)
Process 12050 exited with 31 (Success)
Process 12042 exited with 29 (Success)
Process 12049 exited with 15 (Success)
Process 12036 exited with 9 (Success)
Bye

更新

为了还能够查询哪个子进程仍在运行，请考虑使用 amap而不是 a list（要非常小心您选择的容器的参考稳定性！）。

这是一个演示Live On Coliru

std::map<char, bp::child> children;

for (char name = 'a'; name < 'k'; ++name) {
    std::ostringstream command;
    command << "echo 'hello from " << name << "';";
    command << "sleep " << (rand()%900 + 101)/1000.0 << ";";
    command << "echo 'bye from " << name << "';";
    command << "exit " << (rand()%42) << ";";

    auto& p = children[name];
    p = bp::child(
            sv{"/bin/sh", "-c", command.str()},
            bp::on_exit(std::bind(exit_handler, std::ref(p), _1, _2)),
            io);
}

work.reset(); // allow io to be finished

while (io.run_one()) { // wait for that
    std::cout << "Still running: ";
    for (auto& [name, child] : children) {
        if (child.running())
            std::cout << " " << name;
    }
    std::cout << std::endl;
}

std::cout << "Bye\n";

印刷

hello from a
hello from b
hello from c
hello from d
hello from e
hello from f
hello from g
hello from h
hello from i
Still running:  a b c d e f g h i j
Still running:  a b c d e f g h i j
hello from j
bye from i
Still running:  a b c d e f g h j
Process 30748 exited with -1
Still running:  a b c d e f g h j
bye from e
Still running:  a b c d f g h j
Still running:  a b c d f g h j
Process 30739 exited with -1
Still running:  a b c d f g h j
bye from c
Still running:  a b d f g h j
Still running:  a b d f g h j
Process 30735 exited with -1
Still running:  a b d f g h j
bye from b
Still running:  a d f g h j
Still running:  a d f g h j
Process 30733 exited with -1
Still running:  a d f g h j
bye from h
Still running:  a d f g j
Still running:  a d f g j
Process 30744 exited with -1
Still running:  a d f g j
bye from d
Still running:  a f g j
Still running:  a f g j
Process 30737 exited with -1
Still running:  a f g j
bye from g
Still running:  a f j
Still running:  a f j
Process 30743 exited with -1
Still running:  a f j
bye from f
Still running:  a j
Still running:  a j
Process 30740 exited with -1
Still running:  a j
bye from j
Still running:  a
Still running:  a
Process 30749 exited with -1
Still running:  a
bye from a
Still running: 
Still running: 
Process 30732 exited with -1
Still running: 
Bye
于 2020-04-22T15:56:11.697 回答