Redirect Cerr

redirect.cpp

#include <iostream>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>

#include <sys/epoll.h>

struct Redirecter {
        int writeFd, readFd;

        Redirecter() {
                int pipeFds[2];
                int& readFd = pipeFds[0];
                int& writeFd = pipeFds[1];

                int result = pipe(pipeFds);
                this->readFd = readFd;
                this->writeFd = writeFd;

                dup2(writeFd, 2);
                int defaultFlags = fcntl(readFd, F_GETFL, 0);
                fcntl(readFd, F_SETFL, defaultFlags | O_NONBLOCK);
        }

};

void* actor(void*);
struct RedirecterService {
        Redirecter r;

        static std::string readAvailable(int fd) {
                std::string result;
                char buf[15];
                memset(&buf, 0, sizeof(buf));

                int length;
                while( (length = read(fd, &buf, sizeof(buf))) >0) {
                        result.append(buf, length);
                }
                return result;
        }

        void startActor() {
                pthread_t pt;
                pthread_create(&pt, 0, actor, this);
                pthread_detach(pt);
        }

};
void* actor(void* r_) {
        RedirecterService& r = *reinterpret_cast<RedirecterService*>(r_);

        std::string line;
        char buf[15];
        int epoll_fd = epoll_create(1);
        struct epoll_event ev;
        ev.events = EPOLLIN;
        ev.data.fd = r.r.readFd;
        struct epoll_event ev2;
        epoll_ctl(epoll_fd, EPOLL_CTL_ADD, r.r.readFd, &ev);
        for(;;) {
                memset(&buf, 0, sizeof(buf));
                int nfds = epoll_wait(epoll_fd, &ev2, 1, -1);
                std::cout<<ev2.data.fd<<std::endl;
                std::cout<<"CERR "<<RedirecterService::readAvailable(r.r.readFd)<<std::endl;
        }
        return 0;
}


int main() {
        RedirecterService r;
        r.startActor();

        for(;;) {
                std::string input;
                std::cin>>input;
                std::cerr<<input;
        }
        pthread_exit(0);

}