shm_get

gistfile1.txt

#include <stdio.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>
#include <thread>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>

int main(void) {
    size_t pagesize = getpagesize();

    int hnd = shm_open("arthur", O_CREAT | O_RDWR , 0777);
    if(hnd){
        printf(" return value , %d\n",hnd);
        //hnd = shm_open("arthur", O_CREAT| O_RDWR , S_IRWXO);
        //printf("error occured , %d\n",hnd);
    }



    printf("System page size: %zu bytes\n", pagesize);

    char * region = (char*)mmap(
            //(void*) (pagesize * (1 << 20)),   // Map from the start of the 2^20th page
            (void*)0x1234000000,
            pagesize,                         // for one page length
            PROT_READ|PROT_WRITE|PROT_EXEC,
            MAP_SHARED,             // to a private block of hardware memory
            hnd,
            0
    );
    if (region == MAP_FAILED) {
        perror("Could not mmap");
        return 1;
    }

    //std::thread  loop = std::thread( [region](){   while(1) { strcpy(region, "Hello, poftut.com"); }  }   );

    std::thread  loop2 = std::thread( [hnd, region](){
    
    while(1) {
           //strcpy(region, "thread2: Greatdwb@gmail.com");
           printf("Contents of region: %s\n", region);
           printf("thread2: address is %p, hnd = %d\n" , region,hnd);  }  }   );


    //loop.join();
    loop2.join();


    int unmap_result = munmap(region, 1 << 10);
    if (unmap_result != 0) {
        perror("Could not munmap");
        return 1;
    }



    // getpagesize
    return 0;
}