trying shm

lab4/src/shm1.cpp

@@ -0,0 +1,53 @@
+#include<stdio.h>
+#include<sys/mman.h>
+#include<sys/stat.h>
+#include<fcntl.h>
+#include<unistd.h>
+
+int main() {
+    const char *name = "/my_shared_memory";
+    int shm_fd = shm_open(name, O_CREAT | O_RDWR, 0666);
+    if (shm_fd == -1) {
+        perror("shm_open");
+        return 1;
+    }
+
+    // Set the size of the shared memory region
+    size_t size = 1024;
+
+    // Resize the shared memory object to the desired size
+    if (ftruncate(shm_fd, size) == -1) {
+        perror("ftruncate");
+        return 1;
+    }
+
+    // Map the shared memory object into the process address space
+    void *ptr = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, shm_fd, 0);
+    if (ptr == MAP_FAILED) {
+        perror("mmap");
+        return 1;
+    }
+
+    // Write data to the shared memory
+    sprintf(ptr, "Hello, shared memory!");
+
+    // Unmap the shared memory object
+    if (munmap(ptr, size) == -1) {
+        perror("munmap");
+        return 1;
+    }
+
+    // Close the shared memory file descriptor
+    if (close(shm_fd) == -1) {
+        perror("close");
+        return 1;
+    }
+
+    // Unlink the shared memory object
+    if (shm_unlink(name) == -1) {
+        perror("shm_unlink");
+        return 1;
+    }
+
+    return 0;
+}

lab4/src/shm2.cpp

@@ -0,0 +1,50 @@
+/* reader */
+#include<stdio.h>
+#include<sys/mman.h>
+#include<sys/stat.h>
+#include<fcntl.h>
+#include<unistd.h>
+
+int main() {
+    const char *name = "/my_shared_memory";
+    int shm_fd = shm_open(name, O_CREAT | O_RDWR, 0666);
+    if (shm_fd == -1) {
+        perror("shm_open");
+        return 1;
+    }
+
+    // Set the size of the shared memory region
+    size_t size = 1024;
+
+    // Resize the shared memory object to the desired size
+    if (ftruncate(shm_fd, size) == -1) {
+        perror("ftruncate");
+        return 1;
+    }
+
+    // Map the shared memory object into the process address space
+    void *ptr = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, shm_fd, 0);
+    if (ptr == MAP_FAILED) {
+        perror("mmap");
+        return 1;
+    }
+
+    sleep(2);
+
+    // Print the contents of the shared memory
+    printf("Shared memory contents: %s\n", (char *)ptr);
+
+    // Unmap the shared memory object
+    if (munmap(ptr, size) == -1) {
+        perror("munmap");
+        return 1;
+    }
+
+    // Close the shared memory file descriptor
+    if (close(shm_fd) == -1) {
+        perror("close");
+        return 1;
+    }
+
+    return 0;
+}