69 lines
1.4 KiB
C
69 lines
1.4 KiB
C
// man ftruncate
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// pass any message between two processes using shared memory
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/mman.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <time.h>
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#include <unistd.h>
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#include <sys/wait.h>
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int main(int argc, char *argv[]) {
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srandom(time(NULL));
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const char *memory_name = "/memory";
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char message[] = "Hello there";
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int fd = shm_open(memory_name, O_CREAT | O_RDWR, 0777);
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if (fd < 0) {
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fprintf(stderr, "shm_open: ");
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exit(EXIT_FAILURE);
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}
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printf("Shred memory file descriptor: %d\n", fd);
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if (ftruncate(fd, sizeof(message)) < 0) {
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fprintf(stderr, "ftruncate: \n");
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exit(EXIT_FAILURE);
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}
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pid_t pid;
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pid = fork();
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if (pid == -1) {
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perror("fork: ");
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exit(EXIT_FAILURE);
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}
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if (pid == 0) {
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char *addr = mmap(NULL, sizeof(message), PROT_READ, MAP_SHARED, fd, 0);
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printf("Value: %s\n", addr);
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if (addr == MAP_FAILED) {
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fprintf(stderr, "mmap: ");
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exit(EXIT_FAILURE);
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}
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exit(EXIT_SUCCESS);
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}
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char *addr = mmap(NULL, sizeof(message), PROT_WRITE, MAP_SHARED, fd, 0);
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if (addr == MAP_FAILED) {
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fprintf(stderr, "mmap: ");
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exit(EXIT_FAILURE);
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}
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strcpy(addr, message);
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shm_unlink(memory_name);
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int status;
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wait(&status);
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munmap(addr, sizeof(message));
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return 0;
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}
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