You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
69 lines
1.5 KiB
C
69 lines
1.5 KiB
C
#include <stdlib.h>
|
|
#include <stdio.h>
|
|
#include <sys/types.h>
|
|
#include <unistd.h>
|
|
#include <sys/wait.h>
|
|
#include <unistd.h>
|
|
#include <sys/mman.h>
|
|
#include <sys/stat.h>
|
|
#include <fcntl.h>
|
|
#include <string.h>
|
|
#include <semaphore.h>
|
|
|
|
#define SHARED_MEM "/SHARED_MEM"
|
|
#define NUM_CALLS 5
|
|
|
|
struct shared_str {
|
|
sem_t sem;
|
|
size_t len;
|
|
char buf[256];
|
|
};
|
|
|
|
void errExit(char* msg){
|
|
perror(msg);
|
|
exit(EXIT_FAILURE);
|
|
}
|
|
|
|
int main(){
|
|
int fd = shm_open(SHARED_MEM, O_CREAT | O_RDWR, S_IRUSR);
|
|
if (fd < 0){
|
|
errExit("failed to open shared memory object");
|
|
}
|
|
if (ftruncate(fd, sizeof(struct shared_str))){
|
|
errExit("failed to truncate");
|
|
}
|
|
struct shared_str *sstr = mmap(NULL, sizeof(struct shared_str),
|
|
PROT_READ | PROT_WRITE,
|
|
MAP_SHARED, fd, 0);
|
|
if (sstr == MAP_FAILED)
|
|
errExit("mmap");
|
|
if (sem_init(&sstr->sem, 1, 0) == -1)
|
|
errExit("sem_init-sem1");
|
|
pid_t pid;
|
|
if ((pid = fork()) < 0) {
|
|
errExit("failed to fork");
|
|
}
|
|
if ( pid == 0 ){
|
|
printf("child is running...\n");
|
|
for (int i =0 ; i <NUM_CALLS ; i++) {
|
|
sleep(1);
|
|
sstr -> len = snprintf((char*)&sstr->buf,256,"hallo no. %d",i);
|
|
if (sem_post(&sstr->sem) == -1)
|
|
errExit("sem_post");
|
|
}
|
|
close(fd);
|
|
exit(EXIT_SUCCESS);
|
|
}
|
|
for (int i =0 ; i<NUM_CALLS ; i++) {
|
|
if (sem_wait(&sstr->sem) == -1)
|
|
errExit("sem_wait");
|
|
pread(fd,sstr, sizeof(struct shared_str),0);
|
|
printf("text in shared buffe: %s\n",sstr -> buf);
|
|
}
|
|
int status;
|
|
pid = wait(&status);
|
|
printf("child process %d terminated with status %d\n", pid, WEXITSTATUS(status));
|
|
shm_unlink(SHARED_MEM);
|
|
exit(EXIT_SUCCESS);
|
|
}
|