我必须编写一个具有多个进程的程序，以将共享存储中标准输入所取的字符串写到共享内存中，而不会覆盖先前添加的字符串。当父亲收到信号时，SIGINT将打印所有放入共享内存的字符串。问题是它的表现不符合预期，有人可以帮助我吗？
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <semaphore.h>
#include <sys/stat.h>
#include <sys/sem.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/wait.h>
#include <signal.h>
#include <sys/mman.h>
#define MAXSIZE 50
int n;
char *at;
int *p;
void handler(int sig){
printf("Received signal %d\n", sig);
printf("Printinf all the data in the shared memory\n");
printf("At1 è uguale: %d\n", n);
while(*p != -1){
printf("%s\n", at);
at = at -MAXSIZE;
*p = *p-1;
printf("Valore di p: %d\n", *p);
}
exit(1);
}
int main(int argc, char **argv){
if(argc != 2){
fprintf(stderr, "Usage: %s numberOfProcesses\n", argv[0]);
exit(1);
}
sem_t *sem;
sem = sem_open("femaforo", O_CREAT, 0664, 1);
if(sem == SEM_FAILED){
perror("Error while creating semaphore\n");
exit(-1);
}
n = atoi(argv[1]);
pid_t pid, wpid;
key_t key = 1411;
key_t key1 = 788;
/*int shmid = shmget(key, 1024, IPC_CREAT | 0644);
if(shmid < 0){
perror("Error while creating shared memory\n");
exit(-1);
}*/
at = (char *)mmap(NULL, 1024, PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_SHARED, -1, 0);
if(at == (void *)-1){
perror("Error while attaching memory\n");
exit(-1);
}
int shmid2 = shmget(key1, sizeof(int), 0644 | IPC_CREAT);
if(shmid2 < 0){
perror("Error while creating second memory\n");
exit(-1);
}
p = (int *)shmat(shmid2, NULL,0);
if(p == (void *)-1){
perror("Error while attaching second memory\n");
exit(-1);
}
*p = 0;
for(int i = 0; i < n; i++){
pid = fork();
if(pid == 0){
printf("I am a process with pid: %d\n", getpid());
break;
}else if(pid < 0){
perror("Error while creating a process\n");
exit(-1);
}
}
if(pid == 0){//figlio
sem_wait(sem);
printf("In at c'è: %s\n", at);
char string[MAXSIZE];
printf("Insert a string for the shared memory\n");
scanf("%s", string);
strcpy(at, string);
at = at +MAXSIZE;
*p = *p +1;
printf("Value of p is: %d\n", *p);
sem_post(sem);
}else{ //padre
sigset_t set;
sigfillset(&set);
sigdelset(&set, SIGINT);
struct sigaction act;
act.sa_mask = set;
act.sa_handler = handler;
sigaction(SIGINT, &act, 0);
for(int i = 0; i < n; i++){
wpid = wait(NULL);
}
handler(0);
printf("I am the father and I am exiting\n");
exit(1);
}
}