这可能需要一些调查，但我的问题很简单：
为什么函数中numPassenger总是0 parentHandler2()？
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <wait.h>
#include <signal.h>
#include <sys/time.h>
#include <math.h>
int getRand()
{
return (rand() % 5001);
}
//////////GLOBAL//////////
const int CAPACITY = 100;
const int MEMSIZE = 1024;
char* sharedmem;
pid_t pid;
int numPassenger;
int numTram;
//////////GLOBAL//////////
//handles SIGALRM, generates passengers, sends SIGUSR1
void parentHandler1()
{
numPassenger = getRand();
sprintf(sharedmem, "%d", numPassenger);
kill(getpid(), SIGUSR1);
}
//handles SIGUSR1, calculates number of trams needed, sends SIGUSR2
void childHandler()
{
double n = atoi(sharedmem);
numTram = (ceil(n/100));
sprintf(sharedmem, "%d", numTram);
kill(pid, SIGUSR2);
}
//outputs
void parentHandler2()
{
int n = atoi(sharedmem);
printf("Passengers: %d, Trams: %d\n", numPassenger, n);
}
int main (int argc, char* argv[])
{
srand(time(0));
key_t key;
int shmemaddr;
//shared memory
key=ftok(argv[0],1);
shmemaddr=shmget(key,MEMSIZE,IPC_CREAT|S_IRUSR|S_IWUSR);
sharedmem = shmat(shmemaddr,NULL,0);
pid = fork();
if ( pid > 0 )
{
//timer
struct itimerval timer;
timer.it_value.tv_sec = 3;
timer.it_value.tv_usec = 0;
timer.it_interval.tv_sec = 3;
timer.it_interval.tv_usec = 0;
setitimer (ITIMER_REAL, &timer, NULL);
signal(SIGALRM, parentHandler1);
signal(SIGUSR1, childHandler);
}
else if ( pid == 0 )
{
signal(SIGUSR2, parentHandler2);
}
//not so busy waiting
while(1) sleep(1);
return 0;
}