1.父子进程间的通信举例

#include<stdio.h>
#include<signal.h>
#include<unistd.h>
#include<stdlib.h>int n=0,flag=0;void sys_err(char *str)
{perror(str);exit(1);
}void do_sig_child(int num)
{printf("i am child %d\t%d\n",getpid(),n);n +=2;flag = 1;sleep(1);
}void do_sig_parent(int num)
{printf("i am parent %d\t%d\n",getpid(),n);n +=2;flag = 1;sleep(1);
}int main()
{pid_t pid;struct sigaction act;if((pid=fork())<0){sys_err("fork");}else if(pid>0){n=1;sleep(1);act.sa_handler = do_sig_parent;sigemptyset(&act.sa_mask);act.sa_flags = 0;sigaction(SIGUSR2,&act,NULL);do_sig_parent(0);while(1){if(flag==1){kill(pid,SIGUSR1);flag=0;}}}else if(pid==0){n=2;act.sa_handler = do_sig_child;sigemptyset(&act.sa_mask);act.sa_flags=0;sigaction(SIGUSR1,&act,NULL);while(1){if(flag==1){kill(getppid(),SIGUSR2);flag=0;}}}return 0;
}