1. 测试代码：
 

#include<stdio.h>
#include<stdlib.h>
#include<signal.h>
#include<errno.h>
#include<unistd.h>void catch_sigalrm(int signo)
{;
}unsigned int mysleep(unsigned int seconds)
{struct sigaction newact, oldact;sigset_t newmask, oldmask, suspmask;unsigned int unmask;//1. 为SIGALRM设置捕捉函数，一个空函数newact.sa_handler = sig_alrm;sigemptyset(&newact.sa_mask);newact.sa_flags = 0;sigaction(SIGALRM, &newact, &oldact);// 2. 设置阻塞信号集，阻塞SIGLARM信号sigemptyset(&newmask);sigaddset(*newact.sa_mask， SIGALRM);sigpromask(SIG_BLOCK, &newact, &oldact);   //信号屏蔽字// 3、定时h秒，到时可以产生SIGALRM信号alarm(nsecs);/* 4. 构造一个调用sigsuspend临时有效的阻塞信号集，*   临时阻塞信号集里面解除SIGALRM的阻塞*/suspmask = oldmask;sigdelset(&suspmask, SIGALRM);/* 5. sigsuspend调用期间，采用临时阻塞信号集suspmask替换原有阻塞信号集*   这个信号集中不包含SIGALRM信号，同时挂起等待*   当sigsuspend被信号唤醒返回时，恢复原有的阻塞信号集*/sigsuspend(&suspmask);unslept = alarm(0);//6. 恢复SIGALRM原有的处理动作，呼应前面注释1sigaction(SIGLARM, &oldact, NULL);//7. 解除对SIGALRM的阻塞，呼应前面注释2 sigprocmask(SIG_SETMASK, &oldmask, NULL);return (unslept);
}int main()
{while (1) {mysleep(3);printf("----------------------------\n");}return 0;
}

 

2. 测试代码：

#include <unistd.h> 
#include <signal.h>
#include <stdio.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; //数数完成 sleep(1);
}int main(void)
{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); //祖册自己的信号捕捉函数 父用SIGUSR2信号 do_sig_parent(0);while (1) {/* wait for signal*/if (flag == 1) {kill(pid, SIGUSR1);  //父进程数数完成flag = 0;            //标志已经给子进程发送信号完信号 }}}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) {/* wait for signal*/if (flag == 1) {kill(getppid(), SIGUSR2);flag = 0;           //标志已经给父进程发送信号了 }}}return 0;
}

测试代码：

#include <unistd.h> 
#include <signal.h>
#include <stdio.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; //数数完成 //sleep(1);
}int main(void)
{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); //祖册自己的信号捕捉函数 父用SIGUSR2信号 do_sig_parent(0);while (1) {/* wait for signal*/if (flag == 1) {kill(pid, SIGUSR1);  //父进程数数完成flag = 0;            //标志已经给子进程发送信号完信号 }}}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) {/* wait for signal*/if (flag == 1) {kill(getppid(), SIGUSR2);flag = 0;           //标志已经给父进程发送信号了 }}}return 0;
}