Linux多进程多线程例子

看了apue3，关于进程线程和进程间通信写了一个例子，方便自己理解相关知识，备忘。

 #include <stdlib.h>
 #include <stdio.h>
 #include <unistd.h>
 #include <pthread.h>
 #include <sys/types.h>
 #include <sys/ipc.h>
 #include <sys/shm.h>
 #include <sys/sem.h>

 //这里全局变量简化线程代码量而已，实际应该在线程获取这些变量再操作。
 long *shmaddr;
 int semid;

 /**
  * 互斥量加或减
  * @param  semid 互斥量id
  * @param  pv    整数加，负数减
  */
 void sem_pv(int semid, short pv)
 {
     struct sembuf buf = {, , };
     buf.sem_op = pv;
     buf.sem_num = ;
     semop(semid, &buf, );
 }

 void *do_thread(void *arg)
 {
     long index = (long)arg;
     srand(index + time());    //(时间 + 索引号)生成随机种子
     while () {
         sleep(rand() %  + );    //睡眠1~8s
         sem_pv(semid, -);    //sem - 1，若sem = 1，不阻塞，若sem = 0，阻塞
         *shmaddr += index;    //共享值 += 线程号
         printf("This is %ld thread, *shmaddr = %ld!!\n", index, *shmaddr);
         sem_pv(semid, +);    //sem + 1，唤醒其他已经阻塞的线程
     }
     pthread_exit((arg));
 }

 #define PROJ_ID 8

 int main(int argc, char const *argv[])
 {
     pid_t pid[];
     pthread_t thid[];
     key_t key;
     int shmid;
     int i;
     long index;    //这里使用long是(void *)<---->long，long和指针占用内存大小(主机64bit)一样，否则gcc会报warnning
     union semun {
         int            val;
         struct semid_ds        *buf;
         unsigned short        *array;
     } semopts;

     if ((key = ftok("." , PROJ_ID )) == -) {
         perror("ftok error");
         exit();
     }
     if ((shmid = shmget(key, sizeof(long), IPC_CREAT | )) == -) {
         perror("shmget error");
         exit();
     }
     if ((shmaddr = (long *)shmat(shmid, NULL, )) == (long *) - ) {
         perror("shmat error");
         exit();
     }
     *shmaddr = ;    //初始化共享量

     if ((semid = semget(key, , IPC_CREAT | )) == -) {
         perror("semget failed");
         exit();
     }
     semopts.val = ;    //信号量初始为1

     if (semctl(semid, , SETVAL, semopts) == -) {
         perror("semctl failed");
         exit();
     }
     //创建4进程 & 8线程
     for (i = ; i < ; ++i) {
         pid[i] = fork();
         if (pid[i] == ) {
             index =  * i + ;
             if (pthread_create(&thid[index], NULL, do_thread, (void *)index) != ) {
                 perror("thread error");
                 exit();
             }
             index++;
             if (pthread_create(&thid[index], NULL, do_thread, (void *)index) != ) {
                 perror("thread error");
                 exit();
             }
             sleep();
             printf("This is %d process\n", i);
             printf("Children's pid = %d, ppid = %d\n", getpid(), getppid());
             while ()
                 sleep();
             exit();

         } else if (pid[i] < ) {
             perror("fork error");
             exit();
         }
     }
     //父进程退出，4个子进程成为孤儿进程
     exit();
 }

程序开启4进程8线程同时一起累加。线程可以用全局变量同步，但4个子进程间不能共享累加结果，需要用进程共享量。同时涉及到多线程多进程的并发，需要用进程互斥量。