linuxC多进程通讯---pipe同步

例子

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>

#define handle_error(msg) \
    {perror(msg);exit(EXIT_FAILURE);}

int main (void)
{
    int i = 0;
	int pipe_fd[2];
	int buf;

	setbuf (stdout, NULL);
	printf ("parent process(%d) run...\n", getpid());

	if (pipe(pipe_fd) == -1)
        handle_error("pipe");

	for (i = 0; i < 4; i++)
	{
		int ret_from_fork;
		ret_from_fork = fork ();

		if (ret_from_fork == -1)
            handle_error("fork");
		if (ret_from_fork == 0) // child process
		{
			if (close (pipe_fd[0]) == -1)
                handle_error("close");
			sleep (i * i);
			printf ("child process(%d) closing pipe\n", getpid());
            while (1);
			if (close (pipe_fd[1]) == -1)
                handle_error("close");
			_exit (EXIT_SUCCESS);
		}
	}

    while (1);

	if (close (pipe_fd[1]) == -1)
        handle_error("close");

	if (read (pipe_fd[0], &buf, 1) != 0)
		perror ("parent read can't get EOF");

	printf ("parent process(%d) exited\n", getpid());

	return 0;
}

解析

pipe生成的管道，读和写是有锁机制的，也就是当写描述符不close，读请求将一直阻塞。