pipe.c

操作系统编程

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>

int main(int argc, char *argv[])
{
	int pfd[2];
	int rtn, rtn_1, flag;
	pid_t pid, pid_1;
	long v;
	ssize_t nread;
	char buf[256];

	memset(buf, 0, sizeof(buf));
	if(pipe(pfd) == -1){
		printf("pipe() error\n");
		exit(1);
	}
	v = fpathconf(pfd[0], _PC_PIPE_BUF);
	if(v == -1){
		printf("no limit for PIPE_BUF");
	}else{
		printf("\nPIPE_BUF = %ld\n", v);
	}
	if((pid = fork()) == -1){
		printf("fork() error\n");
		exit(1);
	}
	else if(pid == 0){
		/* child process */
		close(pfd[0]);
		write(pfd[1], "child 1 hello!", sizeof("child 1 hello!"));
		//printf("child 1 process write \"child 1 hello!\" to the pipe\n");
		//sleep(10);
		//close(pfd[1]);
		exit(0);
	}
	else if(pid > 0){
		/* parent process */
		pid_1 = fork();
		if(pid_1 == -1){
			printf("fork() 2 error\n");
			exit(1);
		}
		if(pid_1 == 0){
			/*second child process*/
			/* printf("\nchild 2 returned pid 1: %d\n", rtn = waitpid(pid, NULL, 0)); */
			/* printf("\nerror code: %d, info: %s\n", errno, strerror(errno)); */				
			close(pfd[0]);
			sleep(0);
			rtn = write(pfd[1], "child 2 world!", sizeof("child 2 world!"));
			if(rtn == -1){
				printf("write 2 error\n");
			}
			//close(pfd[1]);
			//printf("\nchild 2 process write \"child 2 world!\" to the pipe\n");
			exit(0);			
		}
		//close(pfd[1]); /*block model*/
		while(1){
			/* printf("\nparent returned pid 1: %d\n", rtn = waitpid(pid, NULL, 0)); */
			/* printf("\nerror code: %d, info: %s\n", errno, strerror(errno)); */
			nread = read(pfd[0], buf, sizeof(buf));			
			if(nread == -1){
				printf("read() error\n");
				exit(1);
			}
			if(nread == 0){
				/*No Use when Block Model*/
				printf("\nNothin in Pipe\n");
				break;
			}else{
				printf("\nparent read from the pipe: \"%s\"\n", buf);
			}
			/* printf("\nparent returned pid 2: %d\n", rtn_1 = waitpid(pid_1, NULL, 0)); */
			/* printf("\nerror code: %d, info: %s\n", errno, strerror(errno)); */
			rtn_1 = waitpid(pid_1, NULL, 0);
			if(rtn_1 == -1){
				printf("\nAll Done\n");
				break;
			}
		}	
	}
	exit(0);
}