pipe2.c

#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

int main(int argc, char *argv[])
{
	int pipefd[2];
	pid_t cpid;
	char buf[128];
	if (argc != 2)
	{
		fprintf(stderr, "Usage: %s <string>\n", argv[0]);
		exit(EXIT_FAILURE);
	}

	if (pipe(pipefd) == -1)
	{
		perror("pipe");
		exit(EXIT_FAILURE);
	}

	cpid = fork();
	if (cpid == -1)
	{
		perror("fork");
		exit(EXIT_FAILURE);
	}
	if (cpid == 0)
	{
		/* Child reads from pipe */
		close(pipefd[1]);          /* Close unused write end */
		while (read(pipefd[0], buf, 128) > 0)
		{
			fprintf(stderr, "cpid: %d, read [%s] from pipefd[0]\n", cpid, buf);
			//write(STDOUT_FILENO, &buf, 1);
		}
		write(STDOUT_FILENO, "\n", 1);
		close(pipefd[0]);
		_exit(EXIT_SUCCESS);
	}
	else
	{
		/* Parent writes argv[1] to pipe */
		close(pipefd[0]);          /* Close unused read end */
		fprintf(stderr, "cpid: %d, write [%s] into pipefd[1]\n", cpid, argv[1]);
		write(pipefd[1], argv[1], strlen(argv[1]));
		close(pipefd[1]);          /* Reader will see EOF */
		wait(NULL);                /* Wait for child */
		exit(EXIT_SUCCESS);
	}
}