Named Pipes: named pipes, grep, ps -ef

Named Pipes

Asked by: FIsh

I am working with unnamed and named pipes. I have already figured out the unnamed pipe, but have worked up a named pipe program, but it does not work. Could someone please tell me if I am even close.

I need the code to be able to use a named pipe function to have the output of the "ps -ef" command sent through the pipe to the "grep cm415b"command.

so: nova> ps -ef | grep cm415b

/******************************************
 * Class: CMIS 415
 * Assignment: P3
 * Author: 
 *Date created: 02 Nov 2009
 *Date last modified:
 *Comments: Implement an example of pipe-based communication between two UNIX
 commands.  The commands will be hardcoded inside the program to avoid parsing the 
 command line.
 ********************************************/ 
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h> 
int main() {
	int fd;
	
	if (mkfifo("/tmp/fifo", cm415a)  == -1) {
		perror("error FIFO");
		exit(1);
	}
	switch(fork()) {
		case -1:
			perror("creating process");
			exit(1);
			
		case 0:
			close(1);
			fd = open("/tmp/fifo", O_WRONLY);
			if (fd == -1) {
				perror("Opening FIFO for writing");
				exit(1);
			}
			else if (fd != 1) {
				fprintf(stderr, "Write descriptor failed");
				exit(1);
			}
			execl("/usr/bin/grep", "grep", "cm415a", (char*) NULL);
			perror("Running grep command");
			exit(1);
			
		default:
			close(0);
			fd = open("tmp/fifo", O_RDONLY);
			if (fd == -1) {
				perror("Opening FIFO for reading");
				exit(1);
			}
			else if (fd != 0) {
				fprintf(stderr, "Write descriptor failed");
				exit(1);
			}
			execl("/bin/ps", "ps", "-ef", (char*) NULL);
			perror("Running ps command");
			exit(1);
	}
}

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Named Pipes

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named pipes

grep

ps -ef

C Programming Language

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