Bidirectional pipe

bipipe.c

/*
 * Bidirectional pipe
 *
 * Compile:
 * $ cc -o bipipe bipipe.c
 *
 * Examples:
 *
 * * Unix domain socket chat over SSH:
 *
 * On host A
 * $ bipipe socket -s ./a.sock '<=>' ssh B socket -s ./b.sock
 * $ socket ./a.sock
 *
 * On host B
 * $ socket ./b.sock
 *
 * Then write on the terminals to chat.
 *
 * Copyright (C) 2013 Alessandro Ghedini <alessandro@ghedini.me>
 * --------------------------------------------------------------
 * "THE BEER-WARE LICENSE" (Revision 42):
 * Alessandro Ghedini wrote this file. As long as you retain this
 * notice you can do whatever you want with this stuff. If we
 * meet some day, and you think this stuff is worth it, you can
 * buy me a beer in return.
 * --------------------------------------------------------------
 */

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

int main(int argc, char *argv[]) {
	int i, rc;
	int split = argc;

	int pipe1[2], pipe2[2];

	for (i = 1; i < argc; i++) {
		if (strcmp(argv[i], "<=>") == 0) {
			argv[i] = '\0';

			split = i + 1;
		}
	}

	rc = pipe(pipe1);
	if (rc < 0) {
		fprintf(stderr, "ERROR: Can't create pipe: %d: %s\n",
			errno, strerror(errno));
		exit(EXIT_FAILURE);
	}

	rc = pipe(pipe2);
	if (rc < 0) {
		fprintf(stderr, "ERROR: Can't create pipe: %d: %s\n",
			errno, strerror(errno));
		exit(EXIT_FAILURE);
	}

	switch (fork()) {
		case -1:
			fprintf(stderr, "ERROR: Can't fork(): %d: %s\n",
					errno, strerror(errno));
			exit(EXIT_FAILURE);

		case 0:
			close(pipe1[0]);
			close(pipe2[1]);

			dup2(pipe2[0], STDIN_FILENO);
			dup2(pipe1[1], STDOUT_FILENO);

			close(pipe1[1]);
			close(pipe2[0]);

			puts(argv[split]);
			printf("%d\n", split);

			rc = execvp(argv[split], (argv + split));
			if (rc < 0) {
				fprintf(stderr,
					"ERROR: Can't exec command: %d: %s\n",
					errno, strerror(errno));
				exit(EXIT_FAILURE);
			}
			break;

		default:
			close(pipe1[1]);
			close(pipe2[0]);

			dup2(pipe1[0], STDIN_FILENO);
			dup2(pipe2[1], STDOUT_FILENO);

			close(pipe1[0]);
			close(pipe2[1]);

			puts(argv[1]);

			rc = execvp(argv[1], (argv + 1));
			if (rc < 0) {
				fprintf(stderr,
					"ERROR: Can't exec command: %d: %s\n",
					errno, strerror(errno));
				exit(EXIT_FAILURE);
			}
			break;
	}

	return 0;
}