fork

main.c

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

int main() {
	int mypipe[2];
	pipe(mypipe);

	int r = fork();
	if(r == -1) {
		perror("Fork failed");
		exit(1);
	} else if(r == 0) {
		printf("child pid: %d\n", getpid());
		close(mypipe[0]);

		char buffer[100];
		for(int i = 0; i < 100; i++) {
			sprintf(buffer, "%d;", i);

			write(mypipe[1], buffer, strlen(buffer));
		}

		close(mypipe[1]);

		printf("child ends\n");

	} else {
		printf("Master process\n");
		close(mypipe[1]);

		int sum = 0;

		char buffer[100];
		ssize_t bytesRead;
		ssize_t offset = 0;
		while((bytesRead = read(mypipe[0], buffer + offset, sizeof(buffer) - 1 - offset)) != 0) {
			buffer[offset + bytesRead + 1] = 0;

			// parse numbers in string
			int pos = 0, bytesScanned = 0;
			int num;
			char c = 0;
			while(sscanf(buffer + pos, "%d%c%n", &num, &c, &bytesScanned) == 2) {
				if(c != ';') {
					break;
				}

				pos += bytesScanned;
				sum += num;
			}

			ssize_t remaining = bytesRead - pos;

			// copy not processed bytes to the beginning
			offset = 0;
			if(remaining > 0) {
				strcpy(buffer, buffer + pos);
				offset = remaining;
			}
		}


		printf("Master ends with sum: %d\n", sum);
		wait(NULL);
	}

	return 0;
}