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

/* Remember to free the returned pointer */
char* getoutput(char *command){
	size_t space = 16;
	char *output = malloc(space);
	int pipe_ends[2]; // pipefd[0] is the read end, pipefd[1] is the write end
	pipe(pipe_ends);
	pid_t pid = fork();
	if(pid) { // We're the parent
		close(pipe_ends[1]);	
		size_t position = 0;
		ssize_t readlen;
		while((readlen = read(pipe_ends[0], output + position, 16)) > 0 ){
			position += readlen;
			output = realloc(output, space + 16);
			space += 16;
		}
		output[position] = 0;	
		wait(NULL);
		return output;
	} else { // We're the child
		dup2(pipe_ends[1], 1);
		execl("/bin/sh", "sh", "-c", command, NULL);
		printf("This won't happen\n");
		exit(1);
	}
}

int main(){
	char *cmd_output = getoutput("uptime");

	printf("The output:  %s\n", cmd_output);
	free(cmd_output);

	return 0;
}