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

char* getoutput(char* command){
	// We'll need a pipe to put the output into
	// The command will have to run, and put output into the pipe
	// We'll have to read from the pipe
	int pipe_fds[2];
	char *buffer = malloc(16);
	pipe(pipe_fds);
	pid_t child = fork();

	if(!child){
		// Command part:
		// 	1.  Do plumbing as needed to send output into the pipe
		// 	2.  Run the command
		dup2(pipe_fds[1], 1);
		execl("/bin/sh", "sh", "-c", command, (char *) 0);
	} else {
		// Capture part:
		// 	1.  Wait for the command to run
		// 	2.  Collect the output from the pipe
		// while there's more to read:
		// 	read more stuff
		size_t sofar = 0;
		close(pipe_fds[1]);
		for(;;) {
			ssize_t readlen = read(pipe_fds[0], buffer + sofar, 16);
			if(readlen <= 0)
				break;
			sofar += readlen;
			buffer = realloc(buffer, sofar + 16);
		}
		buffer[sofar] = 0;
//		printf("We read:  %s\n", buffer);
		return buffer;
	}
}

int main(){
	char* output;
	output = getoutput("who | grep seth");
	printf("Output:  %s\n", output);
	free(output);
	return 0;
}