#include<unistd.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<sys/wait.h>
#include<fcntl.h>
#include<stdio.h>
		
char* getoutput(char* command){
	int pipefds[2];
	pipe(pipefds);
	int read_end = pipefds[0];
	int write_end = pipefds[1];
	pid_t pid = fork();
	if(pid){ // We're the parent process
		close(write_end);
		char* buffer = (char*)malloc(128);
		size_t allocation_size = 128;
		size_t actually_read = 0;
		size_t readlen = read(read_end, buffer, 128);
		actually_read += readlen;
		while(readlen > 0){
			// read more out of the pipe!
			buffer = (char*)realloc(buffer, allocation_size + 128);
			allocation_size += 128;
			readlen = read(read_end, buffer+actually_read, 128);
			actually_read += readlen;
		}
		buffer[actually_read] = 0;
		wait(0);
		close(read_end);
		return buffer;
	} else { // We're the child process
		close(read_end);
		dup2(write_end, 1);
		execl("/bin/sh", "sh", "-c", command, 0);	
		perror("exec");	
		close(write_end);
	}	
}

int main(){
	char* output = getoutput("uname");
	printf("Output was:  %s\n", output);
	char* other_output = getoutput("whoami");
	printf("Output was:  %s\n", other_output);
	printf("Original Output was:  %s\n", output);
	free(output);
	free(other_output);
	char* long_test = getoutput("last");
	printf("Last output was:  ");
	puts(long_test);
	free(long_test);
	
	char* pipe_test = getoutput("ps axu | grep a.out");
	printf("Pipe test output:  %s\n", pipe_test);
	free(pipe_test);

	return 0;
}