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

char* user_report(){
	static char report_buffer[1024];
	system("who | sed 's/ .*//g' | sort -u > /tmp/user_report");
	int fd = open("/tmp/user_report", O_RDONLY);
	read(fd, report_buffer, 1024);
	close(fd);
	return report_buffer;
}

char* user_report_r(char *restrict report_buffer){
	system("who | sed 's/ .*//g' | sort -u > /tmp/user_report");
	int fd = open("/tmp/user_report", O_RDONLY);
	read(fd, report_buffer, 1024);
	close(fd);
	return report_buffer;
}

int main(){
	char *report = user_report();
	
	if(strstr(report, "fred")){
		printf("Fred is logged in\n");
	} else {
		printf("Fred is not logged in\n");
	}
	sleep(5);
	char new_report[100];
	user_report_r(new_report);
	printf("Original Report:  \n%s", report);
	printf("\n**\nNew Report:  \n%s", new_report);
	return 0;
}