#include <pthread.h>
#include <stdio.h>

char buf[100];

void* logger(void* file){
FILE* fp;
	if((fp=fopen(file, "w"))==NULL) return;
	while(strcmp(buf, "end\n")){
		fprintf(fp, buf);
		usleep(100000); // 0.1 sec
	}
	fclose(fp);
}

void* reader(void* x){
	while(fgets(buf, 100, stdin)!=NULL && strcmp(buf, "end\n")){
		;
	}
}

main(){
pthread_t thre1, thre2;

	strcpy(buf, "not read\n");
	pthread_create(&thre1, NULL, logger, "log.txt");
	pthread_create(&thre2, NULL, reader, NULL);

	pthread_join(thre1, NULL);
	pthread_join(thre2, NULL);

}