#include <stdio.h>
#include <sys/types.h>
#include <pwd.h>

int main()
{
	struct passwd *info;
	int	uid;

	printf("user id #? " );
	scanf("%d", &uid);

	info = getpwuid(uid);		/* look it up */

	if ( info == NULL )
		printf("no such uid\n");
	else
		printf("%d -> %s\n", uid, info->pw_name);
}