micro-utils/src/coreutils/logname/logname.c

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

int main(void) {
	char *p = getlogin();
	if (p != NULL) {
		puts(p);
		return 0;
	}

	fprintf(stderr, "logname: %s\n", strerror(errno));
	return 1;
}