ref: 8adc5a0fce7e50f8bf8e69e51274092a1a581cd6
dir: /sys/src/ape/lib/ap/plan9/cuserid.c/
#include <unistd.h>
#include <stdio.h>
#include <string.h>
/*
 * BUG: supposed to be for effective uid,
 * but plan9 doesn't have that concept
 */
char *
cuserid(char *s)
{
	char *logname;
	static char buf[L_cuserid];
	if((logname = getlogin()) == NULL)
		return(NULL);
	if(s == 0)
		s = buf;
	strncpy(s, logname, sizeof buf);
	return(s);
}