avoid return pointer to a null string; return 0 instead

[unix-history] / usr / src / lib / libc / gen / getlogin.c

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)getlogin.c  5.3 (Berkeley) %G%";
#endif LIBC_SCCS and not lint

#include <utmp.h>

static  char UTMP[]     = "/etc/utmp";
static  struct utmp ubuf;

char *
getlogin()
{
       register int me, uf;
       register char *cp;

       if (!(me = ttyslot()))
               return(0);
       if ((uf = open(UTMP, 0)) < 0)
               return (0);
       lseek (uf, (long)(me*sizeof(ubuf)), 0);
       if (read(uf, (char *)&ubuf, sizeof (ubuf)) != sizeof (ubuf)) {
               close(uf);
               return (0);
       }
       close(uf);
       ubuf.ut_name[sizeof (ubuf.ut_name)] = ' ';
       for (cp = ubuf.ut_name; *cp++ != ' '; )
               ;
       *--cp = '\0';
       return (ubuf.ut_name);
}