if kernel returns NULL string, return NULL to user; KNF

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

/*
* Copyright (c) 1988 The Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms are permitted
* provided that the above copyright notice and this paragraph are
* duplicated in all such forms and that any documentation,
* advertising materials, and other materials related to such
* distribution and use acknowledge that the software was developed
* by the University of California, Berkeley.  The name of the
* University may not be used to endorse or promote products derived
* from this software without specific prior written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)getlogin.c  5.5 (Berkeley) %G%";
#endif /* LIBC_SCCS and not lint */

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

static  char    logname[UT_NAMESIZE+1];

char *
getlogin()
{
       static int notcalled = 1;

       if (notcalled) {
               if (getlogname(logname, sizeof(logname) - 1) < 0)
                       return((char *)NULL);
               notcalled = 0;
       }
       return(*logname ? logname : (char *)NULL);
}

uid_t   geteuid();

char *
cuserid(s)
       char    *s;
{
       register struct passwd *pwd;

       if ((pwd = getpwuid(geteuid())) == NULL) {
               if (s)
                       *s = '\0';
               return(NULL);
       }
       if (s) {
               (void)strncpy(s, pwd->pw_name, L_cuserid);
               return(s);
       }
       return(pwd->pw_name);
}