1/* Copyright (C) 1991-2017 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <http://www.gnu.org/licenses/>. */
17
18#include <errno.h>
19#include <unistd.h>
20#include <string.h>
21#include <stdio.h>
22#include <limits.h>
23#include <fcntl.h>
24
25#include <utmp.h>
26
27static char name[UT_NAMESIZE + 1];
28
29/* Return the login name of the user, or NULL if it can't be determined.
30 The returned pointer, if not NULL, is good only until the next call. */
31
32#ifdef STATIC
33STATIC
34#endif
35char *
36getlogin (void)
37{
38 char tty_pathname[2 + 2 * NAME_MAX];
39 char *real_tty_path = tty_pathname;
40 int err;
41 char *result = NULL;
42 struct utmp *ut, line, buffer;
43
44 /* Get name of tty connected to fd 0. Return NULL if not a tty or
45 if fd 0 isn't open. Note that a lot of documentation says that
46 getlogin() is based on the controlling terminal---what they
47 really mean is "the terminal connected to standard input". The
48 getlogin() implementation of DEC Unix, SunOS, Solaris, HP-UX all
49 return NULL if fd 0 has been closed, so this is the compatible
50 thing to do. Note that ttyname(open("/dev/tty")) on those
51 systems returns /dev/tty, so that is not a possible solution for
52 getlogin(). */
53 err = __ttyname_r (0, real_tty_path, sizeof (tty_pathname));
54 if (err != 0)
55 {
56 __set_errno (err);
57 return NULL;
58 }
59
60 real_tty_path += 5; /* Remove "/dev/". */
61
62 __setutent ();
63 strncpy (line.ut_line, real_tty_path, sizeof line.ut_line);
64 if (__getutline_r (&line, &buffer, &ut) < 0)
65 {
66 if (errno == ESRCH)
67 /* The caller expects ENOENT if nothing is found. */
68 __set_errno (ENOENT);
69 result = NULL;
70 }
71 else
72 {
73 strncpy (name, ut->ut_user, UT_NAMESIZE);
74 name[UT_NAMESIZE] = '\0';
75 result = name;
76 }
77
78 __endutent ();
79
80 return result;
81}
82