get_default_username.c revision 55682
1/*
2 * Copyright (c) 1997 - 1999 Kungliga Tekniska H�gskolan
3 * (Royal Institute of Technology, Stockholm, Sweden).
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 *
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 *
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * 3. Neither the name of the Institute nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#ifdef HAVE_CONFIG_H
35#include <config.h>
36RCSID("$Id: get_default_username.c,v 1.3 1999/12/02 16:58:46 joda Exp $");
37#endif /* HAVE_CONFIG_H */
38
39#include "roken.h"
40
41/*
42 * Try to return what should be considered the default username or
43 * NULL if we can't guess at all.
44 */
45
46const char *
47get_default_username (void)
48{
49    const char *user;
50
51    user = getenv ("USER");
52    if (user == NULL)
53	user = getenv ("LOGNAME");
54    if (user == NULL)
55	user = getenv ("USERNAME");
56
57#if defined(HAVE_GETLOGIN) && !defined(POSIX_GETLOGIN)
58    if (user == NULL) {
59	user = (const char *)getlogin ();
60	if (user != NULL)
61	    return user;
62    }
63#endif
64#ifdef HAVE_PWD_H
65    {
66	uid_t uid = getuid ();
67	struct passwd *pwd;
68
69	if (user != NULL) {
70	    pwd = k_getpwnam (user);
71	    if (pwd != NULL && pwd->pw_uid == uid)
72		return user;
73	}
74	pwd = k_getpwuid (uid);
75	if (pwd != NULL)
76	    return pwd->pw_name;
77    }
78#endif
79    return user;
80}
81