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13 .TH GETLOGIN 3C "Apr 19, 2013"
14 .SH NAME
15 getlogin, getlogin_r \- get login name
16 .SH SYNOPSIS
17 .LP
18 .nf
19 #include <unistd.h>
20
21 \fBchar *\fR\fBgetlogin\fR(\fBvoid\fR);
22 .fi
23
24 .LP
25 .nf
26 \fBchar *\fR\fBgetlogin_r\fR(\fBchar *\fR\fIname\fR, \fBint\fR \fInamelen\fR);
27 .fi
28
29 .SS "Standard conforming"
30 .LP
31 .nf
32 cc [ \fIflag \fR... ] \fIfile\fR... \fB-D_POSIX_PTHREAD_SEMANTICS\fR [ \fIlibrary \fR... ]
33
34 \fBint\fR \fBgetlogin_r\fR(\fBchar *\fR\fIname\fR, \fBsize_t\fR \fInamesize\fR);
35 .fi
36
37 .SH DESCRIPTION
38 .sp
39 .LP
40 The \fBgetlogin()\fR function returns a pointer to the login name as found in
41 \fB/var/adm/utmpx\fR. It can be used in conjunction with \fBgetpwnam\fR(3C) to
42 locate the correct password file entry when the same user \fBID\fR is shared by
43 several login names.
44 .sp
45 .LP
46 The login name plus the terminating null byte can be up to 33 characters
47 in length. For programs that call \fBgetlogin()\fR and expect only the
48 legacy 9-character length, the user compatibility library
49 \fB/usr/lib/getlogin8.so.1\fR truncates long login names to fit a
50 9-character buffer. This library should be added to such an application
51 at runtime using \fBLD_PRELOAD\fR.
52 .sp
53 .LP
54 If \fBgetlogin()\fR is called within a process that is not attached to a
55 terminal, it returns a null pointer. The correct procedure for determining the
56 login name is to call \fBcuserid\fR(3C), or to call \fBgetlogin()\fR and if it
57 fails to call \fBgetpwuid\fR(3C).
58 .sp
59 .LP
60 The \fBgetlogin_r()\fR function has the same functionality as \fBgetlogin()\fR
61 except that the caller must supply a buffer \fIname\fR with length
62 \fInamelen\fR to store the result. The \fIname\fR buffer must be at least
63 \fB_POSIX_LOGIN_NAME_MAX\fR bytes in size (defined in <\fBlimits.h\fR>). The
64 POSIX version (see \fBstandards\fR(5)) of \fBgetlogin_r()\fR takes a
65 \fInamesize\fR parameter of type \fBsize_t\fR.
66 .SH RETURN VALUES
67 .sp
68 .LP
69 Upon successful completion, \fBgetlogin()\fR returns a pointer to the login
70 name or a null pointer if the user's login name cannot be found. Otherwise it
71 returns a null pointer and sets \fBerrno\fR to indicate the error.
72 .sp
73 .LP
74 The standard-conforming \fBgetlogin_r()\fR returns \fB0\fR if successful, or
75 the error number upon failure.
76 .SH ERRORS
77 .sp
78 .LP
79 The \fBgetlogin_r()\fR function will fail if:
80 .sp
81 .ne 2
82 .na
83 \fB\fBERANGE\fR\fR
84 .ad
85 .RS 10n
86 The size of the buffer is smaller than the result to be returned.
87 .RE
88
89 .sp
90 .ne 2
91 .na
92 \fB\fBEINVAL\fR\fR
93 .ad
94 .RS 10n
95 And entry for the current user was not found in the \fB/var/adm/utmpx\fR file.
96 .RE
97
98 .sp
99 .LP
100 The \fBgetlogin()\fR and \fBgetlogin_r()\fR functions may fail if:
101 .sp
102 .ne 2
103 .na
104 \fB\fBEMFILE\fR\fR
105 .ad
106 .RS 10n
107 There are {\fBOPEN_MAX\fR} file descriptors currently open in the calling
108 process.
109 .RE
110
111 .sp
112 .ne 2
113 .na
114 \fB\fBENFILE\fR\fR
115 .ad
116 .RS 10n
117 The maximum allowable number of files is currently open in the system.
118 .RE
119
120 .sp
121 .ne 2
122 .na
123 \fB\fBENXIO\fR\fR
124 .ad
125 .RS 10n
126 The calling process has no controlling terminal.
127 .RE
128
129 .sp
130 .LP
131 The \fBgetlogin_r()\fR function may fail if:
132 .sp
133 .ne 2
134 .na
135 \fB\fBERANGE\fR\fR
136 .ad
137 .RS 10n
138 The size of the buffer is smaller than the result to be returned.
139 .RE
140
141 .SH USAGE
142 .sp
143 .LP
144 The return value of \fBgetlogin()\fR points to thread-specific data whose
145 content is overwritten on each call by the same thread.
146 .sp
147 .LP
148 Three names associated with the current process can be determined:
149 \fBgetpwuid(\fR\fBgeteuid()\fR\fB)\fR returns the name associated with the
150 effective user ID of the process; \fBgetlogin()\fR returns the name associated
151 with the current login activity; and \fBgetpwuid(\fR\fBgetuid()\fR\fB)\fR
152 returns the name associated with the real user ID of the process.
153 .SH FILES
154 .sp
155 .ne 2
156 .na
157 \fB\fB/var/adm/utmpx\fR\fR
158 .ad
159 .RS 18n
160 user access and administration information
161 .RE
162
163 .sp
164 .ne 2
165 .na
166 \fB\fB/usr/lib/getlogin8.so.1\fR\fR
167 .ad
168 .RS 18n
169 A compatibility library to truncate long login names.
170 .RE
171
172 .sp
173 .ne 2
174 .na
175 \fB\fB/usr/lib/64/getlogin8.so.1\fR\fR
176 .ad
177 .RS 18n
178 A 64-bit compatibility library to runcate long login names.
179 .RE
180
181 .SH ATTRIBUTES
182 .sp
183 .LP
184 See \fBattributes\fR(5) for descriptions of the following attributes:
185 .sp
186
187 .sp
188 .TS
189 box;
190 c | c
191 l | l .
192 ATTRIBUTE TYPE ATTRIBUTE VALUE
193 _
194 Interface Stability Standard
195 _
196 MT-Level See below.
197 .TE
198
199 .SH SEE ALSO
200 .sp
201 .LP
202 \fBgeteuid\fR(2), \fBgetuid\fR(2), \fBcuserid\fR(3C), \fBgetgrnam\fR(3C),
203 \fBgetpwnam\fR(3C), \fBgetpwuid\fR(3C), \fButmpx\fR(4), \fBattributes\fR(5),
204 \fBstandards\fR(5)
205 .SH NOTES
206 .sp
207 .LP
208 When compiling multithreaded programs, see \fBIntro\fR(3).
209 .sp
210 .LP
211 The \fBgetlogin()\fR function is safe to use in multithreaded applications, but
212 is discouraged. The \fBgetlogin_r()\fR function should be used instead.
213 .sp
214 .LP
215 Solaris 2.4 and earlier releases provided a \fBgetlogin_r()\fR as specified in
216 POSIX.1c Draft 6. The final POSIX.1c standard changed the interface as
217 described above. Support for the Draft 6 interface is provided for
218 compatibility only and may not be supported in future releases. New
219 applications and libraries should use the standard-conforming interface.