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13 .TH GETLOGIN 3C "May 25, 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.
48 Newly-compiled programs should use the \fBLOGIN_NAME_MAX\fR symbol,
49 defined in <\fBlimits.h\fR>, to size the buffer.
50 Older programs that call \fBgetlogin()\fR expect only the legacy
51 9-character length.
52 These automatically link to a version of the \fBgetlogin()\fR functions that
53 truncates longer login names.
54 It's also possible to compile new programs that link to truncating versions
55 of these functions by defining \fB__USE_LEGACY_LOGNAME__\fR in the
56 compile environment.
57 .sp
58 .LP
59 Some older programs will correctly handle long login names returned
60 by the \fBgetlogin()\fR function.
61 For this case, the user compatibility library
62 \fB/usr/lib/getloginx.so.1\fR redirects to a version of the \fBgetlogin()\fR
63 function that returns the long name.
64 This library should be added to such an application
65 at runtime using \fBLD_PRELOAD\fR.
66 .sp
67 .LP
68 If \fBgetlogin()\fR is called within a process that is not attached to a
69 terminal, it returns a null pointer. The correct procedure for determining the
70 login name is to call \fBcuserid\fR(3C), or to call \fBgetlogin()\fR and if it
71 fails to call \fBgetpwuid\fR(3C).
72 .sp
73 .LP
74 The \fBgetlogin_r()\fR function has the same functionality as \fBgetlogin()\fR
75 except that the caller must supply a buffer \fIname\fR with length
76 \fInamelen\fR to store the result. The \fIname\fR buffer must be at least
77 \fBLOGIN_NAME_MAX\fR bytes in size (defined in <\fBlimits.h\fR>). The
78 POSIX version (see \fBstandards\fR(5)) of \fBgetlogin_r()\fR takes a
79 \fInamesize\fR parameter of type \fBsize_t\fR.
80 .SH RETURN VALUES
81 .sp
82 .LP
83 Upon successful completion, \fBgetlogin()\fR returns a pointer to the login
84 name or a null pointer if the user's login name cannot be found. Otherwise it
85 returns a null pointer and sets \fBerrno\fR to indicate the error.
86 .sp
87 .LP
88 The standard-conforming \fBgetlogin_r()\fR returns \fB0\fR if successful, or
89 the error number upon failure.
90 .SH ERRORS
91 .sp
92 .LP
93 The \fBgetlogin_r()\fR function will fail if:
94 .sp
95 .ne 2
96 .na
97 \fB\fBERANGE\fR\fR
98 .ad
99 .RS 10n
100 The size of the buffer is smaller than the result to be returned.
101 .RE
102
103 .sp
104 .ne 2
105 .na
106 \fB\fBEINVAL\fR\fR
107 .ad
108 .RS 10n
109 And entry for the current user was not found in the \fB/var/adm/utmpx\fR file.
110 .RE
111
112 .sp
113 .LP
114 The \fBgetlogin()\fR and \fBgetlogin_r()\fR functions may fail if:
115 .sp
116 .ne 2
117 .na
118 \fB\fBEMFILE\fR\fR
119 .ad
120 .RS 10n
121 There are {\fBOPEN_MAX\fR} file descriptors currently open in the calling
122 process.
123 .RE
124
125 .sp
126 .ne 2
127 .na
128 \fB\fBENFILE\fR\fR
129 .ad
130 .RS 10n
131 The maximum allowable number of files is currently open in the system.
132 .RE
133
134 .sp
135 .ne 2
136 .na
137 \fB\fBENXIO\fR\fR
138 .ad
139 .RS 10n
140 The calling process has no controlling terminal.
141 .RE
142
143 .sp
144 .LP
145 The \fBgetlogin_r()\fR function may fail if:
146 .sp
147 .ne 2
148 .na
149 \fB\fBERANGE\fR\fR
150 .ad
151 .RS 10n
152 The size of the buffer is smaller than the result to be returned.
153 .RE
154
155 .SH USAGE
156 .sp
157 .LP
158 The return value of \fBgetlogin()\fR points to thread-specific data whose
159 content is overwritten on each call by the same thread.
160 .sp
161 .LP
162 Three names associated with the current process can be determined:
163 \fBgetpwuid(\fR\fBgeteuid()\fR\fB)\fR returns the name associated with the
164 effective user ID of the process; \fBgetlogin()\fR returns the name associated
165 with the current login activity; and \fBgetpwuid(\fR\fBgetuid()\fR\fB)\fR
166 returns the name associated with the real user ID of the process.
167 .SH FILES
168 .sp
169 .ne 2
170 .na
171 \fB\fB/var/adm/utmpx\fR\fR
172 .ad
173 .RS 18n
174 user access and administration information
175 .RE
176
177 .sp
178 .ne 2
179 .na
180 \fB\fB/usr/lib/getloginx.so.1\fR\fR
181 .ad
182 .RS 18n
183 A compatibility library that returns long login names to older applications.
184 .RE
185
186 .sp
187 .ne 2
188 .na
189 \fB\fB/usr/lib/64/getloginx.so.1\fR\fR
190 .ad
191 .RS 18n
192 A 64-bit compatibility library to return long login names.
193 .RE
194
195 .SH ATTRIBUTES
196 .sp
197 .LP
198 See \fBattributes\fR(5) for descriptions of the following attributes:
199 .sp
200
201 .sp
202 .TS
203 box;
204 c | c
205 l | l .
206 ATTRIBUTE TYPE ATTRIBUTE VALUE
207 _
208 Interface Stability Standard
209 _
210 MT-Level See below.
211 .TE
212
213 .SH SEE ALSO
214 .sp
215 .LP
216 \fBgeteuid\fR(2), \fBgetuid\fR(2), \fBcuserid\fR(3C), \fBgetgrnam\fR(3C),
217 \fBgetpwnam\fR(3C), \fBgetpwuid\fR(3C), \fButmpx\fR(4), \fBattributes\fR(5),
218 \fBstandards\fR(5)
219 .SH NOTES
220 .sp
221 .LP
222 When compiling multithreaded programs, see \fBIntro\fR(3).
223 .sp
224 .LP
225 The \fBgetlogin()\fR function is safe to use in multithreaded applications, but
226 is discouraged. The \fBgetlogin_r()\fR function should be used instead.
227 .sp
228 .LP
229 Solaris 2.4 and earlier releases provided a \fBgetlogin_r()\fR as specified in
230 POSIX.1c Draft 6. The final POSIX.1c standard changed the interface as
231 described above. Support for the Draft 6 interface is provided for
232 compatibility only and may not be supported in future releases. New
233 applications and libraries should use the standard-conforming interface.