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  12 .TH GETLOGIN 3C "May 18, 2004"
  13 .SH NAME
  14 getlogin, getlogin_r \- get login name
  15 .SH SYNOPSIS
  16 .LP
  17 .nf
  18 #include <unistd.h>
  19 
  20 \fBchar *\fR\fBgetlogin\fR(\fBvoid\fR);
  21 .fi
  22 
  23 .LP
  24 .nf
  25 \fBchar *\fR\fBgetlogin_r\fR(\fBchar *\fR\fIname\fR, \fBint\fR \fInamelen\fR);
  26 .fi
  27 
  28 .SS "Standard conforming"
  29 .LP
  30 .nf
  31 cc [ \fIflag \fR... ] \fIfile\fR... \fB-D_POSIX_PTHREAD_SEMANTICS\fR [ \fIlibrary \fR... ]
  32 
  33 \fBint\fR \fBgetlogin_r\fR(\fBchar *\fR\fIname\fR, \fBsize_t\fR \fInamesize\fR);
  34 .fi
  35 
  36 .SH DESCRIPTION
  37 .sp
  38 .LP
  39 The \fBgetlogin()\fR function returns a pointer to the login name as found in
  40 \fB/var/adm/utmpx\fR. It can be used in conjunction with \fBgetpwnam\fR(3C) to
  41 locate the correct password file entry when the same user \fBID\fR is shared by
  42 several login names.
  43 .sp
  44 .LP
  45 If \fBgetlogin()\fR is called within a process that is not attached to a
  46 terminal, it returns a null pointer. The correct procedure for determining the
  47 login name is to call \fBcuserid\fR(3C), or to call \fBgetlogin()\fR and if it
  48 fails to call \fBgetpwuid\fR(3C).
  49 .sp
  50 .LP
  51 The \fBgetlogin_r()\fR function has the same functionality as \fBgetlogin()\fR
  52 except that the caller must supply a buffer \fIname\fR with length
  53 \fInamelen\fR to store the result.  The \fIname\fR buffer must be at least
  54 \fB_POSIX_LOGIN_NAME_MAX\fR bytes in size (defined in <\fBlimits.h\fR>). The
  55 POSIX version (see \fBstandards\fR(5)) of \fBgetlogin_r()\fR takes a
  56 \fInamesize\fR parameter of type \fBsize_t\fR.
  57 .SH RETURN VALUES
  58 .sp
  59 .LP
  60 Upon successful completion, \fBgetlogin()\fR returns a pointer to the login
  61 name or a null pointer if the user's login name cannot be found.  Otherwise it
  62 returns a null pointer and sets \fBerrno\fR to indicate the error.
  63 .sp
  64 .LP
  65 The standard-conforming \fBgetlogin_r()\fR returns \fB0\fR if successful, or
  66 the error number upon failure.
  67 .SH ERRORS
  68 .sp
  69 .LP
  70 The \fBgetlogin_r()\fR function will fail if:
  71 .sp
  72 .ne 2
  73 .na
  74 \fB\fBERANGE\fR\fR
  75 .ad
  76 .RS 10n
  77 The size of the buffer is smaller than the result to be returned.
  78 .RE
  79 
  80 .sp
  81 .ne 2
  82 .na
  83 \fB\fBEINVAL\fR\fR
  84 .ad
  85 .RS 10n
  86 And entry for the current user was not found in the \fB/var/adm/utmpx\fR file.
  87 .RE
  88 
  89 .sp
  90 .LP
  91 The \fBgetlogin()\fR and \fBgetlogin_r()\fR functions may fail if:
  92 .sp
  93 .ne 2
  94 .na
  95 \fB\fBEMFILE\fR\fR
  96 .ad
  97 .RS 10n
  98 There are {\fBOPEN_MAX\fR} file descriptors currently open in the calling
  99 process.
 100 .RE
 101 
 102 .sp
 103 .ne 2
 104 .na
 105 \fB\fBENFILE\fR\fR
 106 .ad
 107 .RS 10n
 108 The maximum allowable number of files is currently open in the system.
 109 .RE
 110 
 111 .sp
 112 .ne 2
 113 .na
 114 \fB\fBENXIO\fR\fR
 115 .ad
 116 .RS 10n
 117 The calling process has no controlling terminal.
 118 .RE
 119 
 120 .sp
 121 .LP
 122 The \fBgetlogin_r()\fR function may fail if:
 123 .sp
 124 .ne 2
 125 .na
 126 \fB\fBERANGE\fR\fR
 127 .ad
 128 .RS 10n
 129 The size of the buffer is smaller than the result to be returned.
 130 .RE
 131 
 132 .SH USAGE
 133 .sp
 134 .LP
 135 The return value of \fBgetlogin()\fR points to thread-specific data whose
 136 content is overwritten on each call by the same thread.
 137 .sp
 138 .LP
 139 Three names associated with the current process can be determined:
 140 \fBgetpwuid(\fR\fBgeteuid()\fR\fB)\fR returns the name associated with the
 141 effective user ID of the process; \fBgetlogin()\fR returns the name associated
 142 with the current login activity; and \fBgetpwuid(\fR\fBgetuid()\fR\fB)\fR
 143 returns the name associated with the real user ID of the process.
 144 .SH FILES
 145 .sp
 146 .ne 2
 147 .na
 148 \fB\fB/var/adm/utmpx\fR\fR
 149 .ad
 150 .RS 18n
 151 user access and administration information
 152 .RE
 153 
 154 .SH ATTRIBUTES
 155 .sp
 156 .LP
 157 See \fBattributes\fR(5) for descriptions of the following attributes:
 158 .sp
 159 
 160 .sp
 161 .TS
 162 box;
 163 c | c
 164 l | l .
 165 ATTRIBUTE TYPE  ATTRIBUTE VALUE
 166 _
 167 Interface Stability     Standard
 168 _
 169 MT-Level        See below.
 170 .TE
 171 
 172 .SH SEE ALSO
 173 .sp
 174 .LP
 175 \fBgeteuid\fR(2), \fBgetuid\fR(2), \fBcuserid\fR(3C), \fBgetgrnam\fR(3C),
 176 \fBgetpwnam\fR(3C), \fBgetpwuid\fR(3C), \fButmpx\fR(4), \fBattributes\fR(5),
 177 \fBstandards\fR(5)
 178 .SH NOTES
 179 .sp
 180 .LP
 181 When compiling multithreaded programs, see \fBIntro\fR(3).
 182 .sp
 183 .LP
 184 The \fBgetlogin()\fR function is safe to use in multithreaded applications, but
 185 is discouraged. The \fBgetlogin_r()\fR function should be used instead.
 186 .sp
 187 .LP
 188 Solaris 2.4 and earlier releases provided a \fBgetlogin_r()\fR as specified in
 189 POSIX.1c Draft 6. The final POSIX.1c standard changed the interface as
 190 described above. Support for the Draft 6 interface is provided for
 191 compatibility only and may not be supported in future releases. New
 192 applications and libraries should use the standard-conforming interface.