bsd/man/man2/getlogin.2

   1 .\"     $NetBSD: getlogin.2,v 1.4 1995/02/27 12:33:03 cgd Exp $
   2 .\"
   3 .\" Copyright (c) 1989, 1991, 1993
   4 .\"     The Regents of the University of California.  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 .\" 1. Redistributions of source code must retain the above copyright
  10 .\"    notice, this list of conditions and the following disclaimer.
  11 .\" 2. Redistributions in binary form must reproduce the above copyright
  12 .\"    notice, this list of conditions and the following disclaimer in the
  13 .\"    documentation and/or other materials provided with the distribution.
  14 .\" 3. All advertising materials mentioning features or use of this software
  15 .\"    must display the following acknowledgement:
  16 .\"     This product includes software developed by the University of
  17 .\"     California, Berkeley and its contributors.
  18 .\" 4. Neither the name of the University nor the names of its contributors
  19 .\"    may be used to endorse or promote products derived from this software
  20 .\"    without specific prior written permission.
  21 .\"
  22 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32 .\" SUCH DAMAGE.
  33 .\"
  34 .\"     @(#)getlogin.2  8.1 (Berkeley) 6/9/93
  35 .\"
  36 .Dd June 9, 1993
  37 .Dt GETLOGIN 2
  38 .Os BSD 4.2
  39 .Sh NAME
  40 .Nm getlogin ,
  41 .Nm setlogin
  42 .Nd get/set login name
  43 .Sh SYNOPSIS
  44 .Fd #include <unistd.h>
  45 .Ft char *
  46 .Fn getlogin void
  47 .Ft int
  48 .Fn setlogin "const char *name"
  49 .Sh DESCRIPTION
  50 The
  51 .Fn getlogin
  52 routine
  53 returns the login name of the user associated with the current session,
  54 as previously set by
  55 .Fn setlogin .
  56 The name is normally associated with a login shell
  57 at the time a session is created,
  58 and is inherited by all processes descended from the login shell.
  59 (This is true even if some of those processes assume another user ID,
  60 for example when
  61 .Xr su 1
  62 is used.)
  63 .Pp
  64 .Fn Setlogin
  65 sets the login name of the user associated with the current session to
  66 .Fa name .
  67 This call is restricted to the super-user, and
  68 is normally used only when a new session is being created on behalf
  69 of the named user
  70 (for example, at login time, or when a remote shell is invoked).
  71 .Sh RETURN VALUES
  72 If a call to
  73 .Fn getlogin
  74 succeeds, it returns a pointer to a null-terminated string in a static buffer.
  75 If the name has not been set, it returns
  76 .Dv NULL .
  77 If a call to
  78 .Fn setlogin
  79 succeeds, a value of 0 is returned.  If
  80 .Fn setlogin
  81 fails, a value of -1 is returned and an error code is
  82 placed in the global location
  83 .Va errno .
  84 .Sh ERRORS
  85 The following errors may be returned by these calls:
  86 .Bl -tag -width Er
  87 .It Bq Er EFAULT
  88 The
  89 .Fa name
  90 parameter gave an
  91 invalid address.
  92 .It Bq Er EINVAL
  93 The
  94 .Fa name
  95 parameter
  96 pointed to a string that was too long.
  97 Login names are limited to
  98 .Dv MAXLOGNAME
  99 (from
 100 .Ao Pa sys/param.h Ac )
 101 characters, currently 12.
 102 .It Bq Er EPERM
 103 The caller tried to set the login name and was not the super-user.
 104 .El
 105 .Sh SEE ALSO
 106 .Xr setsid 2
 107 .Sh BUGS
 108 Login names are limited in length by
 109 .Fn setlogin .
 110 However, lower limits are placed on login names elsewhere in the system
 111 .Pf ( Dv UT_NAMESIZE
 112 in
 113 .Ao Pa utmp.h Ac ) .
 114 .Pp
 115 In earlier versions of the system,
 116 .Fn getlogin
 117 failed unless the process was associated with a login terminal.
 118 The current implementation (using
 119 .Fn setlogin )
 120 allows getlogin to succeed even when the process has no controlling terminal.
 121 In earlier versions of the system, the value returned by
 122 .Fn getlogin
 123 could not be trusted without checking the user ID.
 124 Portable programs should probably still make this check.
 125 .Sh HISTORY
 126 The
 127 .Fn getlogin
 128 function first appeared in 4.4BSD.