bsd/man/man2/getlogin.2

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  34 .\"     @(#)getlogin.2  8.1 (Berkeley) 6/9/93
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  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 .Fo getlogin
  47 .Fa void
  48 .Fc
  49 .Ft int
  50 .Fo setlogin
  51 .Fa "const char *name"
  52 .Fc
  53 .Sh DESCRIPTION
  54 The
  55 .Fn getlogin
  56 routine
  57 returns the login name of the user associated with the current session,
  58 as previously set by
  59 .Fn setlogin .
  60 The name is normally associated with a login shell
  61 at the time a session is created,
  62 and is inherited by all processes descended from the login shell.
  63 (This is true even if some of those processes assume another user ID,
  64 for example when
  65 .Xr su 1
  66 is used.)
  67 .Pp
  68 .Fn Setlogin
  69 sets the login name of the user associated with the current session to
  70 .Fa name .
  71 This call is restricted to the super-user, and
  72 is normally used only when a new session is being created on behalf
  73 of the named user
  74 (for example, at login time, or when a remote shell is invoked).
  75 .Sh RETURN VALUES
  76 If a call to
  77 .Fn getlogin
  78 succeeds, it returns a pointer to a null-terminated string in a static buffer.
  79 If the name has not been set, it returns
  80 .Dv NULL .
  81 If a call to
  82 .Fn setlogin
  83 succeeds, a value of 0 is returned.  If
  84 .Fn setlogin
  85 fails, a value of -1 is returned and an error code is
  86 placed in the global location
  87 .Va errno .
  88 .Sh ERRORS
  89 The following errors may be returned by these calls:
  90 .Bl -tag -width Er
  91 .It Bq Er EFAULT
  92 The
  93 .Fa name
  94 parameter gave an
  95 invalid address.
  96 .It Bq Er EINVAL
  97 The
  98 .Fa name
  99 parameter
 100 pointed to a string that was too long.
 101 Login names are limited to
 102 .Dv MAXLOGNAME
 103 (from
 104 .Ao Pa sys/param.h Ac )
 105 characters, currently 12.
 106 .It Bq Er EPERM
 107 The caller tried to set the login name and was not the super-user.
 108 .El
 109 .Sh SEE ALSO
 110 .Xr setsid 2
 111 .Sh BUGS
 112 Login names are limited in length by
 113 .Fn setlogin .
 114 However, lower limits are placed on login names elsewhere in the system
 115 .Pf ( Dv UT_NAMESIZE
 116 in
 117 .Ao Pa utmp.h Ac ) .
 118 .Pp
 119 In earlier versions of the system,
 120 .Fn getlogin
 121 failed unless the process was associated with a login terminal.
 122 The current implementation (using
 123 .Fn setlogin )
 124 allows getlogin to succeed even when the process has no controlling terminal.
 125 In earlier versions of the system, the value returned by
 126 .Fn getlogin
 127 could not be trusted without checking the user ID.
 128 Portable programs should probably still make this check.
 129 .Sh HISTORY
 130 The
 131 .Fn getlogin
 132 function first appeared in 4.4BSD.