[apple/xnu.git] / bsd / man / man2 / getlogin.2

.\"	$NetBSD: getlogin.2,v 1.4 1995/02/27 12:33:03 cgd Exp $
.\"
.\" Copyright (c) 1989, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"	@(#)getlogin.2	8.1 (Berkeley) 6/9/93
.\"
.Dd June 9, 1993
.Dt GETLOGIN 2
.Os BSD 4.2
.Sh NAME
.Nm getlogin ,
.Nm setlogin
.Nd get/set login name
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft char *
.Fn getlogin void
.Ft int
.Fn setlogin "const char *name"
.Sh DESCRIPTION
The
.Fn getlogin
routine
returns the login name of the user associated with the current session,
as previously set by
.Fn setlogin .
The name is normally associated with a login shell
at the time a session is created,
and is inherited by all processes descended from the login shell.
(This is true even if some of those processes assume another user ID,
for example when
.Xr su 1
is used.)
.Pp
.Fn Setlogin
sets the login name of the user associated with the current session to
.Fa name .
This call is restricted to the super-user, and
is normally used only when a new session is being created on behalf
of the named user
(for example, at login time, or when a remote shell is invoked).
.Sh RETURN VALUES
If a call to
.Fn getlogin
succeeds, it returns a pointer to a null-terminated string in a static buffer.
If the name has not been set, it returns
.Dv NULL .
If a call to
.Fn setlogin
succeeds, a value of 0 is returned.  If
.Fn setlogin
fails, a value of -1 is returned and an error code is
placed in the global location
.Va errno .
.Sh ERRORS
The following errors may be returned by these calls:
.Bl -tag -width Er
.It Bq Er EFAULT
The
.Fa name
parameter gave an
invalid address.
.It Bq Er EINVAL
The
.Fa name
parameter
pointed to a string that was too long.
Login names are limited to
.Dv MAXLOGNAME
(from
.Ao Pa sys/param.h Ac )
characters, currently 12.
.It Bq Er EPERM
The caller tried to set the login name and was not the super-user.
.El
.Sh SEE ALSO
.Xr setsid 2
.Sh BUGS
Login names are limited in length by
.Fn setlogin .
However, lower limits are placed on login names elsewhere in the system
.Pf ( Dv UT_NAMESIZE
in
.Ao Pa utmp.h Ac ) .
.Pp
In earlier versions of the system,
.Fn getlogin
failed unless the process was associated with a login terminal.
The current implementation (using
.Fn setlogin )
allows getlogin to succeed even when the process has no controlling terminal.
In earlier versions of the system, the value returned by
.Fn getlogin
could not be trusted without checking the user ID.
Portable programs should probably still make this check.
.Sh HISTORY
The
.Fn getlogin
function first appeared in 4.4BSD.
Commit	Line	Data
9bccf70c A	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.