135 lines
4.3 KiB
Groff
135 lines
4.3 KiB
Groff
.\" $NetBSD: getlogin.2,v 1.6 1998/02/03 21:12:48 perry Exp $
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.\"
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.\" Copyright (c) 1989, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)getlogin.2 8.1 (Berkeley) 6/9/93
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.\"
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.Dd June 9, 1993
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.Dt GETLOGIN 2
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.Os BSD 4.2
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.Sh NAME
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.Nm getlogin ,
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.Nm setlogin
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.Nd get/set login name
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.Sh SYNOPSIS
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.Fd #include <unistd.h>
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.Ft char *
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.Fn getlogin void
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.Ft int
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.Fn setlogin "const char *name"
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.Sh DESCRIPTION
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The
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.Fn getlogin
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routine
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returns the login name of the user associated with the current session,
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as previously set by
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.Fn setlogin .
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The name is normally associated with a login shell
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at the time a session is created,
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and is inherited by all processes descended from the login shell.
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(This is true even if some of those processes assume another user ID,
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for example when
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.Xr su 1
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is used.)
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.Pp
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.Fn Setlogin
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sets the login name of the user associated with the current session to
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.Fa name .
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This call is restricted to the super-user, and
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is normally used only when a new session is being created on behalf
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of the named user
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(for example, at login time, or when a remote shell is invoked).
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.Sh RETURN VALUES
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If a call to
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.Fn getlogin
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succeeds, it returns a pointer to a null-terminated string in a static buffer.
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If the name has not been set, it returns
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.Dv NULL .
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If a call to
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.Fn setlogin
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succeeds, a value of 0 is returned. If
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.Fn setlogin
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fails, a value of -1 is returned and an error code is
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placed in the global location
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.Va errno .
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.Sh ERRORS
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The following errors may be returned by these calls:
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.Bl -tag -width Er
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.It Bq Er EFAULT
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The
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.Fa name
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parameter gave an
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invalid address.
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.It Bq Er EINVAL
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The
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.Fa name
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parameter
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pointed to a string that was too long.
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Login names are limited to
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.Dv MAXLOGNAME
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(from
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.Ao Pa sys/param.h Ac )
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characters, currently 12.
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.It Bq Er EPERM
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The caller tried to set the login name and was not the super-user.
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.El
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.Sh SEE ALSO
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.Xr setsid 2
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.Sh STANDARDS
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The
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.Fn getlogin
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function conforms to
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.St -p1003.1-90 .
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.Sh BUGS
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Login names are limited in length by
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.Fn setlogin .
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However, lower limits are placed on login names elsewhere in the system
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.Pf ( Dv UT_NAMESIZE
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in
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.Ao Pa utmp.h Ac ) .
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.Pp
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In earlier versions of the system,
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.Fn getlogin
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failed unless the process was associated with a login terminal.
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The current implementation (using
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.Fn setlogin )
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allows getlogin to succeed even when the process has no controlling terminal.
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In earlier versions of the system, the value returned by
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.Fn getlogin
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could not be trusted without checking the user ID.
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Portable programs should probably still make this check.
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.Sh HISTORY
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The
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.Fn getlogin
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function first appeared in
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.Bx 4.4 .
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