diff options
| author | Jacob McDonnell <jacob@jacobmcdonnell.com> | 2026-04-25 19:55:15 -0400 |
|---|---|---|
| committer | Jacob McDonnell <jacob@jacobmcdonnell.com> | 2026-04-25 19:55:15 -0400 |
| commit | 253e67c8b3a72b3a4757fdbc5845297628db0a4a (patch) | |
| tree | adf53b66087aa30dfbf8bf391a1dadb044c3bf4d /static/netbsd/man2/getlogin.2 | |
| parent | a9157ce950dfe2fc30795d43b9d79b9d1bffc48b (diff) | |
docs: Added All NetBSD Manuals
Diffstat (limited to 'static/netbsd/man2/getlogin.2')
| -rw-r--r-- | static/netbsd/man2/getlogin.2 | 208 |
1 files changed, 208 insertions, 0 deletions
diff --git a/static/netbsd/man2/getlogin.2 b/static/netbsd/man2/getlogin.2 new file mode 100644 index 00000000..316c294f --- /dev/null +++ b/static/netbsd/man2/getlogin.2 @@ -0,0 +1,208 @@ +.\" $NetBSD: getlogin.2,v 1.22 2009/01/11 02:46:30 christos 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. 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 January 6, 2009 +.Dt GETLOGIN 2 +.Os +.Sh NAME +.Nm getlogin , +.Nm getlogin_r , +.Nm setlogin +.Nd get/set login name +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.In unistd.h +.Ft char * +.Fn getlogin void +.Ft int +.Fn getlogin_r "char *name" "size_t len" +.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 +The +.Fn getlogin_r +function +provides the same service as +.Fn getlogin , +however the caller must provide the buffer +.Fa name +with length +.Fa len +bytes +to hold the result. +The buffer should be at least +.Dv MAXLOGNAME +bytes in length. +.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). +.Pp +.Em NOTE : +There is only one login name per session. +.Pp +It is +.Em CRITICALLY +important to ensure that +.Fn setlogin +is only ever called after the process has taken adequate steps to ensure +that it is detached from its parent's session. +The +.Em ONLY +way to do this is via the +.Fn setsid +function. +The +.Fn daemon +function calls +.Fn setsid +which is an ideal way of detaching from a controlling terminal and +forking into the background. +.Pp +In particular, neither +.Fn ioctl ttyfd TIOCNOTTY ... +nor +.Fn setpgid ... +is sufficient to create a new session. +.Pp +Once a parent process has called +.Fn setsid , +it is acceptable for some child of that process to then call +.Fn setlogin , +even though it is not the session leader. +Beware, however, that +.Em ALL +processes in the session will change their login name at the same time, +even the parent. +.Pp +This is different from traditional +.Ux +privilege inheritance and as such can be counter-intuitive. +.Pp +Since the +.Fn setlogin +routine is restricted to the super-user, it is assumed that (like +all other privileged programs) the programmer has taken adequate +precautions to prevent security violations. +.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 . +.Pp +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 . +.Pp +The +.Fn getlogin_r +function +returns zero if successful, or the error number upon failure. +.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 16. +.It Bq Er EPERM +The caller tried to set the login name and was not the super-user. +.It Bq Er ERANGE +The size of the buffer is smaller than the result to be returned. +.El +.Sh SEE ALSO +.Xr setsid 2 +.Sh STANDARDS +The +.Fn getlogin +and +.Fn getlogin_r +functions conform to +.St -p1003.1-96 . +.Sh HISTORY +The +.Fn getlogin +function first appeared in +.Bx 4.4 . +.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. |
