mirror of https://github.com/mkerrisk/man-pages
174 lines
4.7 KiB
Groff
174 lines
4.7 KiB
Groff
.\" Copyright (C) 2001 Andries Brouwer <aeb@cwi.nl>.
|
|
.\"
|
|
.\" %%%LICENSE_START(VERBATIM)
|
|
.\" Permission is granted to make and distribute verbatim copies of this
|
|
.\" manual provided the copyright notice and this permission notice are
|
|
.\" preserved on all copies.
|
|
.\"
|
|
.\" Permission is granted to copy and distribute modified versions of this
|
|
.\" manual under the conditions for verbatim copying, provided that the
|
|
.\" entire resulting derived work is distributed under the terms of a
|
|
.\" permission notice identical to this one.
|
|
.\"
|
|
.\" Since the Linux kernel and libraries are constantly changing, this
|
|
.\" manual page may be incorrect or out-of-date. The author(s) assume no
|
|
.\" responsibility for errors or omissions, or for damages resulting from
|
|
.\" the use of the information contained herein. The author(s) may not
|
|
.\" have taken the same level of care in the production of this manual,
|
|
.\" which is licensed free of charge, as they might when working
|
|
.\" professionally.
|
|
.\"
|
|
.\" Formatted or processed versions of this manual, if unaccompanied by
|
|
.\" the source, must acknowledge the copyright and authors of this work.
|
|
.\" %%%LICENSE_END
|
|
.\"
|
|
.\" 2007-07-05 mtk: Added details on underlying system call interfaces
|
|
.\"
|
|
.TH UNAME 2 2021-03-22 "Linux" "Linux Programmer's Manual"
|
|
.SH NAME
|
|
uname \- get name and information about current kernel
|
|
.SH SYNOPSIS
|
|
.nf
|
|
.B #include <sys/utsname.h>
|
|
.PP
|
|
.BI "int uname(struct utsname *" buf );
|
|
.fi
|
|
.SH DESCRIPTION
|
|
.BR uname ()
|
|
returns system information in the structure pointed to by
|
|
.IR buf .
|
|
The
|
|
.I utsname
|
|
struct is defined in
|
|
.IR <sys/utsname.h> :
|
|
.PP
|
|
.in +4n
|
|
.EX
|
|
struct utsname {
|
|
char sysname[]; /* Operating system name (e.g., "Linux") */
|
|
char nodename[]; /* Name within "some implementation\-defined
|
|
network" */
|
|
char release[]; /* Operating system release
|
|
(e.g., "2.6.28") */
|
|
char version[]; /* Operating system version */
|
|
char machine[]; /* Hardware identifier */
|
|
#ifdef _GNU_SOURCE
|
|
char domainname[]; /* NIS or YP domain name */
|
|
#endif
|
|
};
|
|
.EE
|
|
.in
|
|
.PP
|
|
The length of the arrays in a
|
|
.I struct utsname
|
|
is unspecified (see NOTES);
|
|
the fields are terminated by a null byte (\(aq\e0\(aq).
|
|
.SH RETURN VALUE
|
|
On success, zero is returned.
|
|
On error, \-1 is returned, and
|
|
.I errno
|
|
is set to indicate the error.
|
|
.SH ERRORS
|
|
.TP
|
|
.B EFAULT
|
|
.I buf
|
|
is not valid.
|
|
.SH CONFORMING TO
|
|
POSIX.1-2001, POSIX.1-2008, SVr4.
|
|
There is no
|
|
.BR uname ()
|
|
call in 4.3BSD.
|
|
.PP
|
|
The
|
|
.I domainname
|
|
member (the NIS or YP domain name) is a GNU extension.
|
|
.SH NOTES
|
|
This is a system call, and the operating system presumably knows
|
|
its name, release, and version.
|
|
It also knows what hardware it runs on.
|
|
So, four of the fields of the struct are meaningful.
|
|
On the other hand, the field
|
|
.I nodename
|
|
is meaningless:
|
|
it gives the name of the present machine in some undefined
|
|
network, but typically machines are in more than one network
|
|
and have several names.
|
|
Moreover, the kernel has no way of knowing
|
|
about such things, so it has to be told what to answer here.
|
|
The same holds for the additional
|
|
.I domainname
|
|
field.
|
|
.PP
|
|
To this end, Linux uses the system calls
|
|
.BR sethostname (2)
|
|
and
|
|
.BR setdomainname (2).
|
|
Note that there is no standard that says that the hostname set by
|
|
.BR sethostname (2)
|
|
is the same string as the
|
|
.I nodename
|
|
field of the struct returned by
|
|
.BR uname ()
|
|
(indeed, some systems allow a 256-byte hostname and an 8-byte nodename),
|
|
but this is true on Linux.
|
|
The same holds for
|
|
.BR setdomainname (2)
|
|
and the
|
|
.I domainname
|
|
field.
|
|
.PP
|
|
The length of the fields in the struct varies.
|
|
Some operating systems
|
|
or libraries use a hardcoded 9 or 33 or 65 or 257.
|
|
Other systems use
|
|
.B SYS_NMLN
|
|
or
|
|
.B _SYS_NMLN
|
|
or
|
|
.B UTSLEN
|
|
or
|
|
.BR _UTSNAME_LENGTH .
|
|
Clearly, it is a bad
|
|
idea to use any of these constants; just use sizeof(...).
|
|
Often 257 is chosen in order to have room for an internet hostname.
|
|
.PP
|
|
Part of the utsname information is also accessible via
|
|
.IR /proc/sys/kernel/ { ostype ,
|
|
.IR hostname ,
|
|
.IR osrelease ,
|
|
.IR version ,
|
|
.IR domainname }.
|
|
.SS C library/kernel differences
|
|
Over time, increases in the size of the
|
|
.I utsname
|
|
structure have led to three successive versions of
|
|
.BR uname ():
|
|
.IR sys_olduname ()
|
|
(slot
|
|
.IR __NR_oldolduname ),
|
|
.IR sys_uname ()
|
|
(slot
|
|
.IR __NR_olduname ),
|
|
and
|
|
.IR sys_newuname ()
|
|
(slot
|
|
.IR __NR_uname) .
|
|
The first one
|
|
.\" That was back before Linux 1.0
|
|
used length 9 for all fields;
|
|
the second
|
|
.\" That was also back before Linux 1.0
|
|
used 65;
|
|
the third also uses 65 but adds the
|
|
.I domainname
|
|
field.
|
|
The glibc
|
|
.BR uname ()
|
|
wrapper function hides these details from applications,
|
|
invoking the most recent version of the system call provided by the kernel.
|
|
.SH SEE ALSO
|
|
.BR uname (1),
|
|
.BR getdomainname (2),
|
|
.BR gethostname (2),
|
|
.BR uts_namespaces (7)
|