.\" 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.
.\"
.\" 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 2007-07-05 "Linux" "Linux Programmer's Manual"
+.TH UNAME 2 2019-03-06 "Linux" "Linux Programmer's Manual"
.SH NAME
uname \- get name and information about current kernel
.SH SYNOPSIS
.B #include <sys/utsname.h>
-.sp
+.PP
.BI "int uname(struct utsname *" buf );
.SH DESCRIPTION
.BR uname ()
.I utsname
struct is defined in
.IR <sys/utsname.h> :
+.PP
.in +4n
-.nf
-
+.EX
struct utsname {
- char sysname[];
- char nodename[];
- char release[];
- char version[];
- char machine[];
+ 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[];
+ char domainname[]; /* NIS or YP domain name */
#endif
};
-
-.fi
+.EE
.in
+.PP
The length of the arrays in a
.I struct utsname
-is unspecified; the fields are terminated by a null byte ('\\0').
-.SH "RETURN VALUE"
+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
.B EFAULT
.I buf
is not valid.
-.SH "CONFORMING TO"
-SVr4, POSIX.1-2001.
+.SH CONFORMING TO
+POSIX.1-2001, POSIX.1-2008, SVr4.
There is no
.BR uname ()
call in 4.3BSD.
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 \fInodename\fP is meaningless:
+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 \fIdomainname\fP field.
-.LP
-To this end Linux uses the system calls
+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 \fInodename\fP field of the struct returned by
+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 \fIdomainname\fP field.
-.LP
+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.
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.
-.LP
+.PP
Part of the utsname information is also accessible via
-.BR sysctl (2)
-and via
.IR /proc/sys/kernel/ { ostype ,
.IR hostname ,
.IR osrelease ,
.IR version ,
.IR domainname }.
-.SS Underlying kernel interface
-.LP
+.SS C library/kernel differences
+.PP
Over time, increases in the size of the
-.I utsuname
+.I utsname
structure have led to three successive versions of
.BR uname ():
.IR sys_olduname ()
.IR sys_newuname ()
(slot
.IR __NR_uname) .
-The first one used length 9 for all fields;
-the second used 65;
-the third also uses 65 but adds the \fIdomainname\fP field.
+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"
+.SH SEE ALSO
.BR uname (1),
.BR getdomainname (2),
-.BR gethostname (2)
+.BR gethostname (2),
+.BR namespaces (7)
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