uname — get name and information about current kernel
#include <sys/utsname.h>
int
uname( |
struct utsname * | buf); |
uname() returns system
information in the structure pointed to by buf. The utsname struct is defined in <sys/utsname.h>
struct utsname { char sysname[]; char nodename[]; char release[]; char version[]; char machine[]; #ifdef _GNU_SOURCE char domainname[]; #endif };
The length of the arrays in a struct utsname is unspecified; the fields are terminated by a null byte ('\0').
On success, zero is returned. On error, −1 is
returned, and errno is set
appropriately.
SVr4, POSIX.1-2001. There is no uname() call in 4.3BSD.
The domainname
member (the NIS or YP domain name) is a GNU extension.
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 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 domainname field.
To this end Linux uses the system calls sethostname(2) and
setdomainname(2). Note that
there is no standard that says that the hostname set by
sethostname(2) is the same
string as the nodename field of the struct
returned by uname() (indeed,
some systems allow a 256-byte hostname and an 8-byte
nodename), but this is true on Linux. The same holds for
setdomainname(2) and the
domainname
field.
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 SYS_NMLN or _SYS_NMLN or UTSLEN or _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.
Part of the utsname information is also accessible via
sysctl(2) and via
/proc/sys/kernel/{ostype, hostname, osrelease, version, domainname}.
Over time, increases in the size of the utsuname structure have led
to three successive versions of uname(): sys_olduname() (slot __NR_oldolduname),
sys_uname() (slot __NR_olduname), and
sys_newuname() (slot
__NR_uname). The
first one used length 9 for all fields; the second used 65;
the third also uses 65 but adds the domainname field. The glibc
uname() wrapper function
hides these details from applications, invoking the most
recent version of the system call provided by the
kernel.
This page is part of release 2.79 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at
http://www.kernel.org/doc/man-pages/.
|
Copyright (C) 2001 Andries Brouwer <aebcwi.nl>. 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. 2007-07-05 mtk: Added details on underlying system call interfaces |