Name
uname — get name and information about current
kernel
Synopsis
#include <sys/utsname.h>
int
uname( |
struct utsname * |
buf); |
DESCRIPTION
uname() returns system
information in the structure pointed to by buf. The utsname struct is defined in
<sys/utsname.h>:
The length of the arrays in a struct utsname is unspecified; the
fields are terminated by a null byte ('\0').
RETURN VALUE
On success, zero is returned. On error, −1 is
returned, and errno is set
appropriately.
CONFORMING TO
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.
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 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.
There have been three Linux system calls uname(). The first one used length 9, the
second one used 65, the third one also uses 65 but adds the
domainname
field.
Part of the utsname information is also accessible via
sysctl(2) and via
/proc/sys/kernel/{ostype, hostname, osrelease, version, domainname}.
SEE ALSO
uname(1), getdomainname(2), gethostname(2)
Copyright (C) 2001 Andries Brouwer <aeb@cwi.nl>.
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