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.
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
}.
uname(1), getdomainname(2), gethostname(2)
|