UNAME(2) Linux Programmer's Manual UNAME(2)
NAME
uname - get name and information about current kernel
SYNOPSIS
#include<sys/utsname.h>
intuname(structutsname*buf);
DESCRIPTION
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 NUL-terminated.
RETURNVALUE
On success, zero is returned. On error, -1 is returned, and errno is
set appropriately.
ERRORS
EFAULT buf is not valid.
CONFORMINGTO
SVr4, SVID, POSIX, X/OPEN. There is no uname call in BSD 4.3.
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 setdomain-
name(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 host-
name 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 and via
/proc/sys/kernel/{ostype, hostname, osrelease, version, domainname}.
SEEALSO
uname(1), getdomainname(2), gethostname(2)
Linux 2.5.0 2001-12-15 UNAME(2)
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