View Source: uname(2) - Waikato Linux Users Group

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!!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>:
 struct utsname {
         char sysname[];
         char nodename[];
         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.

!!RETURN VALUE

On success, zero is returned. On error, -1 is returned, and errno is set appropriately.

!!ERRORS

;[EFAULT]:buf is not valid.

!!CONFORMING TO

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 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  and  via /proc/sys/kernel/{ostype, hostname, osrelease, version, domainname}.

!!SEE ALSO

uname(1), getdomainname(2), gethostname(2)

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Last edited on Saturday, August 30, 2003 11:24:43 am by CraigBox

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