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UNAME(2)		   Linux Programmers Manual		     UNAME(2)

       uname - get name and information about current kernel


       int uname(struct utsname *buf);

       uname()	returns system information in the structure pointed to by buf.
       The utsname struct is defined in :

	   struct utsname {
	       char sysname[];
	       char nodename[];
	       char release[];
	       char version[];
	       char machine[];
	   #ifdef _GNU_SOURCE
	       char domainname[];

       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.

       EFAULT buf is not valid.

       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 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.

       Part of the utsname information is also accessible  via	sysctl(2)  and
       via  /proc/sys/kernel/{ostype,  hostname,  osrelease,  version, domain

   Underlying kernel interface
       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 applica
       tions, invoking the most recent version of the system call provided  by
       the kernel.

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

       This  page  is  part of release 3.05 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/.

Linux				  2007-07-05			      UNAME(2)

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