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RedHat 9 (Linux i386) - man page for uname (redhat section 2)

UNAME(2)			    Linux Programmer's Manual				 UNAME(2)

       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[];
       The length of the arrays in a struct utsname is unspecified;  the  fields  are  NUL-termi-

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

       EFAULT buf is not valid.

       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.

       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/ker-
       nel/{ostype, hostname, osrelease, version, domainname}.

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

Linux 2.5.0				    2001-12-15					 UNAME(2)

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