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



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[];    /* Operating system name (e.g., "Linux") */
               char nodename[];   /* Name within "some implementation-defined
                                     network" */
               char release[];    /* OS release (e.g., "2.6.28") */
               char version[];    /* OS version */
               char machine[];    /* Hardware identifier */
           #ifdef _GNU_SOURCE
               char domainname[]; /* NIS or YP domain name */
           #endif
           };

       The length of the arrays in a struct utsname is unspecified (see NOTES); the fields are terminated by a null byte ('\0').

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, POSIX.1-2001.  There is no uname() call in 4.3BSD.

       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 hard-
       ware it runs on.  So, four of the fields of the struct are meaningful.  On the other hand, the field nodename is meaning-
       less:  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 con-
       stants; 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 /proc/sys/kernel/{ostype, hostname,  osrelease,  version,  domain-
       name}.

   Underlying kernel interface
       Over  time,  increases  in  the  size  of  the  utsname  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 applications, invoking the most recent version of the system call
       provided by the kernel.

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

COLOPHON
       This  page  is  part of release 3.25 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                                                      2008-12-03                                                   UNAME(2)