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[];    /* Operating system release (e.g., "2.6.28") */
               char version[];    /* Operating system 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

       POSIX.1-2001, POSIX.1-2008, SVr4.  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 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.

       Part of the utsname information is also accessible  via  /proc/sys/kernel/{ostype,  hostname,  osrelease,
       version, domainname}.

   C library/kernel differences
       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), namespaces(7)

COLOPHON

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