uname(2) - Linux manual page (original) (raw)

uname(2) System Calls Manual uname(2)

NAME top

   uname - get name and information about current kernel

LIBRARY top

   Standard C library (_libc_, _-lc_)

SYNOPSIS top

   **#include <sys/utsname.h>**

   **int uname(struct utsname ***_buf_**);**

DESCRIPTION top

   **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 communications network
                                 to which the node is attached, if any */
           char release[];    /* Operating system release
                                 (e.g., "2.6.28") */
           char version[];    /* Operating system version */
           char machine[];    /* Hardware type identifier */
       #ifdef _GNU_SOURCE
           char domainname[]; /* NIS or YP domain name */
       #endif
       };

   The length of the arrays in a _struct utsname_ is unspecified (see
   VERSIONS and HISTORY); the fields are terminated by a null byte
   ('\0').

RETURN VALUE top

   On success, zero is returned.  On error, -1 is returned, and _[errno](../man3/errno.3.html)_
   is set to indicate the error.

ERRORS top

   **EFAULT** _buf_ is not valid.

VERSIONS top

   The _domainname_ member (the NIS or YP domain name) is a GNU
   extension.

   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(...).  SVr4 uses 257, "to support Internet hostnames" —
   this is the largest value likely to be encountered in the wild.

STANDARDS top

   POSIX.1-2008.

HISTORY top

   POSIX.1-2001, SVr4, 4.4BSD.

C library/kernel differences Over time, increases in the size of the utsname structure have led to three successive versions of uname(): sysolduname() (slot _NRoldolduname), sysuname() (slot _NRolduname), and sysnewuname() (slot _NRuname). 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.

NOTES top

   The kernel has the name, release, version, and supported machine
   type built in.  Conversely, the _nodename_ field is configured by
   the administrator to match the network (this is what the BSD
   historically calls the "hostname", and is set via [sethostname(2)](../man2/sethostname.2.html)).
   Similarly, the _domainname_ field is set via [setdomainname(2)](../man2/setdomainname.2.html).

   Part of the utsname information is also accessible via
   _/proc/sys/kernel/_{_ostype_, _hostname_, _osrelease_, _version_,
   _domainname_}.

SEE ALSO top

   [uname(1)](../man1/uname.1.html), [getdomainname(2)](../man2/getdomainname.2.html), [gethostname(2)](../man2/gethostname.2.html), [uts_namespaces(7)](../man7/uts%5Fnamespaces.7.html)

COLOPHON top

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Linux man-pages 6.10 2024-07-23 uname(2)

Pages that refer to this page:arch(1), systemd-nspawn(1), uname(1), getdomainname(2), gethostname(2), personality(2), syscalls(2), kbuffer_alloc(3), core(5), org.freedesktop.hostname1(5), systemd.exec(5), systemd.unit(5), lvmsystemid(7), signal-safety(7), uts_namespaces(7), modprobe(8), sm-notify(8), systemd-sysext(8)