.\" Copyright (C) 2001 Andries Brouwer . .\" .\" %%%LICENSE_START(VERBATIM) .\" Permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" Permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" Since the Linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. The author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. The author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" Formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%LICENSE_END .\" .\" 2007-07-05 mtk: Added details on underlying system call interfaces .\" .TH UNAME 2 2017-09-15 "Linux" "Linux Programmer's Manual" .SH NAME uname \- get name and information about current kernel .SH SYNOPSIS .B #include .PP .BI "int uname(struct utsname *" buf ); .SH DESCRIPTION .BR uname () returns system information in the structure pointed to by .IR buf . The .I utsname struct is defined in .IR : .PP .in +4n .EX 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 }; .EE .in .PP The length of the arrays in a .I struct utsname is unspecified (see NOTES); the fields are terminated by a null byte (\(aq\\0\(aq). .SH RETURN VALUE On success, zero is returned. On error, \-1 is returned, and .I errno is set appropriately. .SH ERRORS .TP .B EFAULT .I buf is not valid. .SH CONFORMING TO POSIX.1-2001, POSIX.1-2008, SVr4. There is no .BR uname () call in 4.3BSD. .PP The .I domainname member (the NIS or YP domain name) is a GNU extension. .SH 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 .I 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 .I domainname field. .PP To this end, Linux uses the system calls .BR sethostname (2) and .BR setdomainname (2). Note that there is no standard that says that the hostname set by .BR sethostname (2) is the same string as the .I nodename field of the struct returned by .BR uname () (indeed, some systems allow a 256-byte hostname and an 8-byte nodename), but this is true on Linux. The same holds for .BR setdomainname (2) and the .I domainname field. .PP 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 .B SYS_NMLN or .B _SYS_NMLN or .B UTSLEN or .BR _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. .PP Part of the utsname information is also accessible via .IR /proc/sys/kernel/ { ostype , .IR hostname , .IR osrelease , .IR version , .IR domainname }. .SS C library/kernel differences .PP Over time, increases in the size of the .I utsname structure have led to three successive versions of .BR uname (): .IR sys_olduname () (slot .IR __NR_oldolduname ), .IR sys_uname () (slot .IR __NR_olduname ), and .IR sys_newuname () (slot .IR __NR_uname) . The first one .\" That was back before Linux 1.0 used length 9 for all fields; the second .\" That was also back before Linux 1.0 used 65; the third also uses 65 but adds the .I domainname field. The glibc .BR uname () wrapper function hides these details from applications, invoking the most recent version of the system call provided by the kernel. .SH SEE ALSO .BR uname (1), .BR getdomainname (2), .BR gethostname (2), .BR namespaces (7) .SH COLOPHON This page is part of release 4.16 of the Linux .I man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/.