1 .\" Copyright (C) 2001 Andries Brouwer <aeb@cwi.nl>.
3 .\" Permission is granted to make and distribute verbatim copies of this
4 .\" manual provided the copyright notice and this permission notice are
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7 .\" Permission is granted to copy and distribute modified versions of this
8 .\" manual under the conditions for verbatim copying, provided that the
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12 .\" Since the Linux kernel and libraries are constantly changing, this
13 .\" manual page may be incorrect or out-of-date. The author(s) assume no
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17 .\" which is licensed free of charge, as they might when working
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21 .\" the source, must acknowledge the copyright and authors of this work.
23 .\" 2007-07-05 mtk: Added details on underlying system call interfaces
25 .TH UNAME 2 2008-12-03 "Linux" "Linux Programmer's Manual"
27 uname \- get name and information about current kernel
29 .B #include <sys/utsname.h>
31 .BI "int uname(struct utsname *" buf );
34 returns system information in the structure pointed to by
44 char sysname[]; /* Operating system name (e.g., "Linux") */
45 char nodename[]; /* Name within "some implementation-defined
47 char release[]; /* OS release (e.g., "2.6.28") */
48 char version[]; /* OS version */
49 char machine[]; /* Hardware identifier */
51 char domainname[]; /* NIS or YP domain name */
57 The length of the arrays in a
59 is unspecified (see NOTES);
60 the fields are terminated by a null byte (\(aq\\0\(aq).
62 On success, zero is returned.
63 On error, \-1 is returned, and
79 member (the NIS or YP domain name) is a GNU extension.
81 This is a system call, and the operating system presumably knows
82 its name, release and version.
83 It also knows what hardware it runs on.
84 So, four of the fields of the struct are meaningful.
85 On the other hand, the field \fInodename\fP is meaningless:
86 it gives the name of the present machine in some undefined
87 network, but typically machines are in more than one network
88 and have several names.
89 Moreover, the kernel has no way of knowing
90 about such things, so it has to be told what to answer here.
91 The same holds for the additional \fIdomainname\fP field.
93 To this end Linux uses the system calls
96 .BR setdomainname (2).
97 Note that there is no standard that says that the hostname set by
99 is the same string as the \fInodename\fP field of the struct returned by
101 (indeed, some systems allow a 256-byte hostname and an 8-byte nodename),
102 but this is true on Linux.
104 .BR setdomainname (2)
105 and the \fIdomainname\fP field.
107 The length of the fields in the struct varies.
108 Some operating systems
109 or libraries use a hardcoded 9 or 33 or 65 or 257.
117 .BR _UTSNAME_LENGTH .
119 idea to use any of these constants; just use sizeof(...).
120 Often 257 is chosen in order to have room for an internet hostname.
122 Part of the utsname information is also accessible via
123 .IR /proc/sys/kernel/ { ostype ,
128 .SS Underlying kernel interface
130 Over time, increases in the size of the
132 structure have led to three successive versions of
136 .IR __NR_oldolduname ),
145 .\" That was back before Linux 1.0
146 used length 9 for all fields;
148 .\" That was also back before Linux 1.0
150 the third also uses 65 but adds the \fIdomainname\fP field.
153 wrapper function hides these details from applications,
154 invoking the most recent version of the system call provided by the kernel.
157 .BR getdomainname (2),