uname
Section: System Calls (2)
Updated: 2023-02-05
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NAME
uname - get name and information about current kernel
LIBRARY
Standard C library
(libc, -lc)
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 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 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 to indicate the error.
ERRORS
- EFAULT
-
buf
is not valid.
STANDARDS
POSIX.1-2001, POSIX.1-2008, SVr4, 4.4BSD.
The
domainname
member (the NIS or YP domain name) is a GNU extension.
NOTES
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)).
Similarly, the
domainname
field is set via
setdomainname(2).
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.
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),
uts_namespaces(7)
Index
- NAME
-
- LIBRARY
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- STANDARDS
-
- NOTES
-
- C library/kernel differences
-
- SEE ALSO
-
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