Name
gethostname, sethostname — get/set hostname
Synopsis
#include <unistd.h>
int
gethostname( |
char *name, |
size_t len); |
int
sethostname( |
const char *name, |
size_t len); |
![[Note]](../stylesheet/note.png) |
Note | |||||||
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DESCRIPTION
These system calls are used to access or to change the hostname of the current processor.
sethostname() sets the
hostname to the value given in the character array name. The len argument specifies the
number of bytes in name. (Thus, name does not require a
terminating null byte.)
gethostname() returns the
null-terminated hostname in the character array name, which has a length of
len bytes. If the
null-terminated hostname is too large to fit, then the name
is truncated, and no error is returned (but see NOTES below).
POSIX.1-2001 says that if such truncation occurs, then it is
unspecified whether the returned buffer includes a
terminating null byte.
RETURN VALUE
On success, zero is returned. On error, −1 is
returned, and errno is set
appropriately.
ERRORS
- EFAULT
-
nameis an invalid address. - EINVAL
-
lenis negative or, forsethostname(),lenis larger than the maximum allowed size. - ENAMETOOLONG
-
(glibc
gethostname())lenis smaller than the actual size. (Before version 2.1, glibc uses EINVAL for this case.) - EPERM
-
For
sethostname(), the caller did not have theCAP_SYS_ADMINcapability.
CONFORMING TO
SVr4, 4.4BSD (these interfaces first appeared in 4.2BSD).
POSIX.1-2001 specifies gethostname() but not sethostname().
NOTES
SUSv2 guarantees that "Host names are limited to 255
bytes". POSIX.1-2001 guarantees that "Host names (not
including the terminating null byte) are limited to
HOST_NAME_MAX bytes". On Linux,
HOST_NAME_MAX is defined with
the value 64, which has been the limit since Linux 1.0
(earlier kernels imposed a limit of 8 bytes).
Glibc Notes
The GNU C library does not employ the gethostname() system call; instead, it
implements gethostname() as a
library function that calls uname(2) and copies up to
len bytes from the
returned nodename
field into name.
Having performed the copy, the function then checks if the
length of the nodename was greater than
or equal to len,
and if it is, then the function returns −1 with
errno set to ENAMETOOLONG; in this case, a
terminating null byte is not included in the returned
name.
Versions of glibc before 2.2 handle the case where the
length of the nodename was greater than
or equal to len
differently: nothing is copied into name and the function returns
−1 with errno set to
ENAMETOOLONG.
COLOPHON
This page is part of release 3.33 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at http://man7.org/linux/man-pages/.
|
Copyright 1993 Rickard E. Faith (faithcs.unc.edu) 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. Modified 1995-07-22 by Michael Chastain <mecduracef.shout.net>: 'gethostname' is real system call on Linux/Alpha. Modified 1997-01-31 by Eric S. Raymond <esrthyrsus.com> Modified 2000-06-04, 2001-12-15 by aeb Modified 2004-06-17 by mtk Modified 2008-11-27 by mtk |