gethostname(2)
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);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
gethostname():
Since glibc 2.12: _BSD_SOURCE || _XOPEN_SOURCE >= 500
|| /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200112L
sethostname():
Since glibc 2.21:
_DEFAULT_SOURCE
In glibc 2.19 and 2.20:
_DEFAULT_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE < 500)
Up to and including glibc 2.19:
_BSD_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE < 500)
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 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 name is an invalid address.
EINVAL len is negative or, for sethostname(), len is larger than the
maximum allowed size.
ENAMETOOLONG
(glibc gethostname()) len is smaller than the actual size.
(Before version 2.1, glibc uses EINVAL for this case.)
EPERM For sethostname(), the caller did not have the CAP_SYS_ADMIN
capability in the user namespace associated with its UTS
namespace (see namespaces(7)).
CONFORMING TO
SVr4, 4.4BSD (these interfaces first appeared in 4.2BSD). POSIX.1-2001 and POSIX.1-2008 specify gethostname() but not sethostname().
NOTES
SUSv2 guarantees that "Host names are limited to 255 bytes". POSIX.1 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). C library/kernel differences 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.
SEE ALSO
hostname(1), getdomainname(2), setdomainname(2), uname(2)
COLOPHON
This page is part of release 4.09 of the Linux 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/.
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
