NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON
GETHOSTNAME(2) Linux Programmer's Manual GETHOSTNAME(2)
gethostname, sethostname - get/set hostname
#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(): _BSD_SOURCE || _XOPEN_SOURCE >= 500
sethostname(): _BSD_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE < 500)
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.
On success, zero is returned. On error, -1 is returned, and errno is set
appropriately.
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.
SVr4, 4.4BSD (these interfaces first appeared in 4.2BSD). POSIX.1-2001
specifies gethostname() but not sethostname().
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).
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, no null-terminator is 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.
getdomainname(2), setdomainname(2), uname(2)
This page is part of release 3.23 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
Linux 2008-11-27 GETHOSTNAME(2)