gethostname, sethostname − get/set host name

#include <unistd.h>

int gethostname(char *name, size_t len);
int sethostname(const char *name, size_t len);

These functions are used to access or to change the host name of the current processor. The gethostname() function returns a NUL-terminated hostname (set earlier by sethostname()) in the array name that has a length of len bytes. In case the NUL-terminated hostname does not fit, no error is returned, but the hostname is truncated. It is unspecified whether the truncated hostname will be NUL-terminated.

On success, zero is returned. On error, −1 is returned, and errno is set appropriately.

EINVAL

len is negative or, for sethostname, len is larger than the maximum allowed size, or, for gethostname on Linux/i386, len is smaller than the actual size. (In this last case glibc 2.1 uses ENAMETOOLONG.)

EPERM

For sethostname, the caller was not the superuser.

EFAULT

name is an invalid address.

SVr4, 4.4BSD (this function first appeared in 4.2BSD). POSIX 1003.1-2001 specifies gethostname but not sethostname.

For many Linux kernel / libc combinations gethostname will return an error instead of returning a truncated hostname.

SUSv2 guarantees that ‘Host names are limited to 255 bytes’. POSIX 1003.1-2001 guarantees that ‘Host names (not including the terminating NUL) are limited to HOST_NAME_MAX bytes’.

getdomainname(2), setdomainname(2), uname(2)