GETHOSTNAME(2)                                      Linux Programmer's Manual                                     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(): _BSD_SOURCE || _XOPEN_SOURCE >= 500
       sethostname(): _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.1-2001 says that if such truncation occurs, then it is unspecified whether the returned buffer includes a terminat-
       ing 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.

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 func-
       tion 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  differ-
       ently: nothing is copied into name and the function returns -1 with errno set to ENAMETOOLONG.

SEE ALSO
       getdomainname(2), setdomainname(2), uname(2)

COLOPHON
       This  page  is  part of release 3.25 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)