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():
           _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.

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

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

COLOPHON

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