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Linux 2.6 - man page for gethostname (linux section 2)

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)):

	   Since glibc 2.12: _BSD_SOURCE || _XOPEN_SOURCE >= 500
	   || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200112L

       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	terminat-
       ing 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 ter-
       minating 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.

	      (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  geth-
       ostname() 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).

   Glibc notes
       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.

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

       This  page  is  part of release 3.55 of the Linux man-pages project.  A description of the
       project,    and	  information	 about	  reporting    bugs,	can    be    found     at

Linux					    2010-09-26				   GETHOSTNAME(2)

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