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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 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 trunca-
       tion 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.

	      (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

       SVr4,   4.4BSD	 (these	  interfaces   first   appeared	  in  4.2BSD).
       POSIX.1-2001 and POSIX.1-2008 specify gethostname()  but	 not  sethost-

       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 ENAME-

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

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Linux				  2015-07-23			GETHOSTNAME(2)