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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 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  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 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, no  null-termina-
       tor 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
       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
       This page is part of release 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                             2008-11-27                    GETHOSTNAME(2)