man-pages/man2/getdomainname.2

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.TH GETDOMAINNAME 2 2012-10-25 "Linux" "Linux Programmer's Manual"
.SH NAME
getdomainname, setdomainname \- get/set NIS domain name
.SH SYNOPSIS
.B #include <unistd.h>
.sp
.BI "int getdomainname(char *" name ", size_t " len );
.br
.BI "int setdomainname(const char *" name ", size_t " len );
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.ad l
.BR getdomainname (),
.BR setdomainname ():
.RS 4
_BSD_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE\ <\ 500)
.RE
.ad
.SH DESCRIPTION
These functions are used to access or to change the NIS domain name of the
host system.

.BR setdomainname ()
sets the domain name to the value given in the character array
.IR name .
The
.I len
argument specifies the number of bytes in
.IR name .
(Thus,
.I name
does not require a terminating null byte.)

.BR getdomainname ()
returns the null-terminated domain name in the character array
.IR name ,
which has a length of
.I len
bytes.
If the null-terminated domain name requires more than \fIlen\fP bytes,
.BR getdomainname ()
returns the first \fIlen\fP bytes (glibc) or gives an error (libc).
.SH "RETURN VALUE"
On success, zero is returned.
On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS
.BR setdomainname ()
can fail with the following errors:
.TP
.B EFAULT
.I name
pointed outside of user address space.
.TP
.B EINVAL
.I len
was negative or too large.
.TP
.B EPERM
the caller is unprivileged (Linux: does not have the
.B CAP_SYS_ADMIN
capability).
.PP
.BR getdomainname ()
can fail with the following errors:
.TP
.B EINVAL
For
.BR getdomainname ()
under libc:
.I name
is NULL or
.I name
is longer than
.I len
bytes.
.SH "CONFORMING TO"
POSIX does not specify these calls.
.\" But they appear on most systems...
.SH NOTES
Since Linux 1.0, the limit on the length of a domain name,
including the terminating null byte, is 64 bytes.
In older kernels, it was 8 bytes.

On most Linux architectures (including x86),
there is no
.BR getdomainname ()
system call; instead, glibc implements
.BR getdomainname ()
as a library function that returns a copy of the
.I domainname
field returned from a call to
.BR uname (2).
.SH "SEE ALSO"
.BR gethostname (2),
.BR sethostname (2),
.BR uname (2)