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.\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu)
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.\" Modified 1995-07-22 by Michael Chastain <mec@duracef.shout.net>:
.\"   'gethostname' is real system call on Linux/Alpha.
.\" Modified 1997-01-31 by Eric S. Raymond <esr@thyrsus.com>
.\" Modified 2000-06-04, 2001-12-15 by aeb
.\" Modified 2004-06-17 by mtk
.\"
.TH GETHOSTNAME 2 2004-06-17 "Linux 2.6.7" "Linux Programmer's Manual"
.SH NAME
gethostname, sethostname \- get/set host name
.SH SYNOPSIS
.B #include <unistd.h>
.sp
.BI "int gethostname(char *" name ", size_t " len );
.br
.BI "int sethostname(const char *" name ", size_t " len );
.SH DESCRIPTION
These system calls are used to access or to change the host name of the
current processor.
The
.BR gethostname ()
system call returns a null-terminated hostname (set earlier by
.BR sethostname ())
in the array \fIname\fP that has a length of \fIlen\fP bytes.
In case the null-terminated hostname does not fit, no error is
returned, but the hostname is truncated.
It is unspecified
whether the truncated hostname will be null-terminated.
.SH "RETURN VALUE"
On success, zero is returned.
On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B EFAULT
.I name
is an invalid address.
.TP
.B EINVAL
.I len
is negative or, for
.BR sethostname (),
.I len
is larger than the maximum allowed size,
or, for
.BR gethostname ()
on Linux/i386,
.I len
is smaller than the actual size.
(In this last case glibc 2.1 uses ENAMETOOLONG.)
.TP
.B EPERM
For
.BR sethostname (),
the caller did not have the
.B CAP_SYS_ADMIN
capability.
.SH "CONFORMING TO"
SVr4, 4.4BSD  (these interfaces first appeared in 4.2BSD).
POSIX.1-2001 specifies
.BR gethostname ()
but not
.BR sethostname ().
.SH 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'.
.SH "GLIBC NOTES"
The GNU C library implements
.BR gethostname ()
as a library function that calls
.BR uname (2)
and copies up to
.I len
bytes from the returned
.I nodename
field into
.IR name .
Having performed the copy, the function then checks if the length of the
.I nodename
was greater than or equal to
.IR len ,
and if it is, then the function returns \-1 with
.I errno
set to
.BR ENAMETOOLONG .
Versions of glibc before 2.2
.\" At least glibc 2.0 and 2.1, older versions not checked
handle the case where the length of the
.I nodename
was greater than or equal to
.IR len
differently: nothing is copied into
.I name
and the function returns \-1 with
.I errno
set to
.BR ENAMETOOLONG .
.SH "SEE ALSO"
.BR getdomainname (2),
.BR setdomainname (2),
.BR uname (2)