1.\" $OpenBSD: gethostname.3,v 1.28 2018/01/12 04:36:44 deraadt Exp $ 2.\" 3.\" Copyright (c) 1983, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.Dd $Mdocdate: January 12 2018 $ 31.Dt GETHOSTNAME 3 32.Os 33.Sh NAME 34.Nm gethostname , 35.Nm sethostname 36.Nd get/set name of current host 37.Sh SYNOPSIS 38.In unistd.h 39.Ft int 40.Fn gethostname "char *name" "size_t namelen" 41.Ft int 42.Fn sethostname "const char *name" "size_t namelen" 43.Sh DESCRIPTION 44The 45.Fn gethostname 46function returns the standard host name for the current 47machine, as previously set by 48.Fn sethostname . 49The parameter 50.Fa namelen 51specifies the size of the 52.Fa name 53array. 54If insufficient space is provided, the returned name is truncated. 55The returned name is always NUL terminated. 56If no space is provided, an error is returned. 57.Pp 58.Fn sethostname 59sets the name of the host machine to be 60.Fa name , 61which has length 62.Fa namelen . 63This call is restricted to the superuser and 64is normally used only when the system is bootstrapped. 65.Sh RETURN VALUES 66If the call succeeds a value of 0 is returned. 67If the call fails, a value of \-1 is returned and an error code is 68placed in the global variable 69.Va errno . 70.Sh ERRORS 71The following errors may be returned by these calls: 72.Bl -tag -width Er 73.It Bq Er EFAULT 74The 75.Fa name 76parameter gave an invalid address. 77.It Bq Er ENOMEM 78The 79.Ar namelen 80parameter was zero. 81.It Bq Er EPERM 82The caller tried to set the hostname and was not the superuser. 83.El 84.Sh SEE ALSO 85.Xr hostname 1 , 86.Xr getdomainname 3 , 87.Xr gethostid 3 , 88.Xr sysctl 2 , 89.Xr sysctl 8 , 90.Xr yp 8 91.Sh STANDARDS 92The 93.Fn gethostname 94function call conforms to 95.St -xpg4.2 . 96.Sh HISTORY 97The 98.Fn gethostname 99function call appeared in 100.Bx 4.2 . 101.Sh BUGS 102Host names are limited to 103.Dv MAXHOSTNAMELEN 104(from 105.In sys/param.h ) 106characters, currently 256. 107This includes the terminating NUL character. 108Note that the corresponding POSIX definition 109.Dv HOST_NAME_MAX 110in 111.In limits.h 112does 113.Em not 114include the terminating NUL character. 115.Pp 116If the buffer passed to 117.Fn gethostname 118is smaller than 119.Dv MAXHOSTNAMELEN , 120other operating systems may not guarantee termination with NUL. 121