projects / unix-history / blame
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1 | .\" Copyright (c) 1987, 1990 The Regents of the University of California. |
| 2 | .\" All rights reserved. | |
| 3 | .\" | |
| 4 | .\" Redistribution and use in source and binary forms, with or without | |
| 5 | .\" modification, are permitted provided that the following conditions | |
| 6 | .\" are met: | |
| 7 | .\" 1. Redistributions of source code must retain the above copyright | |
| 8 | .\" notice, this list of conditions and the following disclaimer. | |
| 9 | .\" 2. Redistributions in binary form must reproduce the above copyright | |
| 10 | .\" notice, this list of conditions and the following disclaimer in the | |
| 11 | .\" documentation and/or other materials provided with the distribution. | |
| 12 | .\" 3. All advertising materials mentioning features or use of this software | |
| 13 | .\" must display the following acknowledgement: | |
| 14 | .\" This product includes software developed by the University of | |
| 15 | .\" California, Berkeley and its contributors. | |
| 16 | .\" 4. Neither the name of the University nor the names of its contributors | |
| 17 | .\" may be used to endorse or promote products derived from this software | |
| 18 | .\" without specific prior written permission. | |
| 19 | .\" | |
| 20 | .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND | |
| 21 | .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
| 22 | .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
| 23 | .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE | |
| 24 | .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
| 25 | .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
| 26 | .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
| 27 | .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
| 28 | .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
| 29 | .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
| 30 | .\" SUCH DAMAGE. | |
| 31 | .\" | |
| 32 | .\" @(#)hostname.7 6.5 (Berkeley) 6/24/90 | |
| 33 | .\" | |
| 34 | .Dd June 24, 1990 | |
| 35 | .Dt HOSTNAME 7 | |
| 36 | .Os BSD 4.2 | |
| 37 | .Sh NAME | |
| 38 | .Nm hostname | |
| 39 | .Nd host name resolution description | |
| 40 | .Sh DESCRIPTION | |
| 41 | Hostnames are domains, where a domain is a hierarchical, dot-separated | |
| 42 | list of subdomains; for example, the machine monet, in the Berkeley | |
| 43 | subdomain of the EDU subdomain of the Internet would be represented as | |
| 44 | .Pp | |
| 45 | .Dl monet.Berkeley.EDU | |
| 46 | .Pp | |
| 47 | (with no trailing dot). | |
| 48 | .Pp | |
| 49 | Hostnames are often used with network client and server programs, | |
| 50 | which must generally translate the name to an address for use. | |
| 51 | (This function is generally performed by the library routine | |
| 52 | .Xr gethostbyname 3 . ) | |
| 53 | Hostnames are resolved by the Internet name resolver in the following | |
| 54 | fashion. | |
| 55 | .Pp | |
| 56 | If the name consists of a single component, i.e. contains no dot, | |
| 57 | and if the environment variable | |
| 58 | .Dq Ev HOSTALIASES | |
| 59 | is set to the name of a file, | |
| 60 | that file is searched for an string matching the input hostname. | |
| 61 | The file should consist of lines made up of two white-space separated strings, | |
| 62 | the first of which is the hostname alias, | |
| 63 | and the second of which is the complete hostname | |
| 64 | to be substituted for that alias. | |
| 65 | If a case-insensitive match is found between the hostname to be resolved | |
| 66 | and the first field of a line in the file, the substituted name is looked | |
| 67 | up with no further processing. | |
| 68 | .Pp | |
| 69 | If the input name ends with a trailing dot, | |
| 70 | the trailing dot is removed, | |
| 71 | and the remaining name is looked up with no further processing. | |
| 72 | .Pp | |
| 73 | If the input name does not end with a trailing dot, it is looked up | |
| 74 | by searching through a list of domains until a match is found. | |
| 75 | The default search list includes first the local domain, | |
| 76 | then its parent domains with at least 2 name components (longest first). | |
| 77 | For example, | |
| 78 | in the domain CS.Berkeley.EDU, the name lithium.CChem will be checked first | |
| 79 | as lithium.CChem.CS.Berkeley.EDU and then as lithium.CChem.Berkeley.EDU. | |
| 80 | Lithium.CChem.EDU will not be tried, as the there is only one component | |
| 81 | remaining from the local domain. | |
| 82 | The search path can be changed from the default | |
| 83 | by a system-wide configuration file (see | |
| 84 | .Xr resolver 5 ) . | |
| 85 | .Sh SEE ALSO | |
| 86 | .Xr gethostbyname 3 , | |
| 87 | .Xr resolver 5 , | |
| 88 | .Xr mailaddr 7 , | |
| 89 | .Xr named 8 | |
| 90 | .Sh HISTORY | |
| 91 | .Nm Hostname | |
| 92 | appeared in 4.2 BSD. |