wget/doc/wget.texi

\input texinfo   @c -*-texinfo-*-

@c %**start of header
@setfilename wget.info
@settitle GNU Wget Manual
@c Disable the monstrous rectangles beside overfull hbox-es.
@finalout
@c Use `odd' to print double-sided.
@setchapternewpage on
@c %**end of header

@iftex
@c Remove this if you don't use A4 paper.
@afourpaper
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@c This should really be auto-generated!
@set VERSION 1.5.3+dev
@set UPDATED Feb 2000

@dircategory Net Utilities
@dircategory World Wide Web
@direntry
* Wget: (wget).         The non-interactive network downloader.
@end direntry

@ifinfo
This file documents the the GNU Wget utility for downloading network
data.

Copyright (C) 1996, 1997, 1998, 2000 Free Software Foundation, Inc.

Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.

@ignore
Permission is granted to process this file through TeX and print the
results, provided the printed document carries a copying permission
notice identical to this one except for the removal of this paragraph
(this paragraph not being relevant to the printed manual).
@end ignore
Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided also that the
sections entitled ``Copying'' and ``GNU General Public License'' are
included exactly as in the original, and provided that the entire
resulting derived work is distributed under the terms of a permission
notice identical to this one.
@end ifinfo

@titlepage
@title GNU Wget
@subtitle The noninteractive downloading utility
@subtitle Updated for Wget @value{VERSION}, @value{UPDATED}
@author by Hrvoje Nik@v{s}i@'{c} and the developers

@page
@vskip 0pt plus 1filll
Copyright @copyright{} 1996, 1997, 1998 Free Software Foundation, Inc.

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided also that the
sections entitled ``Copying'' and ``GNU General Public License'' are
included exactly as in the original, and provided that the entire
resulting derived work is distributed under the terms of a permission
notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation
approved by the Free Software Foundation.
@end titlepage

@ifinfo
@node Top, Overview, (dir), (dir)
@top Wget @value{VERSION}

This manual documents version @value{VERSION} of GNU Wget, the freely
available utility for network download.

Copyright @copyright{} 1996, 1997, 1998 Free Software Foundation, Inc.

@menu
* Overview::            Features of Wget.
* Invoking::            Wget command-line arguments.
* Recursive Retrieval:: Description of recursive retrieval.
* Following Links::     The available methods of chasing links.
* Time-Stamping::       Mirroring according to time-stamps.
* Startup File::        Wget's initialization file.
* Examples::            Examples of usage.
* Various::             The stuff that doesn't fit anywhere else.
* Appendices::          Some useful references.
* Copying::             You may give out copies of Wget.
* Concept Index::       Topics covered by this manual.
@end menu
@end ifinfo

@node Overview, Invoking, Top, Top
@chapter Overview
@cindex overview
@cindex features

GNU Wget is a freely available network utility to retrieve files from
the World Wide Web, using @sc{http} (Hyper Text Transfer Protocol) and
@sc{ftp} (File Transfer Protocol), the two most widely used Internet
protocols.  It has many useful features to make downloading easier, some
of them being:

@itemize @bullet
@item
Wget is non-interactive, meaning that it can work in the background,
while the user is not logged on.  This allows you to start a retrieval
and disconnect from the system, letting Wget finish the work.  By
contrast, most of the Web browsers require constant user's presence,
which can be a great hindrance when transferring a lot of data.

@sp 1
@item
Wget is capable of descending recursively through the structure of
@sc{html} documents and @sc{ftp} directory trees, making a local copy of
the directory hierarchy similar to the one on the remote server.  This
feature can be used to mirror archives and home pages, or traverse the
web in search of data, like a @sc{www} robot (@xref{Robots}).  In that
spirit, Wget understands the @code{norobots} convention.

@sp 1
@item
File name wildcard matching and recursive mirroring of directories are
available when retrieving via @sc{ftp}.  Wget can read the time-stamp
information given by both @sc{http} and @sc{ftp} servers, and store it
locally.  Thus Wget can see if the remote file has changed since last
retrieval, and automatically retrieve the new version if it has.  This
makes Wget suitable for mirroring of @sc{ftp} sites, as well as home
pages.

@sp 1
@item
Wget works exceedingly well on slow or unstable connections,
retrying the document until it is fully retrieved, or until a
user-specified retry count is surpassed.  It will try to resume the
download from the point of interruption, using @code{REST} with @sc{ftp}
and @code{Range} with @sc{http} servers that support them.

@sp 1
@item
By default, Wget supports proxy servers, which can lighten the network
load, speed up retrieval and provide access behind firewalls.  However,
if you are behind a firewall that requires that you use a socks style
gateway, you can get the socks library and build wget with support for
socks.  Wget also supports the passive @sc{ftp} downloading as an
option.

@sp 1
@item
Builtin features offer mechanisms to tune which links you wish to follow
(@xref{Following Links}).

@sp 1
@item
The retrieval is conveniently traced with printing dots, each dot
representing a fixed amount of data received (1KB by default).  These
representations can be customized to your preferences.

@sp 1
@item
Most of the features are fully configurable, either through command line
options, or via the initialization file @file{.wgetrc} (@xref{Startup
File}).  Wget allows you to define @dfn{global} startup files
(@file{/usr/local/etc/wgetrc} by default) for site settings.

@sp 1
@item
Finally, GNU Wget is free software.  This means that everyone may use
it, redistribute it and/or modify it under the terms of the GNU General
Public License, as published by the Free Software Foundation
(@xref{Copying}).
@end itemize

@node Invoking, Recursive Retrieval, Overview, Top
@chapter Invoking
@cindex invoking
@cindex command line
@cindex arguments
@cindex nohup

By default, Wget is very simple to invoke.  The basic syntax is:

@example
wget [@var{option}]@dots{} [@var{URL}]@dots{}
@end example

Wget will simply download all the @sc{url}s specified on the command
line.  @var{URL} is a @dfn{Uniform Resource Locator}, as defined below.

However, you may wish to change some of the default parameters of
Wget.  You can do it two ways: permanently, adding the appropriate
command to @file{.wgetrc} (@xref{Startup File}), or specifying it on
the command line.

@menu
* URL Format::
* Option Syntax::
* Basic Startup Options::
* Logging and Input File Options::
* Download Options::
* Directory Options::
* HTTP Options::
* FTP Options::
* Recursive Retrieval Options::
* Recursive Accept/Reject Options::
@end menu

@node URL Format, Option Syntax, Invoking, Invoking
@section URL Format
@cindex URL
@cindex URL syntax

@dfn{URL} is an acronym for Uniform Resource Locator.  A uniform
resource locator is a compact string representation for a resource
available via the Internet.  Wget recognizes the @sc{url} syntax as per
@sc{rfc1738}.  This is the most widely used form (square brackets denote
optional parts):

@example
http://host[:port]/directory/file
ftp://host[:port]/directory/file
@end example

You can also encode your username and password within a @sc{url}:

@example
ftp://user:password@@host/path
http://user:password@@host/path
@end example

Either @var{user} or @var{password}, or both, may be left out.  If you
leave out either the @sc{http} username or password, no authentication
will be sent.  If you leave out the @sc{ftp} username, @samp{anonymous}
will be used.  If you leave out the @sc{ftp} password, your email
address will be supplied as a default password.@footnote{If you have a
@file{.netrc} file in your home directory, password will also be
searched for there.}

You can encode unsafe characters in a @sc{url} as @samp{%xy}, @code{xy}
being the hexadecimal representation of the character's @sc{ascii}
value.  Some common unsafe characters include @samp{%} (quoted as
@samp{%25}), @samp{:} (quoted as @samp{%3A}), and @samp{@@} (quoted as
@samp{%40}).  Refer to @sc{rfc1738} for a comprehensive list of unsafe
characters.

Wget also supports the @code{type} feature for @sc{ftp} @sc{url}s.  By
default, @sc{ftp} documents are retrieved in the binary mode (type
@samp{i}), which means that they are downloaded unchanged.  Another
useful mode is the @samp{a} (@dfn{ASCII}) mode, which converts the line
delimiters between the different operating systems, and is thus useful
for text files.  Here is an example:

@example
ftp://host/directory/file;type=a
@end example

Two alternative variants of @sc{url} specification are also supported,
because of historical (hysterical?) reasons and their widespreaded use.

@sc{ftp}-only syntax (supported by @code{NcFTP}):
@example
host:/dir/file
@end example

@sc{http}-only syntax (introduced by @code{Netscape}):
@example
host[:port]/dir/file
@end example

These two alternative forms are deprecated, and may cease being
supported in the future.

If you do not understand the difference between these notations, or do
not know which one to use, just use the plain ordinary format you use
with your favorite browser, like @code{Lynx} or @code{Netscape}.

@node Option Syntax, Basic Startup Options, URL Format, Invoking
@section Option Syntax
@cindex option syntax
@cindex syntax of options

Since Wget uses GNU getopts to process its arguments, every option has a
short form and a long form.  Long options are more convenient to
remember, but take time to type.  You may freely mix different option
styles, or specify options after the command-line arguments. Thus you
may write:

@example
wget -r --tries=10 http://fly.cc.fer.hr/ -o log
@end example

The space between the option accepting an argument and the argument may
be omitted.  Instead @samp{-o log} you can write @samp{-olog}.

You may put several options that do not require arguments together,
like:

@example
wget -drc @var{URL}
@end example

This is a complete equivalent of:

@example
wget -d -r -c @var{URL}
@end example

Since the options can be specified after the arguments, you may
terminate them with @samp{--}.  So the following will try to download
@sc{url} @samp{-x}, reporting failure to @file{log}:

@example
wget -o log -- -x
@end example

The options that accept comma-separated lists all respect the convention
that specifying an empty list clears its value.  This can be useful to
clear the @file{.wgetrc} settings.  For instance, if your @file{.wgetrc}
sets @code{exclude_directories} to @file{/cgi-bin}, the following
example will first reset it, and then set it to exclude @file{/~nobody}
and @file{/~somebody}.  You can also clear the lists in @file{.wgetrc}
(@xref{Wgetrc Syntax}).

@example
wget -X '' -X /~nobody,/~somebody
@end example

@node Basic Startup Options, Logging and Input File Options, Option Syntax, Invoking
@section Basic Startup Options

@table @samp
@item -V
@itemx --version
Display the version of Wget.

@item -h
@itemx --help
Print a help message describing all of Wget's command-line options.

@item -b
@itemx --background
Go to background immediately after startup.  If no output file is
specified via the @samp{-o}, output is redirected to @file{wget-log}.

@cindex execute wgetrc command
@item -e @var{command}
@itemx --execute @var{command}
Execute @var{command} as if it were a part of @file{.wgetrc}
(@xref{Startup File}).  A command thus invoked will be executed
@emph{after} the commands in @file{.wgetrc}, thus taking precedence over
them.
@end table

@node Logging and Input File Options, Download Options, Basic Startup Options, Invoking
@section Logging and Input File Options

@table @samp
@cindex output file
@cindex log file
@item -o @var{logfile}
@itemx --output-file=@var{logfile}
Log all messages to @var{logfile}.  The messages are normally reported
to standard error.

@cindex append to log
@item -a @var{logfile}
@itemx --append-output=@var{logfile}
Append to @var{logfile}.  This is the same as @samp{-o}, only it appends
to @var{logfile} instead of overwriting the old log file.  If
@var{logfile} does not exist, a new file is created.

@cindex debug
@item -d
@itemx --debug
Turn on debug output, meaning various information important to the
developers of Wget if it does not work properly.  Your system
administrator may have chosen to compile Wget without debug support, in
which case @samp{-d} will not work.  Please note that compiling with
debug support is always safe---Wget compiled with the debug support will
@emph{not} print any debug info unless requested with @samp{-d}.
@xref{Reporting Bugs} for more information on how to use @samp{-d} for
sending bug reports.

@cindex quiet
@item -q
@itemx --quiet
Turn off Wget's output.

@cindex verbose
@item -v
@itemx --verbose
Turn on verbose output, with all the available data.  The default output
is verbose.

@item -nv
@itemx --non-verbose
Non-verbose output---turn off verbose without being completely quiet
(use @samp{-q} for that), which means that error messages and basic
information still get printed.

@cindex input-file
@item -i @var{file}
@itemx --input-file=@var{file}
Read @sc{url}s from @var{file}, in which case no @sc{url}s need to be on
the command line.  If there are @sc{url}s both on the command line and
in an input file, those on the command lines will be the first ones to
be retrieved.  The @var{file} need not be an @sc{html} document (but no
harm if it is)---it is enough if the @sc{url}s are just listed
sequentially.

However, if you specify @samp{--force-html}, the document will be
regarded as @samp{html}.  In that case you may have problems with
relative links, which you can solve either by adding @code{<base
href="@var{url}">} to the documents or by specifying
@samp{--base=@var{url}} on the command line.

@cindex force html
@item -F
@itemx --force-html
When input is read from a file, force it to be treated as an @sc{html}
file.  This enables you to retrieve relative links from existing
@sc{html} files on your local disk, by adding @code{<base
href="@var{url}">} to @sc{html}, or using the @samp{--base} command-line
option.
@end table

@node Download Options, Directory Options, Logging and Input File Options, Invoking
@section Download Options

@table @samp
@cindex retries
@cindex tries
@cindex number of retries
@item -t @var{number}
@itemx --tries=@var{number}
Set number of retries to @var{number}.  Specify 0 or @samp{inf} for
infinite retrying.

@item -O @var{file}
@itemx --output-document=@var{file}
The documents will not be written to the appropriate files, but all will
be concatenated together and written to @var{file}.  If @var{file}
already exists, it will be overwritten.  If the @var{file} is @samp{-},
the documents will be written to standard output.  Including this option
automatically sets the number of tries to 1.

@cindex clobbering, file
@cindex downloading multiple times
@cindex no-clobber
@item -nc
@itemx --no-clobber
If a file is downloaded more than once in the same directory, wget's
behavior depends on a few options, including @samp{-nc}.  In certain
cases, the local file will be "clobbered", or overwritten, upon repeated
download.  In other cases it will be preserved.

When running wget without @samp{-N}, @samp{-nc}, or @samp{-r},
downloading the same file in the same directory will result in the
original copy of @samp{@var{file}} being preserved and the second copy
being named @samp{@var{file}.1}.  If that file is downloaded yet again,
the third copy will be named @samp{@var{file}.2}, and so on.  When
@samp{-nc} is specified, this behavior is suppressed, and wget will
refuse to download newer copies of @samp{@var{file}}.  Therefore,
"no-clobber" is actually a misnomer in this mode -- it's not clobbering
that's prevented (as the numeric suffixes were already preventing
clobbering), but rather the multiple version saving that's prevented.

When running wget with @samp{-r}, but without @samp{-N} or @samp{-nc},
re-downloading a file will result in the new copy simply overwriting the
old.  Adding @samp{-nc} will prevent this behavior, instead causing the
original version to be preserved and any newer copies on the server to
be ignored.

When running wget with @samp{-N}, with or without @samp{-r}, the
decision as to whether or not to download a newer copy of a file depends
on the local and remote timestamp and size of the file
(@xref{Time-Stamping}).  @samp{-nc} may not be specified at the same
time as @samp{-N}.

Note that when @samp{-nc} is specified, files with the suffixes
@samp{.html} or (yuck) @samp{.htm} will be loaded from the local disk
and parsed as if they had been retrieved from the Web.

@cindex continue retrieval
@item -c
@itemx --continue
Continue getting an existing file.  This is useful when you want to
finish up the download started by another program, or a previous
instance of Wget.  Thus you can write:

@example
wget -c ftp://sunsite.doc.ic.ac.uk/ls-lR.Z
@end example

If there is a file name @file{ls-lR.Z} in the current directory, Wget
will assume that it is the first portion of the remote file, and will
require the server to continue the retrieval from an offset equal to the
length of the local file.

Note that you need not specify this option if all you want is Wget to
continue retrieving where it left off when the connection is lost---Wget
does this by default.  You need this option only when you want to
continue retrieval of a file already halfway retrieved, saved by another
@sc{ftp} client, or left by Wget being killed.

Without @samp{-c}, the previous example would just begin to download the
remote file to @file{ls-lR.Z.1}.  The @samp{-c} option is also
applicable for @sc{http} servers that support the @code{Range} header.

@cindex dot style
@cindex retrieval tracing style
@item --dot-style=@var{style}
Set the retrieval style to @var{style}.  Wget traces the retrieval of
each document by printing dots on the screen, each dot representing a
fixed amount of retrieved data.  Any number of dots may be separated in
a @dfn{cluster}, to make counting easier.  This option allows you to
choose one of the pre-defined styles, determining the number of bytes
represented by a dot, the number of dots in a cluster, and the number of
dots on the line.

With the @code{default} style each dot represents 1K, there are ten dots
in a cluster and 50 dots in a line.  The @code{binary} style has a more
``computer''-like orientation---8K dots, 16-dots clusters and 48 dots
per line (which makes for 384K lines).  The @code{mega} style is
suitable for downloading very large files---each dot represents 64K
retrieved, there are eight dots in a cluster, and 48 dots on each line
(so each line contains 3M).  The @code{micro} style is exactly the
reverse; it is suitable for downloading small files, with 128-byte dots,
8 dots per cluster, and 48 dots (6K) per line.

@item -N
@itemx --timestamping
Turn on time-stamping.  @xref{Time-Stamping} for details.

@cindex server response, print
@item -S
@itemx --server-response
Print the headers sent by @sc{http} servers and responses sent by
@sc{ftp} servers.

@cindex Wget as spider
@cindex spider
@item --spider
When invoked with this option, Wget will behave as a Web @dfn{spider},
which means that it will not download the pages, just check that they
are there.  You can use it to check your bookmarks, e.g. with:

@example
wget --spider --force-html -i bookmarks.html
@end example

This feature needs much more work for Wget to get close to the
functionality of real @sc{www} spiders.

@cindex timeout
@item -T seconds
@itemx --timeout=@var{seconds}
Set the read timeout to @var{seconds} seconds.  Whenever a network read
is issued, the file descriptor is checked for a timeout, which could
otherwise leave a pending connection (uninterrupted read).  The default
timeout is 900 seconds (fifteen minutes).  Setting timeout to 0 will
disable checking for timeouts.

Please do not lower the default timeout value with this option unless
you know what you are doing.

@cindex pause
@cindex wait
@item -w @var{seconds}
@itemx --wait=@var{seconds}
Wait the specified number of seconds between the retrievals.  Use of
this option is recommended, as it lightens the server load by making the
requests less frequent.  Instead of in seconds, the time can be
specified in minutes using the @code{m} suffix, in hours using @code{h}
suffix, or in days using @code{d} suffix.

Specifying a large value for this option is useful if the network or the
destination host is down, so that Wget can wait long enough to
reasonably expect the network error to be fixed before the retry.

@cindex retries, waiting between
@cindex waiting between retries
@item --waitretry=@var{seconds}
If you don't want Wget to wait between @emph{every} retrieval, but only
between retries of failed downloads, you can use this option.  Wget will
use "linear backoff", waiting 1 second after the first failure on a
given file, then waiting 2 seconds after the second failure on that
file, up to the maximum number of @var{seconds} you specify.  Therefore,
a value of 10 will actually make Wget wait up to (1 + 2 + ... + 10) = 55
seconds per file.

Note that this option is turned on by default in the global
@file{wgetrc} file.

@cindex proxy
@item -Y on/off
@itemx --proxy=on/off
Turn proxy support on or off. The proxy is on by default if the
appropriate environmental variable is defined.

@cindex quota
@item -Q @var{quota}
@itemx --quota=@var{quota}
Specify download quota for automatic retrievals.  The value can be
specified in bytes (default), kilobytes (with @samp{k} suffix), or
megabytes (with @samp{m} suffix).

Note that quota will never affect downloading a single file.  So if you
specify @samp{wget -Q10k ftp://wuarchive.wustl.edu/ls-lR.gz}, all of the
@file{ls-lR.gz} will be downloaded.  The same goes even when several
@sc{url}s are specified on the command-line.  However, quota is
respected when retrieving either recursively, or from an input file.
Thus you may safely type @samp{wget -Q2m -i sites}---download will be
aborted when the quota is exceeded.

Setting quota to 0 or to @samp{inf} unlimits the download quota.
@end table

@node Directory Options, HTTP Options, Download Options, Invoking
@section Directory Options

@table @samp
@item -nd
@itemx --no-directories
Do not create a hierarchy of directories when retrieving
recursively. With this option turned on, all files will get saved to the
current directory, without clobbering (if a name shows up more than
once, the filenames will get extensions @samp{.n}).

@item -x
@itemx --force-directories
The opposite of @samp{-nd}---create a hierarchy of directories, even if
one would not have been created otherwise.  E.g. @samp{wget -x
http://fly.cc.fer.hr/robots.txt} will save the downloaded file to
@file{fly.cc.fer.hr/robots.txt}.

@item -nH
@itemx --no-host-directories
Disable generation of host-prefixed directories.  By default, invoking
Wget with @samp{-r http://fly.cc.fer.hr/} will create a structure of
directories beginning with @file{fly.cc.fer.hr/}.  This option disables
such behavior.

@cindex cut directories
@item --cut-dirs=@var{number}
Ignore @var{number} directory components.  This is useful for getting a
fine-grained control over the directory where recursive retrieval will
be saved.

Take, for example, the directory at
@samp{ftp://ftp.xemacs.org/pub/xemacs/}.  If you retrieve it with
@samp{-r}, it will be saved locally under
@file{ftp.xemacs.org/pub/xemacs/}.  While the @samp{-nH} option can
remove the @file{ftp.xemacs.org/} part, you are still stuck with
@file{pub/xemacs}.  This is where @samp{--cut-dirs} comes in handy; it
makes Wget not ``see'' @var{number} remote directory components.  Here
are several examples of how @samp{--cut-dirs} option works.

@example
@group
No options        -> ftp.xemacs.org/pub/xemacs/
-nH               -> pub/xemacs/
-nH --cut-dirs=1  -> xemacs/
-nH --cut-dirs=2  -> .

--cut-dirs=1      -> ftp.xemacs.org/xemacs/
...
@end group
@end example

If you just want to get rid of the directory structure, this option is
similar to a combination of @samp{-nd} and @samp{-P}.  However, unlike
@samp{-nd}, @samp{--cut-dirs} does not lose with subdirectories---for
instance, with @samp{-nH --cut-dirs=1}, a @file{beta/} subdirectory will
be placed to @file{xemacs/beta}, as one would expect.

@cindex directory prefix
@item -P @var{prefix}
@itemx --directory-prefix=@var{prefix}
Set directory prefix to @var{prefix}.  The @dfn{directory prefix} is the
directory where all other files and subdirectories will be saved to,
i.e. the top of the retrieval tree.  The default is @samp{.} (the
current directory).
@end table

@node HTTP Options, FTP Options, Directory Options, Invoking
@section HTTP Options

@table @samp
@cindex http user
@cindex http password
@cindex authentication
@item --http-user=@var{user}
@itemx --http-passwd=@var{password}
Specify the username @var{user} and password @var{password} on an
@sc{http} server.  According to the type of the challenge, Wget will
encode them using either the @code{basic} (insecure) or the
@code{digest} authentication scheme.

Another way to specify username and password is in the @sc{url} itself
(@xref{URL Format}).  For more information about security issues with
Wget, @xref{Security Considerations}.

@cindex proxy
@cindex cache
@item -C on/off
@itemx --cache=on/off
When set to off, disable server-side cache.  In this case, Wget will
send the remote server an appropriate directive (@samp{Pragma:
no-cache}) to get the file from the remote service, rather than
returning the cached version.  This is especially useful for retrieving
and flushing out-of-date documents on proxy servers.

Caching is allowed by default.

@cindex Content-Length, ignore
@cindex ignore length
@item --ignore-length
Unfortunately, some @sc{http} servers (@sc{cgi} programs, to be more
precise) send out bogus @code{Content-Length} headers, which makes Wget
go wild, as it thinks not all the document was retrieved.  You can spot
this syndrome if Wget retries getting the same document again and again,
each time claiming that the (otherwise normal) connection has closed on
the very same byte.

With this option, Wget will ignore the @code{Content-Length} header---as
if it never existed.

@cindex header, add
@item --header=@var{additional-header}
Define an @var{additional-header} to be passed to the @sc{http} servers.
Headers must contain a @samp{:} preceded by one or more non-blank
characters, and must not contain newlines.

You may define more than one additional header by specifying
@samp{--header} more than once.

@example
@group
wget --header='Accept-Charset: iso-8859-2' \
     --header='Accept-Language: hr'        \
       http://fly.cc.fer.hr/
@end group
@end example

Specification of an empty string as the header value will clear all
previous user-defined headers.

@cindex proxy user
@cindex proxy password
@cindex proxy authentication
@item --proxy-user=@var{user}
@itemx --proxy-passwd=@var{password}
Specify the username @var{user} and password @var{password} for
authentication on a proxy server.  Wget will encode them using the
@code{basic} authentication scheme.

@cindex http referer
@cindex referer, http
@item --referer=@var{url}
Include `Referer: @var{url}' header in HTTP request.  Useful for
retrieving documents with server-side processing that assume they are
always being retrieved by interactive web browsers and only come out
properly when Referer is set to one of the pages that point to them.

@cindex server response, save
@item -s
@itemx --save-headers
Save the headers sent by the @sc{http} server to the file, preceding the
actual contents, with an empty line as the separator.

@cindex user-agent
@item -U @var{agent-string}
@itemx --user-agent=@var{agent-string}
Identify as @var{agent-string} to the @sc{http} server.

The @sc{http} protocol allows the clients to identify themselves using a
@code{User-Agent} header field.  This enables distinguishing the
@sc{www} software, usually for statistical purposes or for tracing of
protocol violations.  Wget normally identifies as
@samp{Wget/@var{version}}, @var{version} being the current version
number of Wget.

However, some sites have been known to impose the policy of tailoring
the output according to the @code{User-Agent}-supplied information.
While conceptually this is not such a bad idea, it has been abused by
servers denying information to clients other than @code{Mozilla} or
Microsoft @code{Internet Explorer}.  This option allows you to change
the @code{User-Agent} line issued by Wget.  Use of this option is
discouraged, unless you really know what you are doing.

@strong{NOTE} that Netscape Communications Corp. has claimed that false
transmissions of @samp{Mozilla} as the @code{User-Agent} are a copyright
infringement, which will be prosecuted.  @strong{DO NOT} misrepresent
Wget as Mozilla.
@end table

@node FTP Options, Recursive Retrieval Options, HTTP Options, Invoking
@section FTP Options

@table @samp
@cindex retrieve symbolic links
@item --retr-symlinks
Retrieve symbolic links on @sc{ftp} sites as if they were plain files,
i.e. don't just create links locally.

@cindex globbing, toggle
@item -g on/off
@itemx --glob=on/off
Turn @sc{ftp} globbing on or off.  Globbing means you may use the
shell-like special characters (@dfn{wildcards}), like @samp{*},
@samp{?}, @samp{[} and @samp{]} to retrieve more than one file from the
same directory at once, like:

@example
wget ftp://gnjilux.cc.fer.hr/*.msg
@end example

By default, globbing will be turned on if the @sc{url} contains a
globbing character.  This option may be used to turn globbing on or off
permanently.

You may have to quote the @sc{url} to protect it from being expanded by
your shell.  Globbing makes Wget look for a directory listing, which is
system-specific.  This is why it currently works only with Unix @sc{ftp}
servers (and the ones emulating Unix @code{ls} output).

@cindex passive ftp
@item --passive-ftp
Use the @dfn{passive} @sc{ftp} retrieval scheme, in which the client
initiates the data connection.  This is sometimes required for @sc{ftp}
to work behind firewalls.
@end table

@node Recursive Retrieval Options, Recursive Accept/Reject Options, FTP Options, Invoking
@section Recursive Retrieval Options

@table @samp
@item -r
@itemx --recursive
Turn on recursive retrieving.  @xref{Recursive Retrieval} for more
details.

@item -l @var{depth}
@itemx --level=@var{depth}
Specify recursion maximum depth level @var{depth} (@xref{Recursive
Retrieval}).  The default maximum depth is 5.

@cindex proxy filling
@cindex delete after retrieval
@cindex filling proxy cache
@item --delete-after
This option tells Wget to delete every single file it downloads,
@emph{after} having done so.  It is useful for pre-fetching popular
pages through proxy, e.g.:

@example
wget -r -nd --delete-after http://whatever.com/~popular/page/
@end example

The @samp{-r} option is to retrieve recursively, and @samp{-nd} not to
create directories.

@cindex conversion of links
@cindex link conversion
@item -k
@itemx --convert-links
Convert the non-relative links to relative ones locally.  Only the
references to the documents actually downloaded will be converted; the
rest will be left unchanged.

Note that only at the end of the download can Wget know which links have
been downloaded.  Because of that, much of the work done by @samp{-k}
will be performed at the end of the downloads.

@cindex backing up converted files
@item -K
@itemx --backup-converted
When converting a file, back up the original version with a @samp{.orig}
suffix.  Affects the behavior of @samp{-N} (@xref{HTTP Time-Stamping
Internals}).

@item -m
@itemx --mirror
Turn on options suitable for mirroring.  This option turns on recursion
and time-stamping, sets infinite recursion depth and keeps @sc{ftp}
directory listings.  It is currently equivalent to
@samp{-r -N -l inf -nr}.

@item -nr
@itemx --dont-remove-listing
Don't remove the temporary @file{.listing} files generated by @sc{ftp}
retrievals.  Normally, these files contain the raw directory listings
received from @sc{ftp} servers.  Not removing them can be useful to
access the full remote file list when running a mirror, or for debugging
purposes.
@end table

@node Recursive Accept/Reject Options,  , Recursive Retrieval Options, Invoking
@section Recursive Accept/Reject Options

@table @samp
@item -A @var{acclist} --accept @var{acclist}
@itemx -R @var{rejlist} --reject @var{rejlist}
Specify comma-separated lists of file name suffixes or patterns to
accept or reject (@xref{Types of Files} for more details).

@item -D @var{domain-list}
@itemx --domains=@var{domain-list}
Set domains to be accepted and @sc{dns} looked-up, where
@var{domain-list} is a comma-separated list.  Note that it does
@emph{not} turn on @samp{-H}.  This option speeds things up, even if
only one host is spanned (@xref{Domain Acceptance}).

@item --exclude-domains @var{domain-list}
Exclude the domains given in a comma-separated @var{domain-list} from
@sc{dns}-lookup (@xref{Domain Acceptance}).

@cindex follow FTP links
@item --follow-ftp
Follow @sc{ftp} links from @sc{html} documents.  Without this option,
Wget will ignore all the @sc{ftp} links.

@cindex tag-based recursive pruning
@item --follow-tags=@var{list}
Wget has an internal table of HTML tag / attribute pairs that it
considers when looking for linked documents during a recursive
retrieval.  If a user wants only a subset of those tags to be
considered, however, he or she should be specify such tags in a
comma-separated @var{list} with this option.

@item -G @var{list}
@itemx --ignore-tags=@var{list}
This is the opposite of the @samp{--follow-tags} option.  To skip
certain HTML tags when recursively looking for documents to download,
specify them in a comma-separated @var{list}.  The author of this option
likes to use the following command to download a single HTML page and
all files (e.g. images, sounds, and stylesheets) necessary to display it
properly:

@example
wget -Ga,area -H -k -K -nh -r http://@var{site}/@var{document}
@end example

@item -H
@itemx --span-hosts
Enable spanning across hosts when doing recursive retrieving (@xref{All
Hosts}).

@item -L
@itemx --relative
Follow relative links only.  Useful for retrieving a specific home page
without any distractions, not even those from the same hosts
(@xref{Relative Links}).

@item -I @var{list}
@itemx --include-directories=@var{list}
Specify a comma-separated list of directories you wish to follow when
downloading (@xref{Directory-Based Limits} for more details.)  Elements
of @var{list} may contain wildcards.

@item -X @var{list}
@itemx --exclude-directories=@var{list}
Specify a comma-separated list of directories you wish to exclude from
download (@xref{Directory-Based Limits} for more details.)  Elements of
@var{list} may contain wildcards.

@item -nh
@itemx --no-host-lookup
Disable the time-consuming @sc{dns} lookup of almost all hosts
(@xref{Host Checking}).

@item -np
@item --no-parent
Do not ever ascend to the parent directory when retrieving recursively.
This is a useful option, since it guarantees that only the files
@emph{below} a certain hierarchy will be downloaded.
@xref{Directory-Based Limits} for more details.
@end table

@node Recursive Retrieval, Following Links, Invoking, Top
@chapter Recursive Retrieval
@cindex recursion
@cindex retrieving
@cindex recursive retrieval

GNU Wget is capable of traversing parts of the Web (or a single
@sc{http} or @sc{ftp} server), depth-first following links and directory
structure.  This is called @dfn{recursive} retrieving, or
@dfn{recursion}.

With @sc{http} @sc{url}s, Wget retrieves and parses the @sc{html} from
the given @sc{url}, documents, retrieving the files the @sc{html}
document was referring to, through markups like @code{href}, or
@code{src}.  If the freshly downloaded file is also of type
@code{text/html}, it will be parsed and followed further.

The maximum @dfn{depth} to which the retrieval may descend is specified
with the @samp{-l} option (the default maximum depth is five layers).
@xref{Recursive Retrieval}.

When retrieving an @sc{ftp} @sc{url} recursively, Wget will retrieve all
the data from the given directory tree (including the subdirectories up
to the specified depth) on the remote server, creating its mirror image
locally.  @sc{ftp} retrieval is also limited by the @code{depth}
parameter.

By default, Wget will create a local directory tree, corresponding to
the one found on the remote server.

Recursive retrieving can find a number of applications, the most
important of which is mirroring.  It is also useful for @sc{www}
presentations, and any other opportunities where slow network
connections should be bypassed by storing the files locally.

You should be warned that invoking recursion may cause grave overloading
on your system, because of the fast exchange of data through the
network; all of this may hamper other users' work.  The same stands for
the foreign server you are mirroring---the more requests it gets in a
rows, the greater is its load.

Careless retrieving can also fill your file system uncontrollably, which
can grind the machine to a halt.

The load can be minimized by lowering the maximum recursion level
(@samp{-l}) and/or by lowering the number of retries (@samp{-t}).  You
may also consider using the @samp{-w} option to slow down your requests
to the remote servers, as well as the numerous options to narrow the
number of followed links (@xref{Following Links}).

Recursive retrieval is a good thing when used properly.  Please take all
precautions not to wreak havoc through carelessness.

@node Following Links, Time-Stamping, Recursive Retrieval, Top
@chapter Following Links
@cindex links
@cindex following links

When retrieving recursively, one does not wish to retrieve loads of
unnecessary data.  Most of the time the users bear in mind exactly what
they want to download, and want Wget to follow only specific links.

For example, if you wish to download the music archive from
@samp{fly.cc.fer.hr}, you will not want to download all the home pages
that happen to be referenced by an obscure part of the archive.

Wget possesses several mechanisms that allows you to fine-tune which
links it will follow.

@menu
* Relative Links::         Follow relative links only.
* Host Checking::          Follow links on the same host.
* Domain Acceptance::      Check on a list of domains.
* All Hosts::              No host restrictions.
* Types of Files::         Getting only certain files.
* Directory-Based Limits:: Getting only certain directories.
* FTP Links::              Following FTP links.
@end menu

@node Relative Links, Host Checking, Following Links, Following Links
@section Relative Links
@cindex relative links

When only relative links are followed (option @samp{-L}), recursive
retrieving will never span hosts.  No time-expensive @sc{dns}-lookups
will be performed, and the process will be very fast, with the minimum
strain of the network.  This will suit your needs often, especially when
mirroring the output of various @code{x2html} converters, since they
generally output relative links.

@node Host Checking, Domain Acceptance, Relative Links, Following Links
@section Host Checking
@cindex DNS lookup
@cindex host lookup
@cindex host checking

The drawback of following the relative links solely is that humans often
tend to mix them with absolute links to the very same host, and the very
same page.  In this mode (which is the default mode for following links)
all @sc{url}s that refer to the same host will be retrieved.

The problem with this option are the aliases of the hosts and domains.
Thus there is no way for Wget to know that @samp{regoc.srce.hr} and
@samp{www.srce.hr} are the same host, or that @samp{fly.cc.fer.hr} is
the same as @samp{fly.cc.etf.hr}.  Whenever an absolute link is
encountered, the host is @sc{dns}-looked-up with @code{gethostbyname} to
check whether we are maybe dealing with the same hosts.  Although the
results of @code{gethostbyname} are cached, it is still a great
slowdown, e.g. when dealing with large indices of home pages on different
hosts (because each of the hosts must be @sc{dns}-resolved to see
whether it just @emph{might} be an alias of the starting host).

To avoid the overhead you may use @samp{-nh}, which will turn off
@sc{dns}-resolving and make Wget compare hosts literally.  This will
make things run much faster, but also much less reliable
(e.g. @samp{www.srce.hr} and @samp{regoc.srce.hr} will be flagged as
different hosts).

Note that modern @sc{http} servers allow one IP address to host several
@dfn{virtual servers}, each having its own directory hierarchy.  Such
``servers'' are distinguished by their hostnames (all of which point to
the same IP address); for this to work, a client must send a @code{Host}
header, which is what Wget does.  However, in that case Wget @emph{must
not} try to divine a host's ``real'' address, nor try to use the same
hostname for each access, i.e. @samp{-nh} must be turned on.

In other words, the @samp{-nh} option must be used to enable the
retrieval from virtual servers distinguished by their hostnames.  As the
number of such server setups grow, the behavior of @samp{-nh} may become
the default in the future.

@node Domain Acceptance, All Hosts, Host Checking, Following Links
@section Domain Acceptance

With the @samp{-D} option you may specify the domains that will be
followed.  The hosts the domain of which is not in this list will not be
@sc{dns}-resolved.  Thus you can specify @samp{-Dmit.edu} just to make
sure that @strong{nothing outside of @sc{mit} gets looked up}.  This is
very important and useful.  It also means that @samp{-D} does @emph{not}
imply @samp{-H} (span all hosts), which must be specified explicitly.
Feel free to use this options since it will speed things up, with almost
all the reliability of checking for all hosts.  Thus you could invoke

@example
wget -r -D.hr http://fly.cc.fer.hr/
@end example

to make sure that only the hosts in @samp{.hr} domain get
@sc{dns}-looked-up for being equal to @samp{fly.cc.fer.hr}.  So
@samp{fly.cc.etf.hr} will be checked (only once!) and found equal, but
@samp{www.gnu.ai.mit.edu} will not even be checked.

Of course, domain acceptance can be used to limit the retrieval to
particular domains with spanning of hosts in them, but then you must
specify @samp{-H} explicitly.  E.g.:

@example
wget -r -H -Dmit.edu,stanford.edu http://www.mit.edu/
@end example

will start with @samp{http://www.mit.edu/}, following links across
@sc{mit} and Stanford.

If there are domains you want to exclude specifically, you can do it
with @samp{--exclude-domains}, which accepts the same type of arguments
of @samp{-D}, but will @emph{exclude} all the listed domains.  For
example, if you want to download all the hosts from @samp{foo.edu}
domain, with the exception of @samp{sunsite.foo.edu}, you can do it like
this:

@example
wget -rH -Dfoo.edu --exclude-domains sunsite.foo.edu http://www.foo.edu/
@end example

@node All Hosts, Types of Files, Domain Acceptance, Following Links
@section All Hosts
@cindex all hosts
@cindex span hosts

When @samp{-H} is specified without @samp{-D}, all hosts are freely
spanned.  There are no restrictions whatsoever as to what part of the
net Wget will go to fetch documents, other than maximum retrieval depth.
If a page references @samp{www.yahoo.com}, so be it.  Such an option is
rarely useful for itself.

@node Types of Files, Directory-Based Limits, All Hosts, Following Links
@section Types of Files
@cindex types of files

When downloading material from the web, you will often want to restrict
the retrieval to only certain file types.  For example, if you are
interested in downloading @sc{gif}s, you will not be overjoyed to get
loads of PostScript documents, and vice versa.

Wget offers two options to deal with this problem.  Each option
description lists a short name, a long name, and the equivalent command
in @file{.wgetrc}.

@cindex accept wildcards
@cindex accept suffixes
@cindex wildcards, accept
@cindex suffixes, accept
@table @samp
@item -A @var{acclist}
@itemx --accept @var{acclist}
@itemx accept = @var{acclist}
The argument to @samp{--accept} option is a list of file suffixes or
patterns that Wget will download during recursive retrieval.  A suffix
is the ending part of a file, and consists of ``normal'' letters,
e.g. @samp{gif} or @samp{.jpg}.  A matching pattern contains shell-like
wildcards, e.g. @samp{books*} or @samp{zelazny*196[0-9]*}.

So, specifying @samp{wget -A gif,jpg} will make Wget download only the
files ending with @samp{gif} or @samp{jpg}, i.e. @sc{gif}s and
@sc{jpeg}s.  On the other hand, @samp{wget -A "zelazny*196[0-9]*"} will
download only files beginning with @samp{zelazny} and containing numbers
from 1960 to 1969 anywhere within.  Look up the manual of your shell for
a description of how pattern matching works.

Of course, any number of suffixes and patterns can be combined into a
comma-separated list, and given as an argument to @samp{-A}.

@cindex reject wildcards
@cindex reject suffixes
@cindex wildcards, reject
@cindex suffixes, reject
@item -R @var{rejlist}
@itemx --reject @var{rejlist}
@itemx reject = @var{rejlist}
The @samp{--reject} option works the same way as @samp{--accept}, only
its logic is the reverse; Wget will download all files @emph{except} the
ones matching the suffixes (or patterns) in the list.

So, if you want to download a whole page except for the cumbersome
@sc{mpeg}s and @sc{.au} files, you can use @samp{wget -R mpg,mpeg,au}.
Analogously, to download all files except the ones beginning with
@samp{bjork}, use @samp{wget -R "bjork*"}.  The quotes are to prevent
expansion by the shell.
@end table

The @samp{-A} and @samp{-R} options may be combined to achieve even
better fine-tuning of which files to retrieve.  E.g. @samp{wget -A
"*zelazny*" -R .ps} will download all the files having @samp{zelazny} as
a part of their name, but @emph{not} the PostScript files.

Note that these two options do not affect the downloading of @sc{html}
files; Wget must load all the @sc{html}s to know where to go at
all---recursive retrieval would make no sense otherwise.

@node Directory-Based Limits, FTP Links, Types of Files, Following Links
@section Directory-Based Limits
@cindex directories
@cindex directory limits

Regardless of other link-following facilities, it is often useful to
place the restriction of what files to retrieve based on the directories
those files are placed in.  There can be many reasons for this---the
home pages may be organized in a reasonable directory structure; or some
directories may contain useless information, e.g. @file{/cgi-bin} or
@file{/dev} directories.

Wget offers three different options to deal with this requirement.  Each
option description lists a short name, a long name, and the equivalent
command in @file{.wgetrc}.

@cindex directories, include
@cindex include directories
@cindex accept directories
@table @samp
@item -I @var{list}
@itemx --include @var{list}
@itemx include_directories = @var{list}
@samp{-I} option accepts a comma-separated list of directories included
in the retrieval.  Any other directories will simply be ignored.  The
directories are absolute paths.

So, if you wish to download from @samp{http://host/people/bozo/}
following only links to bozo's colleagues in the @file{/people}
directory and the bogus scripts in @file{/cgi-bin}, you can specify:

@example
wget -I /people,/cgi-bin http://host/people/bozo/
@end example

@cindex directories, exclude
@cindex exclude directories
@cindex reject directories
@item -X @var{list}
@itemx --exclude @var{list}
@itemx exclude_directories = @var{list}
@samp{-X} option is exactly the reverse of @samp{-I}---this is a list of
directories @emph{excluded} from the download.  E.g. if you do not want
Wget to download things from @file{/cgi-bin} directory, specify @samp{-X
/cgi-bin} on the command line.

The same as with @samp{-A}/@samp{-R}, these two options can be combined
to get a better fine-tuning of downloading subdirectories.  E.g. if you
want to load all the files from @file{/pub} hierarchy except for
@file{/pub/worthless}, specify @samp{-I/pub -X/pub/worthless}.

@cindex no parent
@item -np
@itemx --no-parent
@itemx no_parent = on
The simplest, and often very useful way of limiting directories is
disallowing retrieval of the links that refer to the hierarchy
@dfn{above} than the beginning directory, i.e. disallowing ascent to the
parent directory/directories.

The @samp{--no-parent} option (short @samp{-np}) is useful in this case.
Using it guarantees that you will never leave the existing hierarchy.
Supposing you issue Wget with:

@example
wget -r --no-parent http://somehost/~luzer/my-archive/
@end example

You may rest assured that none of the references to
@file{/~his-girls-homepage/} or @file{/~luzer/all-my-mpegs/} will be
followed.  Only the archive you are interested in will be downloaded.
Essentially, @samp{--no-parent} is similar to
@samp{-I/~luzer/my-archive}, only it handles redirections in a more
intelligent fashion.
@end table

@node FTP Links,  , Directory-Based Limits, Following Links
@section Following FTP Links
@cindex following ftp links

The rules for @sc{ftp} are somewhat specific, as it is necessary for
them to be.  @sc{ftp} links in @sc{html} documents are often included
for purposes of reference, and it is often inconvenient to download them
by default.

To have @sc{ftp} links followed from @sc{html} documents, you need to
specify the @samp{--follow-ftp} option.  Having done that, @sc{ftp}
links will span hosts regardless of @samp{-H} setting.  This is logical,
as @sc{ftp} links rarely point to the same host where the @sc{http}
server resides.  For similar reasons, the @samp{-L} options has no
effect on such downloads.  On the other hand, domain acceptance
(@samp{-D}) and suffix rules (@samp{-A} and @samp{-R}) apply normally.

Also note that followed links to @sc{ftp} directories will not be
retrieved recursively further.

@node Time-Stamping, Startup File, Following Links, Top
@chapter Time-Stamping
@cindex time-stamping
@cindex timestamping
@cindex updating the archives
@cindex incremental updating

One of the most important aspects of mirroring information from the
Internet is updating your archives.

Downloading the whole archive again and again, just to replace a few
changed files is expensive, both in terms of wasted bandwidth and money,
and the time to do the update.  This is why all the mirroring tools
offer the option of incremental updating.

Such an updating mechanism means that the remote server is scanned in
search of @dfn{new} files.  Only those new files will be downloaded in
the place of the old ones.

A file is considered new if one of these two conditions are met:

@enumerate
@item
A file of that name does not already exist locally.

@item
A file of that name does exist, but the remote file was modified more
recently than the local file.
@end enumerate

To implement this, the program needs to be aware of the time of last
modification of both remote and local files.  Such information are
called the @dfn{time-stamps}.

The time-stamping in GNU Wget is turned on using @samp{--timestamping}
(@samp{-N}) option, or through @code{timestamping = on} directive in
@file{.wgetrc}.  With this option, for each file it intends to download,
Wget will check whether a local file of the same name exists.  If it
does, and the remote file is older, Wget will not download it.

If the local file does not exist, or the sizes of the files do not
match, Wget will download the remote file no matter what the time-stamps
say.

@menu
* Time-Stamping Usage::
* HTTP Time-Stamping Internals::
* FTP Time-Stamping Internals::
@end menu

@node Time-Stamping Usage, HTTP Time-Stamping Internals, Time-Stamping, Time-Stamping
@section Time-Stamping Usage
@cindex time-stamping usage
@cindex usage, time-stamping

The usage of time-stamping is simple.  Say you would like to download a
file so that it keeps its date of modification.

@example
wget -S http://www.gnu.ai.mit.edu/
@end example

A simple @code{ls -l} shows that the time stamp on the local file equals
the state of the @code{Last-Modified} header, as returned by the server.
As you can see, the time-stamping info is preserved locally, even
without @samp{-N}.

Several days later, you would like Wget to check if the remote file has
changed, and download it if it has.

@example
wget -N http://www.gnu.ai.mit.edu/
@end example

Wget will ask the server for the last-modified date.  If the local file
is newer, the remote file will not be re-fetched.  However, if the remote
file is more recent, Wget will proceed fetching it normally.

The same goes for @sc{ftp}.  For example:

@example
wget ftp://ftp.ifi.uio.no/pub/emacs/gnus/*
@end example

@code{ls} will show that the timestamps are set according to the state
on the remote server.  Reissuing the command with @samp{-N} will make
Wget re-fetch @emph{only} the files that have been modified.

In both @sc{http} and @sc{ftp} retrieval Wget will time-stamp the local
file correctly (with or without @samp{-N}) if it gets the stamps,
i.e. gets the directory listing for @sc{ftp} or the @code{Last-Modified}
header for @sc{http}.

If you wished to mirror the GNU archive every week, you would use the
following command every week:

@example
wget --timestamping -r ftp://prep.ai.mit.edu/pub/gnu/
@end example

@node HTTP Time-Stamping Internals, FTP Time-Stamping Internals, Time-Stamping Usage, Time-Stamping
@section HTTP Time-Stamping Internals
@cindex http time-stamping

Time-stamping in @sc{http} is implemented by checking of the
@code{Last-Modified} header.  If you wish to retrieve the file
@file{foo.html} through @sc{http}, Wget will check whether
@file{foo.html} exists locally.  If it doesn't, @file{foo.html} will be
retrieved unconditionally.

If the file does exist locally, Wget will first check its local
time-stamp (similar to the way @code{ls -l} checks it), and then send a
@code{HEAD} request to the remote server, demanding the information on
the remote file.

The @code{Last-Modified} header is examined to find which file was
modified more recently (which makes it ``newer'').  If the remote file
is newer, it will be downloaded; if it is older, Wget will give
up.@footnote{As an additional check, Wget will look at the
@code{Content-Length} header, and compare the sizes; if they are not the
same, the remote file will be downloaded no matter what the time-stamp
says.}

When @samp{--backup-converted} (@samp{-K}) is specified in conjunction
with @samp{-N}, server file @samp{@var{X}} is compared to local file
@samp{@var{X}.orig}, if extant, rather than being compared to local file
@samp{@var{X}}, which will always differ if it's been converted by
@samp{--convert-links} (@samp{-k}).

Arguably, @sc{http} time-stamping should be implemented using the
@code{If-Modified-Since} request.

@node FTP Time-Stamping Internals,  , HTTP Time-Stamping Internals, Time-Stamping
@section FTP Time-Stamping Internals
@cindex ftp time-stamping

In theory, @sc{ftp} time-stamping works much the same as @sc{http}, only
@sc{ftp} has no headers---time-stamps must be received from the
directory listings.

For each directory files must be retrieved from, Wget will use the
@code{LIST} command to get the listing.  It will try to analyze the
listing, assuming that it is a Unix @code{ls -l} listing, and extract
the time-stamps.  The rest is exactly the same as for @sc{http}.

Assumption that every directory listing is a Unix-style listing may
sound extremely constraining, but in practice it is not, as many
non-Unix @sc{ftp} servers use the Unixoid listing format because most
(all?) of the clients understand it.  Bear in mind that @sc{rfc959}
defines no standard way to get a file list, let alone the time-stamps.
We can only hope that a future standard will define this.

Another non-standard solution includes the use of @code{MDTM} command
that is supported by some @sc{ftp} servers (including the popular
@code{wu-ftpd}), which returns the exact time of the specified file.
Wget may support this command in the future.

@node Startup File, Examples, Time-Stamping, Top
@chapter Startup File
@cindex startup file
@cindex wgetrc
@cindex .wgetrc
@cindex startup
@cindex .netrc

Once you know how to change default settings of Wget through command
line arguments, you may wish to make some of those settings permanent.
You can do that in a convenient way by creating the Wget startup
file---@file{.wgetrc}.

Besides @file{.wgetrc} is the ``main'' initialization file, it is
convenient to have a special facility for storing passwords.  Thus Wget
reads and interprets the contents of @file{$HOME/.netrc}, if it finds
it.  You can find @file{.netrc} format in your system manuals.

Wget reads @file{.wgetrc} upon startup, recognizing a limited set of
commands.

@menu
* Wgetrc Location::   Location of various wgetrc files.
* Wgetrc Syntax::     Syntax of wgetrc.
* Wgetrc Commands::   List of available commands.
* Sample Wgetrc::     A wgetrc example.
@end menu

@node Wgetrc Location, Wgetrc Syntax, Startup File, Startup File
@section Wgetrc Location
@cindex wgetrc location
@cindex location of wgetrc

When initializing, Wget will look for a @dfn{global} startup file,
@file{/usr/local/etc/wgetrc} by default (or some prefix other than
@file{/usr/local}, if Wget was not installed there) and read commands
from there, if it exists.

Then it will look for the user's file.  If the environmental variable
@code{WGETRC} is set, Wget will try to load that file.  Failing that, no
further attempts will be made.

If @code{WGETRC} is not set, Wget will try to load @file{$HOME/.wgetrc}.

The fact that user's settings are loaded after the system-wide ones
means that in case of collision user's wgetrc @emph{overrides} the
system-wide wgetrc (in @file{/usr/local/etc/wgetrc} by default).
Fascist admins, away!

@node Wgetrc Syntax, Wgetrc Commands, Wgetrc Location, Startup File
@section Wgetrc Syntax
@cindex wgetrc syntax
@cindex syntax of wgetrc

The syntax of a wgetrc command is simple:

@example
variable = value
@end example

The @dfn{variable} will also be called @dfn{command}.  Valid
@dfn{values} are different for different commands.

The commands are case-insensitive and underscore-insensitive.  Thus
@samp{DIr__PrefiX} is the same as @samp{dirprefix}.  Empty lines, lines
beginning with @samp{#} and lines containing white-space only are
discarded.

Commands that expect a comma-separated list will clear the list on an
empty command.  So, if you wish to reset the rejection list specified in
global @file{wgetrc}, you can do it with:

@example
reject =
@end example

@node Wgetrc Commands, Sample Wgetrc, Wgetrc Syntax, Startup File
@section Wgetrc Commands
@cindex wgetrc commands

The complete set of commands is listed below, the letter after @samp{=}
denoting the value the command takes. It is @samp{on/off} for @samp{on}
or @samp{off} (which can also be @samp{1} or @samp{0}), @var{string} for
any non-empty string or @var{n} for a positive integer.  For example,
you may specify @samp{use_proxy = off} to disable use of proxy servers
by default. You may use @samp{inf} for infinite values, where
appropriate.

Most of the commands have their equivalent command-line option
(@xref{Invoking}), except some more obscure or rarely used ones.

@table @asis
@item accept/reject = @var{string}
Same as @samp{-A}/@samp{-R} (@xref{Types of Files}).

@item add_hostdir = on/off
Enable/disable host-prefixed file names.  @samp{-nH} disables it.

@item continue = on/off
Enable/disable continuation of the retrieval, the same as @samp{-c}
(which enables it).

@item background = on/off
Enable/disable going to background, the same as @samp{-b} (which enables
it).

@item backup_converted = on/off
Enable/disable saving pre-converted files with the suffix @samp{.orig}
-- the same as @samp{-K} (which enables it).

@c @item backups = @var{number}
@c #### Document me!
@item base = @var{string}
Set base for relative @sc{url}s, the same as @samp{-B}.

@item cache = on/off
When set to off, disallow server-caching.  See the @samp{-C} option.

@item convert links = on/off
Convert non-relative links locally.  The same as @samp{-k}.

@item cut_dirs = @var{n}
Ignore @var{n} remote directory components.

@item debug = on/off
Debug mode, same as @samp{-d}.

@item delete_after = on/off
Delete after download, the same as @samp{--delete-after}.

@item dir_prefix = @var{string}
Top of directory tree, the same as @samp{-P}.

@item dirstruct = on/off
Turning dirstruct on or off, the same as @samp{-x} or @samp{-nd},
respectively.

@item domains = @var{string}
Same as @samp{-D} (@xref{Domain Acceptance}).

@item dot_bytes = @var{n}
Specify the number of bytes ``contained'' in a dot, as seen throughout
the retrieval (1024 by default).  You can postfix the value with
@samp{k} or @samp{m}, representing kilobytes and megabytes,
respectively.  With dot settings you can tailor the dot retrieval to
suit your needs, or you can use the predefined @dfn{styles}
(@xref{Download Options}).

@item dots_in_line = @var{n}
Specify the number of dots that will be printed in each line throughout
the retrieval (50 by default).

@item dot_spacing = @var{n}
Specify the number of dots in a single cluster (10 by default).

@item dot_style = @var{string}
Specify the dot retrieval @dfn{style}, as with @samp{--dot-style}.

@item exclude_directories = @var{string}
Specify a comma-separated list of directories you wish to exclude from
download, the same as @samp{-X} (@xref{Directory-Based Limits}).

@item exclude_domains = @var{string}
Same as @samp{--exclude-domains} (@xref{Domain Acceptance}).

@item follow_ftp = on/off
Follow @sc{ftp} links from @sc{html} documents, the same as @samp{-f}.

@item follow_tags = @var{string}
Only follow certain HTML tags when doing a recursive retrieval, just like
@samp{--follow-tags}. 

@item force_html = on/off
If set to on, force the input filename to be regarded as an @sc{html}
document, the same as @samp{-F}.

@item ftp_proxy = @var{string}
Use @var{string} as @sc{ftp} proxy, instead of the one specified in
environment.

@item glob = on/off
Turn globbing on/off, the same as @samp{-g}.

@item header = @var{string}
Define an additional header, like @samp{--header}.

@item http_passwd = @var{string}
Set @sc{http} password.

@item http_proxy = @var{string}
Use @var{string} as @sc{http} proxy, instead of the one specified in
environment.

@item http_user = @var{string}
Set @sc{http} user to @var{string}.

@item ignore_length = on/off
When set to on, ignore @code{Content-Length} header; the same as
@samp{--ignore-length}.

@item ignore_tags = @var{string}
Ignore certain HTML tags when doing a recursive retrieval, just like
@samp{-G} / @samp{--ignore-tags}. 

@item include_directories = @var{string}
Specify a comma-separated list of directories you wish to follow when
downloading, the same as @samp{-I}.

@item input = @var{string}
Read the @sc{url}s from @var{string}, like @samp{-i}.

@item kill_longer = on/off
Consider data longer than specified in content-length header
as invalid (and retry getting it). The default behaviour is to save
as much data as there is, provided there is more than or equal
to the value in @code{Content-Length}.

@item logfile = @var{string}
Set logfile, the same as @samp{-o}.

@item login = @var{string}
Your user name on the remote machine, for @sc{ftp}.  Defaults to
@samp{anonymous}.

@item mirror = on/off
Turn mirroring on/off.  The same as @samp{-m}.

@item netrc = on/off
Turn reading netrc on or off.

@item noclobber = on/off
Same as @samp{-nc}.

@item no_parent = on/off
Disallow retrieving outside the directory hierarchy, like
@samp{--no-parent} (@xref{Directory-Based Limits}).

@item no_proxy = @var{string}
Use @var{string} as the comma-separated list of domains to avoid in
proxy loading, instead of the one specified in environment.

@item output_document = @var{string}
Set the output filename, the same as @samp{-O}.

@item passive_ftp = on/off
Set passive @sc{ftp}, the same as @samp{--passive-ftp}.

@item passwd = @var{string}
Set your @sc{ftp} password to @var{password}.  Without this setting, the
password defaults to @samp{username@@hostname.domainname}.

@item proxy_user = @var{string}
Set proxy authentication user name to @var{string}, like
@samp{--proxy-user}.

@item proxy_passwd = @var{string}
Set proxy authentication password to @var{string}, like
@samp{--proxy-passwd}.

@item quiet = on/off
Quiet mode, the same as @samp{-q}.

@item quota = @var{quota}
Specify the download quota, which is useful to put in the global
@file{wgetrc}. When download quota is specified, Wget will stop retrieving
after the download sum has become greater than quota.  The quota can be
specified in bytes (default), kbytes @samp{k} appended) or mbytes
(@samp{m} appended).  Thus @samp{quota = 5m} will set the quota to 5
mbytes. Note that the user's startup file overrides system settings.

@item reclevel = @var{n}
Recursion level, the same as @samp{-l}.

@item recursive = on/off
Recursive on/off, the same as @samp{-r}.

@item relative_only = on/off
Follow only relative links, the same as @samp{-L} (@xref{Relative
Links}).

@item remove_listing = on/off
If set to on, remove @sc{ftp} listings downloaded by Wget.  Setting it
to off is the same as @samp{-nr}.

@item retr_symlinks = on/off
When set to on, retrieve symbolic links as if they were plain files; the
same as @samp{--retr-symlinks}.

@item robots = on/off
Use (or not) @file{/robots.txt} file (@xref{Robots}).  Be sure to know
what you are doing before changing the default (which is @samp{on}).

@item server_response = on/off
Choose whether or not to print the @sc{http} and @sc{ftp} server
responses, the same as @samp{-S}.

@item simple_host_check = on/off
Same as @samp{-nh} (@xref{Host Checking}).

@item span_hosts = on/off
Same as @samp{-H}.

@item timeout = @var{n}
Set timeout value, the same as @samp{-T}.

@item timestamping = on/off
Turn timestamping on/off. The same as @samp{-N} (@xref{Time-Stamping}).

@item tries = @var{n}
Set number of retries per @sc{url}, the same as @samp{-t}.

@item use_proxy = on/off
Turn proxy support on/off. The same as @samp{-Y}.

@item verbose = on/off
Turn verbose on/off, the same as @samp{-v}/@samp{-nv}.

@item wait = @var{n}
Wait @var{n} seconds between retrievals, the same as @samp{-w}.

@item waitretry = @var{n}
Wait up to @var{n} seconds between retries of failed retrievals only --
the same as @samp{--waitretry}.  Note that this is turned on by default
in the global @file{wgetrc}.
@end table

@node Sample Wgetrc,  , Wgetrc Commands, Startup File
@section Sample Wgetrc
@cindex sample wgetrc

This is the sample initialization file, as given in the distribution.
It is divided in two section---one for global usage (suitable for global
startup file), and one for local usage (suitable for
@file{$HOME/.wgetrc}).  Be careful about the things you change.

Note that almost all the lines are commented out.  For a command to have
any effect, you must remove the @samp{#} character at the beginning of
its line.

@example
@include sample.wgetrc.munged_for_texi_inclusion
@end example

@node Examples, Various, Startup File, Top
@chapter Examples
@cindex examples

The examples are classified into three sections, because of clarity.
The first section is a tutorial for beginners.  The second section
explains some of the more complex program features.  The third section
contains advice for mirror administrators, as well as even more complex
features (that some would call perverted).

@menu
* Simple Usage::        Simple, basic usage of the program.
* Advanced Usage::      Advanced techniques of usage.
* Guru Usage::          Mirroring and the hairy stuff.
@end menu

@node Simple Usage, Advanced Usage, Examples, Examples
@section Simple Usage

@itemize @bullet
@item
Say you want to download a @sc{url}.  Just type:

@example
wget http://fly.cc.fer.hr/
@end example

The response will be something like:

@example
@group
--13:30:45--  http://fly.cc.fer.hr:80/en/
           => `index.html'
Connecting to fly.cc.fer.hr:80... connected!
HTTP request sent, awaiting response... 200 OK
Length: 4,694 [text/html]

    0K -> ....                                                   [100%]

13:30:46 (23.75 KB/s) - `index.html' saved [4694/4694]
@end group
@end example

@item
But what will happen if the connection is slow, and the file is lengthy?
The connection will probably fail before the whole file is retrieved,
more than once.  In this case, Wget will try getting the file until it
either gets the whole of it, or exceeds the default number of retries
(this being 20).  It is easy to change the number of tries to 45, to
insure that the whole file will arrive safely:

@example
wget --tries=45 http://fly.cc.fer.hr/jpg/flyweb.jpg
@end example

@item
Now let's leave Wget to work in the background, and write its progress
to log file @file{log}.  It is tiring to type @samp{--tries}, so we
shall use @samp{-t}.

@example
wget -t 45 -o log http://fly.cc.fer.hr/jpg/flyweb.jpg &
@end example

The ampersand at the end of the line makes sure that Wget works in the
background.  To unlimit the number of retries, use @samp{-t inf}.

@item
The usage of @sc{ftp} is as simple.  Wget will take care of login and
password.

@example
@group
$ wget ftp://gnjilux.cc.fer.hr/welcome.msg
--10:08:47--  ftp://gnjilux.cc.fer.hr:21/welcome.msg
           => `welcome.msg'
Connecting to gnjilux.cc.fer.hr:21... connected!
Logging in as anonymous ... Logged in!
==> TYPE I ... done.  ==> CWD not needed.
==> PORT ... done.    ==> RETR welcome.msg ... done.
Length: 1,340 (unauthoritative)

    0K -> .                                                      [100%]

10:08:48 (1.28 MB/s) - `welcome.msg' saved [1340]
@end group
@end example

@item
If you specify a directory, Wget will retrieve the directory listing,
parse it and convert it to @sc{html}.  Try:

@example
wget ftp://prep.ai.mit.edu/pub/gnu/
lynx index.html
@end example
@end itemize

@node Advanced Usage, Guru Usage, Simple Usage, Examples
@section Advanced Usage

@itemize @bullet
@item
You would like to read the list of @sc{url}s from a file?  Not a problem
with that:

@example
wget -i file
@end example

If you specify @samp{-} as file name, the @sc{url}s will be read from
standard input.

@item
Create a mirror image of GNU @sc{www} site (with the same directory structure
the original has) with only one try per document, saving the log of the
activities to @file{gnulog}:

@example
wget -r -t1 http://www.gnu.ai.mit.edu/ -o gnulog
@end example

@item
Retrieve the first layer of yahoo links:

@example
wget -r -l1 http://www.yahoo.com/
@end example

@item
Retrieve the index.html of @samp{www.lycos.com}, showing the original
server headers:

@example
wget -S http://www.lycos.com/
@end example

@item
Save the server headers with the file:
@example
wget -s http://www.lycos.com/
more index.html
@end example

@item
Retrieve the first two levels of @samp{wuarchive.wustl.edu}, saving them
to /tmp.

@example
wget -P/tmp -l2 ftp://wuarchive.wustl.edu/
@end example

@item
You want to download all the @sc{gif}s from an @sc{http} directory.
@samp{wget http://host/dir/*.gif} doesn't work, since @sc{http}
retrieval does not support globbing.  In that case, use:

@example
wget -r -l1 --no-parent -A.gif http://host/dir/
@end example

It is a bit of a kludge, but it works.  @samp{-r -l1} means to retrieve
recursively (@xref{Recursive Retrieval}), with maximum depth of 1.
@samp{--no-parent} means that references to the parent directory are
ignored (@xref{Directory-Based Limits}), and @samp{-A.gif} means to
download only the @sc{gif} files.  @samp{-A "*.gif"} would have worked
too.

@item
Suppose you were in the middle of downloading, when Wget was
interrupted.  Now you do not want to clobber the files already present.
It would be:

@example
wget -nc -r http://www.gnu.ai.mit.edu/
@end example

@item
If you want to encode your own username and password to @sc{http} or
@sc{ftp}, use the appropriate @sc{url} syntax (@xref{URL Format}).

@example
wget ftp://hniksic:mypassword@@jagor.srce.hr/.emacs
@end example

@item
If you do not like the default retrieval visualization (1K dots with 10
dots per cluster and 50 dots per line), you can customize it through dot
settings (@xref{Wgetrc Commands}).  For example, many people like the
``binary'' style of retrieval, with 8K dots and 512K lines:

@example
wget --dot-style=binary ftp://prep.ai.mit.edu/pub/gnu/README
@end example

You can experiment with other styles, like:

@example
wget --dot-style=mega ftp://ftp.xemacs.org/pub/xemacs/xemacs-20.4/xemacs-20.4.tar.gz
wget --dot-style=micro http://fly.cc.fer.hr/
@end example

To make these settings permanent, put them in your @file{.wgetrc}, as
described before (@xref{Sample Wgetrc}).
@end itemize

@node Guru Usage,  , Advanced Usage, Examples
@section Guru Usage

@cindex mirroring
@itemize @bullet
@item
If you wish Wget to keep a mirror of a page (or @sc{ftp}
subdirectories), use @samp{--mirror} (@samp{-m}), which is the shorthand
for @samp{-r -N}.  You can put Wget in the crontab file asking it to
recheck a site each Sunday:

@example
crontab
0 0 * * 0 wget --mirror ftp://ftp.xemacs.org/pub/xemacs/ -o /home/me/weeklog
@end example

@item
You may wish to do the same with someone's home page.  But you do not
want to download all those images---you're only interested in @sc{html}.

@example
wget --mirror -A.html http://www.w3.org/
@end example

@item
But what about mirroring the hosts networkologically close to you?  It
seems so awfully slow because of all that @sc{dns} resolving.  Just use
@samp{-D} (@xref{Domain Acceptance}).

@example
wget -rN -Dsrce.hr http://www.srce.hr/
@end example

Now Wget will correctly find out that @samp{regoc.srce.hr} is the same
as @samp{www.srce.hr}, but will not even take into consideration the
link to @samp{www.mit.edu}.

@item
You have a presentation and would like the dumb absolute links to be
converted to relative?  Use @samp{-k}:

@example
wget -k -r @var{URL}
@end example

@cindex redirecting output
@item
You would like the output documents to go to standard output instead of
to files?  OK, but Wget will automatically shut up (turn on
@samp{--quiet}) to prevent mixing of Wget output and the retrieved
documents.

@example
wget -O - http://jagor.srce.hr/ http://www.srce.hr/
@end example

You can also combine the two options and make weird pipelines to
retrieve the documents from remote hotlists:

@example
wget -O - http://cool.list.com/ | wget --force-html -i -
@end example
@end itemize

@node Various, Appendices, Examples, Top
@chapter Various
@cindex various

This chapter contains all the stuff that could not fit anywhere else.

@menu
* Proxies::             Support for proxy servers
* Distribution::        Getting the latest version.
* Mailing List::        Wget mailing list for announcements and discussion.
* Reporting Bugs::      How and where to report bugs.
* Portability::         The systems Wget works on.
* Signals::             Signal-handling performed by Wget.
@end menu

@node Proxies, Distribution, Various, Various
@section Proxies
@cindex proxies

@dfn{Proxies} are special-purpose @sc{http} servers designed to transfer
data from remote servers to local clients.  One typical use of proxies
is lightening network load for users behind a slow connection.  This is
achieved by channeling all @sc{http} and @sc{ftp} requests through the
proxy which caches the transferred data.  When a cached resource is
requested again, proxy will return the data from cache.  Another use for
proxies is for companies that separate (for security reasons) their
internal networks from the rest of Internet.  In order to obtain
information from the Web, their users connect and retrieve remote data
using an authorized proxy.

Wget supports proxies for both @sc{http} and @sc{ftp} retrievals.  The
standard way to specify proxy location, which Wget recognizes, is using
the following environment variables:

@table @code
@item http_proxy
This variable should contain the @sc{url} of the proxy for @sc{http}
connections.

@item ftp_proxy
This variable should contain the @sc{url} of the proxy for @sc{http}
connections.  It is quite common that @sc{http_proxy} and @sc{ftp_proxy}
are set to the same @sc{url}.

@item no_proxy
This variable should contain a comma-separated list of domain extensions
proxy should @emph{not} be used for.  For instance, if the value of
@code{no_proxy} is @samp{.mit.edu}, proxy will not be used to retrieve
documents from MIT.
@end table

In addition to the environment variables, proxy location and settings
may be specified from within Wget itself.

@table @samp
@item -Y on/off
@itemx --proxy=on/off
@itemx proxy = on/off
This option may be used to turn the proxy support on or off.  Proxy
support is on by default, provided that the appropriate environment
variables are set.

@item http_proxy = @var{URL}
@itemx ftp_proxy = @var{URL}
@itemx no_proxy = @var{string}
These startup file variables allow you to override the proxy settings
specified by the environment.
@end table

Some proxy servers require authorization to enable you to use them.  The
authorization consists of @dfn{username} and @dfn{password}, which must
be sent by Wget.  As with @sc{http} authorization, several
authentication schemes exist.  For proxy authorization only the
@code{Basic} authentication scheme is currently implemented.

You may specify your username and password either through the proxy
@sc{url} or through the command-line options.  Assuming that the
company's proxy is located at @samp{proxy.srce.hr} at port 8001, a proxy
@sc{url} location containing authorization data might look like this:

@example
http://hniksic:mypassword@@proxy.company.com:8001/
@end example

Alternatively, you may use the @samp{proxy-user} and
@samp{proxy-password} options, and the equivalent @file{.wgetrc}
settings @code{proxy_user} and @code{proxy_passwd} to set the proxy
username and password.

@node Distribution, Mailing List, Proxies, Various
@section Distribution
@cindex latest version

Like all GNU utilities, the latest version of Wget can be found at the
master GNU archive site prep.ai.mit.edu, and its mirrors.  For example,
Wget @value{VERSION} can be found at
@url{ftp://prep.ai.mit.edu/gnu/wget/wget-@value{VERSION}.tar.gz}

@node Mailing List, Reporting Bugs, Distribution, Various
@section Mailing List
@cindex mailing list
@cindex list

Wget has its own mailing list at @email{wget@@sunsite.auc.dk}, thanks
to Karsten Thygesen.  The mailing list is for discussion of Wget
features and web, reporting Wget bugs (those that you think may be of
interest to the public) and mailing announcements.  You are welcome to
subscribe.  The more people on the list, the better!

To subscribe, send mail to @email{wget-subscribe@@sunsite.auc.dk}.
the magic word @samp{subscribe} in the subject line.  Unsubscribe by
mailing to @email{wget-unsubscribe@@sunsite.auc.dk}.

The mailing list is archived at @url{http://fly.cc.fer.hr/archive/wget}.

@node Reporting Bugs, Portability, Mailing List, Various
@section Reporting Bugs
@cindex bugs
@cindex reporting bugs
@cindex bug reports

You are welcome to send bug reports about GNU Wget to
@email{bug-wget@@gnu.org}.  The bugs that you think are of the
interest to the public (i.e. more people should be informed about them)
can be Cc-ed to the mailing list at @email{wget@@sunsite.auc.dk}.

Before actually submitting a bug report, please try to follow a few
simple guidelines.

@enumerate
@item
Please try to ascertain that the behaviour you see really is a bug.  If
Wget crashes, it's a bug.  If Wget does not behave as documented,
it's a bug.  If things work strange, but you are not sure about the way
they are supposed to work, it might well be a bug.

@item
Try to repeat the bug in as simple circumstances as possible.  E.g. if
Wget crashes on @samp{wget -rLl0 -t5 -Y0 http://yoyodyne.com -o
/tmp/log}, you should try to see if it will crash with a simpler set of
options.

Also, while I will probably be interested to know the contents of your
@file{.wgetrc} file, just dumping it into the debug message is probably
a bad idea.  Instead, you should first try to see if the bug repeats
with @file{.wgetrc} moved out of the way.  Only if it turns out that
@file{.wgetrc} settings affect the bug, should you mail me the relevant
parts of the file.

@item
Please start Wget with @samp{-d} option and send the log (or the
relevant parts of it).  If Wget was compiled without debug support,
recompile it.  It is @emph{much} easier to trace bugs with debug support
on.

@item
If Wget has crashed, try to run it in a debugger, e.g. @code{gdb `which
wget` core} and type @code{where} to get the backtrace.

@item
Find where the bug is, fix it and send me the patches. :-)
@end enumerate

@node Portability, Signals, Reporting Bugs, Various
@section Portability
@cindex portability
@cindex operating systems

Since Wget uses GNU Autoconf for building and configuring, and avoids
using ``special'' ultra--mega--cool features of any particular Unix, it
should compile (and work) on all common Unix flavors.

Various Wget versions have been compiled and tested under many kinds of
Unix systems, including Solaris, Linux, SunOS, OSF (aka Digital Unix),
Ultrix, *BSD, IRIX, and others; refer to the file @file{MACHINES} in the
distribution directory for a comprehensive list.  If you compile it on
an architecture not listed there, please let me know so I can update it.

Wget should also compile on the other Unix systems, not listed in
@file{MACHINES}.  If it doesn't, please let me know.

Thanks to kind contributors, this version of Wget compiles and works on
Microsoft Windows 95 and Windows NT platforms.  It has been compiled
successfully using MS Visual C++ 4.0, Watcom, and Borland C compilers,
with Winsock as networking software.  Naturally, it is crippled of some
features available on Unix, but it should work as a substitute for
people stuck with Windows.  Note that the Windows port is
@strong{neither tested nor maintained} by me---all questions and
problems should be reported to Wget mailing list at
@email{wget@@sunsite.auc.dk} where the maintainers will look at them.

@node Signals,  , Portability, Various
@section Signals
@cindex signal handling
@cindex hangup

Since the purpose of Wget is background work, it catches the hangup
signal (@code{SIGHUP}) and ignores it.  If the output was on standard
output, it will be redirected to a file named @file{wget-log}.
Otherwise, @code{SIGHUP} is ignored.  This is convenient when you wish
to redirect the output of Wget after having started it.

@example
$ wget http://www.ifi.uio.no/~larsi/gnus.tar.gz &
$ kill -HUP %%     # Redirect the output to wget-log
@end example

Other than that, Wget will not try to interfere with signals in any
way. @kbd{C-c}, @code{kill -TERM} and @code{kill -KILL} should kill it
alike.

@node Appendices, Copying, Various, Top
@chapter Appendices

This chapter contains some references I consider useful, like the Robots
Exclusion Standard specification, as well as a list of contributors to
GNU Wget.

@menu
* Robots::                  Wget as a WWW robot.
* Security Considerations:: Security with Wget.
* Contributors::            People who helped.
@end menu

@node Robots, Security Considerations, Appendices, Appendices
@section Robots
@cindex robots
@cindex robots.txt
@cindex server maintenance

Since Wget is able to traverse the web, it counts as one of the Web
@dfn{robots}.  Thus Wget understands @dfn{Robots Exclusion Standard}
(@sc{res})---contents of @file{/robots.txt}, used by server
administrators to shield parts of their systems from wanderings of Wget.

Norobots support is turned on only when retrieving recursively, and
@emph{never} for the first page.  Thus, you may issue:

@example
wget -r http://fly.cc.fer.hr/
@end example

First the index of fly.cc.fer.hr will be downloaded.  If Wget finds
anything worth downloading on the same host, only @emph{then} will it
load the robots, and decide whether or not to load the links after all.
@file{/robots.txt} is loaded only once per host.  Wget does not support
the robots @code{META} tag.

The description of the norobots standard was written, and is maintained
by Martijn Koster @email{m.koster@@webcrawler.com}.  With his
permission, I contribute a (slightly modified) TeXified version of the
@sc{res}.

@menu
* Introduction to RES::
* RES Format::
* User-Agent Field::
* Disallow Field::
* Norobots Examples::
@end menu

@node Introduction to RES, RES Format, Robots, Robots
@subsection Introduction to RES
@cindex norobots introduction

@dfn{WWW Robots} (also called @dfn{wanderers} or @dfn{spiders}) are
programs that traverse many pages in the World Wide Web by recursively
retrieving linked pages. For more information see the robots page.

In 1993 and 1994 there have been occasions where robots have visited
@sc{www} servers where they weren't welcome for various
reasons. Sometimes these reasons were robot specific, e.g. certain
robots swamped servers with rapid-fire requests, or retrieved the same
files repeatedly. In other situations robots traversed parts of @sc{www}
servers that weren't suitable, e.g. very deep virtual trees, duplicated
information, temporary information, or cgi-scripts with side-effects
(such as voting).

These incidents indicated the need for established mechanisms for
@sc{www} servers to indicate to robots which parts of their server
should not be accessed. This standard addresses this need with an
operational solution.

This document represents a consensus on 30 June 1994 on the robots
mailing list (@code{robots@@webcrawler.com}), between the majority of
robot authors and other people with an interest in robots. It has also
been open for discussion on the Technical World Wide Web mailing list
(@code{www-talk@@info.cern.ch}). This document is based on a previous
working draft under the same title.

It is not an official standard backed by a standards body, or owned by
any commercial organization. It is not enforced by anybody, and there
no guarantee that all current and future robots will use it. Consider
it a common facility the majority of robot authors offer the @sc{www}
community to protect @sc{www} server against unwanted accesses by their
robots.

The latest version of this document can be found at
@url{http://info.webcrawler.com/mak/projects/robots/norobots.html}.

@node RES Format, User-Agent Field, Introduction to RES, Robots
@subsection RES Format
@cindex norobots format

The format and semantics of the @file{/robots.txt} file are as follows:

The file consists of one or more records separated by one or more blank
lines (terminated by @code{CR}, @code{CR/NL}, or @code{NL}).  Each
record contains lines of the form:

@example
<field>:<optionalspace><value><optionalspace>
@end example

The field name is case insensitive.

Comments can be included in file using UNIX Bourne shell conventions:
the @samp{#} character is used to indicate that preceding space (if any)
and the remainder of the line up to the line termination is discarded.
Lines containing only a comment are discarded completely, and therefore
do not indicate a record boundary.

The record starts with one or more User-agent lines, followed by one or
more Disallow lines, as detailed below. Unrecognized headers are
ignored.

The presence of an empty @file{/robots.txt} file has no explicit
associated semantics, it will be treated as if it was not present,
i.e. all robots will consider themselves welcome.

@node User-Agent Field, Disallow Field, RES Format, Robots
@subsection User-Agent Field
@cindex norobots user-agent

The value of this field is the name of the robot the record is
describing access policy for.

If more than one User-agent field is present the record describes an
identical access policy for more than one robot.  At least one field
needs to be present per record.

The robot should be liberal in interpreting this field. A case
insensitive substring match of the name without version information is
recommended.

If the value is @samp{*}, the record describes the default access policy
for any robot that has not matched any of the other records. It is not
allowed to have multiple such records in the @file{/robots.txt} file.

@node Disallow Field, Norobots Examples, User-Agent Field, Robots
@subsection Disallow Field
@cindex norobots disallow

The value of this field specifies a partial @sc{url} that is not to be
visited. This can be a full path, or a partial path; any @sc{url} that
starts with this value will not be retrieved. For example,
@w{@samp{Disallow: /help}} disallows both @samp{/help.html} and
@samp{/help/index.html}, whereas @w{@samp{Disallow: /help/}} would
disallow @samp{/help/index.html} but allow @samp{/help.html}.

Any empty value, indicates that all @sc{url}s can be retrieved. At least
one Disallow field needs to be present in a record.

@node Norobots Examples,  , Disallow Field, Robots
@subsection Norobots Examples
@cindex norobots examples

The following example @samp{/robots.txt} file specifies that no robots
should visit any @sc{url} starting with @samp{/cyberworld/map/} or
@samp{/tmp/}:

@example
# robots.txt for http://www.site.com/

User-agent: *
Disallow: /cyberworld/map/ # This is an infinite virtual URL space
Disallow: /tmp/ # these will soon disappear
@end example

This example @samp{/robots.txt} file specifies that no robots should
visit any @sc{url} starting with @samp{/cyberworld/map/}, except the
robot called @samp{cybermapper}:

@example
# robots.txt for http://www.site.com/

User-agent: *
Disallow: /cyberworld/map/ # This is an infinite virtual URL space

# Cybermapper knows where to go.
User-agent: cybermapper
Disallow:
@end example

This example indicates that no robots should visit this site further:

@example
# go away
User-agent: *
Disallow: /
@end example

@node Security Considerations, Contributors, Robots, Appendices
@section Security Considerations
@cindex security

When using Wget, you must be aware that it sends unencrypted passwords
through the network, which may present a security problem.  Here are the
main issues, and some solutions.

@enumerate
@item
The passwords on the command line are visible using @code{ps}.  If this
is a problem, avoid putting passwords from the command line---e.g. you
can use @file{.netrc} for this.

@item
Using the insecure @dfn{basic} authentication scheme, unencrypted
passwords are transmitted through the network routers and gateways.

@item
The @sc{ftp} passwords are also in no way encrypted.  There is no good
solution for this at the moment.

@item
Although the ``normal'' output of Wget tries to hide the passwords,
debugging logs show them, in all forms.  This problem is avoided by
being careful when you send debug logs (yes, even when you send them to
me).
@end enumerate

@node Contributors,  , Security Considerations, Appendices
@section Contributors
@cindex contributors

@iftex
GNU Wget was written by Hrvoje Nik@v{s}i@'{c} @email{hniksic@@iskon.hr}.
@end iftex
@ifinfo
GNU Wget was written by Hrvoje Niksic @email{hniksic@@iskon.hr}.
@end ifinfo
However, its development could never have gone as far as it has, were it
not for the help of many people, either with bug reports, feature
proposals, patches, or letters saying ``Thanks!''.

Special thanks goes to the following people (no particular order):

@itemize @bullet
@item
Karsten Thygesen---donated the mailing list and the initial @sc{ftp}
space.

@item
Shawn McHorse---bug reports and patches.

@item
Kaveh R. Ghazi---on-the-fly @code{ansi2knr}-ization.

@item
Gordon Matzigkeit---@file{.netrc} support.

@item
@iftex
Zlatko @v{C}alu@v{s}i@'{c}, Tomislav Vujec and Dra@v{z}en
Ka@v{c}ar---feature suggestions and ``philosophical'' discussions.
@end iftex
@ifinfo
Zlatko Calusic, Tomislav Vujec and Drazen Kacar---feature suggestions
and ``philosophical'' discussions.
@end ifinfo

@item
Darko Budor---initial port to Windows.

@item
Antonio Rosella---help and suggestions, plus the Italian translation.

@item
@iftex
Tomislav Petrovi@'{c}, Mario Miko@v{c}evi@'{c}---many bug reports and
suggestions.
@end iftex
@ifinfo
Tomislav Petrovic, Mario Mikocevic---many bug reports and suggestions.
@end ifinfo

@item
@iftex
Fran@,{c}ois Pinard---many thorough bug reports and discussions.
@end iftex
@ifinfo
Francois Pinard---many thorough bug reports and discussions.
@end ifinfo

@item
Karl Eichwalder---lots of help with internationalization and other
things.

@item
Junio Hamano---donated support for Opie and @sc{http} @code{Digest}
authentication.

@item
Brian Gough---a generous donation.
@end itemize

The following people have provided patches, bug/build reports, useful
suggestions, beta testing services, fan mail and all the other things
that make maintenance so much fun:

Tim Adam,
Martin Baehr,
Dieter Baron,
Roger Beeman and the Gurus at Cisco,
Dan Berger,
Mark Boyns,
John Burden,
Wanderlei Cavassin,
Gilles Cedoc,
Tim Charron,
Noel Cragg,
@iftex
Kristijan @v{C}onka@v{s},
@end iftex
@ifinfo
Kristijan Conkas,
@end ifinfo
Andrew Deryabin,
@iftex
Damir D@v{z}eko,
@end iftex
@ifinfo
Damir Dzeko,
@end ifinfo
Andrew Davison,
Ulrich Drepper,
Marc Duponcheel,
@iftex
Aleksandar Erkalovi@'{c},
@end iftex
@ifinfo
Aleksandar Erkalovic,
@end ifinfo
Andy Eskilsson,
Masashi Fujita,
Howard Gayle,
Marcel Gerrits,
Hans Grobler,
Mathieu Guillaume,
Dan Harkless,
Heiko Herold,
Karl Heuer,
HIROSE Masaaki,
Gregor Hoffleit,
Erik Magnus Hulthen,
Richard Huveneers,
Simon Josefsson,
@iftex
Mario Juri@'{c},
@end iftex
@ifinfo
Mario Juric,
@end ifinfo
@iftex
Goran Kezunovi@'{c},
@end iftex
@ifinfo
Goran Kezunovic,
@end ifinfo
Robert Kleine,
Fila Kolodny,
Alexander Kourakos,
Martin Kraemer,
@tex
$\Sigma\acute{\iota}\mu o\varsigma\;
\Xi\varepsilon\nu\iota\tau\acute{\epsilon}\lambda\lambda\eta\varsigma$
(Simos KSenitellis),
@end tex
@ifinfo
Simos KSenitellis,
@end ifinfo
Hrvoje Lacko,
Daniel S. Lewart,
Dave Love,
Jordan Mendelson,
Lin Zhe Min,
Charlie Negyesi,
Andrew Pollock,
Steve Pothier,
Jan Prikryl,
Marin Purgar,
Keith Refson,
Tobias Ringstrom,
@c Texinfo doesn't grok @'{@i}, so we have to use TeX itself.
@tex
Juan Jos\'{e} Rodr\'{\i}gues,
@end tex
@ifinfo
Juan Jose Rodrigues,
@end ifinfo
Edward J. Sabol,
Heinz Salzmann,
Robert Schmidt,
Toomas Soome,
Tage Stabell-Kulo,
Sven Sternberger,
Markus Strasser,
Szakacsits Szabolcs,
Mike Thomas,
Russell Vincent,
Charles G Waldman,
Douglas E. Wegscheid,
Jasmin Zainul,
@iftex
Bojan @v{Z}drnja,
@end iftex
@ifinfo
Bojan Zdrnja,
@end ifinfo
Kristijan Zimmer.

Apologies to all who I accidentally left out, and many thanks to all the
subscribers of the Wget mailing list.

@node Copying, Concept Index, Appendices, Top
@unnumbered GNU GENERAL PUBLIC LICENSE
@cindex copying
@cindex GPL
@center Version 2, June 1991

@display
Copyright @copyright{} 1989, 1991 Free Software Foundation, Inc.
675 Mass Ave, Cambridge, MA 02139, USA

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
@end display

@unnumberedsec Preamble

  The licenses for most software are designed to take away your
freedom to share and change it.  By contrast, the GNU General Public
License is intended to guarantee your freedom to share and change free
software---to make sure the software is free for all its users.  This
General Public License applies to most of the Free Software
Foundation's software and to any other program whose authors commit to
using it.  (Some other Free Software Foundation software is covered by
the GNU Library General Public License instead.)  You can apply it to
your programs, too.

  When we speak of free software, we are referring to freedom, not
price.  Our General Public Licenses are designed to make sure that you
have the freedom to distribute copies of free software (and charge for
this service if you wish), that you receive source code or can get it
if you want it, that you can change the software or use pieces of it
in new free programs; and that you know you can do these things.

  To protect your rights, we need to make restrictions that forbid
anyone to deny you these rights or to ask you to surrender the rights.
These restrictions translate to certain responsibilities for you if you
distribute copies of the software, or if you modify it.

  For example, if you distribute copies of such a program, whether
gratis or for a fee, you must give the recipients all the rights that
you have.  You must make sure that they, too, receive or can get the
source code.  And you must show them these terms so they know their
rights.

  We protect your rights with two steps: (1) copyright the software, and
(2) offer you this license which gives you legal permission to copy,
distribute and/or modify the software.

  Also, for each author's protection and ours, we want to make certain
that everyone understands that there is no warranty for this free
software.  If the software is modified by someone else and passed on, we
want its recipients to know that what they have is not the original, so
that any problems introduced by others will not reflect on the original
authors' reputations.

  Finally, any free program is threatened constantly by software
patents.  We wish to avoid the danger that redistributors of a free
program will individually obtain patent licenses, in effect making the
program proprietary.  To prevent this, we have made it clear that any
patent must be licensed for everyone's free use or not licensed at all.

  The precise terms and conditions for copying, distribution and
modification follow.

@iftex
@unnumberedsec TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
@end iftex
@ifinfo
@center TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
@end ifinfo

@enumerate
@item
This License applies to any program or other work which contains
a notice placed by the copyright holder saying it may be distributed
under the terms of this General Public License.  The ``Program'', below,
refers to any such program or work, and a ``work based on the Program''
means either the Program or any derivative work under copyright law:
that is to say, a work containing the Program or a portion of it,
either verbatim or with modifications and/or translated into another
language.  (Hereinafter, translation is included without limitation in
the term ``modification''.)  Each licensee is addressed as ``you''.

Activities other than copying, distribution and modification are not
covered by this License; they are outside its scope.  The act of
running the Program is not restricted, and the output from the Program
is covered only if its contents constitute a work based on the
Program (independent of having been made by running the Program).
Whether that is true depends on what the Program does.

@item
You may copy and distribute verbatim copies of the Program's
source code as you receive it, in any medium, provided that you
conspicuously and appropriately publish on each copy an appropriate
copyright notice and disclaimer of warranty; keep intact all the
notices that refer to this License and to the absence of any warranty;
and give any other recipients of the Program a copy of this License
along with the Program.

You may charge a fee for the physical act of transferring a copy, and
you may at your option offer warranty protection in exchange for a fee.

@item
You may modify your copy or copies of the Program or any portion
of it, thus forming a work based on the Program, and copy and
distribute such modifications or work under the terms of Section 1
above, provided that you also meet all of these conditions:

@enumerate a
@item
You must cause the modified files to carry prominent notices
stating that you changed the files and the date of any change.

@item
You must cause any work that you distribute or publish, that in
whole or in part contains or is derived from the Program or any
part thereof, to be licensed as a whole at no charge to all third
parties under the terms of this License.

@item
If the modified program normally reads commands interactively
when run, you must cause it, when started running for such
interactive use in the most ordinary way, to print or display an
announcement including an appropriate copyright notice and a
notice that there is no warranty (or else, saying that you provide
a warranty) and that users may redistribute the program under
these conditions, and telling the user how to view a copy of this
License.  (Exception: if the Program itself is interactive but
does not normally print such an announcement, your work based on
the Program is not required to print an announcement.)
@end enumerate

These requirements apply to the modified work as a whole.  If
identifiable sections of that work are not derived from the Program,
and can be reasonably considered independent and separate works in
themselves, then this License, and its terms, do not apply to those
sections when you distribute them as separate works.  But when you
distribute the same sections as part of a whole which is a work based
on the Program, the distribution of the whole must be on the terms of
this License, whose permissions for other licensees extend to the
entire whole, and thus to each and every part regardless of who wrote it.

Thus, it is not the intent of this section to claim rights or contest
your rights to work written entirely by you; rather, the intent is to
exercise the right to control the distribution of derivative or
collective works based on the Program.

In addition, mere aggregation of another work not based on the Program
with the Program (or with a work based on the Program) on a volume of
a storage or distribution medium does not bring the other work under
the scope of this License.

@item
You may copy and distribute the Program (or a work based on it,
under Section 2) in object code or executable form under the terms of
Sections 1 and 2 above provided that you also do one of the following:

@enumerate a
@item
Accompany it with the complete corresponding machine-readable
source code, which must be distributed under the terms of Sections
1 and 2 above on a medium customarily used for software interchange; or,

@item
Accompany it with a written offer, valid for at least three
years, to give any third party, for a charge no more than your
cost of physically performing source distribution, a complete
machine-readable copy of the corresponding source code, to be
distributed under the terms of Sections 1 and 2 above on a medium
customarily used for software interchange; or,

@item
Accompany it with the information you received as to the offer
to distribute corresponding source code.  (This alternative is
allowed only for noncommercial distribution and only if you
received the program in object code or executable form with such
an offer, in accord with Subsection b above.)
@end enumerate

The source code for a work means the preferred form of the work for
making modifications to it.  For an executable work, complete source
code means all the source code for all modules it contains, plus any
associated interface definition files, plus the scripts used to
control compilation and installation of the executable.  However, as a
special exception, the source code distributed need not include
anything that is normally distributed (in either source or binary
form) with the major components (compiler, kernel, and so on) of the
operating system on which the executable runs, unless that component
itself accompanies the executable.

If distribution of executable or object code is made by offering
access to copy from a designated place, then offering equivalent
access to copy the source code from the same place counts as
distribution of the source code, even though third parties are not
compelled to copy the source along with the object code.

@item
You may not copy, modify, sublicense, or distribute the Program
except as expressly provided under this License.  Any attempt
otherwise to copy, modify, sublicense or distribute the Program is
void, and will automatically terminate your rights under this License.
However, parties who have received copies, or rights, from you under
this License will not have their licenses terminated so long as such
parties remain in full compliance.

@item
You are not required to accept this License, since you have not
signed it.  However, nothing else grants you permission to modify or
distribute the Program or its derivative works.  These actions are
prohibited by law if you do not accept this License.  Therefore, by
modifying or distributing the Program (or any work based on the
Program), you indicate your acceptance of this License to do so, and
all its terms and conditions for copying, distributing or modifying
the Program or works based on it.

@item
Each time you redistribute the Program (or any work based on the
Program), the recipient automatically receives a license from the
original licensor to copy, distribute or modify the Program subject to
these terms and conditions.  You may not impose any further
restrictions on the recipients' exercise of the rights granted herein.
You are not responsible for enforcing compliance by third parties to
this License.

@item
If, as a consequence of a court judgment or allegation of patent
infringement or for any other reason (not limited to patent issues),
conditions are imposed on you (whether by court order, agreement or
otherwise) that contradict the conditions of this License, they do not
excuse you from the conditions of this License.  If you cannot
distribute so as to satisfy simultaneously your obligations under this
License and any other pertinent obligations, then as a consequence you
may not distribute the Program at all.  For example, if a patent
license would not permit royalty-free redistribution of the Program by
all those who receive copies directly or indirectly through you, then
the only way you could satisfy both it and this License would be to
refrain entirely from distribution of the Program.

If any portion of this section is held invalid or unenforceable under
any particular circumstance, the balance of the section is intended to
apply and the section as a whole is intended to apply in other
circumstances.

It is not the purpose of this section to induce you to infringe any
patents or other property right claims or to contest validity of any
such claims; this section has the sole purpose of protecting the
integrity of the free software distribution system, which is
implemented by public license practices.  Many people have made
generous contributions to the wide range of software distributed
through that system in reliance on consistent application of that
system; it is up to the author/donor to decide if he or she is willing
to distribute software through any other system and a licensee cannot
impose that choice.

This section is intended to make thoroughly clear what is believed to
be a consequence of the rest of this License.

@item
If the distribution and/or use of the Program is restricted in
certain countries either by patents or by copyrighted interfaces, the
original copyright holder who places the Program under this License
may add an explicit geographical distribution limitation excluding
those countries, so that distribution is permitted only in or among
countries not thus excluded.  In such case, this License incorporates
the limitation as if written in the body of this License.

@item
The Free Software Foundation may publish revised and/or new versions
of the General Public License from time to time.  Such new versions will
be similar in spirit to the present version, but may differ in detail to
address new problems or concerns.

Each version is given a distinguishing version number.  If the Program
specifies a version number of this License which applies to it and ``any
later version'', you have the option of following the terms and conditions
either of that version or of any later version published by the Free
Software Foundation.  If the Program does not specify a version number of
this License, you may choose any version ever published by the Free Software
Foundation.

@item
If you wish to incorporate parts of the Program into other free
programs whose distribution conditions are different, write to the author
to ask for permission.  For software which is copyrighted by the Free
Software Foundation, write to the Free Software Foundation; we sometimes
make exceptions for this.  Our decision will be guided by the two goals
of preserving the free status of all derivatives of our free software and
of promoting the sharing and reuse of software generally.

@iftex
@heading NO WARRANTY
@end iftex
@ifinfo
@center NO WARRANTY
@end ifinfo
@cindex no warranty

@item
BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
PROVIDE THE PROGRAM ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS
TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE
PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
REPAIR OR CORRECTION.

@item
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.
@end enumerate

@iftex
@heading END OF TERMS AND CONDITIONS
@end iftex
@ifinfo
@center END OF TERMS AND CONDITIONS
@end ifinfo

@page
@unnumberedsec How to Apply These Terms to Your New Programs

  If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these terms.

  To do so, attach the following notices to the program.  It is safest
to attach them to the start of each source file to most effectively
convey the exclusion of warranty; and each file should have at least
the ``copyright'' line and a pointer to where the full notice is found.

@smallexample
@var{one line to give the program's name and an idea of what it does.}
Copyright (C) 19@var{yy}  @var{name of author}

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
@end smallexample

Also add information on how to contact you by electronic and paper mail.

If the program is interactive, make it output a short notice like this
when it starts in an interactive mode:

@smallexample
Gnomovision version 69, Copyright (C) 19@var{yy} @var{name of author}
Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
type `show w'.  This is free software, and you are welcome
to redistribute it under certain conditions; type `show c'
for details.
@end smallexample

The hypothetical commands @samp{show w} and @samp{show c} should show
the appropriate parts of the General Public License.  Of course, the
commands you use may be called something other than @samp{show w} and
@samp{show c}; they could even be mouse-clicks or menu items---whatever
suits your program.

You should also get your employer (if you work as a programmer) or your
school, if any, to sign a ``copyright disclaimer'' for the program, if
necessary.  Here is a sample; alter the names:

@smallexample
@group
Yoyodyne, Inc., hereby disclaims all copyright
interest in the program `Gnomovision'
(which makes passes at compilers) written
by James Hacker.

@var{signature of Ty Coon}, 1 April 1989
Ty Coon, President of Vice
@end group
@end smallexample

This General Public License does not permit incorporating your program into
proprietary programs.  If your program is a subroutine library, you may
consider it more useful to permit linking proprietary applications with the
library.  If this is what you want to do, use the GNU Library General
Public License instead of this License.

@node Concept Index,  , Copying, Top
@unnumbered Concept Index
@printindex cp

@contents

@bye