How To Download A Website With Wget The Right Way

Overview

To download an entire website from Linux it is often recommended to use wget, however, it must be done using the right parameters or the downloaded website won’t be similar to the original one, with probably relative broken links. This tutorial explores the right combination to download a website:

• converting relative links to full paths so they can be browsed offline.
• preventing requesting too many web pages too fast, overloading the server and possibly being blocked from requesting more.
• avoid overwriting or creating duplicates of already downloaded files.

Alternatives

The download can be made using a recursive traversal approach or visiting each URL of the sitemap.

1. Recursive traversal

For this we use the well known command wget.

GNU Wget is a free utility for non-interactive download of files from the Web

Wget needed parameters

The wget command is very popular in Linux and present in most distributions.

To download an entire website we use the following Wget download options:

--wait=2

Wait the specified number of seconds between the retrievals.. In this case 2 seconds.

--limit-rate=20K

Limit the download speed to amount bytes per second.

--recursive

Turn on recursive retrieving. The default maximum depth is 5. If the website has more levels than 5, then you can specify it with --level=depth

--page-requisites

download all the files that are necessary to properly display a given HTML page. This includes such things as inlined images, sounds, and referenced stylesheets.

--user-agent=Mozilla

Identify as Mozilla to the HTTP server.

--no-parent

Do not ever ascend to the parent directory when retrieving recursively.

--convert-links

After the download is complete, convert the links in the document to make them suitable for local viewing.

--adjust-extension

If a file of type application/xhtml+xml or text/html is downloaded and the URL does not end with the regexp \.[Hh][Tt][Mm][Ll]?, this option will cause the suffix .html to be appended to the local filename.

--no-clobber

When running Wget with -r, re-downloading a file will result in the new copy simply overwriting the old. Adding -nc will prevent this behavior, instead causing the original version to be preserved and any newer copies on the server to be ignored.

-e robots=off

turn off the robot exclusion

--level

Specify recursion maximum depth level depth. Use inf as the value for inifinite.

Summary

Summarizing, these are the needed parameters:

wget --wait=2 \
     --level=inf \
	 --limit-rate=20K \
	 --recursive \
	 --page-requisites \
	 --user-agent=Mozilla \
	 --no-parent \
	 --convert-links \
	 --adjust-extension \
	 --no-clobber \
	 -e robots=off \
	 https://example.com

Or in one line:

wget --wait=2 --level=inf --limit-rate=20K --recursive --page-requisites --user-agent=Mozilla --no-parent --convert-links --adjust-extension --no-clobber -e robots=off https://example.com

Example

Let’s try to download the https://example.com website (single page) to see how verbose is wget and how it behaves.

$ wget --wait=2
--limit-rate=20K --recursive --page-requisites --user-agent=Mozilla
--no-parent --convert-links --adjust-extension --no-clobber  https://example.com
--2017-06-30 19:48:46--  https://example.com/
Resolving example.com (example.com)... 93.184.216.34
Connecting to example.com (example.com)|93.184.216.34|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1270 (1,2K) [text/html]
Saving to: ‘example.com/index.html’

example.com/index.html            100%[===========================================================>]   1,24K  --.-KB/s    in 0,003s

2017-06-30 19:48:46 (371 KB/s) - ‘example.com/index.html’ saved [1270/1270]

FINISHED --2017-06-30 19:48:46--
Total wall clock time: 0,6s
Downloaded: 1 files, 1,2K in 0,003s (371 KB/s)
Converting links in example.com/index.html... nothing to do.
Converted links in 1 files in 0 seconds.
$ tree example.com/
example.com/
└── index.html

0 directories, 1 file

Wget mirror

Wget already comes with a handy --mirror paramater that is the same to use -r -l inf -N. That is:

• recursive download
• with infinite depth
• turn on time-stamping.

2. Using website’s sitemap

Another approach is to avoid doing a recursive traversal of the website and download all the URLs present in website’s sitemap.xml.

Filtering url from sitemap

A sitemap file typically has the form:

<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd" xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
<url>
<loc>https://marcanuy.com/en/projects/conversions</loc>
<lastmod>2014-09-15T00:00:00-03:00</lastmod>
</url>
<url>
<loc>https://marcanuy.com/en/projects/games-for-kids</loc>
<lastmod>2014-09-15T00:00:00-03:00</lastmod>
</url>
</urlset>

We need to get all the URLs present in sitemap.xml, using grep: grep “” sitemap.xml.

Removing loc tags

Now to remove the superfluous tags: sed -e ’s/<[^>]*>//g’`

Putting it all together

After the previous two command we have a list of URLs, and that is the parameter read by wget -i:

wget -i grep "<loc>" sitemap.xml| sed -e 's/<[^>]*>//g'

And wget will start downloading them sequentially.

Conclusion

wget is a fantastic command line tool, it has everything you will ever need without having to use any other GUI tool, just be sure to browse its manual for the right parameters you want.

The above parameters combination will make you have a browseable website locally.

You should be careful to check that .html extensions works for your case, sometimes you may want that wget generates them based on the Content Type but sometimes you should avoid wget generating them as is the case when using pretty urls.

Reference

• wget manual https://www.gnu.org/software/wget/
  • Parameters: https://www.gnu.org/software/wget/manual/html_node/Download-Options.html