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linkchecker - command line client to check HTML documents and websites for broken links


linkchecker [options] [file-or-url]...


LinkChecker features

· recursive and multithreaded checking,

· output in colored or normal text, HTML, SQL, CSV, XML or a sitemap graph in
different formats,

· support for HTTP/1.1, HTTPS, FTP, mailto:, news:, nntp:, Telnet and local file

· restriction of link checking with URL filters,

· proxy support,

· username/password authorization for HTTP, FTP and Telnet,

· support for robots.txt exclusion protocol,

· support for Cookies

· support for HTML5

· HTML and CSS syntax check

· Antivirus check

· a command line, GUI and web interface


The most common use checks the given domain recursively:
linkchecker http://www.example.com/
Beware that this checks the whole site which can have thousands of URLs. Use the -r
option to restrict the recursion depth.
Don't check URLs with /secret in its name. All other links are checked as usual:
linkchecker --ignore-url=/secret mysite.example.com
Checking a local HTML file on Unix:
linkchecker ../bla.html
Checking a local HTML file on Windows:
linkchecker c:\temp\test.html
You can skip the http:// url part if the domain starts with www.:
linkchecker www.example.com
You can skip the ftp:// url part if the domain starts with ftp.:
linkchecker -r0 ftp.example.com
Generate a sitemap graph and convert it with the graphviz dot utility:
linkchecker -odot -v www.example.com | dot -Tps > sitemap.ps


General options
Use FILENAME as configuration file. As default LinkChecker uses

-h, --help
Help me! Print usage information for this program.

Read list of white-space separated URLs to check from stdin.

-tNUMBER, --threads=NUMBER
Generate no more than the given number of threads. Default number of threads is
100. To disable threading specify a non-positive number.

-V, --version
Print version and exit.

Print available check plugins and exit.

Output options
Print debugging output for the given logger. Available loggers are cmdline,
checking, cache, gui, dns and all. Specifying all is an alias for specifying all
available loggers. The option can be given multiple times to debug with more than
one logger. For accurate results, threading will be disabled during debug runs.

Output to a file linkchecker-out.TYPE, $HOME/.linkchecker/blacklist for blacklist
output, or FILENAME if specified. The ENCODING specifies the output encoding, the
default is that of your locale. Valid encodings are listed at
The FILENAME and ENCODING parts of the none output type will be ignored, else if
the file already exists, it will be overwritten. You can specify this option more
than once. Valid file output types are text, html, sql, csv, gml, dot, xml,
sitemap, none or blacklist. Default is no file output. The various output types
are documented below. Note that you can suppress all console output with the option
-o none.

Do not print check status messages.

Don't log warnings. Default is to log warnings.

Specify output type as text, html, sql, csv, gml, dot, xml, sitemap, none or
blacklist. Default type is text. The various output types are documented below.
The ENCODING specifies the output encoding, the default is that of your locale.
Valid encodings are listed at http://docs.python.org/library/codecs.html#standard-

-q, --quiet
Quiet operation, an alias for -o none. This is only useful with -F.

-v, --verbose
Log all checked URLs. Default is to log only errors and warnings.

-WREGEX, --warning-regex=REGEX
Define a regular expression which prints a warning if it matches any content of the
checked link. This applies only to valid pages, so we can get their content.
Use this to check for pages that contain some form of error, for example "This page
has moved" or "Oracle Application error".
Note that multiple values can be combined in the regular expression, for example
"(This page has moved|Oracle Application error)".
See section REGULAR EXPRESSIONS for more info.

Checking options
Read a file with initial cookie data. The cookie data format is explained below.

Check external URLs.

URLs matching the given regular expression will be ignored and not checked.
This option can be given multiple times.
See section REGULAR EXPRESSIONS for more info.

-NSTRING, --nntp-server=STRING
Specify an NNTP server for news: links. Default is the environment variable
NNTP_SERVER. If no host is given, only the syntax of the link is checked.

Check but do not recurse into URLs matching the given regular expression.
This option can be given multiple times.
See section REGULAR EXPRESSIONS for more info.

-p, --password
Read a password from console and use it for HTTP and FTP authorization. For FTP
the default password is anonymous@. For HTTP there is no default password. See also

-rNUMBER, --recursion-level=NUMBER
Check recursively all links up to given depth. A negative depth will enable
infinite recursion. Default depth is infinite.

Set the timeout for connection attempts in seconds. The default timeout is 60

Try the given username for HTTP and FTP authorization. For FTP the default
username is anonymous. For HTTP there is no default username. See also -p.

Specify the User-Agent string to send to the HTTP server, for example
"Mozilla/4.0". The default is "LinkChecker/X.Y" where X.Y is the current version of


Configuration files can specify all options above. They can also specify some options that
cannot be set on the command line. See linkcheckerrc(5) for more info.


Note that by default only errors and warnings are logged. You should use the --verbose
option to get the complete URL list, especially when outputting a sitemap graph format.

text Standard text logger, logging URLs in keyword: argument fashion.

html Log URLs in keyword: argument fashion, formatted as HTML. Additionally has links
to the referenced pages. Invalid URLs have HTML and CSS syntax check links

csv Log check result in CSV format with one URL per line.

gml Log parent-child relations between linked URLs as a GML sitemap graph.

dot Log parent-child relations between linked URLs as a DOT sitemap graph.

gxml Log check result as a GraphXML sitemap graph.

xml Log check result as machine-readable XML.

Log check result as an XML sitemap whose protocol is documented at

sql Log check result as SQL script with INSERT commands. An example script to create
the initial SQL table is included as create.sql.

Suitable for cron jobs. Logs the check result into a file ~/.linkchecker/blacklist
which only contains entries with invalid URLs and the number of times they have

none Logs nothing. Suitable for debugging or checking the exit code.


LinkChecker accepts Python regular expressions. See http://docs.python.org/
howto/regex.html for an introduction.

An addition is that a leading exclamation mark negates the regular expression.


A cookie file contains standard HTTP header (RFC 2616) data with the following possible

Host (required)
Sets the domain the cookies are valid for.

Path (optional)
Gives the path the cookies are value for; default path is /.

Set-cookie (required)
Set cookie name/value. Can be given more than once.

Multiple entries are separated by a blank line. The example below will send two cookies
to all URLs starting with http://example.com/hello/ and one to all URLs starting with

Host: example.com
Path: /hello
Set-cookie: ID="smee"
Set-cookie: spam="egg"

Host: example.org
Set-cookie: baggage="elitist"; comment="hologram"


To use a proxy on Unix or Windows set the $http_proxy, $https_proxy or $ftp_proxy
environment variables to the proxy URL. The URL should be of the form
http://[user:pass@]host[:port]. LinkChecker also detects manual proxy settings of
Internet Explorer under Windows systems, and gconf or KDE on Linux systems. On a Mac use
the Internet Config to select a proxy. You can also set a comma-separated domain list in
the $no_proxy environment variables to ignore any proxy settings for these domains.
Setting a HTTP proxy on Unix for example looks like this:

export http_proxy="http://proxy.example.com:8080"

Proxy authentication is also supported:

export http_proxy="http://user1:[email protected]:8081"

Setting a proxy on the Windows command prompt:

set http_proxy=http://proxy.example.com:8080


All URLs have to pass a preliminary syntax test. Minor quoting mistakes will issue a
warning, all other invalid syntax issues are errors. After the syntax check passes, the
URL is queued for connection checking. All connection check types are described below.

HTTP links (http:, https:)
After connecting to the given HTTP server the given path or query is requested. All
redirections are followed, and if user/password is given it will be used as
authorization when necessary. All final HTTP status codes other than 2xx are
errors. HTML page contents are checked for recursion.

Local files (file:)
A regular, readable file that can be opened is valid. A readable directory is also
valid. All other files, for example device files, unreadable or non-existing files
are errors. HTML or other parseable file contents are checked for recursion.

Mail links (mailto:)
A mailto: link eventually resolves to a list of email addresses. If one address
fails, the whole list will fail. For each mail address we check the following
1) Check the adress syntax, both of the part before and after
the @ sign.
2) Look up the MX DNS records. If we found no MX record,
print an error.
3) Check if one of the mail hosts accept an SMTP connection.
Check hosts with higher priority first.
If no host accepts SMTP, we print a warning.
4) Try to verify the address with the VRFY command. If we got
an answer, print the verified address as an info.

FTP links (ftp:)

For FTP links we do:

1) connect to the specified host
2) try to login with the given user and password. The default
user is ``anonymous``, the default password is ``anonymous@``.
3) try to change to the given directory
4) list the file with the NLST command

Telnet links (``telnet:``)

We try to connect and if user/password are given, login to the
given telnet server.

NNTP links (``news:``, ``snews:``, ``nntp``)

We try to connect to the given NNTP server. If a news group or
article is specified, try to request it from the server.

Unsupported links (``javascript:``, etc.)

An unsupported link will only print a warning. No further checking
will be made.

The complete list of recognized, but unsupported links can be found
in the linkcheck/checker/unknownurl.py source file.
The most prominent of them should be JavaScript links.


There are two plugin types: connection and content plugins. Connection plugins are run
after a successful connection to the URL host. Content plugins are run if the URL type
has content (mailto: URLs have no content for example) and if the check is not forbidden
(ie. by HTTP robots.txt). See linkchecker --list-plugins for a list of plugins and their
documentation. All plugins are enabled via the linkcheckerrc(5) configuration file.


Before descending recursively into a URL, it has to fulfill several conditions. They are
checked in this order:

1. A URL must be valid.

2. A URL must be parseable. This currently includes HTML files,
Opera bookmarks files, and directories. If a file type cannot
be determined (for example it does not have a common HTML file
extension, and the content does not look like HTML), it is assumed
to be non-parseable.

3. The URL content must be retrievable. This is usually the case
except for example mailto: or unknown URL types.

4. The maximum recursion level must not be exceeded. It is configured
with the --recursion-level option and is unlimited per default.

5. It must not match the ignored URL list. This is controlled with
the --ignore-url option.

6. The Robots Exclusion Protocol must allow links in the URL to be
followed recursively. This is checked by searching for a
"nofollow" directive in the HTML header data.

Note that the directory recursion reads all files in that directory, not just a subset
like index.htm*.


URLs on the commandline starting with ftp. are treated like ftp://ftp., URLs starting with
www. are treated like http://www.. You can also give local files as arguments.

If you have your system configured to automatically establish a connection to the internet
(e.g. with diald), it will connect when checking links not pointing to your local host.
Use the --ignore-url option to prevent this.

Javascript links are not supported.

If your platform does not support threading, LinkChecker disables it automatically.

You can supply multiple user/password pairs in a configuration file.

When checking news: links the given NNTP host doesn't need to be the same as the host of
the user browsing your pages.


NNTP_SERVER - specifies default NNTP server
http_proxy - specifies default HTTP proxy server
ftp_proxy - specifies default FTP proxy server
no_proxy - comma-separated list of domains to not contact over a proxy server
LC_MESSAGES, LANG, LANGUAGE - specify output language


The return value is 2 when

· a program error occurred.

The return value is 1 when

· invalid links were found or

· link warnings were found and warnings are enabled

Else the return value is zero.


LinkChecker consumes memory for each queued URL to check. With thousands of queued URLs
the amount of consumed memory can become quite large. This might slow down the program or
even the whole system.

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