Introduction

Scans PDFs for links written in plaintext and checks if they are active or returns an error code. It then generates a report of its findings. Extract references (PDF, URL, DOI, arXiv) and metadata from a PDF.

Check out our sister project, Rotting Research, for a web app implementation of this project.

Features

• Extract references and metadata from a given PDF.
• Detects PDF, URL, arXiv and DOI references.
• Archives valid links using Internet Archive's Wayback Machine (using the -a flag).
• Checks for valid SSL certificate.
• Find broken hyperlinks (using the -c flag).
• Output as text or JSON (using the -j flag).
• Extract the PDF text (using the --text flag).
• Use as command-line tool or Python package.
• Works with local and online PDFs.

Installation

Grab a copy of the code with pip:

pip install linkrot

Usage

linkrot can be used to extract info from a PDF in two ways:

• Command line/Terminal tool linkrot
• Python library import linkrot

1. Command Line/Terminal tool

linkrot [pdf-file-or-url]

Run linkrot -h to see the help output:

linkrot -h

usage:

linkrot [-h] [-d OUTPUT_DIRECTORY] [-c] [-j] [-v] [-t] [-o OUTPUT_FILE] [--version] pdf

Extract metadata and references from a PDF, and optionally download all referenced PDFs.

Arguments

positional arguments:

pdf (Filename or URL of a PDF file)

optional arguments:

-h, --help            (Show this help message and exit)  
-d OUTPUT_DIRECTORY,  --download-pdfs OUTPUT_DIRECTORY (Download all referenced PDFs into specified directory)  
-c, --check-links     (Check for broken links)  
-j, --json            (Output infos as JSON (instead of plain text))  
-v, --verbose         (Print all references (instead of only PDFs))  
-t, --text            (Only extract text (no metadata or references))  
-a, --archive	  (Archive actvice links)
-o OUTPUT_FILE,        --output-file OUTPUT_FILE (Output to specified file instead of console)  
--version             (Show program's version number and exit)  

PDF Samples

For testing purposes, you can find PDF samples in shared MEGA folder](https://mega.nz/folder/uwBxVSzS#lpBtSz49E9dqHtmrQwp0Ig).

Examples

Extract text to console.

linkrot https://example.com/example.pdf -t

Extract text to file

linkrot https://example.com/example.pdf -t -o pdf-text.txt

Check Links

linkrot https://example.com/example.pdf -c

2. Main Python Library

Import the library:

import linkrot

Create an instance of the linkrot class like so:

pdf = linkrot.linkrot("filename-or-url.pdf") #pdf is the instance of the linkrot class

Now the following function can be used to extract specific data from the pdf:

get_metadata()

Arguments: None

Usage:

metadata = pdf.get_metadata() #pdf is the instance of the linkrot class

Return type: Dictionary <class 'dict'>

Information Provided: All metadata, secret metadata associated with the PDF including Creation date, Creator, Title, etc...

get_text()

Arguments: None

Usage:

text = pdf.get_text() #pdf is the instance of the linkrot class

Return type: String <class 'str'>

Information Provided: The entire content of the PDF in string form.

get_references(reftype=None, sort=False)

Arguments:

reftype: The type of reference that is needed 
	 values: 'pdf', 'url', 'doi', 'arxiv'. 
	 default: Provides all reference types.

sort: Whether reference should be sorted or not
      values: True or False. 
      default: Is not sorted.

Usage:

references_list = pdf.get_references() #pdf is the instance of the linkrot class

Return type: Set <class 'set'> of <linkrot.backends.Reference object>

linkrot.backends.Reference object has 3 member variables:
- ref: actual URL/PDF/DOI/ARXIV
- reftype: type of reference
- page: page on which it was referenced

Information Provided: All references with their corresponding type and page number.

get_references_as_dict(reftype=None, sort=False)

Arguments:

reftype: The type of reference that is needed 
	 values: 'pdf', 'url', 'doi', 'arxiv'. 
	 default: Provides all reference types.

sort: Whether reference should be sorted or not
      values: True or False. 
      default: Is not sorted.

Usage:

references_dict = pdf.get_references_as_dict() #pdf is the instance of the linkrot class

Return type: Dictionary <class 'dict'> with keys 'pdf', 'url', 'doi', 'arxiv' that each have a list <class 'list'> of refs of that type.

Information Provided: All references in their corresponding type list.

download_pdfs(target_dir)

Arguments:

target_dir: The path of the directory to which the reference PDFs should be downloaded 

Usage:

pdf.download_pdfs("target-directory") #pdf is the instance of the linkrot class

Return type: None

Information Provided: Downloads all the reference PDFs to the specified directory.

3. Linkrot downloader functions

Import:

from linkrot.downloader import sanitize_url, get_status_code, check_refs

sanitize_url(url)

Arguments:

url: The url to be sanitized.

Usage:

new_url = sanitize_url(old_url) 

Return type: String <class 'str'>

Information Provided: URL is prefixed with 'http://' if it was not before and makes sure it is in utf-8 format.

get_status_code(url)

Arguments:

url: The url to be checked for its status. 

Usage:

status_code = get_status_code(url) 

Return type: String <class 'str'>

Information Provided: Checks if the URL is active or broken.

check_refs(refs, verbose=True, max_threads=MAX_THREADS_DEFAULT)

Arguments:

refs: set of linkrot.backends.Reference objects
verbose: whether it should print every reference with its code or just the summary of the link checker
max_threads: number of threads for multithreading

Usage:

check_refs(pdf.get_references()) #pdf is the instance of the linkrot class

Return type: None

Information Provided: Prints references with their status code and a summary of all the broken/active links on terminal.

4. Linkrot extractor functions

Import:

from linkrot.extractor import extract_urls, extract_doi, extract_arxiv

Get pdf text:

text = pdf.get_text() #pdf is the instance of the linkrot class

extract_urls(text)

Arguments:

text: String of text to extract urls from

Usage:

urls = extract_urls(text)

Return type: Set <class 'set'> of URLs

Information Provided: All URLs in the text

extract_arxiv(text)

Arguments:

text: String of text to extract arXivs from

Usage:

arxiv = extract_arxiv(text)

Return type: Set <class 'set'> of arxivs

Information Provided: All arXivs in the text

extract_doi(text)

Arguments:

text: String of text to extract DOIs from

Usage:

doi = extract_doi(text)

Return type: Set <class 'set'> of DOIs

Information Provided: All DOIs in the text

Code of Conduct

To view our code of conduct please visit our Code of Conduct page.

License

This program is licensed with an GPLv3 License.