brege Metadata Extraction
Extract bibliographic metadata from ebook files.
Priority Order
- EPUB OPF metadata (most authoritative)
- PDF document properties
- Filename parsing (least reliable)
- User input (for disambiguation only)
EPUB Extraction
Step 1: Find OPF Path
unzip -p "$file" META-INF/container.xml | grep -oP 'full-path="\K[^"]*'
Returns path like OEBPS/content.opf or content.opf.
Step 2: Extract Metadata
unzip -p "$file" "$opf_path" | grep -E '<dc:(creator|title|date|contributor)'
Fields
| Tag | Content |
|---|---|
<dc:creator> |
Author name(s) |
<dc:title> |
Book title |
<dc:date> |
Publication date (extract YYYY) |
<dc:contributor opf:role="trn"> |
Translator |
<dc:contributor opf:role="edt"> |
Editor |
PDF Extraction
pdfinfo "$file" 2>/dev/null | grep -E '^(Title|Author|CreationDate|ModDate):'
Extract:
- Title field
- Author field
- CreationDate year (format: D:YYYYMMDDhhmmss)
Filename Parsing
Parse for hints when metadata insufficient:
- Author: Often at start, before dash or title
- Title: Main text
- Year: Four digits in parentheses or at end
Example: Charles.Bukowski.-.Love.Is.A.Dog.From.Hell.2007.RETAIL.EPUB.eBook-CTO.epub
- Author: Charles Bukowski
- Title: Love Is A Dog From Hell
- Year: 2007
Year Rules
Use publication year of THIS edition, not original work.
- Aristotle's Nicomachean Ethics (ancient) with Irwin translation (2019): use 2019
- Marx's Capital originally 1867: use edition's publication year
- If EPUB date differs from original work date, prefer EPUB date
Useless Metadata
Some EPUBs have placeholder or garbage metadata. Treat these as missing:
- Title:
[No data],Unknown,Untitled, empty - Author:
Unknown,Anonymous(unless actually anonymous work), empty - Date: Only modification date present, no publication date
When OPF metadata is useless, fall back to filename parsing immediately.
Author Name Normalization
Fix common capitalization issues from metadata:
Harold Mcgee→Harold McGee(fix surname caps)CHARLES BUKOWSKI→Charles Bukowski(fix all-caps)- Preserve intentional lowercase particles:
de Beauvoir,van Gogh
Use opf:file-as attribute if present - it often has correct citation format:
<dc:creator opf:file-as="McGee, Harold">Harold Mcgee</dc:creator>
Translator Verification
Translator info in filenames is often wrong or refers to different editions.
- Verify translator matches publisher/edition (e.g., Penguin 2004 Marx = Fowkes, not Guyer-Wood)
- If translator not in metadata, check ISBN against known editions
- When uncertain, ask user
Missing Data
When metadata genuinely unavailable:
- No author: Ask user
- No year: Ask user for "publication year of this edition"
- Ambiguous title: Ask user
- No translator but work is translated: Ask user or look up by ISBN/publisher
Do not guess. Do not proceed without author and title.