bibtextools
I'd like to be able to use a tool like grep to extract an entire bibtex reference rather than just the matching line.
For example, grep Smith mydatabase.bib would return lines that contain the word Smith. I'd like to have a command-line program that returned the entire bibtex reference that encloses the word Smith.
In particular, I'd be interested in whether there is a way of using sed or awk to perform the task?
Have a look at biber which in the current 1.5 dev version on SourceForge has a new "tool" mode which allows you to use biber's reencoding and source mapping features independently of biblatex. The source mapping features are what you mainly need from your description and this is all documented in the PDF manual. I can provide specific examples if you have specific questions. biber will do everything you mention above apart from the @string expansion which would be possible to add but as you say, it's fairly idiosyncratic.
Of course, you can do this dynamically with biber too - with the changes being applied as the .bib is read but the .bib is not touched. The new tool mode allows you to write the changed .bib to another file without writing a .bbl.
For example, here is how in tool mode to tackle points 2, 3 5 and 6 in your examples. Point 1 is better handled semantically with biblatex and its max/min names options. Create a biber.conf with:
<config>
<sourcemap>
<maps datatype="bibtex" map_overwrite="1">
<map>
<map_step map_field_set="issn" map_null="1"/>
</map>
<map>
<per_type>ARTICLE</per_type>
<map_step map_field_set="title" map_null="1"/>
</map>
<map>
<per_type>ARTICLE</per_type>
<map_step map_field_source="pages" map_final="1"/>
<map_step map_field_set="archiveprefix" map_null="1"/>
<map_step map_field_set="eprint" map_null="1"/>
<map_step map_field_set="primaryclss" map_null="1"/>
</map>
</maps>
<map>
<map_step map_field_source="doi" map_match="[\\;]" map_final="1"/>
<map_step map_field_set="doi" map_null="1"/>
</map>
</sourcemap>
</config>
Then run biber with
biber --tool file.bib
Which will look in the default locations for your biber.conf and will output a file called file_bibertool.bib.
This is also all possible, as I said, dynamically using the biber.conf as you process the file normally into a .bbl with biber and also the whole mapping functionality is available in biblatex through macros (see \DeclareSourcemap in the biblatex documentation) if you wanted to do this on a per-document basis dynamically.
If you're interested in merely adding ascii-art diagrams to your document, you can dump the ascii-art content in the verbatim environment:
\documentclass{minimal}
\begin{document}% Taken from http://ditaa.sourceforge.net/
\begin{verbatim}
+--------+ +-------+ +-------+
| | --+ ditaa +--> | |
| Text | +-------+ |diagram|
|Document| |!magic!| | |
| {d}| | | | |
+---+----+ +-------+ +-------+
: ^
| Lots of work |
+-------------------------+
\end{verbatim}
\end{document}
The verbatim environment typesets its contents as-is using the \ttfamily font, keeping the alignment (whitespace).
If you're interested in a converted graphic/image (a ditaa-processed version of your ascii-art), then importing a PNG (or JPG/BMP) from your ditaa outpout would be easiest. This, however, comes with a loss of quality in the output. If the EPS add-on is readily available, then using it to produce EPS images (or even converted to PDF) would achieve the highest quality. Here's a graphic from the website illustrating the difference in quality when using rasterized vs vector graphics:
Finally, TikZ/PGF and PStricks both provide a bounty of native drawing capabilities within (La)TeX. The TikZ/PGF documentation is filled with examples, as is many of the package documentations associated with PStricks. They each come with their own set of macros/commands that allow for drawing diagrams similar to those done by ditaa.
The advantage of using native packages as opposed to some external application (like ditaa) is that it provides the capability to alter an "image" within your (La)TeX code rather than using an external application as a stepping stone. Moreover, with (La)TeX being platform independent, such advantages of native programming add even more value.
Best Answer
bibtool --select {"Smith"} <file>.aux -o <file>.bibcreates a new bibliography data file which has only entries with Smith.bibtoolshould be part of your TeX distribution.