This program creates a compendium of Plain TeX commands, as listed in TeX for the Impatient, by Paul Abrahams, Karl Berry, and Kathryn Hargreaves. You can find a link to the book, which has been made open-source, here.
After building the program, looking up Plain TeX commands is as simple as changing to the root of this project directory, invoking python on query.py, specifying arguments as desired, and selecting the index number corresponding to the command you wish to query.
You can search by pattern, by section, or by both.
make clean
make
python query.py {pattern} [-section [section, ...]]
Searching for the pattern 'par' in sections [genops, paras]
python query.py par -section genops para
pattern: 'par'
sections: genops, math
5 results found\.
=============================
0: math/parallel
1: math/uparrow
2: math/Uparrow
3: math/partial
4: genops/tracingparagraphs
Searching for the pattern 'par' in all sections.
python query.py par
pattern: 'par'
sections: concepts, genops, math, miscellany, modes, pages, paras
13 results found.
=============================
0: math/parallel
1: math/uparrow
2: math/Uparrow
3: math/partial
4: pages/parskip
5: concepts/paragraph
6: concepts/parameter
7: genops/tracingparagraphs
8: paras/parfillskip
9: paras/everypar
10: paras/parshape
11: paras/parindent
12: paras/par
Searching for commands in the section 'paras'.
python query.py -section paras
pattern: '.*'
sections: paras
142 results found.
===============================
0: paras/_italiccorrection
1: paras/S
2: paras/P
3: paras/obeyspaces
4: paras/AE
...