Malleability

This software can be changed after the fact without needing to be recompiled. The binary's structure allows its contents to be zipped out, edited, and zipped back in again.

This is by virtue of the binary format being a so called 'actually portable executable' and built using the cosmopolitan toolset. This project in particular uses a hack that consisting in having a fully featured portable lua interpreter embed all the source code needed for a complete self-contained program. The format is also technically a zip file, which means that its contents can be enumerated and manipulated.

Binary patching: Extract a file, edit it, then re-add it

In the event that there's a bug or an improvement in the routine that takes in command-line args, here's how you would extract that piece of code, edit it, and then reinsert it into the binary.

# extract the file "run.lua" inside the binary's ".lua" directory
unzip sajt.com ".lua/run.lua"
# edit it outside the zip
vim ./lua/run.lua
# re-add it to the zip at the correct location
zip -r sajt.com "./lua/run.lua"

List files inside

unzip -Z1 sajt.com

• -Z print info instead of extracting
• -1 (lowercase L) only print filenames.

unzip -Z1 sajt.com -x "usr/*"

• -x <glob> ignore files when listing output

Remove files

zip -d sajt.com help.txt

• -d <zip> <glob or target-file> remove files within zip

Adding files in a directory

zip -r sajt.com src/

• -r recursively add files

zip -r -j sajt.com src/

• -j add files but don't add persist the parent directory name(s)