• the best example code is your own
  • own bits of rotten code
  • do something really minor
  • junk code valuable
  • commit into CVS, about one third
  • no need to remember things that are difficult to remember
  • example code that reminds of previous research, very valuable
  • e.g. nmap file, filename -> void *
  • 1993: test usleep
  • watch useful command
  • testing library function
  • testing understanding of language feature
  • trigger bug
  • explore idea for larger program
  • buggering around, trying to avoid real work; make sure source code is on screen

I forget stuff fast; function that I’ve used before

junk-code as toolbox

  • instead of “I once wrote a program that does that” I say “here is a program that does that”.
  • A great way of impressing your boss.


  • no error checking
  • bugs exist
  • run gdb print stack trace if segment fault


  • classic junk code
  • low bandwidth link
  • email send/receive over rsync over SSH
  • still quick hack
  • even receives spam
  • does have help


  • smallest program to get packaged in Debian
  • iprint
  • print out bunch of numbers in different formats
  • iprint doesn’t do mail
  • command line help, but nothing written
  • i –help
  • patch doubles length in Debian, 2^-31 didn’t work
  • apt-get install iprint


  • tiny embedded web server
  • embedded applications
  • https://junkcode.samba.org/ is an example
  • NAS vendor, ROM image, complete installation system
  • limited ROM size
  • program CGI easily
  • server side scripting
  • bash already there
  • server side scripting for bash
  • here is an example of an HTML file … please wait while the projector turns itself on and off there are some things man wasn’t meant to see
  • recursion
    • really powerful, not in apache, something about performance???
    • port 8080
    • browser
    • bash compact language
    • setting variables, CGI variables, etc.


  • 4 by 4 by 4 tic tac toe
  • OpenGL
  • change piece to look like teapot
  • nightcap - chess game
  • turn king into teapot? No


  • last week
  • NAS, not one I sent bust, another one which survived
  • initrd in firmware
  • extract gz file from large data file
  • piece together junk code


  • inheriting maintainership of international chess server, Laska
  • also used in Samba 3, version records in database
  • preprocess C headers into C table
  • marshal/unmarchal C structures
  • upgrade C code on the fly
  • entire program in shared library
  • write data structures to disk using genstruct; dlclose library; dlopen library, read data structures again


  • setting up laptop hibernation files and partitions

Escaped/graduated junk code

  • tdb the trivial database
  • dbench useful benchmark emulation
  • ccache compiler cache
  • pidl IDL compiler
  • rsync

start keeping your own junk code, valuable resource, going back many years

Code, not suitable for public release?
yes, check that I own copyright, it is really mine?

not releasing to world is not required
treasure it, back it up

junk code is pre-existing work, managers typically don’t care about copyright

any restrictions on C code, with online changes? Portability?

  • sizeof.c, print size of different types
  • speed.c, print speeds of various operations
  • semspeed, print semaphore speed


  • somebody sent a patch