Author:

• Name: Volker Diels-Grabsch
  Location: DE - Federal Republic of Germany (Germany)

Award: Best one liner

To build:

    make all

To use:

    ./prog n e e d s a r g u m e n t s < infile > outfile.Z

Try:

    ./try.sh

Judges’ remarks:

Some of our wishes are granted after quite a few years, and some previous IOCCC winners turn out prescient by a decade.

A fun challenge

Explain the purpose of the constant 9018655 in prog.c.

The above fun challenge is still open. See the “Fun challenge Info” section for details.

Author’s remarks:

Description

This one-liner is an implementation of the following Judges’ remark on 2019/diels-grabsch1:

can you compress it down to a one-liner, still producing files in the UNIX compress format, albeit sacrificing the compression ratio?

Challenge accepted! This one-liner does exactly that … if you ask nicely.

Usage

    cc -ansi -w -o prog prog.c
    ./prog p l e a s e c o m p r e s s < remarks.md > remarks.md.Z
    wc -c remarks.md
    wc -c remarks.md.Z

Output:

   2638 remarks.md
   1999 remarks.md.Z

This tool produces compressed files with a maximum code word size of 9 bits. Due to a bug in ncompress that was only fixed after the 5.0 release, you should not use that widespread version of ncompress, but instead compile the latest main branch of ncompress to verify the compressed data:

    git clone -b main https://github.com/vapier/ncompress
    cd ncompress
    make
    cd ..
    ./ncompress/compress -dc < remarks.md.Z | diff -s - remarks.md

Output:

Files - and remarks.md are identical

Alternatively, you can use 2015/mills2 which provided a correct 9-bit mode implementation right from the start. This is remarkable as the unmodified 2015/mills2 only supports 16-bit mode, but can be turned into 9-bit mode by changing a single constant from 16 to 9 in the code:

    curl -Lso mills2.c https://github.com/ioccc-src/winner/raw/refs/heads/master/2015/mills2/prog.c
    sed s/16/9/ < mills2.c > mills2-9bit.c
    cc -ansi -w mills2-9bit.c -o mills2-9bit
    ./mills2-9bit remarks.md.Z | diff -s - remarks.md

Output:

Files - and remarks.md are identical

You might be suprised to learn that this one-liner beats ncompress on any random input!

    head -c 10000 /dev/urandom | ./prog p l e a s e c o m p r e s s | wc -c
    11214

    head -c 10000 /dev/urandom | compress | wc -c
    14498

Joking aside, using just 9-bit codes means that this one-liner of course has a worse compression ratio than ncompress:

    cat remarks.md | ./prog p l e a s e c o m p r e s s | wc -c
    1999

    cat remarks.md | compress | wc -c
    1660

But on the other hand, as seen above, using just 9-bit codes also makes it less worse than ncompress on hopelessly incompressible input.

Primary files

• prog.c - entry source code
• Makefile - entry Makefile
• prog.orig.c - original source code
• try.sh - script to try entry

Secondary files

• 2025_diels-grabsch.tar.bz2 - download entry tarball
• README.md - markdown source for this web page
• .entry.json - entry summary and manifest in JSON
• .gitignore - list of files that should not be committed under git
• .path - directory path from top level directory
• .date-range - copyright date range for this directory
• index.html - this web page

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