Japanese developer Keigo Oka demonstrated that using the GNU find and mkdir utilities, it is possible to create a computational environment that is Turing complete, meaning it can perform any computable function and recreate itself. Previously, the ability to create such an environment was shown using the sed and awk utilities. To confirm Turing completeness, implementations of the game Fizz buzz and a cellular automaton operating under 'Rule 110' were provided, using a combination of find and mkdir.
To organize loop operations with the find and mkdir commands, a trick involving recursive subdirectory creation was employed, where the '-maxdepth' option is used to limit the number of iterations (for example, for a loop of 3 iterations, one can run 'find x -maxdepth 3 -execdir mkdir x/x \;'). The number of permissible iterations is limited by the file system constraints on creating nested directories and the maximum file path size. Conditional operation calls are organized using regular expressions available through the '-regex' option (for instance, to output the string 'Buzz' for numbers divisible by 5, one can specify '-regex 'd((/x){5})+' -printf 'Buzz\n').
Source: opennet.ru
