Japanese developer Keigo Oka demonstrated that based on the utility GNU Found and Mkdir, you can form a computational environment that is Complete Turing, allowing you to realize any computable function on it and recreate yourself. Previously, the possibility of creating such an environment was demonstrated for utilities SED and AWK. To confirm the completeness of Turing, the implementation of Find and Mkdir games fizz buzz and the cellular automaton operating on “Rules 110“.
To organize the operation of cycles using Find and MKDIR, a trick with recursive creation of subdirectories is used to limit the number of iterations, using the -Maxdepth option (for example, for a cycle of 3 iterations, you can run “Find X -Maxdepth 3 -execdir Mkdir x/x ;”). The number of permissible iterations depends on the limitations of the file system for creating nested directories and the maximum size of the file path. Conditional operations are called using regular expressions available through the “-rex” option (for example, for the output of the “buzz” line for numbers divisible by 5, you can specify ‘-RigEx’ d ((/x) {5})+’+’+’ -printf “buzz n” ‘).