Single character filenames

When Steve Bourne was writing his Unix shell (which came to be known as the Bourne shell), he made a directory of 254 files with one-character names, one for each byte value except '\0' and slash, the two characters that cannot appear in Unix file names. He used that directory for all manner of tests of pattern-matching and tokenization. (The test directory was of course created by a program.) For years after-wards, that directory was the bane of file-tree-walking programs; it tested them to destruction.

—The Practice of Programming - p158

A program walking a directory structure of arbitrary filenames needs to be very resilient. It needs to handle any valid filename and should not expect the filenames to only be a specific subset of e.g. ASCII. Here is a small C program that takes a directory as input and creates all one byte filenames for testing. A directory containing these files should be considered at minimum and does not constitute an exhaustive test suite. You can compile it with 

cc one_character_filenames.c -o one_character_filenames

and can be used like this 

one_character_filenames DIRECTORY

This program is so simple that it should be considered public domain.