Non-printable characters on Linux, macOS, or Windows are characters that do not represent a symbol, character, or number that is part of the document's text, but rather are used for things like character encoding. A full list of all non-printable characters along with their decimal and hexidecimal codes are shown below.
How to Find Non-Printable Characters in a File
If you need to see all nonprintable characters in a document, you can use cat -v filename.txt in terminal to find them, where filename.txt is the file you want to show. The contents of the file, along with the non-printable characters in caret notation will be shown in your terminal window.