Yammp Shell (ysh) commands are usually saved as text files and redirected to the standard input of mimesis. In the following, shell commands are set in teletype font; variables are italized; choices are separated by |, preset or default values are set in bold type and ellipses ... indicate more of the previous object. Text between # and the end of the line are ignored.

Words can be abbreviated to no fewer than four characters provided there is no ambiguity in doing so. Command words are case-sensitive. Commands cannot be split (they must be written complete in one line) and each line may contain only one command. The entire script is translated first and if there are no syntax errors the assembled commands are then executed. Ysh is not an interactive command language, interpretation of the script stops at the first syntax error and mimesis is stopped. Nevertheless, there are a couple of interactive commands; these are for programming support.