TextEdit is a simple application for quickly writing text and notes. The text can be edited in RTF (Rich Text Format) mode, as well as plain text. With the following defaults write command you can enable plain text as default format in TextEdit.
If you regularly use TextEdit, you will notice that TextEdit displays the ruler by default when creating or opening rich text documents. It’s not possible to turn off the ruler by default in Preferences. Offcorse you can You can disable the ruler in TextEdit with the following OS X Terminal command: