根据man页面pbpaste,
-Prefer {txt | rtf | ps}
tells pbpaste what type of data to look for in the pasteboard
first. As stated above, pbpaste normally looks first for plain
text data; however, by specifying -Prefer ps you can tell
pbpaste to look first for Encapsulated PostScript. If you spec-
ify -Prefer rtf, pbpaste looks first for Rich Text format. In
any case, pbpaste looks for the other formats if the preferred
one is not found. The …