It would be useful to have a command line interface to xfce4-clipman to allow paste and copy operations from scripts and Terminals.

My suggestion would be "-get" and "-put" options, as follows:

-get [CLIPBOARDITEM]
   Prints to stdout the clipboard entry specified by CLIPBOARDITEM,
   or the current entry if CLIPBOARDITEM was not given.
   CLIPBOARDITEM can be:
   -integer n from 0..historysize-1:
      prints current (n=0) or nth clipboard entry
      if n >= historysize print an empty string.
   -a string: print the first clipboard entry matching the string.
      (plain case-sensitive matching is good enough;
       fancy regex nice but not crucial).

-put [STRING]
   Adds STRING to the clipboard. If STRING is not specified, read it from stdin (allow pipes)

Examples:

$ xfce4-clipman -get
orange
$
$ xfce4-clipman -put "not apple"
$ w3m -dump checkip.dyndns.org | awk  '{ print $4 }' | xfce4-clipman -put
$ xfce4-clipman -get 2
orange
$ xfce4-clipman -get "app"
not apple
$