xclip is a command line utility that is designed to run on any system with an
X11 implementation. It provides an interface to X selections ("the clipboard")
from the command line. It can read data from standard in or a file and place it
in an X selection for pasting into other X applications. xclip can also print
an X selection to standard out, which can then be redirected to a file or
another program.

FEATURES
========

* Reads data piped to standard in or files given as arguments
* Prints contents of selection to standard out
* Accesses the XA_PRIMARY, XA_SECONDARY or XA_CLIPBOARD selection
* Supports the INCR mechanism for large transfers
* Connects to the X display in $DISPLAY, or specified with -display host:0
* Waits for selection requests in the background

WWW: http://sourceforge.net/projects/xclip/