xclip a handy utility for manipulating the X Window clipboard

[J65nko]

From the xclip(1) man page:

Reads from standard in, or from one or more files, and makes the data
available as an X selection for pasting into X applications. Prints current X selection to standard out.

When with the left mouse button you copy from a xterm window you also copy a lot of trailing whitespace. See the attached file for an example.

With xclip you can transfer a file or command output to the X clipboard

$ dmesg | head -4 | xclip 
$ xclip -o
OpenBSD 7.1 (GENERIC.MP) #3: Sun May 15 10:27:01 MDT 2022
    root@syspatch-71-amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC.MP
real mem = 4242419712 (4045MB)
avail mem = 4096557056 (3906MB)

Or you can paste into an program/application (e.g. forum message box) with the middle mouse button.

[victorvas]

There is also xsel, which works with X Window clipboard. "Retrieve and set the X selection."