There's pbcopy/paste in MacOS, xsel and wl-copy/paste in Linux, and
clip.exe/powershell.exe -c Get-Clipboard in WSL. This tool selects whichever
command is appropriate.
You don't get to specify which "clipboard" you're copying to or pasting from,
it's going to whichever is used when you press Ctrl+C/Ctrl+V in programs
with a GUI.
See the latest release for instructions.
There are two commands: clipboard_copy and clipboard_paste.
They operate on stdin and stdout respectively. You can also source
clipboard.sh to use them as functions instead.
In Linux wayland wl-copy infers a MIME type from the content using xdg-mime,
this can result in content not being pasteable (e.g. X.509 PEM certificates).
You can override that MIME type using the $CLIPBOARD_MIME_TYPE environment
variable when invoking clipboard_copy.
This variable can also be used to select which MIME type you would like to use
when invoking clipboard_paste.