pbcopy and pbpaste are handy, for a version that works over ssh connections there is osc: https://github.com/theimpostor/osc
 replies(4): 
    if [[ "$(uname)" == "Darwin" ]]; then
      clip() {
        [ -t 0 ] && pbpaste || pbcopy
      }
    else # assume linux if not macos
      clip() {
        [ -t 0 ] && xclip -o -selection clipboard || xclip -selection clipboard
      }
    fi