Windows. Another selection, PRIMARY, is an X11-specific mechanism. Data is "copied" immediately upon highlighting and pasted with the third (middle) mouse button. This copied data is usually separated from the CLIPBOARD selection and does not change its contents. SECONDARY was planned as an alternative to PRIMARY but is only used inconsistently.

Command line access to the three clipboards is available with tools and .$ # to paste standard output to the clipboard using xclip$ echo text | xclip -in -selection clipboard$ # to paste standard output to the clipboard using xsel$ echo text | xsel --clipboard