Is there any way to copy all lines from open file to clipboard in VI editor. I tried yG but it\'s not using clipboard to store those lines.
So
You can use a shortcur, like this one:
noremap :%y+
It means, when you push F6 in normald mode, it will copy the whole file, and add it to the clipboard. Or you just can type in normal mode :%y+ and then push Enter.
:%y+
Enter