Is there any way to copy all lines from a file to clipboard in VI editor. I have tried *yG, +yG, \"+yG and :%y+ from prev
G just means "go to the end of the file", and you need quotes before * or + to make them effective as clipboard registers. You're looking for something more like gg"*yG which means:
gg - go to the top of the file
"* - use the * register
y - begin yank
G - go to the bottom of the file
or you could use :!cat % | pbcopy which is not unlike the fine solutions romainl provided.