How to directly copy screenshot to slack/skype in Mac OS X like snipping does in windows

macOS has more screenshot/snipping tool options than you could know what to do with…

Cmd ⌘ Shift ⇧ 3 - Capture entire screen[s]
Cmd ⌘ Shift ⇧ 4 - Capture selected area
Cmd ⌘ Shift ⇧ 4 then tap Spacebar - Capture next window clicked, with drop-shadow.
Add Ctrl ⌃ to any of the above - Capture to clipboard instead of file.

and the new one since Mojave…
Cmd ⌘ Shift ⇧ 5 - Presents an interface to select from all of the above, plus cursor switch, timed modes, save location options & video recording alternatives.

As all these methods access the same underlying process, any prefs you set in the new Cmd ⌘ Shift ⇧ 5 interface will be carried over into the other methods [except the timer, which you can only do with the new interface.]

Extended Tetsujin answer -

Cmd ⌘ + cntl + Shift ⇧ 3 or 4

It will store in screenshot in clipboard/cache.

For permanent settings below are the steps:

Using clipboard

• Step 1 :- Cmd ⌘ Shift ⇧ 5
• Step 2 :- Now in option change the save to clipboard
• Step 3 :- Goto to slack or skype etc and press Cmd ⌘ + v

Using preview

• Step 1 :- Cmd ⌘ Shift ⇧ 5
• Step 2 :- Now in option change the save to preview
• Step 3 :- From Menu -> Edit -> Copy
• Step 4 :- Goto to slack or skype etc and press Cmd ⌘ + v

This is one time setup after that you can go for any option.

Now you do any type of screenshot option sets for all, i.e press cmd+4, it will do behave similarly