[[XST]O_x]

https://sampwiki.blast.hk/wiki/OnPlayerKeyStateChange -- The public that checks if player has pressed any buttons.
https://sampwiki.blast.hk/wiki/GetPlayerKeys -- Scroll a little bit down to see the key list.

pawn Код:

public OnPlayerKeyStateChange(playerid, newkeys, oldkeys)
{
    if(newkeys & KEY_SECONDARY_ATTACK) // KEY_SECONDARY_ATTACK is enter/f.
    {
        SendClientMessage(playerid,0x00FFFFFF,"You have pressed enter!");
    }
    return 1;
}