There is a command line tool that allows you to work with the wireless connection on your Mac. The tool is very useful but by default hidden and not well documented.

airport

# show airport help
$ /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport --help

networksetup

# find device names
$ networksetup -listallhardwareports

Turn on/off and join

# turn it off
$ networksetup -setairportpower en0 off

# turn it on
$ networksetup -setairportpower en0 on

# join a network
$ networksetup -setairportnetwork en0 <SSID> <Password>

Let`s start a wifi scan and get some information

# scan with interface en0
$ /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport en0 --scan

# show information of en0
$ /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport en0 --getinfo

Note: If do not specify the interface, airport will use the first wifi interface on the system.

Easy way

# create a symbolic link to the command
$ sudo ln -s /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport /usr/sbin/airport

# after link created start the scan
$ airport en0 --scan

Sniff

# find WEP
$ airport en0 scan | grep WEP

# start sniff on channel
$ airport en0 sniff 6

The captured packets you will find as “/tmp/airportSniffXXXXXX.cap”.