for macOS, set your preferred wireless network

setpreferredwirelessnetwork.sh

#!/bin/bash
preferredNetwork="$1"
securityType="$2"
​
# For securityType, 
# use OPEN for none, 
# WPA for WPA Personal, 
# WPA2 for WPA2 Personal, 
# WPA/WPA2 for WPA/WPA2 Personal, 
# WPAE for WPA Enterprise,
# WPA2E for WPA2 Enterprise,
# WPAE/WPA2E for WPA/WPA2 Enterprise,
# WEP for plain WEP, and 
# 8021XWEP for 802.1X WEP.
​
numIF=$(($(ifconfig | grep -E "^en.*:" | wc -l | tr -d "[:space:]")-1))
​
for ((interfaceNum=0;interfaceNum<=$numIF;interfaceNum++)); do
    if networksetup -listpreferredwirelessnetworks en$interfaceNum | grep -q "$preferredNetwork"; then
        networksetup -removepreferredwirelessnetwork "en$interfaceNum" "$preferredNetwork"
        networksetup -addpreferredwirelessnetworkatindex "en$interfaceNum" "$preferredNetwork" 0 "$securityType"
        printf "Set %s to index 0 for %s\n" "$preferredNetwork" "en$interfaceNum"
        ifconfig en$interfaceNum down && ifconfig en$interfaceNum up
        exit 0
    fi
done
printf "Could not set preferred network.\n"
exit 1