When you want to retrieve the surrounding AP's signal strength, you could use the command:
curl -u adm:123456 192.168.2.1:4444/update.cgi -d "exec=wlscan" -H "Content Type:text/plain"
You can see the result as below:
When you want to retrieve the wifi-connected devices' information and signal strength, the command is:
curl -u adm:123456 192.168.2.1:4444/update.cgi -d "exec=stainfo" -H "Content Type:text/plain"
