Question: To scan all available wifi networks, this command is often used :

`sudo iwlist wlp2s0 scan`

The problem is that you need root privileges.
But if you go to Settings/Wi-Fi, you can see the list and properties of Wifi networks even without being sudo.

How is it done ? What is the command used to achieve that ?

Answer: 
I am not sure if you missed this simple command or I understood your Question wrongly..

`nmcli device wifi list` does not require sudo..

Example:

```
pratap@i7-4770:~$ nmcli device wifi list
IN-USE  SSID         MODE   CHAN  RATE        SIGNAL  BARS  SECURITY 
*       Sri Nilayam  Infra  11    270 Mbit/s  54      ▂▄__  WPA2     
pratap@i7-4770:~$ 

```

from `man nmcli`

Some content:

```
   wifi [list [ifname ifname] [bssid BSSID]]
       List available Wi-Fi access points. The ifname and bssid options can be used to list
       APs for a particular interface or with a specific BSSID, respectively.

```
If you want to see all the AP's around you, should disconnect from your own AP first, then run nmcli.

nmcli -f ssid,bssid,freq,chan,signal,security,wpa-flags,bars dev wifi list