In Ubuntu 11.04 I used InSSIDer to scan the available APs and sort them by signal strength.
Unfortunately the program seems to be broken in Ubuntu 11.10, and
iwlist wlan0 scan
doesn't return anything meaningful.
What options do I have to scan for available Wireless Access Point, possibly with a GUI?
sudo iwlist wlan0 scanning | egrep 'Cell |Encryption|Quality|Last beacon|ESSID' should help.
It's the combination of sudo (run as root, do privileged operations), iwlist wlan0 scanning (produce some output on STDOUT), the pipe symbol "|" (connecting STDOUT of the command(s) to the left to the STDIN of the process on the right), and an egrep command with a "single quoted" (to prevent the shell from interpreting the "|" characters) Regular Expression to filter STDIN. See man bash, man sudo, man iwlist, man egrep, and man re_format for details.
ALWAYS do man whatever (as above) BEFORE you execute a command string from someone else. Self-education is much safer than blind trust.
iwI don't have nm-tool installed so I use iw.
This command sorts access points by signal strength, strongest first:
sudo iw wlan0 scan | grep -Po '(signal|SSID):\K.*' | sed 's/ $/ [unknown SSID]/' | paste -d ' ' - - | cut -c2- | sort -gr
iw wlan0 scanScan for access points reachable via interface wlan0.
grep -Po '(signal|SSID):\K.*'Grep gets the text after "signal:" or "SSID:". See this answer to learn more about the used options and \K.
Reduces the output of iw wlan0 scan to something like this:
-77.00 dBm nameOfAccessPoint1 -69.00 dBm-71.00 dBm nameOfAccessPoint2
Note that the access point with signal strength -69 dBm doesn't broadcast an SSID, the output of grep is a single space on that line.
sed 's/ $/ [unknown SSID]/'To make the fact that the SSID is unknown explicit, we replace the single space with [unknown SSID]. The output of sed is:
-77.00 dBm nameOfAccessPoint1 -69.00 dBm [unknown SSID] -71.00 dBm nameOfAccessPoint2
paste -d ' ' - -With paste we join two consecutive lines with a space in between. This produces:
-77.00 dBm nameOfAccessPoint1 -69.00 dBm [unknown SSID] -71.00 dBm nameOfAccessPoint2
cut -c2- | sort -grWith cut -c2- we remove the leading space and sort orders the lines by dBm, smallest numerical value first. Which means the access points are sorted by signal strength, strongest first.
-69.00 dBm [unknown SSID] -71.00 dBm nameOfAccessPoint2 -77.00 dBm nameOfAccessPoint1
Here's another way to get access points sorted by signal strength. Mind that this command does not take care of access points with an empty SSID:
sudo iw wlan0 scan | egrep "signal:|SSID:" | sed -e "s/\tsignal: //" -e "s/\tSSID: //" | awk '{ORS = (NR % 2 == 0)? "\n" : " "; print}' | sort -gr
iw wlan0 scanScan for access points reachable via interface wlan0.
egrep "signal:|SSID:"Get the lines with signal strength and the SSIDs from iw's output. The output looks like this now:
signal: -77.00 dBm
SSID: nameOfAccessPoint1
signal: -71.00 dBm
SSID: nameOfAccessPoint2
sed -e "s/\tsignal: //" -e "s/\tSSID: //"We reduce egrep's output to this:
-77.00 dBm nameOfAccessPoint1 -71.00 dBm nameOfAccessPoint2
awk '{ORS = (NR % 2 == 0)? "\n" : " "; print}'Bring the signal strength and the SSID on the same line. More specifically, when the line number (NR) is even, i.e., we are on a line showing an access point, the output record separator (ORS) should be a line break. Otherwise, we are on the line containing signal strength, so we join the line by making ORS a simple space.
sort -grIf we sort this output by numerical value (-g) and reverse it (-r), we end up with a list of signal strengths and access points, showing the access point with the strongest signal on top:
-71.00 dBm nameOfAccessPoint2
-77.00 dBm nameOfAccessPoint1
Beware: Some access points can have an extended capability:
Extended capabilities:
* SSID List
This means grepping "SSID:" instead of "SSID" helps avoiding this extra output which would make the command fail otherwise.
You can also use nmcli, I found it myself a few months back and it's the easiest one I've used so far.
nmcli device wifi
Example output:
IN-USE BSSID SSID MODE CHAN RATE SIGNAL BARS SECURITY
18:7B:CB:42:EF:8E FRITZ!Box 7530 MS Infra 11 260 Mbit/s 100 ▂▄▆█ WPA2
* D1:12:C8:87:D7:F1 FRITZ!Box 7530 MS Infra 6 130 Mbit/s 75 ▂▄▆_ WPA2
DD:72:2D:64:04:C9 example network Infra 11 130 Mbit/s 65 ▂▄▆_ WPA1 WPA2
2C:A1:F2:9E:97:2E FRITZ!Box 7530 MS Infra 11 130 Mbit/s 57 ▂▄▆_ WPA2
11:22:F5:89:71:9C some_other_network Infra 6 130 Mbit/s 55 ▂▄__ WPA2
nm-tool | grep "Freq.*Strength" | sed -ne "s|\(.*Strength \([0-9]\+\).*\)|\2}\1|p" | sort -n -r
nm-tool to get list of Wireless Access Pointssed to append signal level in front of each linenm-tool is part of "network-manager" package that is obviously installed in a typical Ubuntu system.
If you can install software on your machine, I would recommend wavemon.
To install it run:
sudo apt-get update
sudo apt-get install wavemon
To run it:
sudo wavemon
Then press F3 for the scan window. You should see something similar to this:
wpa_cliUsing wpa_cli , which is part of wpa_supplicant, you can get information about local Wi-Fi networks:
sudo wpa_cli scan && sudo wpa_cli scan_results
Example output:
Selected interface 'wlp3s0'
bssid / frequency / signal level / flags / ssid
23:99:21:91:89:34 2462 -50 [WPA2-PSK-CCMP][WPS][ESS] SSID_8
42:5d:25:a2:f5:7a 2462 -59 [WPA2-PSK-CCMP][WPS][ESS] SSID_7
21:99:94:b1:89:3b 5180 -54 [WPA2-PSK-CCMP][WPS][ESS] SSID_6
52:7d:2d:96:f4:d9 5500 -67 [WPA2-PSK-CCMP][WPS][ESS] SSID_5
54:7d:3d:a6:f4:c0 2412 -52 [WPA2-PSK-CCMP][WPS][ESS] SSID_4
9d:34:16:a0:04:81 2437 -53 [WPA2-PSK-CCMP][WPS][ESS] SSID_3
e9:40:e2:b3:58:dd 2412 -64 [WPA-PSK-CCMP+TKIP][WPA2-PSK-CCMP+TKIP][ESS] SSID_2
4a:5d:25:72:f5:79 5580 -72 [WPA2-PSK-CCMP][WPS][ESS] SSID_1
iwinfo wlan0 scan
wlan0 is you wireless interface
the result like below list ...
Cell 06 - Address: F0:B4:29:50:76:0C
ESSID: "Xiaomi_760B"
Mode: Master Channel: 1
Signal: -38 dBm Quality: 70/70
Encryption: mixed WPA/WPA2 PSK (TKIP, CCMP)
....
the command will return encryption info
system : openwrt 15.05
