For automatic connect to free WiFis i've made the bash script
freewifi_autoconnect.sh in 2010 and do update it every every few months.
The script scanns for free WiFis, sorts them due to their signal strength and connects
one after the other till it finds one which is really online. If the connection
gets lost it reconnects and if that does not work it searches for other free WiFis and so on.
The script status is mature, the changelog is in the header and the script has a good online-help, availible via the parameter --help.
The script is optimized for privacy and leaves no traces: The own MAC-Address gets randomized (changed to a random other) before each scan, so that your hardware MAC-Address(es) can not be seen. The script creates only temporary files, only in RAMFS, and deletes them with a bash trap function to leave no traces.
A free WiFi is a WiFi with an obvious invitation for free usage because it is a) open (unencrypted), b) is public, has a range to a public place like a public street or public way, c) has no obstacles like a MAC filter, d) has a working DHCP server which gives an IP, DNS server, Gateway etc. and e) gives Internet access, with the given IP or the IP of the Gateway (via NAT).
An open WiFi has generally only a), so the free WiFis are a subset of open WiFis. Free WiFis are made obviously for free usage, jurists do name this conduct implying an intent.
An Article about the script is "Automatic Usage of Free Wi-Fi" in 2600 Volume Twenty-Eight, Number one, Spring 2011.
With this script you don't have to look or scan for free WiFis and you don't have to (re-)connect and test them. You only have to start the script, e. g. via a boot script.
It works e. g. under Knoppix 6.2, OpenSuSE 12.3 and Ubuntu 13.04.
No old lock file found (ok). List of 2 availible WIFI device(s): wlan0 wlan15 Device wlan0: Old MAC = 4f:19:9b:0d:ad:50 permanent MAC = c8:f7:33:bf:68:7d new MAC = 4e:de:41:9f:ba:85 Scan number 0, scanning ................................................................... Found 1 open WIFI(s) and 4 closed WIFI(s). List of WIFI(s) with Channel, Encryption, Quality, Signal Level, MAC, ESSID, Vendor: 7 on 48/70 -59 00:0F:DE:00:42:40 "NewYork" "Sony Ericsson Mobile Communications AB" 1 off 66/70 -40 00:17:4D:D5:B5:DA "freitag_2.4_GHz" "DYNAMIC NETWORK FACTORY, INC." 1 on 21/70 -88 10:C5:1F:2C:21:CE "WLAN-21CE46" "" 1 on 26/70 -97 02:25:4D:F4:4B:F3 "" "" 11 on 23/70 -76 10:BE:48:3E:2A:BB "Skynet" "" Sorted list of 1 free WIFI(s): Channel:1 off Quality=66/70 level=-40 00:17:4D:D5:B5:DA "freitag_2.4_GHz" Checking the open WIFI with MAC 00:17:4D:D5:B5:DA, Channel 1, ESSID freitag_2.4_GHz inet addr:192.168.1.132 Bcast:192.168.1.255 Mask:255.255.255.0 Connectet: Station 00:17:4d:d5:b5:da (on wlan0) inactive time: 56 ms rx bytes: 5350 rx packets: 70 tx bytes: 886 tx packets: 5 tx retries: 0 tx failed: 0 signal: -38 dBm signal avg: -38 dBm tx bitrate: 1.0 MBit/s authorized: yes authenticated: yes preamble: long WMM/WME: yes MFP: no TDLS peer: no wlan0 IEEE 802.11abgn ESSID:"freitag_2.4_GHz" Mode:Managed Frequency:2.412 GHz Access Point: 00:17:4D:D5:B5:DA Bit Rate=1 Mb/s Tx-Power=15 dBm Retry limit:30 RTS thr=1 B Fragment thr:off Encryption key:off Power Management:off Link Quality=70/70 Signal level=-38 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:2 Missed beacon:0 Inter-| sta-| Quality | Discarded packets | Missed | WE face | tus | link level noise | nwid crypt frag retry misc | beacon | 22 wlan0: 0000 70. -38. -256 0 0 0 0 2 0 DNS lookup check: 2 DNS lookup(s) successfull! ...It is useful e. g. to test you own Access Point (AP) or to go online to check the emails or read some news even when you have no own internet connection but you can use a free WIFI.
freewifi_autoconnect.sh now prints the wifi data also in files in the
directory /tmp/wifiscan for the program
wifiscan.c. This program makes a list of the wifis with
exponential smoothing of the quality and the level, so that most
of the noise is eleminated. This is much better than signaling the signal
level with only five bars, like from MS-WindowsXP.
Programs like Linssid are much better, do show the level (0... -100), but have the problem that the level is noise, so it can't be used for detailed measurements, e. g. for comparing antennas or boosters with an accuracy of 1 dB.
Example: For the WiFi dlink MS-WindowsXP displays one bar, the program displays a quality of 0.494 and a level of -75.39, where the level is roughly the power in dBm.
The Level is also called RSSI (Received Signal Strength Indikator) and indicates the received power in that channel, including all sources, even thermal noise but no zero-point noise. Without calibration the RSSI is only propotional to the power in dBm and not the same.
Example: With a 18 dBi yagi antenna a WL0162 shows the (channel with the) router with a level of -51, another WL0162 shows -58 and an AWUS051NH shows -65.
Example output, with sorting due to the Level:
Ch. Enc. Qual. Level MAX MIN MAC t f count ESSID 1 1 0.371 -84.00 -84 -84 02:24:01:55:49:50 31 O 5 "dlink" 6 1 0.389 -82.79 -80 -86 14:D6:4D:CF:D8:9C 21 O 34 "DIR-615" 11 1 0.406 -81.61 -78 -82 74:31:70:76:08:D0 1 f "WLAN-760829" 1 1 0.408 -81.46 -76 -86 74:31:70:27:9A:CE 2 2bf "ALICE-WLAN89" 11 1 0.427 -80.13 -68 -86 00:1F:3F:BA:C5:51 2 568 "wi-fi" 6 1 0.449 -78.54 -76 -84 00:12:2A:06:89:23 12 O d "Sinus 7 1 0.494 -75.39 -66 -82 FC:75:16:7A:2B:3B 2 955 "dlink" 2 1 0.527 -73.10 -68 -84 00:1A:2A:18:4C:3F 2 1073 "WLAN-184C85" 9 1 0.575 -69.76 -58 -84 00:1F:3F:75:A8:0B 2 6a9 "Skynet" 1 1 0.687 -61.88 -58 -70 00:26:4D:C8:44:83 1 39d "" 4 1 0.992 -35.78 -24 -70 1C:7E:E5:00:42:40 2 1d02 "NewYork"Via the keys for 0, 1, ... 9 the data can be sorted due to the channel, encryption (0=off, 1=on), Quality, Level, Level Minium, Level Maximum, MAC, time since last successfull scan, Count or ESSID.
If you know the parameters of the Wifi (device, ESSID, channel, IP) you want to use, e. g. your own router,
you can simply use a simple short script:
ifconfig $DEVICE down
iwconfig $DEVICE essid $ESSID
iwconfig $DEVICE channel $CHANNEL
iwconfig $DEVICE mode Managed
iwconfig $DEVICE ap any
ifconfig $DEVICE inet $IP
rfkill unblock wifi
ifconfig $DEVICE up
ping -c 1 $AP
This method connects immediately; there is no waiting for an answer from the router! And the router does not need a DHCP server.
The kernel uses another association method, which silently disables the device after a timeout of a few seconds, when the AP does not answer; ifconfig, iwconfig and other tools can't show the silently disabled status.
A simple workaround is to disable and enable manually, simply "ifconfig $DEVICE down; ifconfig $DEVICE up". And this can be automated with a script wich checks the connection with pings.
For MAC randomisation, default gateway, encryption and other features you have to add some lines more.
I updated the script with few changes, because the DNS root nameserver D has a changed IPV4 IP (now 22.214.171.124, it was 126.96.36.199).
The script uses this IP for testing the translation (resolution) of the current name server, often in the WiFi router.
BTW: At tests with the script under Ubuntu 14.10 i often had the problem of hangsups so that even Magic SysRq does not work and the reason seems to be bootchart: http://forums.linuxmint.com/viewtopic.php?f=46&t=121457 .
I updated the script with several changes, because in the Hotel NH Cordillera in Mendoza, Argentina,
checking the connection only to the AP with (ICMP) pings works good because even downloading of small
files takes longer than 6 seconds. For this mode 4 (and higher) the script now gets the default gw from the route output.
I also added Mode 5 which is like 4 but with ARP instead of ICMP pinging the AP, because more and more APs do a) not connect to the internet directly and b) do not answer ICMP pings. I found this in a hotel in Santiago (Chile), in an Iberia airplane (IBE6830) and on the international airport Madrid. In the plane and at the airport the new mode 5 worked without problems. So i could use the "first free 30 minutes" in Madrid eight times :-)
It should also work at all other places with "First 30 Minutes FREE", e. g. airport Auckland, JFC etc., after clearing the browser history (including Cache and Cookies), because the script always starts with a random MAC which is not the hardware MAC.
BTW: Unter Windows 8.1, after 1.5 years and about 50 boots, suddenly the "Intel WiFi Hotspot-Assistent" poped up on my Ultrabook for the first time and could connect to the hotel WiFi at booting. But after the third reboot something from Windows 8.1 degenerated and this did not work anymore, but my script still works.
I added some lines for terminating/stopping of other processes which would disturb the script, e. g. NetworkManager.
I Changed the scanning of the channel number, which did not work for channel numbers greater 100.