Linux scan wireless card for information

Posted by Vivek Gite [Last updated: May 15, 2007]

Q. How do I scan wireless card under Linux to get information about AP and other details?

A. You can use command line tool called iwlist to get more detailed wireless information from a wireless interface i.e. card.

Iwlist is used to display some additional information from a wireless network interface that is not displayed by iwconfig. The main argument is used to select a category of information, iwlist displays in detailed form all information related to this category, including information already shown by iwconfig.

Task: Scanning wireless card

Type the command as follows:
iwlist {interface-name} scan

If your interface name is eth1, type
$ iwlist eth1 scan
If your interface name is ra0, type
$ iwlist ra0 scan
Sample output:

ra0       Scan completed :
          Cell 01 - Address: 00:18:39:6A:C6:8D
                    ESSID:"nixcraft"
                    Mode:Managed
                    Channel:6
                    Encryption key:on
                    Quality:70/100  Signal level:-59 dBm  Noise level:-256 dBm

scan option give the list of Access Points and Ad-Hoc cells in range, and optionally a whole bunch of information about them (ESSID, Quality, Frequency, Mode...). The type of information returned depends on what the card supports. Triggering scanning is a privileged operation (root only) and normal users can only read left-over scan results. By default, the way scanning is done (the scope of the scan) will be impacted by the current setting of the driver.

You can also find information from Linux proc file system, by typing command:
# cat /proc/net/wireless
Output:

Inter-| sta-|   Quality        |   Discarded packets               | Missed | WE
 face | tus | link level noise |  nwid  crypt   frag  retry   misc | beacon | 21
   ra0: 0000   55.  198   177        0      0      0      0      0        0

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