you can think of this as a warm up exercise
WLAN Pi comes with a small CLI tool called wifichannel
This tool began as a simple conversion utility, for switching between channel numbers and centre frequencies.
Query wifichannel
with the command
The output gives you information about channel 7
Band: 2.4 GHz Channel: 6 Center freq: 2437 MHz
Recommended: Yes
Band: 6 GHz Channel: 17 Center freq: 6035 MHz
PSC: No
Lower 6 GHz
Band: 5 GHz Channel: 60
Center freq: 5300
MHz U-NII-2A
Band: 6 GHz
Channel: 21
PSC: Yes Lower 6 GHz
This command will help you if you are ever in doubts:
Note the Lower 6 GHz and Upper 6 GHz channels. In Czech Republic and most of Europe, we can only use the Lower 6 GHz channels.
You can filter the output of most command line utilities to make the output more efficient.
How many channels in the 2.4 GHz band are 'recommended'?
First, run the command to display all 2.4 GHz channels:
You could count the lines manually, but there is no need. Computers can already do that, really fast.
Using a linux utility called grep we can filter the output to only include lines that contain "a particular string or pattern":
Be precise with your search terms (strings), capitalisation matters.
Finally, we can simply count the number of lines returned by the command using word count, that command looks like this:
The wc
command has nothing to do with restrooms 😉 It stands for "word count" and its "l" parameter stands for lines.
3
You already knew that... right.
but... this filtering allows you to quickly get an answer from the output of command line tools.