Question

1

Filter results into a usable variable

rated 0 times [ 1] [ 0] / answers: 1 / hits: 2067 / 3 Years ago, sat, june 12, 2021, 6:25:33

I run the following command:

sudo iwlist eth0 scan

and get output that looks like this:

Cell 01 - Address: AB:CD:EF:12:34:56

          ESSID:"name"

          Protocol:IEEE 802.11g

          Mode:master

          Frequency:2.417 GHz (Channel 2)

          Encryption key:on

I won't bother filling it all out, as I'm trying to fix a laptop and I cannot simply copy the output.

How can I use built-in tools such as grep, awk, sed, etc. to fetch information given certain criteria? For example:

I want to grab the mac address when knowing the essid. I also don't want to rely on the Cell # or line positions. Knowing common information, like the word Address before the mac is fine.

Expected output:

AB:CD:EF:12:34:56

I want to use it in a variable, like so:

sudo iwconfig eth1 ap $(command)

Where command would result in the expected result. If there's another way of pushing the result as a variable using > or something, that works as well. (command > sudo iwconfig eth1 ap $1)

Thanks.

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cklaceowne

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3 Years ago

answered 3 Years ago atetamme · Accepted Answer

AWK is very powerful and perfect for this. Basically, you want to:

Save the address in the address line

If the ESSID matches your value, print it

The shortest version I could think of:

sudo iwlist wlan0 scan|awk '/Address:/{a=$5}/ESSID:"name"/{print a}'

/pattern/ is a regular expression that is compared with input. If it matches, the part after the curly brackets ({...}) is executed.

The awk command processes input line by line:

If a line matches Address:, the fifth field is stored in a variable named a. Fields are whitepace-delimited lines.

If a line matches ESSID:"name", variable a is printed (the last address that matched).

Both rules are executed, but 1 comes before 2 so a is always set.

Manual page for awk