LinuxQuestions.org - [SOLVED] grep: Am I losing the plot?

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grep: Am I losing the plot?

This is typical output from 'sudo iwlist wlan0 scan'

Code:

wlan0    Scan completed :

          Cell 01 - Address: 90:5C:44:AC:70:A6

                    Channel:6

                    Frequency:2.437 GHz (Channel 6)

                    Quality=50/70  Signal level=-60 dBm  

                    Encryption key:on

                    ESSID:"VM3BE77B4"

It's clear that each entry has a Channel entry, and a Quality. I've been checking things because I have a very slow wifi issue. Mow here's my problem - these checks were within a minute of each other

Code:

pi@raspberrypi:~ $ sudo iwlist wlan0 scan |grep -c Channel

14

pi@raspberrypi:~ $ sudo iwlist wlan0 scan |grep -c Quality

9

pi@raspberrypi:~ $ sudo iwlist wlan0 scan |grep -A2 Channel

                    Channel:6

                    Frequency:2.437 GHz (Channel 6)

                    Quality=48/70  Signal level=-62 dBm  

                    Encryption key:on

--

                    Channel:9

                    Frequency:2.452 GHz (Channel 9)

                    Quality=57/70  Signal level=-53 dBm  

                    Encryption key:on

--

                    Channel:9

                    Frequency:2.452 GHz (Channel 9)

                    Quality=58/70  Signal level=-52 dBm  

                    Encryption key:on

--

                    Channel:44

                    Frequency:5.22 GHz (Channel 44)

                    Quality=55/70  Signal level=-55 dBm  

                    Encryption key:on

--

                    Channel:1

                    Frequency:2.412 GHz (Channel 1)

                    Quality=68/70  Signal level=-42 dBm  

                    Encryption key:on

--

                    Channel:36

                    Frequency:5.18 GHz (Channel 36)

                    Quality=48/70  Signal level=-62 dBm  

                    Encryption key:on

--

                    Channel:6

                    Frequency:2.437 GHz (Channel 6)

                    Quality=47/70  Signal level=-63 dBm  

                    Encryption key:on

--

                    Channel:1

                    Frequency:2.412 GHz (Channel 1)

                    Quality=43/70  Signal level=-67 dBm  

                    Encryption key:on

grep is seeing 14 Channel results, only 9 Quality results, and only 8 results on Channel when I ask for the next 2 lines :confused: :banghead:

That's not a good test for grep, that output changes all the time!
Why don't you test like this:

Code:

sudo iwlist wlan0 scan > text 2>&1

grep -c Channel text

...etc...

Quote:

Originally Posted by business_kid (Post 6151729)

and only 8 results on Channel when I ask for the next 2 lines :confused: :banghead:

x2 - notice that Channel occurs twice in each match.

Got more sanity in the wifi output so this issue disappeared. Marking it solved.

BTW average user, the grep had 'Channel:n' & '(Cannel:n )' in it, and I don't thing the second one showed

I don't understand what you mean but you can make a test:

Code:

$ sudo iwlist wlan0 scan > /tmp/IWLIST_RESULT

$ grep -c Channel /tmp/IWLIST_RESULT

16

$ grep -A2 Channel /tmp/IWLIST_RESULT | grep -c Channel

16

Yeah, here I got 34 & 34.But I went a bit further than your test, adding these lines

Code:

bash-5.0$ grep -A2 Channel /tmp/IWLIST_RESULT | grep -c (Channel

bash: syntax error near unexpected token `('

bash-5.0$ grep -A2 Channel /tmp/IWLIST_RESULT | grep -c \(Channel

17

So it appears the (Channel:n ) are being read and syntax errors ignored. That goes some was to explaining it.