Wifi script to display current connection

[shep]

I'm working on a script which I plan to call from a x11/tint2 panel button. The goal is provide a quick means to display the parameters of the current wifi connection that are available to non-root users.

obsd_wifi_tint2.sh

#!/bin/ksh
echo "Current Wifi Connection:"
echo ""
ifconfig | tr " " "\n" | grep -A5 nwid > wifi.txt
echo "s/n" >> wifi.txt
ifconfig | tr " " "\n" | grep -A6 nwid | tail -n -1 >> wifi.txt
echo "ip" >> wifi.txt
ifconfig | tr " " "\n" | grep -A1 inet | tail -n -2 | tail -n -1 >> wifi.txt
cat wifi.txt | paste -s -d '\t\n' -
rm wifi.txt

The output displays:

Current Wifi Connection:

nwid    Shepnet
chan    8
bssid   d8:eb:97:23:bb:1b
s/n     -80dBm
ip      192.168.2.5

My sense of scripting is that there are many ways to achieve the same result so I'm looking for comments on correctness, efficient methodology and style. It started as a one-liner, but ifconfig inconsistently pairs parameter name/parameter value. Signal strength and IP address had no parameter name so I appended them. I played with different table outputs and ended up using "paste" to 2 columns.

[jggimi]

I'm not much of a script writer, but I do recommend you use mktemp(1) rather than creating and deleting a file in the working directory.

[TronDD]

Not that it probably matters much here, but to possibly improve efficiencyi: you're taking the entire output of ifconfig and translating every space to a new line then using grep and throwing away most of that work.

Grep first, then translate.

But I like to use cut(1) which can return multiple parts. For example:

ifconfig | grep nwid | cut -d ' ' -f 3,5,7

I would also try to build the result in a variable instead of using a file.

[J65nko]

I also would recommend to create a temporary file with mktemp(1) in the /tmp directory.
But if you use a so-called "Here document" you don't need to use a temporary file at all.

#!/bin/sh

IP="$(ifconfig | tr ' ' "\n" | grep -A1 inet | tail -n -2 | tail -n -1)"

cat <<END
--------------------------------
Wifi parameters
-------------------------------
IP      : ${IP}
END

This will produce on my non-Wifi desktop:

--------------------------------
Wifi parameters
-------------------------------
IP      : 192.168.222.242

[shep]

Initially I was able to capture nwid XXXX, chan XX and bssid XX:XX:XX:XX:XX with the first ifconfig invocation but it is messy and not clear what the code is doing. I'm thinking I'll use @j65nk0 "Here Document" strategy and parse out nwid, chan, bssid, s/n and ip to 5 variables and then 'cat' them to sdtout. I think this would make it easier for users to customize their outputs. Also will read up on cut and see if I can extract the values more efficiently than pipeing through 2 instances of tail.

Thanks

[J65nko]

Considering the possibility that the WiFi parameters in theory could change between multiple invocations of ifconfig you could save its text output in a variable once. You then echo that variable multiple times for each processing with grep.
The resulting output could in theory be out of date, but at least it would be a consistent report of the past ....

[shep]

I was thinking in terms of just the current connection when using the new auto-join feature:
OpenBSD gains Wi-Fi "auto-join".
At an area with several Access points, it would be nice to see and perhaps decide to adjust.

Revised script

#!/bin/ksh
NWID="$(ifconfig | grep nwid | cut -d " " -f 3)"
CHAN="$(ifconfig | grep nwid | cut -d " " -f 5)"
BSSID="$(ifconfig | grep nwid | cut -d " " -f 7)"
SN="$(ifconfig | grep nwid | cut -d " " -f 8)"
IP="$(ifconfig | grep inet | cut -d " " -f 2 | tail -n -1)"
cat <<END
----------------------------------
Current WiFi Connection Parameters
----------------------------------

NWID    :  $NWID
CHAN    :  $CHAN
BSSID   :  $BSSID
S/N     :  $SN
IP      :  $IP
END

with this output

-----------------------------------
Current Wifi Connection Parameters
-----------------------------------

NWID     :  Shepnet
CHANNEL  :  8
BSSID    :  d8:eb:97:23:bb:1b
S/N      :  -81dBm
IP       :  192.168.2.5

The next step is a script to scan. I've seen commits that some intel wifi chips can do a full scan without stopping and restarting the connection. Don't believe that this applies to Realtek, RaLink or Atheros chips.

[J65nko]

hp_server$ cat -n shep_final
     1  #!/bin/ksh
     2  NWID="$(ifconfig | grep nwid | cut -d " " -f 3)"
     3  CHAN="$(ifconfig | grep nwid | cut -d " " -f 5)"
     4  BSSID="$(ifconfig | grep nwid | cut -d " " -f 7)"
     5  SN="$(ifconfig | grep nwid | cut -d " " -f 8)"
     6  IP="$(ifconfig | grep inet | cut -d " " -f 2 | tail -n -1)"

Maybe I don't understand you because of my lack of WiFi experience, but what I meant is that the NWID you capture from the ifconfig output in line 2 could be in theory out of date/changed when you capture the IP in line 6. A race condition.

To prevent this race condition the following snippet that runs ifconfig once and reuses it for extracting the other data fields.You only have to keep in mind that newlines are converted to blanks/spaces when text output is saved in a variable. Actually this depends on the value of the shell's internal IFS variable.

#!/bin/sh

# newlines are converted to blanks/spaces ....
IFCONFIG=$(ifconfig)
echo ${IFCONFIG}

# IFS; Inter Field Separator (see man ksh)
# to preserve newlines,save and set IFS to space only   
OLD_IFS="${IFS}"
IFS=" "

# capture 'ifconfig' output once and reuse ....
IFCONFIG=$(ifconfig)
echo ${IFCONFIG}

NWID="$(echo ${IFCONFIG} | grep nwid | cut -d " " -f 3)"
#
#
#
IP="$(echo ${IFCONFIG} | grep inet | cut -d " " -f 2 | tail -n -1)"

cat <<END
--------------------------------
Wifi parameters
-------------------------------
NWID    : ${NWID}



IP      : ${IP}
END

And by using awk(1) you can get a slightly simpler extraction:

hp_server$  ifconfig | grep inet | tail -n1 | awk '{print $2}'           
192.168.222.242

[shep]

@J65nko

It makes sense to capture the output and then parse. With auto-join, a weak signal could drop the connection and establish a new, different connection. If that happened while running the script, the script output would be an inaccurate mix of 2 access points. I will read up on awk and try again tomorrow.

[shep]

The 'awk' extractions when smoothly but then I tested with my wifi turned off. The script still produced an IP address. I spent the morning trying to write a test for an active connection with a conditional if-the-else.

#!/bin/ksh
#TEST=$(nc -dzw1 8.8.8.8 443)
#CONN="$(echo ${TEST} | awk '{print $1}')"
#if test ${CONN} = Connection
#then

# IFS; Inter Field Separator (see man ksh)
# to preserve newlines,save and set IFS to space only   
OLD_IFS="${IFS}"
IFS=" "

# capture 'ifconfig' output once and reuse ....
IFCONFIG=$(ifconfig)
#echo ${IFCONFIG}

NWID="$(echo ${IFCONFIG} | grep nwid | awk '{print $3}')"
CHAN="$(echo ${IFCONFIG} | grep nwid | awk '{print $5}')"
BSSID="$(echo ${IFCONFIG} | grep nwid | awk '{print $7}')"
SN="$(echo ${IFCONFIG} | grep nwid | awk '{print $8}')"
IP="$(echo ${IFCONFIG} | grep inet | tail -n1 | awk '{print $2}')"

cat <<END
----------------------------------
Current WiFi Connection Parameters
----------------------------------

NWID	:  $NWID
CHAN	:  $CHAN
BSSID	:  $BSSID
S/N	:  $SN
IP	:  $IP
END
#else
#cat <<END
#----------------------------------
#Currently No WAN Connection
#----------------------------------
#END
#fi

nc -dwz1 8.8.8.8 443 does output

Connection . . . . successful!

but my attempts to capture "Connection" and match the string fail.

I'm also not completely happy with nc 'ing 8.8.8.8 443. I can envision that the Router/LAN is up but the WAN is down.

Critique/Suggestions?

[J65nko]

If you save the output of ifconfig in a shell variable the newlines are eliminated or replaced with a blank.This results in a single line of text without embedded newlines

hp_server$ X="$(ifconfig bge)"
hp_server$ echo $X
bge0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500 lladdr 98:4b:e1:10:08:6b index 1 priority 0 llprio 3 groups: egress media: Ethernet autoselect (100baseTX full-duplex,rxpause,txpause) status: active inet 192.168.222.242 netmask 0xffffff00 broadcast 192.168.222.255

Your invocations of grep will now all return this single line. ;-)
To prevent this you have to customize the internal shell variable IFS to a space.

hp_server$ sh -c 'IFS=" " ; X="$(ifconfig bge)" ; echo $X'   
bge0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        lladdr 98:4b:e1:10:08:6b
        index 1 priority 0 llprio 3
        groups: egress
        media: Ethernet autoselect (100baseTX full-duplex,rxpause,txpause)
        status: active
        inet 192.168.222.242 netmask 0xffffff00 broadcast 192.168.222.255
hp_server$

By customizing IFS like this grep will only return a single line of which you only have to extract the second field $2

PS. Sorry I missed that you already customized IFS in your latest version .........

[shep]

The code I posted actually outputs correctly. The problem is when I take the connection down, it will still output an IP address. I thought the solution would be to test for a connection with nc -dzw1 8.8.8.8 443.

I'm having difficulty capturing the ouput of nc.

PooBear$ TEST="$(nc -dzw1 8.8.8.8 443)"
Connection to 8.8.8.8 443 port [tcp/https] succeeded!
PooBear$ TEST=$(nc -dzw1 8.8.8.8 443) ; echo $TEST
Connection to 8.8.8.8 443 port [tcp/https] succeeded!
blank line here
PooBear$ echo $TEST
blank line here

I'm confused in that

Connection to 8.8.8.8 443 port [tcp/https] succeeded!

is already a single line and the text is not being written to the $TEXT string.

An unsuccessful connection via nc outputs a string that starts with

nc:

I'm not capturing the output of the nc command even though I'm using the same syntax as the ifconfig capture. Is my syntax wrong or is this specific to the nc command?

Once captured I would like to determine if it starts with "Connection" or "nc". If the string starts with Connection, I would like to run the ifconfig section, else output "There is no WAN Connection"

I'm making this complex but do appreciate the help.

[J65nko]

#!/bin/sh

# we also want STDERR (descriptor 2) text to STDOUT (descriptor 1)
TEST="$(nc -dzw1 8.8.8.8 443 2>&1)"

if echo $TEST | grep '^Connect' >/dev/null ;  then
  echo OK
else
 echo not OK
fi

[shep]

Thanks @J65nko, that did the trick

Huffalump$ sh obsd_wifi_tint2.sh                                               
----------------------------------
Current WiFi Connection Parameters
----------------------------------

NWID    :  Shepnet
CHAN    :  8
BSSID   :  d8:eb:97:23:bb:1b
S/N     :  -81dBm
IP      :  192.168.2.9


---ifconfig ral0 down---

Huffalump$ sh obsd_wifi_tint2.sh  
----------------------------------
Currently No WAN Connection
----------------------------------
Huffalump$

If the nc command runs without errors, I'm not clear on why stderr (descriptor 2) needs to be > to stdout or why the grep ^Connect needs to go to /dev/null. Also thanks for the grep ^ to check the beginning of the line.

The final code:

#!/bin/sh
TEST="$(nc -dzw1 8.8.8.8 443 2>&1)"
if echo $TEST | grep '^Connect' >/dev/null ; then

# IFS; Inter Field Separator (see man ksh)
# to preserve newlines,save and set IFS to space only
OLD_IFS="${IFS}"
IFS=" "

# capture 'ifconfig' output once and reuse ....
IFCONFIG=$(ifconfig)
#echo ${IFCONFIG}

NWID="$(echo ${IFCONFIG} | grep nwid | awk '{print $3}')"
CHAN="$(echo ${IFCONFIG} | grep nwid | awk '{print $5}')"
BSSID="$(echo ${IFCONFIG} | grep nwid | awk '{print $7}')"
SN="$(echo ${IFCONFIG} | grep nwid | awk '{print $8}')"
IP="$(echo ${IFCONFIG} | grep inet | tail -n1 | awk '{print $2}')"

cat <<END
----------------------------------
Current WiFi Connection Parameters
----------------------------------

NWID    :  $NWID
CHAN    :  $CHAN
BSSID   :  $BSSID
S/N     :  $SN
IP      :  $IP
END
else
cat <<END
----------------------------------
Currently No WAN Connection
----------------------------------
END
fi

[J65nko]

You mentioned that nc: is displayed when it cannot connect. I had the impression you wanted to check on that and I was not sure if that message would go to stdout or stderr. Just a matter of defensive programming.

The >/devnull redirect prevents cluttering the output of your script with the output of the grep of the successful connection output.

To improve readability you could put split the code in in a function when there is a connection and another function to handle the no connection output. The logic would then be something like this:

if .nc ....etc........ ; then
   wifi_connected function
else  no_wifi_message function
fi

[Head_on_a_Stick]

Originally Posted by shep

NWID="$(echo ${IFCONFIG} | grep nwid | awk '{print $3}')"
CHAN="$(echo ${IFCONFIG} | grep nwid | awk '{print $5}')"
BSSID="$(echo ${IFCONFIG} | grep nwid | awk '{print $7}')"
SN="$(echo ${IFCONFIG} | grep nwid | awk '{print $8}')"
IP="$(echo ${IFCONFIG} | grep inet | tail -n1 | awk '{print $2}')"

No need for grep if you're using awk:

NWID="$(echo ${IFCONFIG} | awk '/nwid/{print $3}')"
CHAN="$(echo ${IFCONFIG} | awk '/nwid/{print $5}')"
BSSID="$(echo ${IFCONFIG} | awk '/nwid/{print $7}')"
SN="$(echo ${IFCONFIG} | awk '/nwid/{print $8}')"
IP="$(echo ${IFCONFIG} | awk '/inet/{print $2}' | tail -n1)"

It is possible to get the IP line with pure awk:

echo $IFCONFIG | awk '/inet/{i=$2} END{print i}'

But I think tail is quicker.

EDIT: and you could use the -q option for grep to save a redirect:

if echo $TEST | grep -q '^Connect' ; then

Probably not important though

[shep]

@Head_on_a_Stick

Thanks. I will test/integrate the suggestions this weekend. Also plan to see what is involved with a scan for available AP's.