Fixes #387: Display WiFi signal strength in the net block

[bnjbvr]

Hi! I wanted to see the Wifi signal strength in the status bar, and saw there was an open issue with some hints to do it. Turns out that iw provides this information too, so we can parse its output to figure it out. It's a bit inefficient because we may call iw several times to grep for some of its information, but I think it's fine since it doesn't happen a lot.

I've reused the formulas hinted at in the issue, and I can confirm they coincide with the results provided by the original i3status bar on my machine.

[SWW13]

Nice work, thanks :)

Besides the copied error message the code LGTM and works on my machine.

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It's a bit inefficient because we may call iw several times to grep for some of its information, but I think it's fine since it doesn't happen a lot.

That's already the case for SSID and bitrate, I think it's fine to leave that up to a future refactoring. The there could be only one execution of iw for all of them. That would also save the execution of sh and sed, but require more parsing in our code.

[atheriel]

Thanks!

[rsteube]

Oh nice, it's already in.
@bnjbvr i'm getting command failed: Operation not permitted (-1) for the iw dev .. link command - am i missing a group or is a sudo entry necessary?

(fyi: network-manager gives out bars like ▂▄▆_ with: `nmcli device wifi list | grep '^*' | awk '{print $8}' )

[bnjbvr]

@rsteube I have honestly no clues regarding the issue; a quick search seems to tell it could be a driver issue.

Regarding the nmcli line: it also contains the relative signal strength (under the SIGNAL column), so we could directly copy it out from there. Nice thing is that it displays the same value as my code :) (which is obvious, since the code I added is copied from network-manager's...)

[rsteube]

Yes would be nice to have nmcli as option since it seems iw won't work without sudo on some systems.
This looks great for parsing: nmcli -t -f in-use,active,ssid,signal dev wifi:

nmcli -t -f in-use,active,ssid,signal dev wifi
 :no:guestnet:80
 :no:skynet:79
*:yes:skynet:66

(only works if network-manager is used though)

[rsteube]

This works for me: https://github.com/rsteube/i3status-rust/commit/fcf4571c9a2ff45c29fa4209c55150d0893bb49b

[BenFradet]

weird thing, building from master I'm getting:

{"version": 1, "click_events": true}
[[{"background":"#000000","color":"#dc322f","full_text":" Configuration error: failed to deserialize block config.\nCause: unknown field `signal_strength`, expected one of `interval`, `device`, `ssid`, `max_ssid_width`, `bitrate`, `ip`, `hide_inactive`, `hide_missing`, `speed_up`, `speed_down`, `graph_up`, `graph_down`, `on_click` ","separator":false,"separator_block_width":0}]


Configuration error: failed to deserialize block config.
Cause: unknown field `signal_strength`, expected one of `interval`, `device`, `ssid`, `max_ssid_width`, `bitrate`, `ip`, `hide_inactive`, `hide_missing`, `speed_up`, `speed_down`, `graph_up`, `graph_down`, `on_click`
thread '<unnamed>' panicked at 'called `Result::unwrap()` on an `Err` value: "SendError(..)"', src/libcore/result.rs:999:5

when building from 374e709

[BenFradet]

nvm, the wrong artifact was picked up appreantly