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CIsForCookies
Asked: 2020-08-21 01:14:53 +0800 CST

Modifying bluetoothctl automation script - How to remove output from expect & spawn?

  • 772

I'm trying to automate the pairing of my headset to my ubuntu16 machine.

I took this nice script and tried it, but it didn't work. I played around a bit, and found out that I can just work with this minimal script:

#!/usr/bin/expect -f

set prompt '#'
set address [lindex $argv 0]

spawn bluetoothctl &> /dev/null
expect -re $prompt
send "\nconnect <my_mac_addr>\r"
sleep 10

I save this as a ./bluetooth.sh and run it with ./bluetooth.sh & and it works like a charm. However, I get this annoying bluetoothctl output:

[NEW] Controller *** ### [default]
[NEW] Device *** A
[NEW] Device *** B
[NEW] Device *** C
[bluetooth]#

I tried removing it with the redirection I added to the spawn command, but it didn't help as you can see...

Removing the expect would work, but I'm not sure this is the way to go...

scripts command-line bash bluetooth expect

2 Answers

  1. Best Answer

    You don't really need to use expect and can give commands to bluetoothctl directly as arguments.

    # ...
bluetoothctl -- power on
bluetoothctl -- connect $mac
# ...

    For a more complete example, here is the full Bash script that I use in Ubuntu 20.04 for my BT radio :

    #!/bin/bash

mac="90:03:B7:17:00:08" # DEH-4400BT

if [ "$1" = "off" ]; then
    bluetoothctl -- disconnect
    exit $?
fi

# turn on bluetooth in case it's off
rfkill unblock bluetooth

bluetoothctl -- power on
bluetoothctl -- connect $mac

# Use it as default output for PulseAudio

sink=$(pactl list short sinks | grep bluez | awk '{print $2}')

if [ -n "$sink" ]; then
    pacmd set-default-sink "$sink" && echo "OK default sink : $sink"
else
    echo could not find bluetooth sink
    exit 1
fi

    This assumes the destination $mac is already paired of course.

    • 3

  2. Capture the output and strip the prompts...

    typeset -a OUTPUT

clean_line () {
   local LINE

   while read LINE;do
      echo ${LINE} | perl -pe 's/\x1b\[[0-9;]*[mG]//g; s/\[.*\]#?//g; s/\x0d\x1b\x20\x0d\x1b\x5b\x4b//g; s/^ //g'
   done
}

coproc bluetoothctl
echo -e 'agent on\nconnect 00:0C:8A:FE:ED:18\nexit' >&p 
OUTPUT=("${(f)$(cat <&p | clean_line)}")

NDX=0
for L in ${OUTPUT};do
   ((NDX++))
   printf "%d) %s\n" ${NDX} ${L}
done
    • 0