How to get responses in expect (tcl)

Question

I am trying to query bluetoothctl using expect (tcl), but I cannot seem to get the bluetoothctl responses saved to a variable for processing with tcl. For example:

spawn bluetoothctl

exp_send "scan on\n"

expect {
    -re {*NEW*} {
        set new $expect_out(0,string)
        puts "scan - found $new"
        exp_continue
    }
    timeout {
        exp_send "scan off\n"
        exp_send "quit\n"
        close
        wait
        puts "EXPECT timed out"
    }
}

The result of the above is along the lines of:

[bluetooth]# scan on
Discovery started
[CHG] Controller 10:08:B1:57:35:62 Discovering: yes
[NEW] Device EB:06:EF:34:04:B7 MPOW-059
[bluetooth]# 
EXPECT timed out

So nothing is output until expect is closed. I have been trying this all day with different combinations but - I am stuck. Any help would be appreciated. Thanks

Edit: changed the regex to (.NEW.) and that works. So now I get:

[bluetooth]# scan on
Discovery started
[CHG] Controller 10:08:B1:57:35:62 Discovering: yes
[NEW] Device EB:06:EF:34:04:B7 MPOW-059
[bluetooth]# scan - found scan on
Agent registered
[bluetooth]# scan on
Discovery started
[CHG] Controller 10:08:B1:57:35:62 Discovering: yes
[NEW

which is everything except the bit that I wanted to retrieve viz:

[NEW] Device EB:06:EF:34:04:B7 MPOW-059

Answer 1

That regular expression looks syntactically wrong. If you did {.*NEW.*} then it might work. Assuming that those three letters are actually being output by bluetoothctl with no control characters mixed in. (It'd be weird to do that, but some code is weird…)

Apart from that, have you tried the diagnostic mode for expect? Pass the -d flag to the expect program when you start it to get lots of output about what it is really seeing and looking for.

Answer 2

So the answer appears to be:

1. The expect_out(buffer) is cleared by a puts statement
2. Find all the possible responses expected making sure that the expected response specifies the whole line.
3. Save the buffer in a variable if required
4. Issue a puts statement to clear the buffer

So:

expect {
    "Hello" {
         puts "$expect_out(buffer)"
         exp_continue
    }
    -re (How.*) {
         set answer $expect_out(buffer)
         if {$answer == "How are you"} {
             exp_send "Well thank you"
         }
    }
 

or, in the example above:

expect {    
    "Discovery started" {
        puts $expect_out(buffer)
        exp_continue
    }
    -re (.CHG.*) {
        puts $expect_out(buffer)
        exp_continue
    }
    -re (.NEW.*) {
        set new $expect_out(buffer)