Extract EXPECT result to local variable/file - bash

Question

I've been struggling with getting the output from a remote server to a local variable or a local file.
My attempt:
#!/bin/bash
my_pass=!!psw!!
server=10.10.10.10
/usr/bin/expect << ENDOFEXPECT
exp_internal 1 ;# expect internal debugging. remove when not needed
set PROMPT ":~ ?# ?"
set timeout 30
spawn bash -c "ssh root#$server"
expect "assword:"
send "$my_pass\r"
expect -re "$PROMPT"
send -- "df -kh /\r"
expect -re "df\[^\n]+\n.+\n(.+\r\n.+)\r\n"
set command_output $expect_out(1,string)
send_user "$command_output\r"
interact
ENDOFEXPECT
echo "====================="
echo " >> $command_output"
Output:
spawn bash -c ssh root#10.10.10.10
parent: waiting for sync byte
parent: telling child to go ahead
parent: now unsynchronized from child
spawn: returns {154725}
expect: does "" (spawn_id exp4) match glob pattern "assword:"? no
Password:
expect: does "\rPassword: " (spawn_id exp4) match glob pattern "assword:"? yes
expect: set expect_out(0,string) "assword:"
expect: set expect_out(spawn_id) "exp4"
expect: set expect_out(buffer) "\rPassword:"
send: sending "!!psw!!\r" to { exp4 }
Gate keeper glob pattern for '' is ''. Not usable, disabling the performance booster.
expect: does " " (spawn_id exp4) match regular expression ""? (No Gate, RE only) gate=yes re=yes
expect: set expect_out(0,string) ""
expect: set expect_out(spawn_id) "exp4"
expect: set expect_out(buffer) ""
send: sending "df -kh /\r" to { exp4 }
Gate keeper glob pattern for 'df[^
]+
.+
(.+
.+)
' is ''. Not usable, disabling the performance booster.
expect: does " " (spawn_id exp4) match regular expression "df[^\n]+\n.+\n(.+\r\n.+)\r\n"? (No Gate, RE only) gate=yes re=no
expect: does " \r\n" (spawn_id exp4) match regular expression "df[^\n]+\n.+\n(.+\r\n.+)\r\n"? (No Gate, RE only) gate=yes re=no
Last login: Fri Dec 2 23:58:09 2022 from 10.10.10.1
Welcome to server image 2.2
expect: does " \r\nLast login: Fri Dec 2 23:58:09 2022 from 10.10.10.1\r\r\n\r\nWelcome to server image 2.2\r\n\r\n" (spawn_id exp4) match regular expression "df[^\n]+\n.+\n(.+\r\n.+)\r\n"? (No Gate, RE only) gate=yes re=no
REMY_SERVER:~ #
expect: does " \r\nLast login: Fri Dec 2 23:58:09 2022 from 10.10.10.1\r\r\n\r\nWelcome to server image 2.2\r\n\r\n\u001b[?1034h\u001b[1m\u001b[31mREMY_SERVER:~ # \u001b(B\u001b[m" (spawn_id exp4) match regular expression "df[^\n]+\n.+\n(.+\r\n.+)\r\n"? (No Gate, RE only) gate=yes re=no
expect: timed out
interact: received eof from spawn_id exp0
=====================
>>
Expected:
What I ultimately want is to get the output of df -kh into a local variable or even better, append it directly to a local file (on the local machine, not the server on which the command is executed) so that it contains something like:
$ cat ./result.txt
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 20G 18G 1,7G 92% /

Answer 1

Method 1: The proper way is to not use expect and use key pair access :
Step #1
Setup a SSH key pair (google it) and then copy the SSH key to the remote server. To do this I'd recommend using ssh-copy-id.
Step #2
Now with the ability to SSH to a server in place using a key, your above problem turns into this:
$ ssh root#10.10.10.10 "df -kh"
You can get fancy and use here documents (heredocs aka. here-docs) to further enhance this technique.
$ ssh root#10.10.10.10 <<EOF
> df -kh
> EOF
or put the commands in a file and pass them to ssh:
$ ssh root#10.10.10.10 < my.cmds
Method 2: Expect
See the following, expains how to use it properly and a tool to create expect scripts
https://hostadvice.com/how-to/how-to-automate-tasks-in-ssh/

Answer 2

First, your PROMPT regex is not matching. I see the output has some colour codes in it:
expect: does " \r\nLast login: ...REMY_SERVER:~ # \u001b(B\u001b[m" (spawn_id exp4) match regular expression ...
It's good to anchor prompt regexes, and to enclose them in braces. Try
set PROMPT { # \S*$}
Or, assuming the login shell is bash, set a new prompt that's easier to match:
send "$my_pass\r"
expect "Welcome to server"
send -- "PS1='>'\r"
set PROMPT {>$}
expect -re $PROMPT
Next, the relevant code for the question.
send -- "df -kh /\r"
expect -re "df\[^\n]+\n.+\n(.+\r\n.+)\r\n"
set command_output $expect_out(1,string)
send_user "$command_output\r"
I'd adjust your regex a touch:
set cmd "df -kh /"
send -- "$cmd\r"
expect -re "$cmd\r\n(.+)\r\n.*$PROMPT"
Then you're capturing and "echoing" the result correctly
set command_output $expect_out(1,string)
send_user "$command_output\n"
# use a newline here ......^
And to append it to a local file:
set fh [open ./results.txt a]
puts $fh $command_output
close $fh