Prevent Expect's variable substitution for a remote shell command - variables

Question

I need to run this cmd with an expect script:
echo users.1.password=`grep %user% /etc/passwd | awk -F: '{print $2}'` >> /tmp/system.cfg.new
But it errors out because of the $2 in it. How do I fix this? I need the variable to only be visible to the device I am sending the cmd to.
Here is the full script for password change on UBNT equipment via script (works via ssh, but not as script because of $2):
#!/usr/bin/expect
set timeout 30
#Edit for User
set user user
#Edit for Old Password
set old oldpassword
#Edit for New Password
set new newpassword
#get IP List from iplist.txt
set f [open "/iplist.txt"]
set data [read $f]
close $f
foreach line [split $data \n] {
if {$line eq {}} continue
spawn ssh $user#$line
expect {
"assword:" {
send "$old\r"
expect {
"assword:" {
close
continue
}}
expect {
"*" {
send "passwd $user\r"
expect "assword:"
send "$new\r"
expect "assword:"
send "$new\r"
expect "*"
send "grep -v users.1.password= /tmp/system.cfg > /tmp/system.cfg.new\r"
expect "*"
send "echo users.1.password=`grep $user /etc/passwd | awk -F: '{print $2}'` >> /tmp/system.cfg.new\r"
expect "*"
send "cp /tmp/system.cfg.new /tmp/system.cfg\r"
expect "*"
send "save && reboot\r"
close
continue
}}}}
expect {
"*" {
close
continue
}}
expect eof
}

Answer 1

You just have to escape the dollar sign with backslash.
send "echo users.1.password=`grep $user /etc/passwd | awk -F: '{print \$2}'` >> /tmp/system.cfg.new\r"
By the way, using expect * might be dangerous and not a recommended one unless a read need of it.
You could use the a generalized approach for the matching the prompt as,
set prompt "#|%|>|\\\$ $"
Here, we have escaped the literal dollar sign with backslash and the last dollar is meant for the end-of-line regular expression.
After sending any commands to the remote shell, you can expect for the pattern as
expect -re $prompt