SSH and Expect – Simple Script to Execute Remote Command and Display Output

The interact command in the expect here-doc was the problem. I needed to wait for EOF instead:

#! /bin/bash

# this function runs a command like 'ssh' and provides the password
function with_password {
expect << END
set timeout 900
spawn $2
expect *assword:*
send -- $1
expect EOF
END
}

# run "long_running_command" on the remote server
with_password my_password "ssh my_user@some-server long_running_command"

# rsync some data to the remote server
with_password my_password "rsync /some/dir my_user@some-server:/remote/dir"

# run some other random command
with_password my_password "ssh my_user@some-server some_other_command"

The interact command seem to work sometimes when the ssh/rsync command closed the input at the correct time (maybe?), but it wasn't reliable.

First thing, your heredoc acts like a double quoted string, so the $expect_out variable is being substituted by the shell before expect starts. You need to ensure your heredoc is not being touched by the shell. Therefore, any shell variables need to be fetched in a different way. Here, I'm assuming IP is a shell variable, and I'm passing it through the environment.

export IP
/usr/bin/expect << 'ENDOFEXPECT'
  set prompt ":~#"
  spawn ssh root@$env(IP)  
  expect "password:"
  send "xxxx\r"
  expect $prompt
  send "grep hostname /etc/rc.d/rc.local \n"
  expect $prompt
  set line $expect_out(buffer)
  ...more script...
ENDOFEXPECT