Bash/Expect Time-Out on Password returns 0

Question

I have a bash script which contains the following snippet:

function test_sftp_connection() {
expect << EOF
log_user 0
spawn -noecho sftp -P $SFTP_SERVER_PORTNUMBER $SFTP_SERVER_USERNAME@$SFTP_SERVER_HOSTNAME
expect "password:"
send "$SFTP_SERVER_PASSWORD\r"
expect "sftp>"
send "exit\r"
EOF

  # Check the exit status of the expect command
  if [ $? -ne 0 ]; then
    echo "Unable to connect to the SFTP server."
    exit 1
  fi
}

My current understanding is that 'expect "sftp>"' does what it says it does; it expects an sftp> prompt. So if a wrong password was entered by the script, and you are asked to enter the password again; this is obviously not the same. So I expect it to stop executing; returning with a non-zero status code.

Unfortunately, it does not do this. Instead, it times out with status code 0. I don't understand why it does this or how I can solve this. It would be much appreciated if someone knows how to deal with this situation.

Answer 1

I've changed log_user 0 to log_user 1 to enable logging of output and I added an additional expect block to handle the case when the prompt is not sftp>,so in this case I exit with a status code of 1 using the timeout keyword!

check this out :

function test_sftp_connection() {
  expect << EOF > /dev/null
  log_user 0
  spawn -noecho sftp -P $SFTP_SERVER_PORTNUMBER $SFTP_SERVER_USERNAME@$SFTP_SERVER_HOSTNAME
  expect "password:"
  send "$SFTP_SERVER_PASSWORD\r"
  expect {
    "sftp>" {
      send "exit\r"
      expect eof
      exit 0
    }
    timeout {
      exit 1
    }
  }
EOF

  if [ $? -ne 0 ]; then
    echo "Unable to connect to the SFTP server."
    exit 1
  fi
}