Login and get homepage content with a Bash script
You might want to double checking your encoding or the headers that you're sending over that might cause the problem. I've found trying to do this with a pure Bash solution very fickle at times. Here's an example function I've used that will login into a D7 site on the /user page (an easier manner since every D7 install can be logged in from that path).

#!/bin/sh

# https://gist.github.com/cdown/1163649
#Usage: urlencode "string"
function urlencode() {
  old_lc_collate=$LC_COLLATE
  LC_COLLATE=C

  local length="${#1}"
  for (( i = 0; i &lt; length; i++ )); do
    local c="${1:i:1}"
    case $c in
      [a-zA-Z0-9.~_-]) printf "$c" ;;
      *) printf '%%%02X' "'$c" ;;
    esac
  done

  LC_COLLATE=$old_lc_collate
}

#Usage: login "user" "pass"
function login() {
  URL=https://www.example.com/user
  name=$(urlencode "$1")
  pass=$(urlencode "$2")
  post_data="name=$name&amp;pass=$pass"

  #Retrieve login page, login form, &amp; input fields.
  login_page=$(curl -s -H "Content-Type:application/xml"  "$URL")
  login_form=$(echo $login_page | grep -o '&lt;form[^&gt;]*action="/user"[^&gt;]*id="user-login"[^&gt;]*&gt;.*&lt;/form&gt;')
  login_input=$(echo $login_form | grep -o '&lt;input[^&gt;]*/&gt;')

  #Create Post Body
  while read -r input; do
    input_field=$(echo "$input" | sed -e 's/.*name="\([^"]*\)".*/\1/')
    if [[ $input_field != "name" &amp;&amp; $input_field != "pass" ]]; then
      input_value=$(echo "$input" | sed -e 's/.*value="\([^"]*\)".*/\1/')
      input_field=$(urlencode "$input_field")
      input_value=$(urlencode "$input_value")
      post_data="$post_data&amp;$input_field=$input_value"
    fi
  done &lt;&lt;&lt; "$login_input"

  # Depending on your hosting environment you might need additional headers to make yourself not look like a bot
  user_agent="User-Agent:Mozilla/5.0 "
  referer="Referer:https://www.example.com/user"
  origin="Origin:https://www.example.com"
  content_type="Content-Type:application/x-www-form-urlencoded"

  # For further authenticated requests, you will need to parse output "Set-Cookie: ..." and set
  # the session cookie in a -H "Cookie: ..." option
  curl -s -L -H "$content_type" -H "$user_agent" -H "$referer" -H "$origin" --request POST "${URL}?destination=/" --data "$post_data"
}

login 'USER' 'PASS'


I've found logging into Drupal via Bash much easier with if you can work with a scripting language that has built in HTTP clients &amp; parsers. Depending on your scenario, you might want to consider that if you need a more robust solution.