Unable to use local and remote variables within a heredoc or command over SSH

Question

Below is an example of a ssh script using a heredoc (the actual script is more complex). Is it possible to use both local and remote variables within an SSH heredoc or comma

Answer 1

You need to escape the $ sign if you don't want the variable to be expanded:

$ x=abc
$ bash <<EOF
> x=def
> echo $x   # This expands x before sending it to bash. Bash will see only "echo abc"
> echo \$x  # This lets bash perform the expansion. Bash will see "echo $x"
> EOF
abc
def

So in your case:

ssh user@host bash << EOF
# run script with output...
REMOTE_PID=$(cat $FILE_NAME)
echo \$REMOTE_PID
EOF

Or alternatively you can just use a herestring with single quotes:

$ x=abc
$ bash <<< '
> x=def
> echo $x  # This will not expand, because we are inside single quotes
> '
def

Answer 2

remote_user_name=user
instance_ip=127.0.0.1
external=$(ls /home/)

ssh -T -i ${private_key}  -l ${remote_user_name} ${instance_ip} << END
  internal=\$(ls /home/)
  echo "\${internal}"
  echo "${external}"
END