ssh bash -s meets array variable error

Question

The following script throws an error:

declare -a service_ports=(22 80 443 445)

ssh root@host 'bash -s' << EOF

export x=0
while [ \$x -le "${#service_ports[@]}" ]
do
  echo Port ${service_ports[\$x]} # ERROR HERE
  x=\$(( \$x + 1 ))
done

EOF

When I run this bash script I get:

./q.sh: line 6: $x: syntax error: operand expected (error token is "$x")

I need to escape the $x variable because I use a " bash -s " remote shell. When I remove the backslash I only access my local variable and not the one on the server where the script is executed.

Anyone know the solution to access the content of the array?

Answer 1

You can quote the here document terminator declaration to avoid having to escape anything in the input string (of course that also means you can't inject the value of a local variable in the remote script):

my_command << 'EOF'
foo $bar
[...]
EOF

If you need to inject local variable contents, you could instead go for mixed quotes:

my_input='some $literal$ strings'
my_input="${my_input}${my_variable}"
[...]

Also, you can simplify your command in several ways:

• You shouldn't have to specify bash -s when running a remote command, unless that is different from your default shell.
• There's no point in export ing variables which are not used in subsequent script calls
• You don't need to declare -a when you assign an array literal immediately