Passing variables in remote ssh command

The list of accepted environment variables on SSHD by default includes LC_*. Thus:

LC_MY_BUILDN="1.2.3" ssh -o "SendEnv LC_MY_BUILDN" ssh-host 'echo $LC_MY_BUILDN'
1.2.3

Variables in single-quotes are not evaluated. Use double quotes:

ssh [email protected] "~/tools/run_pvt.pl $BUILD_NUMBER"

The shell will expand variables in double-quotes, but not in single-quotes. This will change into your desired string before being passed to the ssh command.

If you use

ssh [email protected] "~/tools/run_pvt.pl $BUILD_NUMBER"

instead of

ssh [email protected] '~/tools/run_pvt.pl $BUILD_NUMBER'

your shell will interpolate the $BUILD_NUMBER before sending the command string to the remote host.

(This answer might seem needlessly complicated, but it’s easily extensible and robust regarding whitespace and special characters, as far as I know.)

You can feed data right through the standard input of the ssh command and read that from the remote location.

In the following example,

1. an indexed array is filled (for convenience) with the names of the variables whose values you want to retrieve on the remote side.
2. For each of those variables, we give to ssh a null-terminated line giving the name and value of the variable.
3. In the shh command itself, we loop through these lines to initialise the required variables.

# Initialize examples of variables.
# The first one even contains whitespace and a newline.
readonly FOO=$'apjlljs ailsi \n ajlls\t éjij'
readonly BAR=ygnàgyààynygbjrbjrb

# Make a list of what you want to pass through SSH.
# (The “unset” is just in case someone exported
# an associative array with this name.)
unset -v VAR_NAMES
readonly VAR_NAMES=(
    FOO
    BAR
)

for name in "${VAR_NAMES[@]}"
do
    printf '%s %s\0' "$name" "${!name}"
done | ssh [email protected] '
    while read -rd '"''"' name value
    do
        export "$name"="$value"
    done

    # Check
    printf "FOO = [%q]; BAR = [%q]\n" "$FOO" "$BAR"
'

Output:

FOO = [$'apjlljs ailsi \n ajlls\t éjij']; BAR = [ygnàgyààynygbjrbjrb]

If you don’t need to export those, you should be able to use declare instead of export.

A really simplified version (if you don’t need the extensibility, have a single variable to process, etc.) would look like:

$ ssh [email protected] 'read foo' <<< "$foo"