variables in remote nested server via ssh

Question

Trying to set and access some variables on a remote server the script will execute on a local server, it will login to remote-server1 and then login again to another second remote server remote-server2 I can successfully set and access variables in both local and remote-server1 without any issues, but having problem doing the same on remote-server2

local1=$(echo "local-srv"); echo "${local1}"
output=$(sshpass -p "${PSSWD}" ssh -t -q -oStrictHostKeyChecking=no admin@$mgmtIP "bash -s" <<EOF
remote1=\$(echo "remote-srv1"); echo "\${remote1}"
ssh -t -q -oStrictHostKeyChecking=no "${targetCompute}" "bash -s" <<EOF2
remote2=\$(echo "remote-srv2"); echo "\${remote2}"
EOF2
EOF
)

Here is my output

local-srv
remote-srv1

as you can see remote-srv2 is missing

----- UPDATE ---

please note that $(echo "text") is just for simplicity but a complex command will be executed here and the output set to a variable

Gordon Davisson · Accepted Answer · 2021-05-01 17:14:31Z

1

You have two nested ssh commands with nested here-documents, and to delay interpretation of the $ expressions in the inner one, you need more escapes. To see the problem, you can replace the ssh command with cat to see what would be sent to the remote computer. Here's an example, using your original code (and some modified variable definitions); note that the $ and > are prompts from my shell.

$ targetCompute=remote-server2
$ local1="local-srv"; echo "${local1}"
local-srv
$ cat <<EOF
> remote1=\$(echo "remote-srv1"); echo "\${remote1}"
> ssh -t -q -oStrictHostKeyChecking=no "${targetCompute}" "bash -s" <<EOF2
> remote2=\$(echo "remote-srv2"); echo "\${remote2}"
> EOF2
> EOF
remote1=$(echo "remote-srv1"); echo "${remote1}"
ssh -t -q -oStrictHostKeyChecking=no "remote-server2" "bash -s" <<EOF2
remote2=$(echo "remote-srv2"); echo "${remote2}"
EOF2

Notice that the lines relating to remote1 and remote2 have both had their escapes removed, so they're both going to have their $ expressions expanded on remote-srv1. That's what you want for the remote1 line, but to delay interpretation of the remote2 line you have to add another escape... and that escape itself needs to be escaped, so there'll actually be three escapes before each $:

$ cat <<EOF
> remote1=\$(echo "remote-srv1"); echo "\${remote1}"
> ssh -t -q -oStrictHostKeyChecking=no "${targetCompute}" "bash -s" <<EOF2
> remote2=\\\$(echo "remote-srv2"); echo "\\\${remote2}"
> EOF2
> EOF
remote1=$(echo "remote-srv1"); echo "${remote1}"
ssh -t -q -oStrictHostKeyChecking=no "remote-server2" "bash -s" <<EOF2
remote2=\$(echo "remote-srv2"); echo "\${remote2}"
EOF2

So \\\$(echo "remote-srv2") and "\\\${remote2}" in the local here-document become \$(echo "remote-srv2") and "\${remote2}" in the here-document on remote-srv1, and then the command actually gets executed and the variable expanded on remote-srv2.

edited May 1, 2021 at 17:14

answered May 1, 2021 at 8:40

Gordon Davisson

128k16 gold badges141 silver badges168 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

electricalbah Over a year ago

thanks for your answer, $(echo "remote-srv2") is just for simplicity, this will be executing a complex command and the output stored in a variable. your anser is correct but the first part is not necessary, updated to question too to reflect this

Gordon Davisson Over a year ago

@electricalbah Ah, that makes sense; I'll edit my answer accordingly.

electricalbah · Accepted Answer · 2021-05-01 10:32:40Z

0

I needed to escape by ///

Thanks to the answer given by @Goron Davisson

local1=$(echo "local-srv"); echo "${local1}"
output=$(sshpass -p "${PSSWD}" ssh -t -q -oStrictHostKeyChecking=no admin@$mgmtIP "bash -s" <<EOF
remote1=\$(echo "remote-srv1"); echo "\${remote1}"
ssh -t -q -oStrictHostKeyChecking=no "${targetCompute}" "bash -s" <<EOF2
remote2=\\\$(echo "remote-srv2"); echo "\\\${remote2}"
EOF2
EOF
)

Output

local-srv
remote-srv1
remote-srv2

edited May 1, 2021 at 10:32

answered May 1, 2021 at 10:15

electricalbah

2,2972 gold badges25 silver badges37 bronze badges

Collectives™ on Stack Overflow

variables in remote nested server via ssh

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related