I am trying to execute some shell script on a remote server via SSH.
Given below is a code sample:
ssh -i $KEYFILE_PATH ubuntu@$TARGET_INSTANCE_IP "bash" << EOF
#!/bin/bash
cat /home/ubuntu/temp.txt
string=$(cat /home/ubuntu/temp.txt )
echo $string
EOF
cat prints the expected result but
$string prints nothing.
How do I store the return value of cat in a variable?
You need to make the content of Here doc literal otherwise they will be expanded in the current shell, not in the desired remote shell.
Quote EOF:
ssh .... <<'EOF'
...
...
EOF
/home/ubuntu/temp.txt file located? Local or remote?You should be able to simply do this:
ssh -i $KEYFILE_PATH ubuntu@$TARGET_INSTANCE_IP "bash" <<'_END_'
cat /home/ubuntu/temp.txt
string=$(cat /home/ubuntu/temp.txt)
echo $string
_END_
<<'_END_' ... _END_ is called a Here Document literal, or "heredoc" literal. The single quotes around '_END_' prevent the local shell from interpreting variables and commands inside the heredoc.
The intermediate shell is not required (assuming you use bash on the remote system).
Also you dont have to use an intermediate HERE-DOC. Just pass a multiline Command:
ssh -i $KEYFILE_PATH ubuntu@$TARGET_INSTANCE_IP '
cat /home/ubuntu/temp.txt
string=$(cat /home/ubuntu/temp.txt )
echo $string
'
Note I am using single quotes to prevent evaluation on the local shell.
