mjhjmtu

The recommended pattern for bash as far as I know is to always quote the shell variables.

E.g. "$VAR" instead of $VAR.

But how can I achieve the same safety the quotes provide for variables meant to be interpreted remotely?

E.g in the following:

ssh server.com<<CODE
TARGET="target dir"
COUNT= $( ls /foo/bar/$TARGET | wc -l ) 
echo $COUNT > count.txt 

CODE 

For the code to work I need to escape $COUNT and $TARGET.

But how do I achieve the same safety that the "$COUNT" or "$TARGET" provides for this specific case?

Update

I have pasted only the part that is problematic.

I have also other lines that the variables are defined outside of the heredoc so if I use <<'CODE' then the snippet breaks.

For a more complete example:

SOME_STRING="SOME VALUE" 
ssh server.com<<CODE 
echo $SOME_VALUE > test_file.txt # <--- does not work if I use <<'CODE'
TARGET="target dir"
COUNT= $( ls /foo/bar/$TARGET | wc -l ) 
echo $COUNT > count.txt 

CODE 

It looks like here-docs leave double quotes in place. For example, consider the following command:

cat <<HEREDOC
"this will still be quoted"
HEREDOC

This will produce the following quoted string as its output:

"this will still be quoted:

So you should just be able to quote your variables as usual:

SOME_STRING="SOME VALUE"
ssh server.com<<CODE
echo "$SOME_VALUE" > test_file.txt
TARGET="target dir"
COUNT="$( ls /foo/bar/$TARGET | wc -l )"
echo "$COUNT" > count.txt
CODE

Regarding quoting variables inside command substitutions, refer to the following post: Quoting within $(command substitution) in Bash

Note that I've copied your snippet verbatim, but it looks like you probably meant to use the variable SOME_STRING instead of SOME_VALUE. Here is a slightly modified version of your snippet that I can run locally with the expected results:

mkdir -p "/foo/bar/target dir"

SOME_STRING="SOME VALUE"
ssh localhost<<CODE
echo "$SOME_STRING" > test_file.txt
TARGET="target dir"
COUNT="$( ls "/foo/bar/$TARGET" | wc -l )"
echo "$COUNT" > count.txt
CODE

We seem to get variations on this question a lot over the last few days.

In this case, quote the here-document:

ssh server.com <<'CODE'
TARGET="target dir"
COUNT= $( ls /foo/bar/$TARGET | wc -l ) 
echo $COUNT > count.txt 
then 
fi 
CODE 

The 'CODE' (as opposed to just CODE) will ensure that the here-document is passed to the utility as it is written, without expanding variables or performing command substitutions.

Note that you also have syntax errors in the here-document (spaces around = and no if ta match the then). You should also double-quote the expansions both $COUNT and $TARGET as usual.

ssh server.com <<'CODE'
TARGET="target dir"
COUNT=$( ls "/foo/bar/$TARGET" | wc -l ) 
printf '%sn' "$COUNT" >count.txt 
CODE 

If you are trying to count the number of files in a remote directory, use this instead:

ssh server 'find "/path/to/dir" -maxdepth 1 -type f -exec echo . ;' | wc -l

This will correctly count the number of files in /path/to/dir.

To write the result to a remote file:

ssh server 'find "/path/to/dir" -maxdepth 1 -type f -exec echo . ; | wc -l >file'

If the code that you need to execute remotely is very complex, then it may be better to create a script on the server to run it. The variable that you need to pass to the script can be passed on its command line:

ssh server ./script.sh "$SOME_VARIABLE"

The script:

#!/bin/sh

VAR="$1"

# do stuff