How to `cat << 'EOF'` within `su $user <<EOF`? - bash

Question

##!/bin/bash
set -e
backup_dir='/home/my/backup'
user='my'
su $user <<EOFHD
cat << 'EOF' > $backup_dir/autorestartnftables.sh
#!/bin/bash
SERVICENAME="nftables"
# return value is 0 if running
STATUS=$?
if [[ "$STATUS" -ne "0" ]]; then
echo "Service '$SERVICENAME' is not curently running... Starting now..."
systemctl start $SERVICENAME
fi
EOF
chmod +x $backup_dir/autorestartnftables.sh
EOFHD
Above script is used to create autorestartnftables.sh,expect result as below:
#!/bin/bash
SERVICENAME="nftables"
# return value is 0 if running
STATUS=$？
if [[ "$STATUS" -ne "0" ]]; then
echo "Service '$SERVICENAME' is not curently running... Starting now..."
systemctl start $SERVICENAME
fi
autorestartnftables.sh after run sudo bash ./example.sh:
#!/bin/bash
SERVICENAME="nftables"
# return value is 0 if running
STATUS=0
if [[ "" -ne "0" ]]; then
echo "Service '' is not curently running... Starting now..."
systemctl start
fi
Where is the problem?

Answer 1

Do not nest, nest, nest. Instead use declare -f and functions to transfer work to unrelated context.
##!/bin/bash
set -e
backup_dir='/home/my/backup'
user='my'
work() {
cat << 'EOF' > $backup_dir/autorestartnftables.sh
#!/bin/bash
SERVICENAME="nftables"
# return value is 0 if running
STATUS=$?
if [[ "$STATUS" -ne "0" ]]; then
echo "Service '$SERVICENAME' is not curently running... Starting now..."
systemctl start $SERVICENAME
fi
EOF
chmod +x $backup_dir/autorestartnftables.sh
}
su "$user" bash -c "$(declare -p backup_dir); $(declare -f work); work"
In this case, you could check if the user running your script is the user you want and then restart your script with that user:
##!/bin/bash
set -e
backup_dir='/home/my/backup'
user='my'
if [[ "$USER" != "$user" ]]; then
# restart yourself as that user
exec sudo -u "$user" "$0" "$#"
fi
cat << 'EOF' > $backup_dir/autorestartnftables.sh
#!/bin/bash
SERVICENAME="nftables"
# return value is 0 if running
STATUS=$?
if [[ "$STATUS" -ne "0" ]]; then
echo "Service '$SERVICENAME' is not curently running... Starting now..."
systemctl start $SERVICENAME
fi
EOF
chmod +x $backup_dir/autorestartnftables.sh
Check your scripts with shellcheck.