Escaping the close-bracket character in a bash v3 heredoc -

i have need embed fragment of shell script in heredoc part of creation of cloud-init script provision ubuntu 14.04 lte machine. simplified version of script demonstrating problem follows:

#!/bin/bash  cloudconfig=$(cat <<eof     if host \$nameserver 1>/dev/null 2>&1;     case \$reason in     bound|renew|rebind|reboot) nsupdate -k /var/lib/dhcp/nsupdate.key << eox     server \$nameserver     update delete \$host_name     update add \$host_name \$ttl \$host_addr     send     eox     ;;     esac     fi eof )  echo "${cloudconfig}" 

running above script fails follows:

little-net:orchestration minfrin$ bash /tmp/test.sh not read key /var/lib/dhcp/nsupdate.{private,key}: file not found couldn't address '$nameserver': not found 

the problematic character closing bracket right of "reboot", , obvious solution escape character:

bound|renew|rebind|reboot\) nsupdate -k /var/lib/dhcp/nsupdate.key << eox 

this backslash character ends in final cloudconfig variable, in turn breaks output:

little-net:orchestration minfrin$ bash /tmp/test.sh     if host $nameserver 1>/dev/null 2>&1;     case $reason in     bound|renew|rebind|reboot\) nsupdate -k /var/lib/dhcp/nsupdate.key << eox     server $nameserver     update delete $host_name     update add $host_name $ttl $host_addr     send     eox     ;;     esac     fi 

this particular fragment above part of larger file being written relies on variable interpolation, quoting there heredoc >>"eof" going break rest of our script.

how escape ")" character without escape character leaking through heredoc?

as seems bash 3.x parsing issue (as works in bash 4.x can seen here) need avoid parser getting confused. seems work me:

#!/bin/bash  rp=")" cloudconfig=$(cat <<eof     if host \$nameserver 1>/dev/null 2>&1;     case \$reason in     bound|renew|rebind|reboot${rp} nsupdate -k /var/lib/dhcp/nsupdate.key << eox     server \$nameserver     update delete \$host_name     update add \$host_name \$ttl \$host_addr     send     eox     ;;     esac     fi eof )  echo "${cloudconfig}"