implement envsubst, so it will only substitute envvars that start with: SD_
here is an example:
#!/usr/bin/env bash
#set -eux
ENVFILE="/etc/default/sms"
if test -f $ENVFILE
then
set -o allexport
source $ENVFILE
set +o allexport
cat | envsubst "$(env | grep '^SD_' | sed -e 's/=.*//' -e 's/^/\$/g')"
else
>&2 echo "${ENVFILE} does not exist"
exit 10
fi
Edited by dreamer