Is there an easy way to substitute/evaluate environment variables in a file? Like let's say I have a file
config.xml that contains:
<property> <name>instanceId</name> <value>$INSTANCE_ID</value> </property> <property> <name>rootPath</name> <value>/services/$SERVICE_NAME</value> </property>
...etc. I want to replace
$INSTANCE_ID in the file with the value of the
INSTANCE_ID environment variable,
$SERVICE_NAME with the value of the
SERVICE_NAME env var. I won't know a priori which environment vars are needed (or rather, I don't want to have to update the script if someone adds a new environment variable to the config file). Thanks!