I have a config.properties file which contains a path like ouputdir=/data1/testdata/output. I am able to extract these in shell and store this path in a variabl
ouputdir=/data1/testdata/output
What you have should work. Check the obvious, that the directory is spelled right and does exist.
For what it's worth, you could combine the grep and awk commands into one:
my_value=$(awk -F= '$1=="outputdir" {print $2}')