Using environment variables in data pump query

Question

I have been trying to use data pump (expdp and impdp) in order to retrieve some data from a database to import it into another.

I am using the expdp using the table and the query parameters in order to select specific data from one table.

Can I use variables from Linux in the expdp and impdp queries?

For example, the directory is not a standard directory. I accept this as a variable from Linux and create a directory in Oracle using a bind variable. The thing is that later on when I want to invoke data pump I cannot have a standard directory but rather a variable. How do I use the variable from Linux in the expdp and impdp query?