Remove multiple columns from writing into a file

i’m looking for an approach where i can remove multiple columns from writing into a file. The catch here is I don’t want to hardcode the column names (at source column) and passing null (in target column).
I want to identify the unwanted column based on the prefix (say Join_) and remove all those columns from writing into a file.

Say Im getting column
A
B
C
D
Join_A
Join_B

I don’t want to write Join_A and Join_B in file. I can’t hardcode the column names because I’m not sure how many such columns with that prefix i will get.

Any pointers would be appreciated. tia