comint-file-name-chars

comint-file-name-chars is a variable defined in `comint.el'.
Its value is

"[]~/A-Za-z0-9+@:_.$#%,={}-"

Documentation:
String of characters valid in a file name.
Note that all non-ASCII characters are considered valid in a file name
regardless of what this variable says.

This is a good thing to set in mode hooks.