On this page:
make-directory*/ ignore-exists-exn

11 Filesystem

Jay McCarthy <jay@racket-lang.org>

 (require unstable/file)

This library is unstable; compatibility will not be maintained. See Unstable: May Change Without Warning for more information.

Like make-directory*, except it ignores errors when the path already exists. Useful to deal with race conditions on processes that create directories.