Displays a list of files and subdirectories in a directory.
DIR [ drive:][path][filename] [/A[[:]attributes]] [/B] [/C] [/D] [/L] [/N]
[/O[[:]sortorder]] [/P] [/Q] [/R] [/S] [/T[[:]timefield]] [/W] [/X] [/4]
[drive:][path][filename]
Specifies drive, directory, and/or files to list.
/A Displays files with specified attributes.
attributes D Directories R Read-only files
H Hidden files A Files ready for archiving
S System files I Not content indexed files
L Reparse Points - Prefix meaning not
just set type of desired file attribute, in your case /A:D (directory)
dir /s/b/o:n/A:D > f.txt