The ListOptions directive of ProFTPD can be used to control how directory listings are generated. Directory listings are sent in response to the LIST and NLST FTP commands.

The ListOptions directive supports the following options:

• -1
  List one file per line
• -A
  List all files except "." and ".."
• -a
  List all files including those whose names start with "."
• -C
  List entries by columns
• -d
  List directory entries instead of directory contents
• -F
  Append file type indicator (one of "*", "/", "=", "@" or "|") to names
• -h
  Print file sizes in human-readable format (e.g. 1K, 234M, 2G)
• -L
  List files pointed to by symlinks
• -l
  Use a long listing format
• -n
  List numeric UIDs/GIDs instead of user/group names
• -R
  List subdirectories recursively
• -r
  Sort filenames in reverse order
• -S
  Sort by file size
• -t
  Sort by modification time

Although not strictly supported by the FTP RFCs, many FTP clients send these options with the LIST and NLST commands, and many FTP servers honor them. The ListOptions directive configures default options to be used, in addition to any sent by the client. For example, to show all files except the "hidden" files for clients, you could use:

  ListOptions -a

Another use of ListOptions is to prevent certain options from being used. The -R option, for recursively listing all subdirectories, can use a lot of system resources, especially on very large and/or very deep directory structures, as proftpd scans all of the files. For this reason, some sites may wish to prevent the -R option from being used. ListOptions supports this with use of the "+" character. Options are enabled using the "-" character, thus they are disabled using "+"--think of the "+" as cancelling out the "-". For example:

  ListOptions +R strict

Where did the strict come from in the example above? ListOptions configures a set of default options, but if a client sends its own directory options, proftpd will use the client's options instead. To ignore the client options and use only the ListOptions configured, one uses the "strict" keyword. That is why the +R example above required "strict"--it causes proftpd to ignore any -R option the client might send.

What if you wanted to enable some options and disable others in the same ListOptions directive? You would surround your options in quotation marks, like so:

  ListOptions "-a +R" strict

The following keywords are supported, in addition to "strict":

• maxfiles
  Sets a maximum limit on the number of files listed in one directory listing
• maxdirs
  Sets a maximum limit on the number of directories listed in one directory listing
• maxdepth
  Sets a maximum recursion depth, if the -R option is allowed

  ListOptions -a maxfiles 2000 maxdepth 3

Note that <Limit> sections can be used to block the LIST and NLST commands altogether.