Is it possible to seed only with aria2?

I understand that it's an old question, but in case someone (like me) finds it -

The -V options works just fine, but if you do not want to verify all files before seeding you can instead use --bt-seed-unverified. Official documentation.

For example, consider the following folder structure:

• torrents data
  • .torrent files

To seed torrents you can use this command from directory with .torrent files:
ls | aria2c --bt-seed-unverified --seed-ratio=0.0 -d "../" -i -

It looks like you can do this with the -V option, although it does not look to be very well documented. From this web page:

You can seed downloaded file using -V option. This will first check piece hashes for the downloaded file.

aria2c -V -d/path/to/dir file.torrent

I'd suggest also adding --seed-ratio=0.0 so that you'll seed the file forever:

aria2c -V --seed-ratio=0.0 -d/path/to/dir file.torrent