I want to list only the directories in specified path (ls doesn\'t have such option).
Also, can this be done with a single line command?
The answer will depend on your shell.
In zsh, for example, you can do the following:
echo *(/)
And all directories within the current working directory will be displayed.
See man zshexpn for more information.
An alternative approach would be to use find(1), which should work on most Unix flavours:
find . -maxdepth 1 -type d -print
find(1) has many uses, so I'd definitely recommend man find.