I’m on a Mac with zsh (on iTerm2) and if I try to use symbolic link for plugins development I get stuck with this errors:
readlink: illegal option -- f
usage: readlink [-n] [file ...]
This because the Mac implementation of the readlink command is slightly different from the GNU one.
The easiest way to solve this is by doing this:
# brew install coreutils
# ln -s "$(which greadlink)" "$(dirname "$(which greadlink)")/readlink"
This will give you the possibility to use a compatible readlink version.
Please remember you need to have dirname "$(which greadlink)" value on your PATH in a position preceding the /usr/bin (where usually the original readlink is). On my case PATH is something like /usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:... and the symbolik link to greadlink is in /usr/local/bin.
Reference: Fixing "readlink: illegal option -- f" error on a Mac