# re-use same name
ln -s path/to/file
# give a different name to the symlink
ln -s path/to/file link-name
# replace existing symlink or file
ln -sf path/to/file
To create symlinks in specific directories:
# example setup
cd /tmp && mkdir foo bar && touch foo/target
# create a bar/target -> ../foo/target
ln -s ../foo/target -t bar
# create a bar/link -> ../foo/target
ln -s ../foo/target -T bar/link