Why does my symlink to /usr/local/bin not work?

Question

I installed Julia locally by unpacking it into a folder. Then I tried to add the executable to /usr/local/bin since I don't want to modify the $PATH.

sudo ln -s bin/julia-1.5.3/bin/julia /usr/local/bin/julia

If I now execute Julia in a new shell window the following message pops up:

$ julia
zsh: command not found: julia

$ ls -l /usr/local/bin/
total 12
lrwxrwxrwx 1 root root 25 Jan  1 10:08 julia -> bin/julia-1.5.3/bin/julia

So obviously the symlink exists nevertheless my shell tells me the command was not found. What is the problem here?

Answer 1

The solution is rather simple. Use an absolute symlink here such that the first argument of ln -s is a full path instead.

sudo ln -s /home/user/bin/julia-1.5.3/bin/julia /usr/local/bin/julia

Now it opens correctly and executes as expected.

The second and more complex solution is to use a relative symlink. However it has to be relative to the folder where the symlink will be created. Thus starting at /usr/local/bin one has to move up three folders to be at / and then descend into the appropriate folder.

sudo ln -s ../../../home/user/bin/julia-1.5.3/bin/julia /usr/local/bin/julia

Update: The comment below is correct and I edited the answer accordingly. Relative symlinks are fine and exist for good reasons however here they don't make any sense since they complicate the path a lot.