“LinkOpen::linke : specified file is not a mathlink executable”

Question

The following code runs fine if I run it interactively:

Clear@realpath;
realpath[path_] := Import["!readlink "<>path, "Text"];
testsymlink = FileNameJoin[{$HomeDirectory, "testsymlink"}];
test = realpath[testsymlink];

In particular, the variable test gets the expected (non-Null) value.

The same code runs fine also if I put it in a standalone script and execute it with

<< "/path/to/script.m";

But if I put the same code, all by itself, in my Kernel/init.m file, it fails: the variable test gets the incorrect value Null. (The variable testsymlink, on the other hand, is still correctly set.)

Furthermore, if I then evaluate

realpath[testsymlink]

interactively (in the newly started Mathematica session), I get the error shown in this post's title, twice:

I can't figure out why I'm getting this error, but I'm having it may give someone else a clue as to why the snippet is failing in the first place (when run as part of executing Kernel/init.m.

PS: It appears that the offending snippet puts the session in a corrupted state, because when I attempted to upload the image shown above, I got this error:

I had first restart Mathematica (after deleting the offending snippet from Kernel/init.m), before I could upload these images.