empty double backquotes unpredictable?

[Joel Spolsky]

In article <779 at unify.UUCP> rk at unify.UUCP (Ron Kuris) writes:
>When running the csh, I typed only two backquotes (``) and got:
>/s2/acct/rk/bin/: cannot execute
>

csh looks for the command "" (null string).  "/s2/acct/rk/bin/" is in
the path and it tries to concatenate "" onto the end of this, getting
"/s2/acct/rk/bin/" ... which exists, so it doesn't have to look
further.  But it can't execute it. So it complains. You would get the
same result by just typing any directory name.

>When I removed /s2/acct/rk/bin from my path, the error changes to:
>: cannot execute

It is looking for the command "" (null string) in your current
directory and not finding it.

>What gives?  I tried nifty things like: ``file
>which runs /s2/acct/rk/bin/file.  
>Then I tried: echo ``
>and got nothing.  Seems real bizzare.  Any explanations?

Because the command `` doesn't generate any output (it fails to run),
it is inline substituted with nothing so "``file" resolves to "file".



Some naive guesses from...
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|  Joel Spolsky  | bitnet: spolsky at yalecs.bitnet     uucp: ...!yale!spolsky |
|                | internet: spolsky at cs.yale.edu     voicenet: 203-436-1483 |
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                                                      #include <disclaimer.h>