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Re: non-executable files in $PATH cause errors

From: Dale R. Worley
Subject: Re: non-executable files in $PATH cause errors
Date: Wed, 13 Jan 2021 21:45:08 -0500

> On 2021/01/09 23:52, n952162 wrote:
>> I consider it a bug that bash (and its hash functionality) includes
>> non-executable files in its execution look-up

Of course, as described in the manual page, Bash first searches for an
executable with the right name in the PATH, and then if that fails, it
searches for a non-executable file in the PATH.  The first part
resembles one of the exec() functions and seems reasonable, but the
second is weird.

My belief is that the reason is compatibility with historical usage.  I
have dim memories that there were days before shell scripts had the
executable bit set and the first line started with "#!".  Instead, they
weren't marked as executable but the first line started with ": "
(either mandatory or by convention).  And the scripting facility was
implemented entirely in the shell -- if the shell's call to the kernel
to execute the script failed, it would decide that the file was a
script, then spawn and initialize a subshell to execute it.  Of course,
there was no check that your file actually was a script, so if you had
named a data file, the subshell would spew a stream of errors.

But the consequence to this day is that scripts without the executable
bit can be executed if they are given as command names to bash, and that
executable scripts take precedence over similarly-named non-executable
scripts earlier in PATH.


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