Re: non-executable files in $PATH cause errors

[Eli Schwartz]

On 1/10/21 10:49 AM, Ángel wrote:
> On 2021-01-10 at 08:52 +0100, n952162 wrote:
> > Hello,
> >
> > I consider it a bug that bash (and its hash functionality) includes
> > non-executable files in its execution look-up and then (inevitably)
> > simply reports an error, because its such files aren't  executable.
> >
> > Perhaps it's there to support PATH look up for arguments to the bash
> > command.  That would also be a bug.  Why should it be okay to execute
> > a
> > non-executable script?  Supporting users who are too lazy to chmod a
> > file ought to be less important than supporting users who want
> > fine-grain control over what's executable and what's not.
>
> Hello
>
> I can't reproduce what you report.
>
> $ mkdir foo bar
> $ printf '#!/bin/sh\necho Program "$0"\n' > foo/program
> $ printf '#!/bin/sh\necho Program "$0"\n' > bar/program
> $ PATH="$PATH:$PWD/foo:$PWD/bar"
> $ chmod +x bar/program
> $ program
>
> It is executing bar/program, not foo/program which is earlier in the
> path, but not executable.
>
> Maybe you just made the earlier program not executable, and the old
> path is still being remembered? You should run  hash -r  after
> making executable changes that will make an already-executed command
> find a different program in the path (in the example above, making
> foo/program executable, or removing again its +x bit).

In the event only $PWD/foo is in PATH, bash fails to find *any* 
executable "program" command, and it then looks for non-executable forms.

$ (PATH="$PATH:$PWD/foo:$PWD/bar"; program)
Program /tmp/bar/program
$ (PATH="$PATH:$PWD/foo"; program)
bash: /tmp/foo/program: Permission denied

This is also the behavior of dash, zsh, and ksh, though only bash 
reported the entire pathname of the file without execute permissions.

dash: 2: program: Permission denied
zsh: permission denied: program
ksh: program: cannot execute [Permission denied]

Hardly a bug in bash, merely a difference of opinion between the OP and 
the people who design shells.

--
Eli Schwartz
Arch Linux Bug Wrangler and Trusted User

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