bash shell script: recently running, now failing

[Scott Smith]

Place the nul on the third line. For example:

#!/bin/bash
#
# ^@ identify as a binary file
...



On Thu, Apr 6, 2023 at 4:03 AM Corinna Vinschen via Cygwin <
cygwin@cygwin.com> wrote:

> On Apr  6 04:43, Fergus Daly via Cygwin wrote:
> > I have a "hash bang" bash shell script i.e. first line
> > #! /bin/sh
> > or equivalently
> > #! /bin/bash
> > For various reasons I want this file to be identified as binary so its
> second line
> > is the single character null \x00 showing up in some editors e.g. nano as
> >  ^@
> > This does not prevent the script from running to a successful conclusion.
> > Or not until recently. Now the script fails with
> > /home/user/bin/file.old.sh: cannot execute binary file
> > Q1 - was bash recently updated? Would this explain the changed behaviour?
>
> bash was recently updated from 4.4.12 to 5.2.15.
>
> The behaviour is the same in bash on Linux.  Take this file with
> a \0 in line 2:
>
>   $ cat -v x.sh
>   #! /bin/bash
>   ^@
>   echo foo
>   $ bash --version | head -1
>   GNU bash, version 5.2.15(1)-release (x86_64-redhat-linux-gnu)
>   $ ./x.sh
>   ./x.sh: ./x.sh: cannot execute binary file
>
> While dash on Linux runs the script:
>
>   $ sed -i -e 's/bash/dash/' x.sh
>   $ ./x.sh
>   foo
>
> > Q2 - if so, is this newly introduced "glitch" known and presumably
> > intended? Or an unintended consequence that will be retracted in a
> > later update?
>
> Bash follows the POSIX standard:
>
> https://pubs.opengroup.org/onlinepubs/9699919799/utilities/sh.html#tag_20_117_07
>
> https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html#tag_03_403
>
> So I don't expect this will change any time soon.
>
> > Q3 - at 1/8 the size of bash and sh, I am not at all sure of the role
> and reach of dash.
>
> Dash is a minimal shell with no bells and whistles.  It loads ands runs
> slightly faster than bash.  If you only need bare minimum bourne shell
> behaviour, it's a good choice for scripts.
>
>
> Corinna
>
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