Re: set -e not ignored in AND-OR list

[Christoph Anton Mitterer <calestyo@xxxxxxxxxxxx>]

The following is probably just another case of these: ...

On Tue, 2024-11-05 at 03:04 +0100, Christoph Anton Mitterer wrote:
> $ $(foo) || true
> a
> $ $(foo) && true
> a
> 
> => these I don't understand
>    it's and AND-OR list, not the last element, so -e should be
> ignored,
>    yet it kicks in at the false


... but I'm not 100% sure, so perhaps some expert can confirm.

I had this function, which was checking whether some file contained
some byte:
is_file_containing_bytes()
{
        local file="$1"
        local octal_bytes="$2"
        
        
        local number_of_matching_bytes=''
        local exit_status=0
        number_of_matching_bytes="$(
                                        export LC_ALL=C
                                        exec 4>&1
                                        exitstatus_command1="$(
                                                                {
                                                                       
{
                                                                       
         cat "${file}" 2>/dev/null 3>&-
                                                                       
         printf "$?" >&3
echo "DEBUG" >&2
                                                                       
} 4>&-  | \
                                                                       
{ tr -d -c "${octal_bytes}"  |  wc -c; } >&4 3>&- 4>&-
                                                                } 3>&1
                                                            )" 4>&1
                                        exec 4>&-
                                        if [ "${exitstatus_command1}"
!= '0' ]; then
                                                exit 1
                                        fi
                                       )"  ||  exit_status="$?"
        if [ "${exit_status}" -ne 0 ]; then
                return 2
        fi
        
        if [ "${number_of_matching_bytes}" != '0' ]; then
                return 0
        else
                return 1
        fi
}

That was from back when there was no portable set -o pipefail and I
wanted to also catch any error in cat (e.g. when file not found) and
let through anything on stderr.

Again, set -e in place, I do:
is_file_containing_bytes non-existent '\000'

The cat/printf are in a pipe but without a leading !, so when cat error
because of the file not found, set -e should kick in and DEBUG not
printed.
The function works nevertheless, because 0 isn't captured in
exitstatus_command1 either.

However, back then I oversaw, that the whole thing is again behind a ||
and that in turn should again cause set -e to be ignored, so
exitstatus_command1 should actually capture the 1 from cat (and the
function properly fail because of that) and should also print the
DEBUG, because set -e is ignored.

But in dash, it doesn't.

Probably it's the same case than above, but it felt a bit convoluted,
because the pipe not ignoring the set -e but the outer AND-OR list
should ignore it.


Cheers,
Chris.