Problem with test -r

[alice]

On Mon Feb 13, 2023 at 10:00 AM CET, David Laight wrote:
> From: Vladimír Macek
> > Sent: 11 February 2023 19:15
> > 
> > Hi,
> > 
> > I'd like to report what seems to be a bug in the busybox's test command. I
> > use the official alpine:3 docker container.
> > 
> > The test -r does not return true even when the file is indeed readable
> > (testing by head command). Yes, the file has an unusual set of permissions,
> > but that does not restrict it from reading. Here's the output of the
> > interactive container shell session:
> > 
> > dd72078df6d2:/task/output/files$ ls -lad . .. cnb_rate_eur_czk.csv
> > drwxrwx---    2 setup    project        4096 Feb 11 18:33 .
> > drwxr-x---    5 setup    project        4096 Feb 11 18:33 ..
> > -rw-r--r--    1 task     project       20512 Feb 11 18:33 cnb_rate_eur_czk.csv
>
> By the look of it the problem is that 'test -r' requires
> directory search access - so why not just say that.
>
> > dd72078df6d2:/task/output/files$ [ -r cnb_rate_eur_czk.csv ] && echo READABLE
> > dd72078df6d2:/task/output/files$ [[ -r cnb_rate_eur_czk.csv ]] && echo READABLE
> > 
> > dd72078df6d2:/task/output/files$ which [
> > /usr/bin/[
> > dd72078df6d2:/task/output/files$ which [[
> > /usr/bin/[[
>
> The output from 'which' doesn't necessarily have any connection
> with the code any specific shell executes for a command.
> 'which' is a bourne shell script that is trying (and must fail) to
> emulate a csh builtin command.
>
> The 'test/[' command is almost certainly a shell builtin.
> The program in /usr/bin is almost never executed.

when one is using busybox ash as a shell, is /usr/bin/test (from busybox
symlink) and "builtin test" not the same code in the end (same for [)? i.e.
this case, which is probably using busybox ash (needs confirmation).

> As for '[[', IIRC that is a bash 'special' that nothing
> portable should be using.
>
> 	David
>
> -
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