linux-kernel - RE: [PATCH v2] selftests/lkdtm: Use /bin/sh not $SHELL

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Date:   Wed, 23 Jun 2021 13:43:04 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Guillaume Tucker' <guillaume.tucker@...labora.com>,
        Kees Cook <keescook@...omium.org>,
        Shuah Khan <shuah@...nel.org>
CC:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] selftests/lkdtm: Use /bin/sh not $SHELL

From: Guillaume Tucker
> Sent: 23 June 2021 13:40
...
> > diff --git a/tools/testing/selftests/lkdtm/run.sh b/tools/testing/selftests/lkdtm/run.sh
> > index bb7a1775307b..0f9f22ac004b 100755
> > --- a/tools/testing/selftests/lkdtm/run.sh
> > +++ b/tools/testing/selftests/lkdtm/run.sh
> > @@ -78,8 +78,9 @@ dmesg > "$DMESG"
> >
> >  # Most shells yell about signals and we're expecting the "cat" process
> >  # to usually be killed by the kernel. So we have to run it in a sub-shell
> > -# and silence errors.
> > -($SHELL -c 'cat <(echo '"$test"') >'"$TRIGGER" 2>/dev/null) || true
> > +# to avoid terminating this script. Leave stderr alone, just in case
> > +# something _else_ happens.
> > +(/bin/sh -c '(echo '"$test"') | cat >'"$TRIGGER") || true

I was having trouble parsing that command - and I'm good
at shell scripts.
I think the extra subshell the 'echo' is in doesn't help.
In fact, is either subshell needed?
Surely:
/bin/sh -c "echo '$test' | cat >$trigger" || true
will work just as well?

	David

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