Re: [PATCH] init.sh: don't waste a subshell just to redirect stderr

[Stefano Lattarini]

Hi Jim.

On 01/05/2012 04:46 PM, Jim Meyering wrote:
> Looking at Bruno's recent test-init.sh failure,
> I noticed the unnecessary sub-shells here:
> 
> From a815c2160e6d6cc27d934e669ef9486bab310db3 Mon Sep 17 00:00:00 2001
> From: Jim Meyering <address@hidden>
> Date: Thu, 5 Jan 2012 16:45:50 +0100
> Subject: [PATCH] init.sh: don't waste a subshell just to redirect stderr
> 
> * tests/init.sh: In testing for diff -u and diff -c, use a
> stderr-redirecting exec inside `...` rather than a subshell.
> ---
>  ChangeLog     |    4 ++++
>  tests/init.sh |    4 ++--
>  2 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/ChangeLog b/ChangeLog
> index eb4a3a1..3eb41be 100644
> --- a/ChangeLog
> +++ b/ChangeLog
> @@ -1,5 +1,9 @@
>  2012-01-05  Jim Meyering  <address@hidden>
> 
> +     init.sh: don't waste a subshell just to redirect stderr
> +     * tests/init.sh: In testing for diff -u and diff -c, use a
> +     stderr-redirecting exec inside `...` rather than a subshell.
> +
>       test-init.sh: avoid failure on HP-UX 11.00
>       * tests/test-init.sh: Skip "diff -u"-comparing step when compare
>       resolves to diff -c or cmp.  Reported by Bruno Haible.
> diff --git a/tests/init.sh b/tests/init.sh
> index 9485492..65458c7 100644
> --- a/tests/init.sh
> +++ b/tests/init.sh
> @@ -255,7 +255,7 @@ compare_dev_null_ ()
>    return 2
>  }
> 
> -if diff_out_=`( diff -u "$0" "$0" < /dev/null ) 2>/dev/null`; then
> +if diff_out_=`exec 2>/dev/null; diff -u "$0" "$0" < /dev/null`; then
>
Wouldn't it be simpler and better to leave that redirection out altogether?
The output of the test scripts should be redirected to `.log' files by the
testsuite harness, so by being more verbose we can make those files more
informative, all without cluttering the make output.

Regards,
  Stefano