Re: [Qemu-trivial] [PATCH v4] tests: Avoid non-portable 'echo -ARG'

[Max Reitz <mreitz@redhat.com>]

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On 2017-07-03 20:09, Eric Blake wrote:
> POSIX says that backslashes in the arguments to 'echo', as well as
> any use of 'echo -n' and 'echo -e', are non-portable; it recommends
> people should favor 'printf' instead.  This is definitely true where
> we do not control which shell is running (such as in makefile snippets
> or in documentation examples).  But even for scripts where we
> require bash (and therefore, where echo does what we want by default),
> it is still possible to use 'shopt -s xpg_echo' to change bash's
> behavior of echo.  And setting a good example never hurts when we are
> not sure if a snippet will be copied from a bash-only script to a
> general shell script (although I don't change the use of non-portable
> \e for ESC when we know the running shell is bash).
> 
> Replace 'echo -n "..."' with 'printf %s "..."', and 'echo -e "..."'
> with 'printf %b "...\n"', with the optimization that the %s/%b
> argument can be omitted if the string being printed is a strict
> literal with no '%', '$', or '`' (we could technically also make
> this optimization when there are $ or `` substitutions but where
> we can prove their results will not be problematic, but proving
> that such substitutions are safe makes the patch less trivial
> compared to just being consistent).
> 
> In the qemu-iotests check script, fix unusual shell quoting
> that would result in word-splitting if 'date' outputs a space.
> 
> In test 051, take an opportunity to shorten the line.
> 
> In test 068, get rid of a pointless second invocation of bash.
> 
> CC: qemu-trivial@nongnu.org
> Signed-off-by: Eric Blake <eblake@redhat.com>
> 
> ---
> v4: even more use of %b/%s [Max]
> v3: use 'printf %s' in a few more places that substitute [Max]
> v2: be robust to potential % in substitutions
> ---
>  qemu-options.hx             |  4 ++--
>  tests/multiboot/run_test.sh | 10 +++++-----
>  tests/qemu-iotests/051      |  7 ++++---
>  tests/qemu-iotests/068      |  2 +-
>  tests/qemu-iotests/142      | 48 ++++++++++++++++++++++-----------------------
>  tests/qemu-iotests/171      | 14 ++++++-------
>  tests/qemu-iotests/check    | 18 ++++++++---------
>  tests/rocker/all            | 10 +++++-----
>  tests/tcg/cris/Makefile     |  8 ++++----
>  9 files changed, 61 insertions(+), 60 deletions(-)

Thanks a lot (not least for bearing my nagging)! Applied to my block branch:

https://github.com/XanClic/qemu/commits/block

(I agree it's fit for qemu-trivial now, but, well...)

Max


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