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Re: [Qemu-block] [PATCH v4] tests: Avoid non-portable 'echo -ARG'
From: |
Max Reitz |
Subject: |
Re: [Qemu-block] [PATCH v4] tests: Avoid non-portable 'echo -ARG' |
Date: |
Wed, 5 Jul 2017 17:08:03 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 |
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: address@hidden
> Signed-off-by: Eric Blake <address@hidden>
>
> ---
> 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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