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

[Eric Blake]

On 06/30/2017 09:38 AM, Max Reitz wrote:
> On 2017-06-28 16:21, 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 "..."', and 'echo -e "..."'
>> with 'printf "...\n"'.
>>
>> In the qemu-iotests check script, also fix unusual shell quoting
>> that would result in word-splitting if 'date' outputs a space.
>>
>> Signed-off-by: Eric Blake <address@hidden>
>> ---

> Question 1: Who's going to take this? :-)

It's test-related, touching mostly iotests. But it's also a candidate
for qemu-trivial (I'll cc them on v2).

> 
> Question 2: This breaks 171 if TEST_DIR contains a % (e.g.
> "TEST_DIR=/tmp/foo%% ./check -raw 171"). Is that OK?

No.  A more formal fix is using 'printf %s "..."' in place of 'echo -n
"..."', if the "..." contains any substitutions.  The extra %s is not
needed when there are no risky substitutions.  I'll spin up a v2.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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