Re: [PATCH 1/4] scripts/run-qemu.sh: better error checks & formatting

[Alyssa Ross <hi@alyssa.is>]

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Demi Marie Obenour <demiobenour@gmail.com> writes:

> On 11/13/25 07:23, Alyssa Ross wrote:
>> Demi Marie Obenour <demiobenour@gmail.com> writes:
>> 
>>> No other functional change intended.
>>>
>>> Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
>>> ---
>>>  scripts/run-qemu.sh | 24 ++++++++++++++----------
>>>  1 file changed, 14 insertions(+), 10 deletions(-)
>> 
>> This is a lot of changes all in one, without individual explanation.
>> I'd appreciate it if they could be broken up and explained, because I'm
>> going to have to ask what the purpose of each change is.
>> 
>>> diff --git a/scripts/run-qemu.sh b/scripts/run-qemu.sh
>>> index 64fd29259ab108bc547cb7c74623ae9dc288b3b7..9c6c8193bbeba5916038c82d8f76992051719c19 100755
>>> --- a/scripts/run-qemu.sh
>>> +++ b/scripts/run-qemu.sh
>>> @@ -1,11 +1,15 @@
>>> -#!/bin/sh -ue
>>> +#!/bin/sh --
>> 
>> The idea here is to be robust against the script being invoked with
>> argv[0] set to "-c" or something?
>
> Correct.

Seems a little paranoid but I suppose it doesn't hurt.  I'd take a
treewide change that did this for every /bin/sh shebang.

>>> +if [ -n ${ARCH+test} ]; then
>>> +	ARCH=$(uname -m)
>>> +fi
>>>  
>>> -case "${ARCH:="$(uname -m)"}" in
>>> +case $ARCH in
>>>  	aarch64)
>>>  		machine=virt,accel=kvm:tcg,gic-version=3,iommu=smmuv3
>>>  		;;
>> 
>> Why is this better?
>
> If uname exits with a non-zero status, the script will exit rather
> than continuing.

I see — makes sense.  And why is the check not just the following?

	if [ -z "${ARCH-}" ]; then

>>> -			set -- "$@" -append "${append:+$append }$1"
>>> +			set -- "$@" -append ${append:+"$append "}"$1"
>>>  			i=$((i + 2))
>>>  			shift
>>>  			continue
>> 
>> Don't understand this one.  We've gone from one set of quotes to two
>> sequential ones.
>
> I remember reading that the first version might not conform to POSIX.
> I'm not sure if it matters though.

POSIX says[1]:

> If a parameter expansion occurs inside double-quotes:
> 
> * Pathname expansion shall not be performed on the results of the expansion.
> 
> * Field splitting shall not be performed on the results of the expansion.

Seems desirable to me.

[1]: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_02

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