Re: [PATCH v2] scripts/make-gpt.sh: allow setting partition size

[Alyssa Ross <hi@alyssa.is>]

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

> On 11/28/25 08:22, Alyssa Ross wrote:
>> We want non-minimally-sized partitions to leave space for updates.
>> All such partitions will also be labelled, so we can just add another
>> optional field at the end.
>> 
>> Since we don't parse partition specifications in sh, we can't keep a
>> running total any more, so instead we just go through the table at the
>> end and add up all the sizes, taking advantage of our knowledge that
>> the size will always be the last thing in each line in our tables.
>> 
>> Signed-off-by: Alyssa Ross <hi@alyssa.is>
>> Message-ID: <20251127174054.2056835-2-hi@alyssa.is>
>> ---
>> v2: fix conflicts after applying Demi's optimization, and avoid awk
>>     to sum partition sizes, taking inspiration from the same.
>> v1: https://spectrum-os.org/lists/archives/spectrum-devel/20251127174054.2056835-2-hi@alyssa.is/
>> 
>>  scripts/make-gpt.sh      | 30 ++++++++++++++++++------------
>>  scripts/sfdisk-field.awk | 22 +++++++++++++++++-----
>>  2 files changed, 35 insertions(+), 17 deletions(-)
>> 
>> diff --git a/scripts/make-gpt.sh b/scripts/make-gpt.sh
>> index 3cae441..cb19868 100755
>> --- a/scripts/make-gpt.sh
>> +++ b/scripts/make-gpt.sh
>> @@ -1,10 +1,10 @@
>>  #!/bin/sh -eu
>>  #
>> -# SPDX-FileCopyrightText: 2021-2023 Alyssa Ross <hi@alyssa.is>
>> +# SPDX-FileCopyrightText: 2021-2023, 2025 Alyssa Ross <hi@alyssa.is>
>>  # SPDX-FileCopyrightText: 2022 Unikie
>>  # SPDX-License-Identifier: EUPL-1.2+
>>  #
>> -# usage: make-gpt.sh GPT_PATH PATH:PARTTYPE[:PARTUUID[:PARTLABEL]]...
>> +# usage: make-gpt.sh GPT_PATH PATH:PARTTYPE[:PARTUUID[:PARTLABEL[:PARTMiB]]]...
>>  
>>  ONE_MiB=1048576
>>  
>> @@ -33,21 +33,27 @@ scriptsDir="$(dirname "$0")"
>>  out="$1"
>>  shift
>>  
>> -nl='
>> -'
>> -table="label: gpt"
>> +table=$(for partition; do
>> +	awk -f "$scriptsDir/sfdisk-field.awk" \
>> +		-v partition="$partition" \
>> +		-v size="$(sizeMiB "${partition%%:*}")"
>> +done)
>
> $(sizeMiB) should be moved into a separate command.  Shellcheck can
> catch this if you enable SC2312.

Good catch, thanks.  Feel free to suggest other optional shellcheck
things we should enable.  (Although I've just noticed
release/checks/shellcheck.nix doesn't seem to be reading the
.shellcheckrc file properly so don't use that for testing.)

>>  # Keep 1MiB free at the start, and 1MiB free at the end.
>> -gptBytes=$((ONE_MiB * 2))
>> -for partition; do
>> -	sizeMiB="$(sizeMiB "${partition%%:*}")"
>> -	table="$table${nl}size=${sizeMiB}MiB,$(awk -f "$scriptsDir/sfdisk-field.awk" -v partition="$partition")"
>> -	gptBytes="$((gptBytes + sizeMiB * ONE_MiB))"
>> -done
>> +gptMiB=2
>> +while read -r partition; do
>> +	# Here we rely on sfdisk-field.awk always putting size last.
>> +	: $((gptMiB += ${partition##*=}))
>> +done <<EOF
>> +$table
>> +EOF
>
> Nit: should ${partition##*=} be in double quotes?

I tried changing it, but it is apparently an "arithmetic syntax error"
to use double quotes here.

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