Yann
2013/7/10 Yann E. MORIN <yann.morin.1998@xxxxxxx>:
> Clément, All,
>
> On 2013-07-10 21:58 +0200, Clement Chauplannaz spake thusly:
>> Script `config' relies on extensions of `GNU sed', and is thus not
>> working on all Unixes:
>> - in-place edition of files (-i), which can be replaced with
>> a temporary file;
>> - extended-regexps (-r), which can be split into basic regexps;
>> - single-line calls to `a' command, while some implementations
>> require a leading newline before the parameter.
>>
>> Rewrite calls to `sed' program to comply with POSIX interface.
>
> Clément, sorry I did not come back to you earlier after your second PM.
> Here is further review:
>
>> Signed-off-by: Clement Chauplannaz <chauplac@xxxxxxxxx>
>> ---
>> scripts/config | 12 +++++++++---
>> 1 file changed, 9 insertions(+), 3 deletions(-)
>>
>> diff --git a/scripts/config b/scripts/config
>> index a65ecbb..3fd95eb 100755
>> --- a/scripts/config
>> +++ b/scripts/config
>> @@ -66,9 +66,14 @@ set_var() {
>> name_re="^($name=|# $name is not set)"
>> before_re="^($before=|# $before is not set)"
>> if test -n "$before" && grep -Eq "$before_re" "$FN"; then
>> - sed -ri "/$before_re/a $new" "$FN"
>> + lf=$'\n'
>
> As you explained me earlier, you expect this to actually set the '\n'
> symbol (0x0a) as first char of variable 'lf'. This is a bashism, and is
> not POSIX. Here is a test script:
>
> #!/bin/dash
> lf=$'\n'
> printf "lf='%s'\n" "${lf}"
> printf "lf='${lf}'\n"
>
> And the output:
> lf='$\n'
> lf='$
> '
>
> Now, if you use #!/bin/bash, it works as you expect, but not with a
> POSIX-only script like dash.
>
> A reliable way to get a single '\n' would be:
>
> lf="$( printf '\n' )"
This looks like a good idea. I need to work it more in depth though,
as the "single-newline" printf seems to get caught by bash as an IFS -
in other words, it produces an empty var. I'll come back to you with
my findings.
>
> Yes, config is already a bash script, but no need to add bashisms when
> they can be avoided. And since this patch is about POSIX compliance in
> the first place... ;-)
Well, it's more about POSIX compliance for utilities (grep, sed, find,
etc.) which share the same name, a somewhat loose common interface,
but a different implementation between GNU & *BSD. I'm assuming bash
under Linux and *BSD comes from the same source :-).
Besides, I can't say to what extent `config' script complies with
POSIX shell interface and how it would run under other shells...
>
> Otherwise, LGTM.
>
Best regards,
Clement
> Regards,
> Yann E. MORIN.
>
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