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From: Junio C Hamano <gitster@pobox.com>
To: Jonathan Tan <jonathantanmy@google.com>
Cc: Ramsay Jones <ramsay@ramsayjones.plus.com>, git@vger.kernel.org
Subject: Re: [PATCH v3 0/4] Changed path filter hash fix and version bump
Date: Tue, 13 Jun 2023 12:16:29 -0700	[thread overview]
Message-ID: <xmqqa5x35g1e.fsf@gitster.g> (raw)
In-Reply-To: <20230613171634.15985-1-jonathantanmy@google.com> (Jonathan Tan's message of "Tue, 13 Jun 2023 10:16:33 -0700")

Jonathan Tan <jonathantanmy@google.com> writes:

>> + - In 'printf' format string, do not use hexadecimals, as they are not
>> +   portable.  Write 
>> +
>> +     CENT=$(printf "\302\242")
>> +
>> +   not
>> +
>> +     CENT=$(printf "\xc2\xa2")
>
> I've checked with "dash" and this applies to any quoted string, not just
> when passed to printf. I'll prepare a patch describing this.

What do you mean by "any quoted string"?

I think built-in 'echo' of dash takes "\302\242" and emits the
cent-sign (but /bin/echo may not), but I do not think it is "any
quoted string".  To wit:

    dash$ echo '\302\242'
    ¢

The echo built into dash shows the cent-sign.  The example does not
let us tell if is the shell (i.e. the 'echo' command sees the
cent-sign in its argv[1]) or if it is the command (i.e. the 'echo'
sees 8-byte string "bs three zero two bs two four two" in its
argv[1], and shows that as the cent-sign), though.

    dash$ /bin/echo '\302\242'
    \302\242

This shows that shell is not doing anything fancy.  /bin/echo gets
the 8-byte string in its argv[1] and emits that as-is.

    dash$ /bin/echo "\302\242"
    \302\242

Again this shows the same; I added this example to demonstrate that
it is _not_ like the shell interprets the backslashed octal strings
depending on how they are quoted.

    dash$ printf "%s\n" '\302\242'
    \302\242
    dash$ printf "%s\n" "\302\242"
    \302\242

And these demonstrates that argv[2] given to printf in these cases
are 8-byte string "bs three zero two bs two four two" and the shell
is not doing anything fancy.

So, I would suggest not saying "any quoted string".  In addition,
even though dash's built-in echo that recognizes "\0num" seems to be
conformant to what POSIX specifies (cf. [*1*]), GNU requires "-e" in
order to do so in both standalone 'echo' binary and one built into
'bash', so we cannot rely on this POSIX behaviour when writing a
portable script.  Hence, I would recommend us to focus on giving a
piece of advice on use of printf in this part of the documentation.


[References]

*1* https://pubs.opengroup.org/onlinepubs/9699919799/utilities/echo.html
*2* https://www.gnu.org/software/coreutils/manual/html_node/echo-invocation.html

  parent reply	other threads:[~2023-06-13 19:16 UTC|newest]

Thread overview: 116+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-22 21:48 [PATCH 0/2] Changed path filter hash fix and version bump Jonathan Tan
2023-05-22 21:48 ` [PATCH 1/2] t4216: test wrong bloom filter version rejection Jonathan Tan
2023-05-22 21:48 ` [PATCH 2/2] commit-graph: fix murmur3, bump filter ver. to 2 Jonathan Tan
2023-05-23 13:00   ` Derrick Stolee
2023-05-23 23:00     ` Jonathan Tan
2023-05-23 23:51     ` Junio C Hamano
2023-05-24 21:26       ` Jonathan Tan
2023-05-26 13:19         ` Derrick Stolee
2023-05-30 17:26           ` Jonathan Tan
2023-05-23  4:42 ` [PATCH 0/2] Changed path filter hash fix and version bump Junio C Hamano
2023-05-31 23:12 ` [PATCH v2 0/3] " Jonathan Tan
2023-05-31 23:12   ` [PATCH v2 1/3] t4216: test changed path filters with high bit paths Jonathan Tan
2023-05-31 23:12   ` [PATCH v2 2/3] repo-settings: introduce commitgraph.changedPathsVersion Jonathan Tan
2023-05-31 23:12   ` [PATCH v2 3/3] commit-graph: new filter ver. that fixes murmur3 Jonathan Tan
2023-06-03  1:01   ` [PATCH v2 0/3] Changed path filter hash fix and version bump Junio C Hamano
2023-06-03  2:24     ` Junio C Hamano
2023-06-07 16:30       ` Jonathan Tan
2023-06-07 21:37         ` Jonathan Tan
2023-06-08 19:21 ` [PATCH v3 0/4] " Jonathan Tan
2023-06-08 19:21   ` [PATCH v3 1/4] gitformat-commit-graph: describe version 2 of BDAT Jonathan Tan
2023-06-08 19:52     ` Ramsay Jones
2023-06-12 21:26       ` Junio C Hamano
2023-06-08 19:21   ` [PATCH v3 2/4] t4216: test changed path filters with high bit paths Jonathan Tan
2023-06-08 19:21   ` [PATCH v3 3/4] repo-settings: introduce commitgraph.changedPathsVersion Jonathan Tan
2023-06-08 19:21   ` [PATCH v3 4/4] commit-graph: new filter ver. that fixes murmur3 Jonathan Tan
2023-06-08 19:50   ` [PATCH v3 0/4] Changed path filter hash fix and version bump Ramsay Jones
2023-06-09  0:08     ` Jonathan Tan
2023-06-12 21:31     ` Junio C Hamano
2023-06-13 17:16       ` Jonathan Tan
2023-06-13 17:29         ` [PATCH] CodingGuidelines: use octal escapes, not hex Jonathan Tan
2023-06-13 18:16           ` Eric Sunshine
2023-06-13 18:43             ` Jonathan Tan
2023-06-13 19:15               ` Eric Sunshine
2023-06-13 19:29                 ` Junio C Hamano
2023-06-13 19:16         ` Junio C Hamano [this message]
2023-06-13 17:39 ` [PATCH v4 0/4] Changed path filter hash fix and version bump Jonathan Tan
2023-06-13 17:39   ` [PATCH v4 1/4] gitformat-commit-graph: describe version 2 of BDAT Jonathan Tan
2023-06-13 21:58     ` Junio C Hamano
2023-06-20 13:22       ` Derrick Stolee
2023-06-21 12:08       ` Taylor Blau
2023-06-22 22:26         ` Jonathan Tan
2023-06-23 13:05           ` Derrick Stolee
2023-06-13 17:39   ` [PATCH v4 2/4] t4216: test changed path filters with high bit paths Jonathan Tan
2023-06-13 17:39   ` [PATCH v4 3/4] repo-settings: introduce commitgraph.changedPathsVersion Jonathan Tan
2023-06-20 13:28     ` Derrick Stolee
2023-06-21 12:14     ` Taylor Blau
2023-06-13 17:39   ` [PATCH v4 4/4] commit-graph: new filter ver. that fixes murmur3 Jonathan Tan
2023-06-20 13:39     ` Derrick Stolee
2023-06-20 18:37       ` Junio C Hamano
2023-06-13 19:21   ` [PATCH v4 0/4] Changed path filter hash fix and version bump Junio C Hamano
2023-06-20 13:43     ` Derrick Stolee
2023-06-20 21:56       ` Jonathan Tan
2023-06-21 12:19       ` Taylor Blau
2023-06-21 17:53         ` Derrick Stolee
2023-06-22 22:27           ` Jonathan Tan
2023-06-23 13:18             ` Derrick Stolee
2023-07-13 21:42 ` [PATCH v5 " Jonathan Tan
2023-07-13 21:42   ` [PATCH v5 1/4] gitformat-commit-graph: describe version 2 of BDAT Jonathan Tan
2023-07-19 17:25     ` Taylor Blau
2023-07-20 20:20       ` Jonathan Tan
2023-07-21  1:38         ` Taylor Blau
2023-07-13 21:42   ` [PATCH v5 2/4] t4216: test changed path filters with high bit paths Jonathan Tan
2023-07-13 22:50     ` Junio C Hamano
2023-07-19 17:27       ` Taylor Blau
2023-07-19 17:55         ` [PATCH 0/4] commit-graph: avoid looking at Bloom filter data directly Taylor Blau
2023-07-19 17:55           ` [PATCH 1/4] t/helper/test-read-graph.c: extract `dump_graph_info()` Taylor Blau
2023-07-19 17:55           ` [PATCH 2/4] bloom.h: make `load_bloom_filter_from_graph()` public Taylor Blau
2023-07-19 17:55           ` [PATCH 3/4] t/helper/test-read-graph: implement `bloom-filters` mode Taylor Blau
2023-07-19 17:55           ` [PATCH 4/4] fixup! t4216: test changed path filters with high bit paths Taylor Blau
2023-07-19 19:24           ` [PATCH 0/4] commit-graph: avoid looking at Bloom filter data directly Junio C Hamano
2023-07-20 20:22           ` Jonathan Tan
2023-07-13 21:42   ` [PATCH v5 3/4] repo-settings: introduce commitgraph.changedPathsVersion Jonathan Tan
2023-07-19 18:10     ` Taylor Blau
2023-07-20 20:42       ` Jonathan Tan
2023-07-20 21:02         ` Taylor Blau
2023-07-13 21:42   ` [PATCH v5 4/4] commit-graph: new filter ver. that fixes murmur3 Jonathan Tan
2023-07-19 18:24     ` Taylor Blau
2023-07-20 21:27       ` Jonathan Tan
2023-07-26 23:32         ` Taylor Blau
2023-07-13 22:16   ` [PATCH v5 0/4] Changed path filter hash fix and version bump Junio C Hamano
2023-07-13 22:59     ` Junio C Hamano
2023-07-14 18:48     ` Jonathan Tan
2023-07-20 21:46 ` [PATCH v6 0/7] " Jonathan Tan
2023-07-20 21:46   ` [PATCH v6 1/7] gitformat-commit-graph: describe version 2 of BDAT Jonathan Tan
2023-07-20 21:46   ` [PATCH v6 2/7] t/helper/test-read-graph.c: extract `dump_graph_info()` Jonathan Tan
2023-07-26 23:26     ` Taylor Blau
2023-07-20 21:46   ` [PATCH v6 3/7] bloom.h: make `load_bloom_filter_from_graph()` public Jonathan Tan
2023-07-20 21:46   ` [PATCH v6 4/7] t/helper/test-read-graph: implement `bloom-filters` mode Jonathan Tan
2023-07-20 21:46   ` [PATCH v6 5/7] t4216: test changed path filters with high bit paths Jonathan Tan
2023-07-26 23:28     ` Taylor Blau
2023-07-20 21:46   ` [PATCH v6 6/7] repo-settings: introduce commitgraph.changedPathsVersion Jonathan Tan
2023-07-20 21:46   ` [PATCH v6 7/7] commit-graph: new filter ver. that fixes murmur3 Jonathan Tan
2023-07-25 20:52   ` [PATCH v6 0/7] Changed path filter hash fix and version bump Junio C Hamano
2023-07-26 20:39   ` Junio C Hamano
2023-07-27  0:17     ` Taylor Blau
2023-07-27  0:49       ` Junio C Hamano
2023-07-27 17:39         ` Jonathan Tan
2023-07-27 17:56           ` Taylor Blau
2023-07-27 20:53             ` Jonathan Tan
2023-08-01 18:08               ` Taylor Blau
2023-08-01 18:52                 ` Jonathan Tan
2023-08-03  0:01                 ` Taylor Blau
2023-08-03 13:18                   ` Derrick Stolee
2023-08-03 18:45                     ` Taylor Blau
2023-07-27 18:44         ` Junio C Hamano
2023-08-01 18:41 ` [PATCH v7 " Jonathan Tan
2023-08-01 18:41   ` [PATCH v7 1/7] gitformat-commit-graph: describe version 2 of BDAT Jonathan Tan
2023-08-01 18:41   ` [PATCH v7 2/7] t/helper/test-read-graph.c: extract `dump_graph_info()` Jonathan Tan
2023-08-01 18:41   ` [PATCH v7 3/7] bloom.h: make `load_bloom_filter_from_graph()` public Jonathan Tan
2023-08-01 18:41   ` [PATCH v7 4/7] t/helper/test-read-graph: implement `bloom-filters` mode Jonathan Tan
2023-08-01 18:41   ` [PATCH v7 5/7] t4216: test changed path filters with high bit paths Jonathan Tan
2023-08-01 18:41   ` [PATCH v7 6/7] repo-settings: introduce commitgraph.changedPathsVersion Jonathan Tan
2023-08-01 18:41   ` [PATCH v7 7/7] commit-graph: new filter ver. that fixes murmur3 Jonathan Tan
2023-08-01 18:44   ` [PATCH v7 0/7] Changed path filter hash fix and version bump Junio C Hamano
2023-08-01 20:58     ` Taylor Blau
2023-08-01 21:07       ` Junio C Hamano

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