Re: [PATCH 01/19] check_bindir: convert test -a/-o to && and ||

From: Junio C Hamano <gitster@pobox.com>
Date: May 20, 2014, 18:54 UTC
Message-ID: <xmqq38g4z3fd.fsf@gitster.dls.corp.google.com>
In-Reply-To: <xmqqsio4z5e5.fsf@gitster.dls.corp.google.com>

Junio C Hamano <gitster@pobox.com> writes:

Show 7 quoted lines

> As I already said, I think "better known" is much less of an issue
> than that "-a/-o" is "more error prone", and that is the reason why
> we may want to do this rewrite.
>
> I do not know offhand how busy the tree would be when we can apply
> these patches post-release without them getting rebased, but the
> zero-th step before this series may want to be a patch like this.

... and this time with a proposed log message.

-- >8 --
Subject: [PATCH] CodingGuidelines: avoid "test <cond> -a/-o <cond>"

The construct is error-prone; "test" being built-in in most modern shells, the reason to avoid "test <cond> && test <cond>" spawning one extra process by using a single "test <cond> -a <cond>" no longer exists.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/CodingGuidelines | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/Documentation/CodingGuidelines b/Documentation/CodingGuidelines
index 3d08671..4d90c77 100644
--- a/Documentation/CodingGuidelines
+++ b/Documentation/CodingGuidelines
@@ -151,6 +151,19 @@ For shell scripts specifically (not exhaustive):
    interface translatable. See "Marking strings for translation" in
    po/README.
 
+ - We do not write our "test" command with "-a" and "-o" and use "&&"
+   or "||" to concatenate multiple "test" commands instead, because
+   the use of "-a/-o" is often error-prone.  E.g.
+
+     test -n "$x" -a "$a" = "$b"
+
+   is buggy and breaks when $x is "=", but
+
+     test -n "$x" && test "$a" = "$b"
+
+   does not have such a problem.
+
+
 For C programs:
 
  - We use tabs to indent, and interpret tabs as taking up to

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