Re: [PATCH] Use wc instead of awk to count subtrees in t0090-cache-tree

From: Junio C Hamano <gitster@pobox.com>
Date: Dec 22, 2014, 23:34 UTC
Message-ID: <xmqq4msn6yyl.fsf@gitster.dls.corp.google.com>
In-Reply-To: <xmqqd27b6zd3.fsf@gitster.dls.corp.google.com>

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

Show 19 quoted lines

> From: Ben Walton <bdwalton@gmail.com>
>
> The awk statements previously used in this test weren't compatible
> with the native versions of awk on Solaris:
>
>     echo "dir" | /bin/awk -v c=0 '$1 {++c} END {print c}'
>     awk: syntax error near line 1
>     awk: bailing out near line 1
>
>     echo "dir" | /usr/xpg4/bin/awk -v c=0 '$1 {++c} END {print c}'
>     0
>
> And with GNU awk for comparison:
>
>     echo "dir" | /opt/csw/gnu/awk -v c=0 '$1 {++c} END {print c}'
>     1
>
> Work it around by using $1 != "" to state more explicitly that we
> are skipping empty lines.

By the way, I was hoping (eh, what kind of hope is that???) that $1 alone is not a kosher POSIX way but a GNUism, but that does not seem to be the case. POSIX has this [*1*]

    When an expression is used in a Boolean context, if it has a
    numeric value, a value of zero shall be treated as false and any
    other value shall be treated as true. Otherwise, a string value
    of the null string shall be treated as false and any other value
    shall be treated as true. A Boolean context shall be one of the
    following:

and among the "Boolean context" listed is:

    * An expression used as a pattern (as in Overall Program Structure)

So the example with /usr/xpg4/bin/awk does not seem to be a behaviour from a conformant implementationd, and it seems to be correct to label this as "work it around by ..." (not "avoid using GNUism").

We learn new things every day (not that I really wanted to learn glitches in various implementations of awk) ;-).

Thanks.

[Reference]

*1* http://pubs.opengroup.org/onlinepubs/9699919799/utilities/awk.html