From mboxrd@z Thu Jan  1 00:00:00 1970
MIME-Version: 1.0
In-Reply-To: <0d3820e90fedfa15c374652fe64f06b4@ladd.quanstro.net>
References: <0d3820e90fedfa15c374652fe64f06b4@ladd.quanstro.net>
Date: Mon, 14 Dec 2009 17:15:40 +0200
Message-ID: <8e04b5820912140715g20e56d31m57bd7e567843d0e4@mail.gmail.com>
From: "Ciprian Dorin, Craciun" <ciprian.craciun@gmail.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Subject: Re: [9fans] rc shell UNIX port repository
Topicbox-Message-UUID: b00cd602-ead5-11e9-9d60-3106f5b1d025

On Mon, Dec 14, 2009 at 4:08 PM, erik quanstrom <quanstro@quanstro.net> wro=
te:
>> =C2=A0 =C2=A0 Unfortunately after playing a little bit more with rc, and=
 trying
>> it's syntax and semantics to the limit, I've also found other nasty
>> bugs (some of which I've fixed, other I was not able to do so)...
>
> what nasty bugs? =C2=A0could you give some specifics.

    One for example (I think it is a bug, but maybe in the semantics
you've described it's not):
    * again if we're using `-e`, and inside a function we write `fn
dosomething { echo 1 ; false ; echo 2 ; return 0 ; }`
    * if we run `dosomething` it shall output only `1`, as the false
breaks the execution;
    * but if we run `dosomething || echo 3`, we see `1 2` outputed,
because the false is not exiting the shell as the invocation of the
function is part of a `||` statement;

    But undoubtedly, the following is a bug (I have an array and want
to display all the elements on a single line, wrapped inside quotes,
and everything with a prefix and a suffix):

~~~~
application__erl_files__short=3D(
                a.erl
                b.erl
                c.erl
)

application__erl_files__long=3D(
                /home/ciprian/workbench/vel/a.erl
                /home/ciprian/workbench/vel/b.erl
                /home/ciprian/workbench/vel/c.erl
)

ifs=3D'\n' echo '  erl files =3D ('^`{ echo -n
'`'^$application__erl_files__short^'`' }^')'
ifs=3D'\n' echo '  erl files =3D ('^`{ echo -n
'`'^$application__erl_files__long^'`' }^')'
~~~~
    it displays:
~~~~
  erl files =3D (`a.erl` `b.erl` `c.erl`)
  erl files =3D (`/home/cipria)   erl files =3D (/workbe)   erl files =3D
(ch/vel/a.erl` `/home/cipria)   erl files =3D (/workbe)   erl files =3D
(ch/vel/b.erl` `/home/cipria)   erl files =3D (/workbe)   erl files =3D
(ch/vel/c.erl`)
~~~~

    See the second line of the output. It's wrong. I think there is a
buffer overrun problem...


>> =C2=A0 =C2=A0 By the way, what is the expected outcome of the following =
snippet
>> of code when the `-e` (exit on non-0 exit code) is on:
>>
>> { echo 1 ; false ; echo 2 } || echo 3
>>
>> =C2=A0 =C2=A0 Case a) it should print `1` and exit because the false in =
the
>> middle of the block just failed;
>> =C2=A0 =C2=A0 Case b) it should print `1`, and then `2`, because `false`=
 is
>> inside a block that is part of a `||` command;
>> =C2=A0 =C2=A0 Case c) it should print `1`, and then `3`, because `false`=
 has
>> stopped the evaluation of the block, and made the entire block exit
>> code be `1`.
>
> that's not a bug. =C2=A0-e is only evaluated at the end of a full rc
> production. =C2=A0in yiour case, there is only one production and
> it $status is '' (true) at the end of it. =C2=A0since echo 3 sets status
> to true.
>
> - erik

    Even though I understand your reasoning, I see `-e` more as a
"accept no errors from commands, and treat any non-0-exit code as an
unhandled exception, except :) if its part of an if, &&, or ||
construct". (I see it as an equivalent for try-throw-except...)

    Ciprian.