From: Bart Schaefer <schaefer@brasslantern.com>
To: zsh-users@zsh.org
Subject: Re: err_return inside function who's return value is checked
Date: Sun, 30 Dec 2012 13:32:57 -0800 [thread overview]
Message-ID: <121230133257.ZM1210@torch.brasslantern.com> (raw)
In-Reply-To: <CA+zrezTHWMmAu-SaZOHYoHQH_ijbYtEVfZ1sCnwWxPKsnUftjQ@mail.gmail.com>
On Dec 30, 3:55pm, Russell Harmon wrote:
}
} On Sun, Dec 30, 2012 at 2:35 PM, Bart Schaefer
} <schaefer@brasslantern.com> wrote:
} > This obviously is a case where err_return might be permitted to behave
} > differently without causing too much consternation, but that's not how
} > it has been defined.
}
} Can this be arranged?
Anything's possible. :-) I'm not personally very familiar with this part
of the internals, so I'm not sure how difficult it would be. However ...
} It would enable idioms like the following to be used:
}
} function get_major_version {
} setopt err_return
} [[ $(program -V) =~ "version ([[:digit:]]+)\." ]]
} REPLY=$match[1]
} }
This isn't really what err_return (or err_exit) is meant for. If you
have cases where you are *expecting* the command to fail, you should
be able to write
[[ $(program -V) =~ "version ([[:digit:]]+)\." ]] || return
just as easily. Instead, err_return is intended to trap unexpected
failures, or conditions that occur so rarely that it over-complicates
the flow of control to constantly test $? after each command.
E.g., suppose you're calling a function someone else wrote. Somewhere
in that function is a "chmod" command, which is never expected to fail
(it's return status isn't tested) but if it does fail it'll leave a
security hole in its wake. So *outside* of that function you setopt
err_return to force it to stop if the chmod does not work.
(Of course the above would lead to the argument that "emulate" should
not mess with err_exit/err_return.)
prev parent reply other threads:[~2012-12-30 21:33 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-30 7:52 Russell Harmon
2012-12-30 19:35 ` Bart Schaefer
2012-12-30 20:55 ` Russell Harmon
2012-12-30 21:32 ` Bart Schaefer [this message]
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