in reply to Perl Style: About error messges opening files

I like having the error messages following the resource in question and a colon; all the rest of the Unix toolkit tends to follow that philosophy, and I don't see any value in bucking the trend.

By force of habit I write my error messages out in longhand, in a vague attempt to make things clearer:

open IN, '<', $file or die "Cannot open $file for input: $!\n";

open OUT, '>>', $file or die "Cannot open $file for append: $!\n";

open P, '|', $cmd or die "Cannot open input pipe from $cmd: $!\n";

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I'm in two minds about your idea. If a non-programmer were to read me the message (or a programmer without shell-redirection experience, which is pretty much the same thing) they might omit pronouncing < altogether or describe it uselessly (e.g. "arrow"). That's why I like wordy error messages.

On the other hand, if I were to adopt this idea, I wouid be tempted to push things to extremes, and factor out the redirection into a variable:

my $whence = '<';
open my $fh, $whence, $file or die "$whence $!:$file";

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... on the principle that if you change it to <+ or something else you only have to do that in one place. But I'll be the first to say that that's getting silly.

Colour me unconvinced. But I think the 3-arg open is the thing. For all of you who have tuned in recently, here's the canonical thread on the subject: Two-arg open() considered dangerous.

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Re: Re: Perl Style: About error messges opening files
by demerphq (Chancellor) on Apr 27, 2004 at 11:40 UTC

    On the other hand, if I were to adopt this idea, I wouid be tempted to push things to extremes, and factor out the redirection into a variable:

    Yep, I use a subroutine very much like that quite often. The sub usually looks more like: 

    sub my_open {
  my ($file,$mode,$error_text)=@_;
  $mode||='<';
  $error_text||="While opening in '$mode':$!:$file";
  open my $fh, $mode, $file 
     or Carp::confess $error_text;
  return $fh
}

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    I like having the error messages following the resource in question and a colon; all the rest of the Unix toolkit tends to follow that philosophy, and I don't see any value in bucking the trend.

    Good point.

    Colour me unconvinced.

    I wasnt trying to convince people, just to see what they thought. :-)


    ---
    demerphq

      First they ignore you, then they laugh at you, then they fight you, then you win.
      -- Gandhi
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