Consider this simple function, which takes a file name and calls another function which processes a string. This wrapper sucks in the entire file and then calls the other function.

sub scanfile ($) {
   my $filename= shift;
   local $/;
   undef $/;
   my $handle;
   open $handle, '<', $filename  or croak "can't open file [$filename]
+ ";
   return scan (<$handle>);
   }
[download]

• Now, we are currently discussing the use of prototypes on another thread. So I won't draw attention to it again, here.

• A few weeks ago (or was it a few months?) someone mentioned that file handles are auto-vivifying now, so using a local variable prevents the use of ugly non-scoped HANDLE's without using a heavy-duity package for what should be a simple task. I said "so should this be the normal way to do it now?" and the only objection raised was that it wouldn't work on older versions of Perl.

• But given that, (1) does the file automatically close when the $handle variable goes out of scope? and (2) would collapsing it to open my $handle, ... work and should it work?

  Using my in the middle of something is idiomatic in places already, but has always seemed forign to me since I'm used to declarations being separate from expressions. I've not explored the limits of this in detail, so just what is allowed in using my $x where a $x is expected? Is it always legal?

• It bugs me that $/ is global. If I use the member function equivilent it warns me of such. Without threads, using it to suck in a whole file like this is well behaved enough, since I know there will not be side effects. So what do you do in the more general case? Set it before every read operation? That implies that it has effect during the <FILE> operation and changing it will have proper effect. Again, I'm worried about assuming that.

• I like the three-argument form of open. We still have the two-arg form and its power of deciding whether to do a file input or a pipe based on run-time input, but having 3 arguments when I know what I'm doing seems more elegant than joining it together just to tear it apart again, and prevents accidently munging odd file names.

• Finally, I always put the filename in an error message in brackets, because it's easier to type than quotes, looks OK when the resulting string is itself put in quotes, and clearly shows oddities like an extra \n or whitespace in the name.

Comments, anyone?

—John

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