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1.4. Filehandles

Unless you're using artificial intelligence to model a solipsistic philosopher, your program needs some way to communicate with the outside world. In lines 3 and 4 of our Average Example you'll see the word GRADES, which exemplifies another of Perl's data types, the filehandle. A filehandle is just a name you give to a file, device, socket, or pipe to help you remember which one you're talking about, and to hide some of the complexities of buffering and such. (Internally, filehandles are similar to streams from a language like C++ or I/O channels from BASIC.)

Filehandles make it easier for you to get input from and send output to many different places. Part of what makes Perl a good glue language is that it can talk to many files and processes at once. Having nice symbolic names for various external objects is just part of being a good glue language.[13]

[13] Some of the other things that make Perl a good glue language are: it's 8-bit clean, it's embeddable, and you can embed other things in it via extension modules. It's concise, and it "networks" easily. It's environmentally conscious, so to speak. You can invoke it in many different ways (as we saw earlier). But most of all, the language itself is not so rigidly structured that you can't get it to "flow" around your problem. It comes back to that TMTOWTDI thing again.


  

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