Perl Cookbook, 2nd Edition

Chapter 16. Process Management and Communication

It is quite a three-pipe problem, and I beg that you won’t speak to me for fifty minutes.

—Sherlock Holmes, The Red-Headed League

Introduction

Perl may be many things to many people, but to most of us it is the glue that connects diverse components. This chapter is about launching commands and connecting separate processes together. It’s about managing their creation, communication, and ultimate demise. It’s about systems programming.

When it comes to systems programming, Perl, as usual, makes easy things easy and hard things possible. If you want to use it as you would the shell, Perl is happy to assist you. If you want to roll up your sleeves for low-level hacking like a hardcore C programmer, you can do that, too.

Because Perl lets you get so close to the system, portability issues can sneak in. This chapter is the most Unix-centric chapter of the book. It will be tremendously useful to those on Unix systems, but of limited use to others. (If you’re not on Unix, consult the perlport(3) manpage that came with Perl to see which of the techniques we describe are available on other operating systems or emulated by Perl.) We deal with features that aren’t as universal as strings and numbers and basic arithmetic. Most basic operations work more or less the same everywhere. But if you’re not using some kind of Unix or other POSIX conformant system, most of the interesting features in this chapter may work differently for you—or not at all. ...