Far More Than Everything You've Ever Wanted to Know about
Interprocess Communication
in Perl

The basic IPC facilities of Perl are built out of the good old Unix signals, named pipes, pipe opens, the Berkeley socket routines, and SysV IPC calls. Each is used in slightly different situations.


If you are running under version 5.000 (dubious) or 5.001, you can still use most of the examples in this document. You may have to remove the use strict and some of the my() statements for 5.000, and for both you'll have to load in version 1.2 of the Socket.pm module, which was/is/shall-be included in perl5.001o.

Most of these routines quietly but politely return undef when they fail instead of causing your program to die right then and there due to an uncaught exception. (Actually, some of the new Socket conversion functions croak() on bad arguments.) It is therefore essential that you should check the return values fo these functions. Always begin your socket programs this way for optimal success, and don't forget to add -T taint checking flag to the pound-bang line for servers:

#!/usr/bin/perl -w require 5.002; use strict; use sigtrap; use Socket;


All these routines create system-specific portability problems. As noted elsewhere, Perl is at the mercy of your C libraries for much of its system behaviour. It's probably safest to assume broken SysV semantics for signals and to stick with simple TCP and UDP socket operations; e.g. don't try to pass open filedescriptors over a local UDP datagram socket if you want your code to stand a chance of being portable.

Because few vendors provide C libraries that are safely re-entrant, the prudent programmer will do little else within a handler beyond die() to raise an exception and longjmp(3) out.


Tom Christiansen, with occasional vestiges of Larry Wall's original version.


Besides the obvious functions in the perlfunc manpage , you should also check out the modules file at your nearest CPAN site. (See the perlmod manpage or best yet, the Perl FAQ for a description of what CPAN is and where to get it.)

Section 5 of the modules file is devoted to Networking, Device Control (modems) and Interprocess Communication, and contains numerous unbundled modules numerous networking modules, Chat and Expect operations, CGI programming, DCE, FTP, IPC, Mail and News, Proxy, Ptty, RPC, SNMP, Telnet, Threads, and ToolTalk--just to name a few.

top / signals / fifos / pipes / safe-pipes / open2 / sockets / AF_INET / AF_UNIX / udp / sys5

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Copyright 1996 Tom Christiansen.
All rights reserved.