Shulou(Shulou.com)06/02 Report--

This article mainly shows you "how to use the Perl daemon", the content is easy to understand, clear, hope to help you solve your doubts, let the editor lead you to study and learn "how to use the Perl daemon" this article.

Perl daemon

Programming method of LinuxPerl daemon

The Perl daemon (Daemon) is a special process that runs in the background. It is independent of the control terminal and periodically performs certain tasks or waits for certain events to be processed. The Perl daemon is a useful process. Most of Linux's servers are implemented using Perl daemons. For example, Internet server, inetd,Web server, httpd, etc. At the same time, the Perl daemon performs many system tasks. For example, job planning process crond, printing process lpd and so on.

The programming of Perl daemon itself is not complicated. What is complicated is that the implementation mechanisms of various versions of Unix are different, resulting in different programming rules of Perl daemons in different Unix environments. This requires the reader's attention that copying some book rules (especially BSD4.3 and earlier versions of SystemV) to Linux will make an error. Following is a comprehensive introduction to the programming points of the Perl daemon under Linux and a detailed example is given.

I. Perl daemon and its characteristics

The most important feature of the Perl daemon is running in the background. At this point, the resident memory program TSR under DOS is similar. Second, the Perl daemon must be isolated from the environment in which it was run. These environments include unclosed file descriptors, control terminals, session and process groups, working directories, and file creation masks. These environments are usually inherited by the Perl daemon from the parent process that executes it, especially the shell. *, the startup method of the Perl daemon has its own special features. It can be started from the startup script / etc/rc.d when the Linux system starts, can be started by the job planning process crond, and can be executed by the user terminal (usually shell).

In short, apart from these particularities, the Perl daemon is basically no different from a normal process. Therefore, writing a Perl daemon is actually transforming an ordinary process into a Perl daemon according to the characteristics of the Perl daemon described above. If the reader has a deeper understanding of the process, it will be easier to understand and program.

2. Perl daemon instance

The example of the Perl daemon consists of two parts: the main program test.c and the initializer init.c. The main program reports the running status to the log test.log in the / tmp directory every other minute. The init_daemon function in the initialization program is responsible for generating the Perl daemon. Readers can use the init_daemon function to generate their own Perl daemons.

1.init.c list

Init.c#include # include voidinit_daemon (void) {intpid; inti; if (pid=fork ()) exit (0); / / is the parent process, ending the parent process elseif (pid)

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.