Documentation And Communication - Red Hat ENTERPRISE LINUX 3 - INTRODUCTION TO SYSTEM ADMINISTRATION Administration Manual

Chapter 1. The Philosophy of System Administration
to months. The
crontab
actually schedules each
The command (and the closely-related command
at
the execution of one-time scripts or commands. These commands implement a rudimentary batch
subsystem consisting of multiple queues with varying scheduling priorities. The priorities are known
as niceness levels (due to the name of the command —
tasks that must start at a given time but are not time-critical in terms of finishing.
Next are the various scripting languages. These are the "programming languages" that the average
system administrator uses to automate manual operations. There are many scripting languages (and
each system administrator tends to have a personal favorite), but the following are currently the most
common:
The command shell
• bash
The scripting language
• perl
The scripting language
•
python
Over and above the obvious differences between these languages, the biggest difference is in the way
in which these languages interact with other utility programs on a Red Hat Enterprise Linux system.
Scripts written with the
(for example, to perform character string manipulation), while
types of operations using features built into the language itself. A script written using
exploit the language's object-oriented capabilities, making complex scripts more easily extensible.
This means that, in order to truly master shell scripting, you must be familiar with the many utility
programs (such as
grep
), on the other hand, tends to be a more "self-contained" process. However, many
python
guage constructs are based on the syntax of various traditional UNIX utility programs, and as such
are familiar to those Red Hat Enterprise Linux system administrators with shell scripting experience.

1.10.2. Documentation and Communication

In the areas of documentation and communication, there is little that is specific to Red Hat Enterprise
Linux. Since documentation and communication can consist of anything from adding comments to a
text-based configuration file to updating a webpage or sending an email, a system administrator using
Red Hat Enterprise Linux must have access to text editors, HTML editors, and mail clients.
Here is a small sample of the many text editors available under Red Hat Enterprise Linux:
The gedit text editor
•
The Emacs text editor
•
The text editor
• Vim
The gedit text editor is a strictly graphical application (in other words, it requires an active X Window
System environment), while
The subject of the best text editor has sparked debate for nearly as long as computers have existed and
will continue to do so. Therefore, the best approach is to try each editor for yourself, and use what
works best for you.
For HTML editors, system administrators can use the Composer function of the Mozilla Web browser.
Of course, some system administrators prefer to hand-code their HTML, making a regular text editor
a perfectly acceptable tool as well.
As far as email is concerned, Red Hat Enterprise Linux includes the Evolution graphical email client,
the Mozilla email client (which is also graphical), and mutt, which is text-based. As with text editors,
command is used to manipulate the files controlling the
job for execution.
cron
shell tend to make more extensive use of the many small utility programs
bash
and ) that are part of Red Hat Enterprise Linux. Learning
sed
and Emacs are primarily text-based in nature.
vim
) are more appropriate for scheduling
batch
). Both and
nice at
scripts perform more of these
perl
daemon that
cron
are perfect for
batch
can fully
python
(and
perl
lan-
perl
9