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8
Where to Go
from Here
Documentation
In this chapter:
• Documentation
• Shell Aliases and
Functions
• Programming
• Using Unix on Non-
Unix Systems
Now that you’re almost to the end of this guide, let’s look at some ways to
continue learning about Unix. Documentation is an obvious choice, but it
isn’t always in obvious places. You can save time by taking advantage of
other shell features — aliases, functions, and scripts—that let you shorten a
repetitive job and “let the computer do the dirty work.”
We’ll close by seeing how you can use Unix commands on non-Unix sys-
tems.
You might want to know the options to the programs we’ve introduced —
and get more information about them and the many other Unix programs.
You’re now ready to consult your system’s documentation and other
resources.
The man Command
Different versions of Unix have adapted Unix documentation in different
ways. Almost all Unix systems have documentation derived from a manual
originally called the
Unix Programmer’s Manual.
The manual has num-
bered sections; each section is a collection of manual pages, often called
“manpages”; each program has its own manpage. Section 1 has manpages
for general Unix programs such as
who
and
ls.
Many Unix installations have individual manual pages stored on the com-
puter; users can read them online. If your system has online manpages,
and you want to know the correct syntax for entering a command or the
136
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Documentation
137
particular features of a program, enter the command
man
and the name of
the command. The syntax is:
man
command
For example, if you want to find information about the program
mail,
which allows you to send messages to other users, enter:
$
man mail
.
.
$
The output of
man
may be filtered through a pager like
less
automatically.
If it isn’t, just pipe the output of
man
to
less
(or
more
or
pg).
After you enter the command, the screen fills with text. Press SPACE or
RETURN to read more, and
q
to quit.
Some systems also have a command called
apropos
or
man –k
to help you
locate a command if you have an idea of what it does but are not sure of
its correct name. Enter
apropos
followed by a descriptive word; you’ll get
a list of commands that might help.
Problem checklist
man
says there is no manual entry for the command.
Some commands—cd and
jobs,
for example—aren’t separate Unix
programs; they’re part of the shell. On some Unix systems, you’ll find
documentation for those commands in the manual page for the shell.
(To find the shell’s name, see the section “The Unix Shell” in Chapter
1.)
If the program isn’t a standard part of your Unix system—that is, your
system staff added the program to your system—there may not be a
manual page, or you may have to configure the
man
program to find
the local manpage files.
The info Command
Linux systems, as well as some others, have a program called
info.
It
serves the same purpose as
man:
to document system programs. The
info
output is in a different format, though. The syntax to start
info
is:
info
command
For example, if you want to find information about the program
find,
which searches for files, enter
info find.
After you enter the command,
press SPACE to read more or “q” to quit.
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Chapter 8: Where to Go from Here
Documentation via the Internet
The Internet changes so quickly that any list of online Unix documenta-
tion we’d give you would soon be out of date. Still, the Internet is a great
place to find out about Unix systems. Remember that there are many dif-
ferent versions of Unix—so some documentation you find may not be
completely right for you. Also, some information you’ll find may be far
too technical for your needs (many computer professionals use and dis-
cuss Unix). But don’t be discouraged! Once you’ve found a site with the
general kind of information you need, you can probably come back later
for more.
Many Unix command names are plain English words, which can make
searching hard. If you’re looking for collections of Unix information, try
searching for the Unix program named
grep.
As this book went to press,
one especially Unix-friendly search engine was Google, at
http://www.google.com.
Here are some other places to try:
•
•
Magazines,
both in print and online-only, have Unix tutorials and links
to more information. Many are written for beginners.
Publishers,
like O’Reilly & Associates, Inc. (http://www.or
eilly.com),
have areas of their websites that feature Unix and have articles written
by their books’ authors. They may also have books online (such as
the O’Reilly Safari service) available for a small monthly fee—which is
a good way to learn a lot quickly without needing to buy a paper
copy of a huge book, most of which you may not need.
Vendors’ sites
like Red Hat (http://www.r
edhat.com),
and Unix-related
organizations like the Free Software Foundation (http://www.fsf.or
g),
usually have documentation and support files online, where you can
search for what you need.
Universities
often use Unix-like systems and will have online docu-
mentation. You’ll probably have better luck at the Computer Services
division (which services the whole campus) than at the Computer Sci-
ence department (which may be more technical).
•
•
Books
Bookstores, both traditional and online, are full of computer books. The
books are written for a wide variety of needs and backgrounds. Unfortu-
nately, many books are rushed to press, written by authors with minimal
Unix experience, full of errors. Before you buy a book, read through parts
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Programming
139
of it. Does the style (brief or lots of detail, chatty and friendly or organized
as a reference) fit your needs? Search the Internet for reviews; online
bookstores may have readers’ comments on file.
Shell Aliases and Functions
If you type command names that are hard for you to remember, or com-
mand lines that seem too long, you’ll want to learn about
shell aliases
and
shell functions.
These shell features let you abbreviate commands, com-
mand lines, and long series of commands. In most cases, you can replace
them with a single word or a word and a few arguments. For example,
one of the long pipelines the section “Pipes and Filters” (Chapter 5) could
be replaced by an alias or function named (for instance) “aug.” When you
type
aug
at a shell prompt, the shell would list files modified in August,
sorted by size.
Making an alias or function is almost as simple as typing in the command
line or lines that you want to run. References in the section “Documenta-
tion,” earlier in this chapter, have more information. Shell aliases and func-
tions are actually a simple case of shell programming.
Programming
We mention earlier that the shell is the system’s command interpreter. It
reads each command line you enter at your terminal and performs the
operation that you call for. Your shell is chosen when your account is set
up.
The shell is just an ordinary program that can be called by a Unix com-
mand. However, it contains some features (such as variables, control struc-
tures, and so on) that make it similar to a programming language. You can
save a series of shell commands in a file, called a
shell script,
to accom-
plish specialized functions.
Programming the shell should be attempted only when you are reason-
ably confident of your ability to use Unix commands. Unix is quite a pow-
erful tool and its capabilities become more apparent when you try your
hand at shell programming.
Take time to learn the basics. Then, when you’re faced with a new task,
take time to browse through references to find programs or options that
will help you get the job done more easily. Once you’ve done that, learn
how to build shell scripts so that you never have to type a complicated
command sequence more than once.
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Chapter 8: Where to Go from Here
You might also want to learn Perl. Like the shell, Perl interprets script files
full of commands. But Perl has a steeper learning curve than the shell.
Also, since you’ve already learned a fair amount about the shell and Unix
commands by reading this book, you’re almost ready to start writing shell
scripts now; on the other hand, Perl will take longer to learn. But if you
have sophisticated needs, learning Perl is another way to use even more
of the power of your Unix system.
Using Unix on Non-Unix Systems
Once you get comfortable working quickly at the Unix command line,
you may miss that power and flexibility when you use another system like
Microsoft Windows. You can get programs — both commercial and freely
available — that let you use a Unix-like shell prompt and Unix utilities
(gr
ep, sort,
and so on) from within other operating systems. You’ll also
find that an increasing number of systems are built on top of the stable
Unix or a Unix-like operating system. Two of the latest examples are Mac
OS X on the Macintosh and a variety of machines with Linux embedded
inside.
Unix, Microsoft Windows, and the Macintosh all use differ-
ent conventions for the way that they mark the end of a
line of text. If you transfer text files between these systems,
you’ll probably need to convert them. (The command-line
FTP client does this automatically if you set its ascii transfer
mode.) And if you have an executable program file that
runs on one system, it won’t run on the others—unless it’s
written in Java or it’s a
script
program from a language such
as the shell or Perl.
Under Microsoft Windows
Cygwin,
from
http://www.cygwin.com,
is a package of Unix-like software
development utilities that runs under Microsoft Windows NT, 98, and 95
(and probably others, as Microsoft Windows evolves). Although it’s aimed
at software developers, it also has a lot of the standard Unix utilities. You
can use Cygwin from its
bash
shell (a Unix-like shell) or from the standard
Windows command shell.
The
MKS Toolkit,
from
http://www.mks.com,
is a commercial package of
Unix-like utilities that runs under Microsoft Windows. MKS Toolkit has
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