Classic Shell Scripting

Conventions Used in This Book

We leave it as understood that, when you enter a shell command, you press Enter at the end. Enter is labeled Return on some keyboards.

Characters called Ctrl-X, where X is any letter, are entered by holding down the Ctrl (or Ctl, or Control) key and then pressing that letter. Although we give the letter in uppercase, you can press the letter without the Shift key.

Other special characters are newline (which is the same as Ctrl-J), Backspace (the same as Ctrl-H), Esc, Tab, and Del (sometimes labeled Delete or Rubout).

This book uses the following font conventions:

Italic

Italic is used in the text for emphasis, to highlight special terms the first time they are defined, for electronic mail addresses and Internet URLs, and in manual page citations. It is also used when discussing dummy parameters that should be replaced with an actual value, and to provide commentary in examples.

Constant Width

This is used when discussing Unix filenames, external and built-in commands, and command options. It is also used for variable names and shell keywords, options, and functions; for filename suffixes; and in examples to show the contents of files or the output from commands, as well as for command lines or sample input when they are within regular text. In short, anything related to computer usage is in this font.

Constant Width Bold

This is used in the text to distinguish regular expressions and shell wildcard patterns from the text to be matched. It is also used in examples to show interaction between the user and the shell; any text the user types in is shown in Constant Width Bold. For example:

$ pwd                                
            User typed this
/home/tolstoy/novels/w+p             System printed this
$

Constant Width Italic

This is used in the text and in example command lines for dummy parameters that should be replaced with an actual value. For example:

$ cd 
            directory

Tip

This icon indicates a tip, suggestion, or general note.

Warning

This icon indicates a warning or caution.

References to entries in the Unix User's Manual are written using the standard style: name(N), where name is the command name and N is the section number (usually 1) where the information is to be found. For example, grep(1) means the manpage for grep in section 1. The reference documentation is referred to as the "man page," or just "manpage" for short.

We refer both to Unix system calls and C library functions like this: open( ), printf( ). You can see the manpage for either kind of call by using the man command:

$ man open                  
            Look at open(2) manpage
$ man printf                
            Look at printf(3) manpage

When programs are introduced, a sidebar, such as shown nearby, describes the tool as well as its significant options, usage, and purpose.

Example

Usage

whizprog [ options ... ] [ arguments ... ]

This section shows how to run the command, here named whizprog.

Purpose

This section describes why the program exists.

Major options

This section lists the options that are important for everyday use of the program under discussion.

Behavior

This section summarizes what the program does.

Caveats

If there's anything to be careful of, it's mentioned here.