Learning the bash Shell, Second Edition

Conventions Used in This Handbook

We leave it as understood that, when you enter a shell command, you press RETURN at the end. RETURN is labeled ENTER 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 pressing that letter. Although we give the letter in uppercase, you can press the letter without the SHIFT key.

Other special characters are LINEFEED (which is the same as CTRL-J), BACKSPACE (same as CTRL-H), ESC, TAB, and DEL (sometimes labeled DELETE or RUBOUT).

This book uses the following font conventions:

Italic	is used for UNIX filenames, commands not built into the shell (which are files anyway), and shell functions. Italic is also used for dummy parameters that should be replaced with an actual value, to distinguish the vi and emacs programs from their bash modes, and to highlight special terms the first time they are defined.
Bold	is used for bash built-in commands, aliases, variables, and options, as well as command lines when they are within regular text. Bold is used for all elements typed in by the user within regular text.
Constant Width	is used in examples to show the contents of files or the output from commands.
Constant Bold	is used in examples to show interaction between the user and the shell; any text the user types in is shown in Constant Bold. For example: $ pwd /home/cam/adventure/carrol $
Constant Italic	is used in displayed command lines for dummy parameters that should be replaced with an actual value.
Reverse Video	is used in Chapter 2, to show the position of the cursor on the command line being edited. For example: grep -l Alice < ~cam/book/[[a]]iw

We use UNIX as a shorthand for “UNIX and Linux.” Purists will correctly insist that Linux is not UNIX—but as far as this book is concerned, they behave identically.