Linux in a Nutshell, Fifth Edition

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Chapter 6: The Bash Shell and Korn Shell

This is the Title of the Book, eMatter Edition

Copyright © 2006 O’Reilly & Associates, Inc. All rights reserved.

Functions may have local variables, and they may be recursive. The syntax

used to define a function is irrelevant.

•Inksh88, all functions have their own traps and local variables, and may be

recursive.

•Inksh93, name () functions share traps with the “parent” shell and may not

be recursive.

•Inksh93, function functions have their own traps and local variables, and

may be recursive. Using the . command with a function function gives it

POSIX shell semantics (i.e., shared traps and variables).

Variables

This section describes the following:

• Variable substitution

• Built-in shell variables

• Other shell variables

• Arrays

• Discipline functions (ksh93 only)

• Special prompt strings

Variable Substitution

ksh93 provides structured variables, such as pos.x and pos.y. To create either

one, pos must already exist, and braces must be used to retrieve their values.

Names beginning with .sh are reserved for use by ksh.

No spaces should be used in the following expressions. The colon (:) is optional;

if it’s included, var must be nonnull, as well as set.

Variableexpression Description

var=value … Set each variable var to a value.

${var} Use value of var; braces are optional if var is separated from the following text. They are

required for array variables, and ...