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.

Built-in Mathematical Functions (ksh93 only)

ksh93 provides access to the standard set of mathematical functions. They are

called using C function call syntax.

Examples

See the let command for more information and examples:

let "count=0" "i = i + 1" Assign i and count

let "num % 2" Test for an even number

(( percent >= 0 && percent <= 100 )) Test the range of a value

Command History

Both shells let you display or modify previous commands. Commands in the

history list can be modified using:

• Line-edit mode

• The fc and hist commands

Bash also supports a command-history mechanism very similar to that of the C

shell. Because the interactive line-editing features are considerably superior, and

because Bash’s command history is almost identical to that of the C shell, we have

|| Logical OR (short-circuit).

?: Inline conditional evaluation.

= += -= Assignment.

*= /= %=

<<= >>=

&= ^= |=

, Sequential expression evaluation.

a

In ksh93, the ** operator is right associative. In bashversions prior to 3.1, it is left associative. It will be changed to right

associative starting with version 3.1.

Name Function Name Function

abs Absolute value hypot Euclidean distance

acos Arc cosine int Integer part of floating-point number

asin Arc sine log Natural logarithm

atan