Linux in a Nutshell, Fifth Edition

Invoking the Shell | 625

Bash and Korn

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

• Associative arrays

• More ways to match patterns

Invoking the Shell

The command interpreter for the Bash shell (bash) or the Korn shell (ksh) can be

invoked as follows:

bash [options] [arguments]

ksh [options] [arguments]

ksh and Bash can execute commands from a terminal, from a file (when the first

argument is an executable script), or from standard input (if no arguments remain

or if -s is specified). Both shells automatically print prompts if standard input is a

terminal, or if -i is given on the command line.

On Linux systems, /bin/sh is generally a link to Bash. When invoked as sh, Bash acts

more like the traditional Bourne shell: Login shells read /etc/profile and ~/.profile,

and regular shells read $ENV, if it’s set. Full details are available on the bash(1)

manpage.

Options

Common options

-c str

Read commands from string str.

-D Print all $"..." strings in the program. Not ksh88.

-i Create an interactive shell (prompt for input).

-p Start up as a privileged user. Bash: Don’t read $ENV or $BASH_ENV, don’t

import functions from the environment, and ignore the value of

$SHELLOPTS. Korn shell: Don’t process $HOME/.profile, read /etc/suid_

profile instead of $ENV.

-r Create a restricted shell.

-s Read commands from standard input; output from built-in ...