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Unix in a Nutshell, 4th Edition by Arnold Robbins

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Common Features

The following table displays features that are common to the Bash, Korn, and C shells. Note that both the Korn shell and Bash are enhanced versions of the Bourne shell; therefore, they include all features of the Bourne shell, plus some others.

Symbol/command

Meaning/action

a Brace expansion is a compile-time feature in the Korn shell. Usually commercial versions don't have it, but if you compile from source code, you do get it by default.

>

Redirect output.

>>

Append to file.

<

Redirect input.

<<

"Here" document (redirect input).

|

Pipe output.

&

Run process in background.

;

Separate commands on same line.

~

Home directory symbol.

*

Match any character(s) in filename.

?

Match single character in filename.

[ ]

Match any characters enclosed.

()

Execute in subshell.

{ }

Expand elements in list.a

' '

Substitute output of enclosed command.

" "

Partial quote (allows variable and command expansion).

' '

Full quote (no expansion).

\

Quote following character.

$ var

Use value for variable.

$$

Process ID.

$0

Command name.

$ n

n th argument (0 ≤ n ≤ 9).

$*

All arguments as simple words.

#

Begin comment.

bg

Background execution.

break

Break from loop statements.

cd

Change directory.

continue

Resume a program loop.

echo

Display output.

eval

Evaluate arguments.

exec

Execute a new shell.

fg

Foreground execution.

history

List previous commands.

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