Unix in a Nutshell, 4th Edition

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.