3.4 Common Features

The following table displays features that are common to the Bourne, Korn, and C shells. Note that the Korn shell is an enhanced version of the Bourne shell; therefore, the Korn shell includes all features of the Bourne shell, plus some others. The commands bg , fg , jobs , stop , and suspend are available only on systems that support job control. (Essentially all modern Unix systems do.)

Symbol/Command	Meaning/Action
>	Redirect output.
>>	Append to file.
<	Redirect input.
<<	"Here" document (redirect input).
|	Pipe output.
|&	Start a coprocess. Korn shell only.
&	Run process in background.
;	Separate commands on same line.
*	Match any character(s) in filename.
?	Match single character in filename.
[ ]	Match any characters enclosed.
( )	Execute in subshell.
` `	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.
jobs	Show active jobs.
kill	Terminate running jobs.
shift	Shift positional parameters.
stop	Suspend a background job.
suspend	Suspend a foreground job (such as a shell created by su ).
time	Time a command.
umask	Set default file permissions for new files.
unset	Erase variable or function definitions.
wait	Wait for a background job to finish.