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	nth 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.