Section 4.3. Common Features

4.3. Common Features

Table 4-1 is a sampling of features that are common to bash and other Unix shells .

Table 4-1. Common shell features

Symbol/command	Meaning/action
>	Redirect output
>>	Append to file
<	Redirect input
<<	Here document (redirect input)
	Pipe output
&	Run process in background
;	Separate commands on same line
*	Match any character(s) in filename
?	Match single character in filename
! n	Repeat command number n
[ ]	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
Tab	Complete current word
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
newgrp	Change to a new group
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