List of Special Characters and Their Meanings

List of Special Characters and Their Meanings

Character	Where	Meaning
ESC	csh	Filename completion.
RETURN	csh, sh	Execute command.
space	csh, sh	Argument separator.
TAB	csh, sh	Argument separator.
TAB	bash	Filename completion.
#	csh, sh	Start a comment.
`	csh, sh	Command substitution (backquotes).
"	csh, sh	Weak quotes.
'	csh, sh	Strong quotes.
\	csh, sh	Single?character quote.
$var	csh, sh	Variable.
${var}	csh, sh	Same as $var.
$var:mod	csh	Edit var with modifier mod
${var?default}	sh	If var not set, use default.
${var=default}	sh	If var not set, set it to default and use that value.
${var+instead}	sh	If var set, use instead. Otherwise, null string.
${var?message}	sh	If var not set, print message (else default). If var set, use its value.
${var#pat}	ksh, bash	Value of var with smallest pat deleted from start.
${var##pat}	ksh, bash	Value of var with largest pat deleted from start.
${var%pat}	ksh, bash	Value of var with smallest pat deleted from end.
${var%%pat}	ksh, bash	Value of var with largest pat deleted from end.
|	csh, sh	Pipe standard output.
|&	csh	Pipe standard output and standard error.
^	sh	Pipe character (obsolete).
^	csh, bash	Edit previous command line.
&	csh, sh	Run program in background.
?	csh, sh	Match one character.
*	csh, sh	Match zero or more characters.
;	csh, sh	Command separator.
;;	sh	[/td]End of case statement.[/tr]
~	csh, ksh, bash	Home directory.
~user	csh, ksh, bash	Home directory of user.
!	csh, bash	Command history.
-	Programs	Start of optional argument.
-	Programs	Read standard input. (Only certain programs.)
$#	csh, sh	Number of arguments to script.
"$@"	sh	Original arguments to script.
$*	csh, sh	Arguments to script.
$-	sh	Flags set in shell.
$?	sh	Status of previous command.
$$	csh, sh	Process identification number.
$!	sh	Process identification number of last background job.
$<	csh	Read input from terminal.
cmd1 && cmd2	csh, sh	Execute cmd2 if cmd1 succeeds.
cmd1 || cmd2	csh, sh	Execute cmd2 if cmd1 succeeds.
$(..)	ksh, bash	Command substitution.
((..))	ksh, bash	Arithmetic evaluation.
\. file	sh	Execute commands from file in this shell.
:	sh	Evaluate arguments, return true.
:	sh	Separate values in paths.
:	csh	Variable modifier.
[]	csh, sh	Match range of characters.
[]	sh	Test.
%job	csh, ksh, bash	Identify job number.
(cmd;cmd)	csh, sh	Run cmd;cmd in a subshell.
{}	csh, bash	In?line expansions.
{cmd;cmd;}	sh	Like (cmd;cmd) without a subshell.
>file	csh, sh	Redirect standard output.
>>file	csh, sh	Append standard output.
	csh, sh	Redirect standard input.
<	csh, sh	Read until word, do command and variable substitution.
<<\word	csh, sh	Read until word, no substitution.
	sh	Read until word, ignoring leading TABs.
>>! file	csh, sh	Append to file, even if noclobber set and file doesn't exist.
>! file	csh	Output to file, even if noclobber set and file exists.
>| file	ksh, bash	Output to file, even if noclobber set and file exists.
>& file	csh	Redirect standard output and standard error to file.
m> file	sh	Redirect output file descriptor m to file.
m>> file	sh	Append output file descriptor m to file.
m< file	sh	Redirect input file descriptor m from file.
<&m	sh	Take standard input from file descriptor m.
<&?	sh	Close standard input.
>&m	sh	Use file descriptor m as standard output.
>&-	sh	Close standard output.
m<&n	sh	Connect input file descriptor n to file descriptor m.
m<&-	sh	Close input file descriptor m.
n>&m	sh	Connect output file descriptor n to file descriptor m.
m>&-	sh	Close output file descriptor m.