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.
<file csh, sh Redirect standard input.
<<word csh, sh Read until word, do command and variable substitution.
<<\word csh, sh Read until word, no substitution.
<?word 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.