Table 9-6. Shell special characters
Character | Use |
|---|
NEWLINE | Initiates execution of a command (page 276) |
; | Separates commands (page 276) |
( ) | Groups commands (page 279) for execution by a subshell or identifies a function (page 321) |
& | Executes a command in the background (pages 219 and 278) |
| | Sends standard output of preceding command to standard input of following command (pipe; page 278) |
> | Redirects standard output (page 210) |
>> | Appends standard output (page 214) |
< | Redirects standard input (page 212) |
<< | Here document (page 909) |
* | Any string of zero or more characters in an ambiguous file reference (page 222) |
? | Any single character in an ambiguous file reference (page 221) |
\ | Quotes the following character (page 126) |
' | Quotes a string, preventing all substitution (page 126) |
" | Quotes a string, allowing only variable and command substitution (pages 126 and 287) |
'...' | Performs command substitution (page 334) |
[ ] | Character class in an ambiguous file reference (page 223) |
$ | References a variable (page 285) |
. (dot builtin) | Executes a command (only at the beginning of a line, page 269) |
# | Begins a comment (page 275) |
{ } | Used to surround the contents of a function (page 321) |
: (null builtin) | Returns true (page 935) |
&& (Boolean AND) | Executes command on right only if command on left succeeds (returns a zero exit status, page 946) |
|| (Boolean OR) | Executes command on right only if command on left fails (returns a nonzero exit status; page 946) |
! (Boolean NOT) | Reverses exit status of a command |
$() | Performs command substitution (preferred form; page 334) |
[] | Evaluates an arithmetic expression (page 332) |
