Regex in Linux

Symbol	Meaning (short)
.	Any single character
*	Repeat 0 or more times
+	Repeat 1 or more times
?	0 or 1 (optional)
{ }	Exact or range quantifier {m}, {m,n}
[ ]	Character class (one character from set)
\|	OR (alternative)
( )	Grouping / capture
^	Start of string/line
$	End of string/line

Escape Character

\.  \*  \+  \?  \{  \}  \[  \]  \|  \(  \)  \^  \$
# or (i need to escape 2x becouse my shell eats one "\")
\\.  \\*  \\+  \\?  \\{  \\}  \\[  \\]  \\|  \\(  \\)  \\^  \\$

Characters that must be escaped INSIDE [ ... ]

-  ]  \

Characters that must be escaped OUTSIDE [ ... ]

.  *  +  ?  { }  [ ]  |  ( )  ^  $ 

Characters that DO not need escaping INSIDE [ ... ]

.   *   +   ?   |   (   )   {   }   $