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Regex

Regular expressions are special characters which help search data, matching complex patterns.

Basic regex

Symbol	Descriptions
.	replaces any character
^	matches start of string
$	matches end of string
*	matches up zero or more times the preceding character
\	Represent special characters
()	Groups regular expressions
?	Matches up exactly one character

These expressions tell us about the number of occurrences of a character in a string.

Expression	Description
{n}	Matches the preceding character appearing 'n' times exactly
{n,m}	Matches the preceding character appearing 'n' times but not more than m
{n, }	Matches the preceding character only when it appears 'n' times or more

These regular expressions contain combinations of more than one expression.

Expression	Description
\+	Matches one or more occurrence of the previous character
\?	Matches zero or one occurrence of the previous character

The syntax for brace expansion is either a sequence or a comma separated list of items inside curly braces “{}”.

The starting and ending items in a sequence are separated by two periods “..”.

Expression	Description
{a,b,c,d}	Matches the actual characters in the braces. Example: echo {a,b,c,d}
{a..z}	Matches a thru z. Example: echo {a..z}
{0..9}	Matches 0 thru 9. Example: echo {0..9}