RegEXP

Regular expressions, RE are always between / /

.

Matches any single character

[abc]

Matches a single occurence of one of the given characters

[^aA]

Matches a single occurence of any of the NOT-given characters

*

Matches zero or more occurences of the previous single character
RE

+

Matches one or more occurences of the previous single character
RE

?

Matches zero or one occurences of the previous single character
RE

^

Matches the begining of a line

$

Matches the End Of Line

n

Matches an embedded newline

.

Matches a literal .

{x,y}

Matches between y an y occurences of the previous single character
RE

{x,}

Matches miminum of x occurences of the previous RE ( /.{65,}/
matches lines of at least 65 characters.

{x}

Matches exact x occurences of the previoussingle character RE

[:digit:]

[0123456789]

[0-9]

Matches any digit (fitst form, character clas only works within [
]

[:alnum:]

[0-9A-Za-z]

Matches any alphanumeric character (fitst form, character clas only
works within [ ]