Regular expression quick start guide

Quick Reference Table

Regular Expression Pattern	Explanations	Examples
Meta characters [^$.|?*+(	Special caracters used in regex. *Must be escape with backslash "" to use a literal characters.
Literal characters	All characters (except the metacharacters) match a single instance of themselves. *{ and } are literal characters, unless they're part of a valid regular expression token (e.g. the {n} quantifier).	/a/ matches "a"
[characters]	Character classes or character set. A character class matches a single character out of all the possibilities offered by the character class.	/[0-9]/ matches a single digit
[\d]	Shorthand character classes matching digits. Same as [0-9].	/[\d]/ matches a single digit
.	Dot matches any characters.	/a.c/ matches both "a4c" and "ayc"** **
^	Matches at the start of the string the regex pattern is applied to. Matches a position rather than a character.
$	Matches at the end of the string the regex pattern is applied to. Matches a position rather than a character.
{m,n}	Matches at least “m” and at most “n” occurrences of preceeding character, character class or group.
*	Matches **zero **or **more **occurrences of preceeding character, character class or group.
+	Matches **one **or **more occurrences of preceeding character, character class or group. **
?	Matches **zero **or **one **occurrences of preceeding character, character class or group.
()	Parentheses are used for group or capturing group
\0, \1, \2, ...	Substitute the value matched by the nth grouped sub-expression, used in remapped fields.
?!	Not, as in "everything except this".

Examples

Here are some examples:

Add 2720 prefix:

/^(\d+)$/2720\1/

or

/^([0-9]*)$/2720\1/

Strip first 4 digits:

/^([0-9]{4})([0-9]*)$/\2/

Strip # and 7 first digits:

/^([#])([0-9]{7})([0-9]*)$/\3/

Web Online Tools

• Regular builder tool (with replace) : www.gskinner.com/RegExr Tips to use:

1. No need to enclose the Regular expression with '/'.

2. Replace : the regular expression must be split in two parts and '' replaced by '$'. For example, with '/^([0-9])$/2720\1/', the '^([0-9])$' would be filled on the first line and '2720$1' on the second line.

• Ruby regular expression editor and tester : rubular.com

References

• How to Use RegEx in Remapped Called and Calling Number Mask