M4 Regexp Examples

Basic Regexp operators and building blocks are explained here.

Regexp for matching

Regexp matching is used to allow/deny CallerID/Destinations for Origination Points, Termination Points, and Dial Peers.

Validate regex

The regex can be validated using https://regexr.com/ (or any other online regex editor).

Examples

Regexp	Explanation
.*	everything
^[0-9]+$	only digits
^[0-9]{9,}$	only digits, number more than 8 digits (9, 10, 11...)
^[0-9]{0,9}$	only digits, number less than 9 digits (1, 2, 3, 4, 5, 6, 7, 8)
^\\+?[0-9]+$	optional + sign and only digits
^370[0-9]+$	only digits starting with 370
^370.*$	anything starting with 370
^(37[0-1]|44)[0-9]*$	only digits starting with 370 or 371 or 44
^380(67|97|68|98)[0-9]*$|^998[0-9]+$	only digits starting with 380(67,97,68,98) or 998(0-9), where 380(67,97,68,98) = 38067,38097,38068,38098 and 998(0-9) = 9980,...,9988,9989.
^380(67|97|68|98)[0-9]{5,9}$|^998[0-9]{5,9}$	only digits starting with 380(67,97,68,98) or 998, but number of digits after each prefix should be between 5 and 9. So, for example, 3809712345 will match, but 380971234 or 380971234567890 will NOT match.
^370[138][0-9]+$	only digits starting with 3701, 3703, 3708

Regexp for transformation

Regexp transformation is used to WIP

Format

Regexp transformation format is:

/match_expression/replacement_expression/flags

• match_expression - POSIX regular expression
• replacement_expression - replacement expression with back references to matched tokes: \1, \2, …, \9
• flags:
  • i - match ignore case
  • g - replace all matches

Before putting Transformations into production, it is advisable to test them on various values.

Test in Linux console

Execute sed command (add s before transformation s/regex/replacement/flags):

echo '00370123456789' | sed -E 's/^00//'

Test in online sed live editor r

If you do not have access to the Linux console, use https://sed.js.org/ (or any other online sed editor).

Examples

Transformation	Original number	Modified number	Comment
/^00//	003701234567	003701234567	Cut prefix 00
/^370/8/	370123456789	8123456789	Replace 370 with 8
/\+//	+370123456789	370123456789	Cut + (here + is escaped by \ since it is special regex symbol)
/\+370/86/	+370123456789	86123456789	Cut prefix +370, add prefix 86
/\+?(.*)/+\1/	370123456789	+370123456789	Add + if it is not present already
^/.*/999\1/	370123456789	999370123456789	Add 999 in front of any string

See also

• M4 Source Transformation
• M4 Destination Transformation
• Standard: http://en.wikipedia.org/wiki/Regular_expression#POSIX_basic_and_extended
• Check your regexp: http://regex101.com/