Appendix E – Regex Syntax

Regex Syntax The alternate forms of the INSTR() and LINSTR() functions can take a regular expression as the search pattern. The alternate form of the commands are: INSTR([start],text$, search$ [,size]) LINSTR(text%(),search$ [,start] [,size]

In both cases specifying the size parameter causes the firmware to interpret the search string as a regular expression. The size parameter is a floating point variable that is used by the firmware to return the size of a matching string. If the variable doesn't exist it is created. As implemented in MMBasic you need to apply the returned start and size values to the MID$ function to extract the matched string. eg,

IF start THEN match$=MID$(text$,start,size) ELSE match$=”” ENDIF The library used for the regular expressions implements POSIX draft P1003.2/D11.2, except for some of the internationalization features. See http://mirror.math.princeton.edu/pub/oldlinux/Linux.old/Refdocs/POSIX/all.pdf section 2.8 for details of constructing Regular Expressions or other online tutorials. The syntax of regular expressions can vary slightly with the various implementations. This document is a summary of the syntax and supported operations used in the MMBasic implementation. Anchors ^ Start of string $ End of string \b Word Boundary \B Not a word boundary < Start of word > End of word Qualifiers

0 or more (not escaped) + 1 or more ? 0 or 1 {3} Exactly 3 {3,} 3 or more {3,5} 3,4 or 5 Groups and Ranges (a|b) a or b (…) group [abc] Range (a or b or c) ¹ Not (a or b or c] [a-q] lower case letters a to q [A-Q] upper case letters A to Q [0-7] Digits from 0 to 7 Escapes Required to Match Normal Characters ^ to match ^ (caret) . to match . (dot) * to match * (asterix) $ to match $ (dollar) [ to match [ (left bracket) \ to match \ (backslash)

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Escapes with Special Functions + See Quantifiers ? See Quantifiers { See Quantifiers } See Quantifiers | See Groups and Ranges ( See Groups and Ranges ) See Groups and Ranges \w See Character Classes Character Classes \w digits,letters and _ [:word:] digits,letters and _ [:upper:] Upper case letters_ [:lower:] Lower case letters_ [:alpha:] All letters [:alnum:] Digits and letters [:digit:] Digits [:xdigit:] Hexidecimal digits [:punct:] Puntuation [:blank:] Space and tab [:space:] Blank charaters [:cntrl:] Control charaters [:graph:] Printed characters [:print:] Printed chars and spaces Example expression to match an IP Address which is contained within a word boundary. "<[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}>"

PicoMite User Manual