Regular Expressions in ColdFusion Applications

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Regular Expressions in ColdFusion
Applications Dave Fauth DOMAIN
technologies d.fauth_at_domain-tech.com
Knowledge Engineering Systems Integration
Web Development Training
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Regular Expressions

• Small language in itself to perform pattern
  matching and text manipulation
• Used for client side validation, server side
  manipulation and virtually any other task
  requiring string matching and manipulation
• Enhanced in CF 4.0 to include REFindNoCase and
  REReplaceNoCase
• Available in CF Studio, CF 4.x, and JavaScript

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CF 4.x supported statements

• REFind
• REFindNoCase
• REReplace
• REReplaceNoCase

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REFind

• Returns the position of the regular expressions
  first occurrence in a block of text
• Case Sensitive
• REFind(reg_expression,string ,start
  ,returnsubexpression
• ltCFSET tmpLoc REFind(\?,display.cfm?a3)gt
  
• ltCFOUTPUTgt
• tmpLoc
• lt/CFOUTPUTgt

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REFindNoCase

• Returns the position of the regular expressions
  first occurrence in a block of text
• Case Insensitive
• REFindNoCase(reg_expression,string ,start
  ,returnsubexpression
• ltCFSET myPath c\reportFinder.cfmgt
• ltCFSET tmpLoc REFindNoCase((\.cfm),myPath)gt
• ltCFOUTPUTgt
• tmpLoc
• lt/CFOUTPUTgt

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REReplace

• Return a string with the regular expression
  replaced with a substring in the specified scope
• Case Sensitive
• ReReplace(string,reg_expression,substring
  ,scope)
• ltCFSET myPath c\reportFinder.cfmgt
• ltCFSET tmpLoc REReplace(myPath,a-z,d)gt
• ltCFOUTPUTgt
• tmpLoc
• lt/CFOUTPUTgt

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REReplaceNoCase

• Return a string with the regular expression
  replaced with a substring in the specified scope
• Case Insensitive
• ReReplaceNoCase(string,reg_expression,substring
  ,scope)
• ltCFSET myPath c\reportFinder.cfmgt
• ltCFSET tmpLoc REReplaceNoCase(myPath,A-Z,d
  )gt
• ltCFOUTPUTgt
• tmpLoc
• lt/CFOUTPUTgt

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Single Character Matching

• Match a single character
• Extensive set of rules for doing single character
  matching
• Rules include
• Special Characters are ? . ( ) \
• Any character not a special character matches
  itself
• A backslash escapes a special character
• A period matches any character except the newline
• A set of characters in brackets is a one
  character RE that matches any of the characters
  in the set. AKM matches A or K or M

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Single Character Matching Cont.

• Rules Cont.
• Any regular expression can be followed by m,n
  forces a match of m through n occurrences of the
  preceding regular expression. Example a2,4
  aa, aaa, aaaa
• A range of characters can be indicated with a
  dash. Example A-Z matches all uppercase
  letters. If the first character of the set is a
  , the RE matches any character except those in
  the set. I.e. AEIOU matches all uppercase
  consonants

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Multi-Character Regular Expressions

• You can use the following rules to build a
  multi-character regular expressions
• Parentheses group parts of regular expressions
  together into grouped sub-expressions that can be
  treated as a single unit. For example, (ha)
• A one-character regular expression or grouped
  sub-expressions followed by an asterisk ()
  matches zero or more occurrences of the regular
  expression. For example, a-z matches zero or
  more lower-case characters.
• A one-character regular expression or grouped
  sub-expressions followed by a question mark (?)
  matches zero or one occurrences of the regular
  expression. For example, xy?z matches either
  "xyz" or "xz".

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Multi-Character cont.

• The concatenation of regular expressions creates
  a regular expression that matches the
  corresponding concatenation of strings. For
  example, A-Za-z matches any capitalized
  word.
• The OR character () allows a choice between two
  regular expressions. For example, jell(yies)
  matches either "jelly" or "jellies".
• Braces () are used to indicate a range of
  occurrences of a regular expression, in the form
  m, n where m is a positive integer equal to or
  greater than zero indicating the start of the
  range and n is equal to or greater than m,
  indicating the end of the range. For example,
  (ba)0,3 matches up to three pairs of the
  expression "ba".

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Character Classes

• Special Commands that can take the place of
  character ranges.
• CF uses double brackets alpha
• Cold Fusion supports the following character
  classes
• alpha Matches any letter. Same as A-Za-z.
• upper Matches any upper-case letter. Same as
  A-Z.
• lower Matches any lower-case letter. Same as
  a-z.
• digit Matches any digit. Same as 0-9.
• Alnum Matches any alphanumeric character. Same
  as A-Za-z0-9.

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Character Classes cont.

• Xdigit - Matches any hexadecimal digit. Same as
  0-9A-Fa-f.
• Space - Matches a tab, new line, vertical tab,
  form feed, carriage return, or space.
• Print - Matches any printable character.
• punct - Matches any punctuation character, that
  is, one of ! S ( ) , - . / lt
  gt ? _at_ / _
• graph - Matches any of the characters defined
  as a printable character except those defined to
  be part of the space character class.
• cntrl - Matches any character not part of the
  character classes upper, lower,
  alpha, digit, punct, graph,
  print, or xdigit.

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Character Classes example

• ltcfset thistext"lthrgtHere is some textlthrgt
• ltbgthere is some bold textlt/bgt
• ltigtHere is italic text.lt/igt"gt
• ltcfset mynewtext REReplaceNoCase(thistext,
  "lt/printgt", "" , "ALL")gt
• ltcfset mynewtext2 REReplace(thistext,
  "ltgtgt", "", "ALL")gt

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Back Referencing

• Capability of regular expressions to remember a
  section of text and refer to it later
• Parenthesis provide grouping for back references
• Grouping is referred to using \1 through \9
• Expressions are counted from left to right
• ex. (a(bc)(d))
• \1 a(bc)(d)
• \2 bc
• \3 d
• Powerful for search and replace functions

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Back Referencing example

• ltcfset secondstring "here is my email address
  d.fauth_at_domain-tech.com "gt
• ltCFSET NewString REReplaceNoCase(
  secondstring,'(space)(a-z0-9\._at_(print
  \.)a-z2,3)(space)', '\1ltA
  HREF"mailto\2"gt\2lt/Agt\4', "ALL")gt

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Using Regular Expressions in Studio

• Extended find and replace in Studio and Homesite
  support Regular Expressions
• Open the extended find or the extended replace
  dialog box. Check the regular expressions box.
  Type in your regular expression. The Studio RE
  engine evaluates the selected files and returns
  each matching pattern

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Example Uses of Regular Expressions

• Removing HTML Tags from Text
• ltcfset amazonPrice Our Price 14.98 gt
• ltcfset amazonPrice ReFindNoCase('\digit1
  ,4\.digit2',text,1,1)gt
• Retrieving Information from a page
• refindnocase("ltbodygtgt(.)lt/bodygt", pagetext,
  1, "TRUE")
• REFindNoCase("upper6-digit2-dig
  it4,6",Body)

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When Not To Use Regular Expressions

• When it is easier to use something else
• Example
• ltcfset myuser engr\dbrowngt
• Rather than write
• ltcfset testname "engr\dbrown"gt
• ltCfset myUsername ReFindNoCase(".\\(.)",testna
  me,1,1)gt
• ltcfset myUsername Mid(testname,myUsername.pos2
  ,myUsername.len2)gt
• Write
• ltcfset myUsername ListLast(testname,\)gt

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Cold Fusion RE Limitation

• Limiting input string size
• In CFML RegExp functions such as REFind and
  REReplace, large input strings (greater than
  approximately 20,000 characters) will cause a
  debug assertion failure and a regular expression
  error will be reported. To avoid this, break up
  your input into smaller chunks as illustrated in
  the following example. Here the variable input
  has a size greater than 50000.
• ltCFSET test mid(input, 1, 20000)gt
• ltCFSET out1 REReplace(test, "
  Chr(9)Chr(13)Chr(10)Chr(13)Chr(10)",
  "chr(10)", "ALL")gt
• ltCFSET test mid(input, 20001, 20000)gt
• ltCFSET out2 REReplace(test, "
  Chr(9)Chr(13)Chr(10)Chr(13)Chr(10)",
  "chr(10)", "ALL")gt
• ltCFSET test mid(input, 40001, len(input) -
  40000)gt
• ltCFSET out3 REReplace(test, "
  Chr(9)Chr(13)Chr(10)Chr(13)Chr(10)",
  "chr(10)", "ALL")gt
• ltCFSET result out1 out2 out3gt

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Resources

• Javascript
• http//developer.netscape.com/library/documentatio
  n/communicator/jsguide/regexp.htm
• http//developer.netscape.com/docs/examples/javasc
  ript/regexp/overview.htm/documentation/communicato
  r/jsguide/regexp.htm
• JavaScript Bible 3rd Edition by Danny Goodman
• CF Studio
• file///C/PROGRAM FILES/ALLAIRE/COLDFUSION
  STUDIO4/Help/Developing_Web_Applications_with_Cold
  Fusion/08_Regular_Expressions
• Cold Fusion
• Advanced Cold Fusion 4.0 Application Development
  by Ben Forta
• CF-Talk Mailing List
• cf-talk-request_at_houseoffusion.com
• General
• An excellent reference on regular expressions is
  Mastering Regular Expressions, Jeffrey E. F.
  Friedl. O'Reilly Associates, Inc., 1997. ISBN
  1-56592-257-3, http//www.oreilly.com.