Expresions regulars

De whats Wiki

XULETARI D'EXPRESIONS REGULARS

   * Patterns ("wildcards") are matched against a string
   * Normal alphanumeric characters are treated as normal
   * Special characters:
         o . (full stop) - match any character
         o * (asterix) - match zero or more of the previous symbol
         o + (plus) - match one or more of the previous symbol
         o ? (question) - match zero or one of the previous symbol
         o \? (backslash-something) - match special characters
         o ^ (caret) - match the start of a string
         o $ (dollar) - match the end of a string
         o [set] - match any one of the symbols inside the square braces.
         o (pattern) - grouping, remember what the pattern matched as a special variable 
   * Examples:
         o a+ matches "a", "aaaa", "aaaaaaaaaaaa", but not "bbb"
         o [ab]+ matches, "a", "b", or any length combination of the two
         o \.s?html? matches ".htm", ".shtm", ".html" or ".shtml"
         o (.+)/1999/(.+) matches "subject/1999/psy1011/", and also stores "subject" in $1 and "psy1011/" in $2. 
   * Regular expressions are very extensive.
         o Documentation on silas: man regex
         o Friedl (1997). Mastering Regular Expressions. O'Reilly.

\{x,y\} = match x to y occurrences of the preceding. \{x\} = match exactly x occurrences of the preceding. \{x,\} = match x or more occurrences of the preceding.

Per a triar gready/nongready en una expresió regular

Per seleccionar el match més gran (per defecte):

\(.*\)

Per seleccionar el match més petit:

\(.*?\)