Regular Expressions
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Public domain
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Patterns of characters that are used in searching databases

<table border=1>
<tr><td><b>Metacharacter</b></td><td><b>Meaning</b>                                               </td><td><b>Example</b></td><td><b>Explanation</b>                     </td></tr>
<tr><td>       .       </td><td>  Exactly one character, not null                                 </td><td>    .       </td><td>  One character, not null.               </td></tr>
<tr><td>       *       </td><td>  zero or more times (like {0,})                                  </td><td>  ab*c      </td><td>  ac, abc, abbc, abbbc, ...              </td></tr>
<tr><td>       +       </td><td>  once or more times (like {1,})                                  </td><td>  ab+c      </td><td>  abc, abbc, abbbc, ...                  </td></tr>
<tr><td>       ?       </td><td>  zero or once (like {0,1})                                       </td><td>  ab?c      </td><td>  ac,abc.                                </td></tr>
<tr><td>       ^       </td><td>  Beginning of the line                                           </td><td>  ^abc      </td><td>  Lines witch begin with "abc".          </td></tr>
<tr><td>       $       </td><td>  End of the line                                                 </td><td>  abc$      </td><td>  Lines witch end with "abc".            </td></tr>
<tr><td>       \       </td><td>  Escape carahcter                                                </td><td>  \.        </td><td>  dot character.                         </td></tr>
<tr><td>       []      </td><td>  One occurence of list                                           </td><td>  [abc]     </td><td>  matches a,b or c.                      </td></tr>
<tr><td>       [-]     </td><td>  Range of characters                                             </td><td>  [a-d]     </td><td>  matches a,b,c or d.                    </td></tr>
<tr><td>       [^]     </td><td>  Reverse range of characters                                     </td><td>  [^a-d]    </td><td>  matches not a,b,c or d.                </td></tr>
<tr><td>       (|)     </td><td>  alternative text                                                </td><td>  (abc|def) </td><td>  matches abc or def.                    </td></tr>
<tr><td>       \d      </td><td>  exactly one digit                                               </td><td>  \d\d      </td><td>  00, 01, ..., 99.                       </td></tr>
<tr><td>       \D      </td><td>  everything except digit                                         </td><td>  \D\D      </td><td>  not 00,...,99.                         </td></tr>
<tr><td>       \w      </td><td>  exactly one letter,number or underscore (like [A-z0-9_])        </td><td>  \w        </td><td>  a, 1, _, ....                          </td></tr>
<tr><td>       \W      </td><td>  everything except letter, number or underscore(like [^A-z0-9_]) </td><td>  \W        </td><td>  @,#,...                                </td></tr>
<tr><td>       \s      </td><td>  exactly one whitespace (space,tab,newline)                      </td><td>  \s        </td><td>                                         </td></tr>
<tr><td>       \S      </td><td>  everything except whitespace                                    </td><td>  \S        </td><td>  @                                      </td></tr>
<tr><td>       \b      </td><td>  word boundary                                                   </td><td>  \bdef     </td><td>  def (not abcdef)                       </td></tr>
<tr><td>       \B      </td><td>  non-word boundary                                               </td><td>  \Bdef     </td><td>  abcdef (not def)                       </td></tr>
<tr><td>       \t      </td><td>  tab character                                                   </td><td>            </td><td>                                         </td></tr>
<tr><td>       \n      </td><td>  carriage return                                                 </td><td>            </td><td>                                         </td></tr>
<tr><td>       \nnn    </td><td>  octal number                                                    </td><td>  \007      </td><td>  bell character                         </td></tr>
<tr><td>      {m}      </td><td>  character repetitions (m times)                                 </td><td>  a{2}      </td><td>  aa                                     </td></tr>
<tr><td>      {m,n}    </td><td>  character repetitions (minimum m, maximum n)                    </td><td>  a{2,3}    </td><td>  aa,aaa                                 </td></tr>
<tr><td>      {m,}     </td><td>  character repetitions (minimum m)                               </td><td>  a{2,}     </td><td>  aa,aaa,aaaa,aaaaa,...                  </td></tr>
</table>

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_BY: Pejman Moghadam_  
_TAG: regex_  
_DATE: 2009-04-25 00:16:37_