what is regular expression?

saravanan · #1 (**permalink**) 03-21-2008, 04:46 AM

in php or Java Script i dont like a word regular expression. How can i understand the regular expression eascilly. please give a example from scratch to massive.

Thanks in advance.

senraj · #2 (**permalink**) 03-21-2008, 05:28 AM

Hi,

A regular expression is a special text string for describing a search pattern. You can think of regular expressions as wildcards on steroids. You are probably familiar with wildcard notations such as *.txt to find all text files in a file manager. The regex equivalent is .*\.txt.

But you can do much more with regular expressions. In a text editor like EditPad Pro or a specialized text processing tool like PowerGREP, you could use the regular expression \b[A-Z0-9._%-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b to search for an email address. Any email address, to be exact. A very similar regular expression can be used by a programmer to check if the user entered a properly formatted email address. In just one line of code, whether that code is written in Perl, PHP, Java, a .NET language or a multitude of other languages.

Since "regular expressions" is a mouthful, you will usually find the term abbreviated as "regex" or "regexp". I prefer "regex", since it can be easily pluralized as "regexes".

saravanan · #3 (**permalink**) 03-23-2008, 08:05 PM

Thank you so much

Jeyaseelansarc · #4 (**permalink**) 03-27-2008, 06:27 AM

Hi,
Here the small example

PHP Code:

  <?php

$str = "Hello World";

// Returns true if "Hell" is found anywhere in $str

ereg("Hell", $str);       

?>

Jeyaseelansarc · #5 (**permalink**) 03-27-2008, 06:30 AM

this example Returns true if client browser is Netscape 2, 3 or MSIE 3.

PHP Code:

  <?php

eregi("(ozilla.[23]|MSIE.3)", $HTTP_USER_AGENT);  

?>

Kamalakannan · #6 (**permalink**) 03-28-2008, 05:35 AM

This example check valid email or not using regular expression if valid returns true.

PHP Code:

  <?php

 
define("EMAIL_REG", "^[_a-zA-Z0-9-]+(\.[_a-zA-Z0-9-]+)*@[a-zA-Z0-9-]+(\.[a-zA-Z0-9-]+)*(\.[a-zA-Z]{2,3})$");

 
$vEmail = 'abc@xyz.com';

 
eregi(EMAIL_REG, $vEmail);

?>

Kamalakannan · #7 (**permalink**) 03-28-2008, 05:40 AM

This example for checking US zipcode format valid or not if valid returns true.

PHP Code:

  <?php

define("US_ZIPCODE_REG", "^[[:digit:]]{5}(-[[:digit:]]{4})?$");

 
$vZip = '12345';

eregi(US_ZIPCODE_REG, $vZip);

?>

Kamalakannan · #8 (**permalink**) 03-28-2008, 06:02 AM

This example for checking US phone number format valid or not if valid returns true otherwise false.

PHP Code:

  <?

define("US_PHONE_REG", "[0-9]{3}-[0-9]{3}-[0-9]{4}$");

 
$vPhone = '123-456-7890';

eregi(US_PHONE_REG, $vPhone);

?>

sureshbabu · #9 (**permalink**) 03-28-2008, 06:12 AM

what is regular expression for address format?

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