Regular Expression for a String

[andarivaadu1]

Hi, I don't have any idea about regular expression. Can some on please suggest a good website for regular expression Tutorial. Also

1.Can some one please help me to generate a regular expression meeting all these requirements

• A strings minmum length must be 3 charcters, and maximum length must be 12 characters.
• A stirng cannot contain any kind of special characters except a period, period is not accepted at beginning of a string.
• String can accept numbers from 0 to 9.
• Spaces are also not allowed

1. Please provide explanation for your answer too

[ChrisPadgham]

Click Here

[Syed-yunus]

Click Here

[seslie]

Hello andarivaadu1,

These links, link1, link 2, link3 would help.

Bonus:

A strings minmum length must be 3 charcters, and maximum length must be 12 characters

     ^[a-zA-z]{3,12}$  

 ^         #start of regex
[a-zA-Z]   # Match characters and symbols in the list, a-z, A-Z
{3,12}     # Length at least 3 characters and maximum length of 12 
$          #end of regex

Regards,
Seslie