Shell Programming and Scripting

I want to allow alphanumeric characters and single dot in between the characters,multiple dots should not be allowed.

ex :
1 . (single) dot should not be allowed in the string
2. ...... (multiple dots should not be allowed in the string)
3. a.b.c (dots in b/w the characters can be allowed)
4. special characters other than alphanumeric characters should not be allowed


regex should pass the above mentioned criteria

Please test this:

Code:

^([a-zA-Z0-9]+\.?)+[a-zA-Z0-9]+$

How about:

Code:

egrep -v "([^a-zA-Z0-9.]|^\.|\.\.|\.$)"

The following is the jquery code.
Here am reading the values entered in the text box and evaluating that string.

variable fName contains the original string here .

Code:

$("#fName").blur(function(){
        var fName = jQuery.trim($("#fName").val());   // removing white spaces
        var words = fName.split(/[^a-zA-Z0-9.]/);   // allowing only alphanumerics and //.(dot character) here
  
        nfName = jQuery.trim(words.join(" "));   // again joining the string
        if(nfName != fName)
        {
                alert("Special characters other than \".\" are not allowed");       
        }       
});

am able to block all special characters except .
but i want the following criteria to be passed.

ex :
1 . (single) dot should not be allowed in the string i.e (complete string should not be single dot)
2. ...... (multiple dots should not be allowed in the string) i.e (string should not be only dots)
3. a.b.c (dots in b/w the characters can be allowed)
4. special characters other than alphanumeric characters should not be allowed


please post the ideas.