Removing nonnumeric and nonalpha characters from a string?

Question

What is the best way to remove all the special characters from a string - like these:

!@#$%^&*(){}|:"?><,./;'[]\=-

The items having these characters removed would rather short, so would it be better to use REGEX on each or just use string manipulation?

Thx

Environment == C#/.NET

Answer 1

It's generally better to have a whitelist than a blacklist.

Regex has a convenient \w that, effectively means alphanumeric plus underscore (some variants also add accented chars (á,é,ô,etc) to the list, others don't).

You can invert that by using \W to mean everything that's not alphanumeric.

So replace \W with empty string will remove all 'special' characters.

Alternatively, if you do need a different set of characters to alphanumeric, you can use a negated character class: [^abc] will match everything that is not a or b or c, and [^a-z] will match everything that is not in the range a,b,c,d...x,y,z

The equivalent to \w is [A-Za-z0-9_] and thus \W is [^A-Za-z0-9_]

Answer 2

in php:

$tests = array(
     'hello, world!'
    ,'this is a test'
    ,'and so is this'
    ,'another test with /slashes/ & (parenthesis)'
    ,'l3375p34k stinks'
);

function strip_non_alphanumerics( $subject )
{
    return preg_replace( '/[^a-z0-9]/i', '', $subject );
}

foreach( $tests as $test )
{
    printf( "%s\n", strip_non_alphanumerics( $test ) );
}

output would be:

helloworld
thisisatest
andsoisthis
anothertestwithslashesparenthesis
l3375p34kstinks