request.env['HTTP_USER_AGENT']

Chrome out put is below
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/534.16 (KHTML, like Gecko) Chrome/10.0.648.205 Safari/534.16
Safari out put is below
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/533.21.1 (KHTML, like Gecko) Version/5.0.5 Safari/533.21.1
FireFox out put is below
Mozilla/5.0 (Windows NT 5.1; rv:2.0) Gecko/20100101 Firefox/4.0
Opera out put is below
Opera/9.80 (Windows NT 5.1; U; en) Presto/2.8.131 Version/11.10
Internet Explorer out put is below
Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 2.0.50727)

if request.env['HTTP_USER_AGENT'] =~ /[^(]*[^)]Chrome//

if request.env['HTTP_USER_AGENT'] =~ /[^(]*[^)]*[^t]Firefox//

def browser_detection
        result  = request.env['HTTP_USER_AGENT']
        browser_compatible = ''
        if result =~ /Safari/
          unless result =~ /Chrome/
            version = result.split('Version/')[1].split(' ').first.split('.').first
            browser_compatible = 'Application is not functional for Safari version's '+version if version.to_i < 5
          else
            version = result.split('Chrome/')[1].split(' ').first.split('.').first
            browser_compatible = 'Application is not functional for Chrome version's '+version if version.to_i < 10
          end
        elsif result =~ /Firefox/
          version = result.split('Firefox/')[1].split('.').first
          browser_compatible = 'Application is not functional for Firefox version's '+version if version.to_i < 5
        elsif result =~ /Opera/
          version = result.split('Version/')[1].split('.').first
          browser_compatible = 'Application is not functional for Opera version's '+version if version.to_i < 11
        elsif result =~ /MSIE/
          version = result.split('MSIE')[1].split(' ').first
          browser_compatible = 'Application is not functional for Microsoft Internet Explorer version's '+version if version.to_i < 9
        end
        return browser_compatible
      end