Within the scope of a tag library there are a number of pre-defined variables including:
actionName
- The currently executing action name
controllerName
- The currently executing controller name
flash
- The flash object
grailsApplication
- The api:org.codehaus.groovy.grails.commons.GrailsApplication instance
out
- The response writer for writing to the output stream
pageScope
- A reference to the pageScope object used for GSP rendering (i.e. the binding)
params
- The params object for retrieving request parameters
pluginContextPath
- The context path to the plugin that contains the tag library
request
- The HttpServletRequest instance
response
- The HttpServletResponse instance
servletContext
- The javax.servlet.ServletContext instance
session
- The HttpSession instance