R Shiny with URL parameters (https://beta.rstudioconnect.com/content/1583/?foo=1&bar=hello)

server.R

library(shiny)

shinyServer(function(input, output, session) {

  # Return the components of the URL in a string:
  output$urlText <- renderText({
    paste(sep = "",
          "protocol: ", session$clientData$url_protocol, "\n",
          "hostname: ", session$clientData$url_hostname, "\n",
          "pathname: ", session$clientData$url_pathname, "\n",
          "port: ",     session$clientData$url_port,     "\n",
          "search: ",   session$clientData$url_search,   "\n"
    )
  })

  # Parse the GET query string
  output$queryText <- renderText({
    query <- parseQueryString(session$clientData$url_search)

    # Return a string with key-value pairs
    paste(names(query), query, sep = "=", collapse = ", ")
  })
})

ui.R

library(shiny)

shinyUI(bootstrapPage(
  h3("URL components"),
  verbatimTextOutput("urlText"),

  h3("Parsed query string"),
  verbatimTextOutput("queryText")
))