Demonstration of file-system persistence in ShinyApps.io.

.gitignore

.Rproj.user
.Rhistory
.RData

log.txt

Remeo: hi there!
Juliet: oh hi!

server.R

library(shiny)

# Read in the log file from the local filesystem.
# Because this is outside of `shinyServer`, it will be shared
# between ALL users connected to this process.
log <- readChar("log.txt", 1024)

shinyServer(function(input, output, session) {
  
  # Format the log to include the existing log + all comments
  logText <- reactive({
    if (is.null(input$name) || input$name == ""){
      # There's nothing new to update here, just return the existing log.
      return(log)
    }
    
    # Format the new entry
    newEntry <- paste0(input$name, ": ", input$comment, "\r\n")
    log <<- paste0(log, newEntry)
    
    # Write the text file out
    writeChar(log, "log.txt")
    
    return(log)
  })  
  
  # Render the output log
  output$log <- renderText({
    txt <- logText()
    
    # Clear out the current value
    updateTextInput(session, "name", value="")
    updateTextInput(session, "comment", value="")
    
    txt
  })
  
})

ui.R

library(shiny)

shinyUI(fluidPage(

  # Application title
  titlePanel("Demonstration of file persistence in Shiny"),

  # Define the side-panel
  sidebarLayout(
    sidebarPanel(
      textInput("name", "Name:"),
      textInput("comment", "Comment:"),
      submitButton("Comment")
    ),

    mainPanel(
      verbatimTextOutput("log")
    )
  )
))

This demo can not be deployed to shinyapps.io since RAmazonS3 package has to be installed from CRAN, BioConductor or GitHub.

Is there a way, to download this log.txt file somehow from shinyapps.io when I am not displaying this file on my app?