Change the directory of a file to be saved - r

Question

I have a shiny app that I deployed as a library. Inside my shiny app, I write a json file in real time, I want to write this file in the working directory of each user. Nevertheless, the file is written in the directory of the library.(Please refer the code below)
app.R
library(Tree)
ui <- htmlTemplate("www/Tree.html",
text_output = tableOutput("table2")
)
server <- function(input, output, session){
# This block fires each time we receive a message from JavaScript
output$table2 <- renderTable({
#Write json file
json_value = input$jsonData
write(json_value, paste0(getwd(),"/",fileName, ".json"))
})
}
# Run the application
shinyApp(ui , server)
I though that with the function getwd()I will be able to see my json file in my working directory but taht is not happening. My json file is written in the directory of the library
This directory
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/Tree/
How can I change my code to be able to see my jsonfile in the RProject which the user wants to work?

Answer 1

A shiny app is running in your browser and, as a concequence, subject to strict safety regulations imposed by the browser. There are plenty of restrictions regarding the file system to make sure that web pages cannot freely roam your hard drive. That is why there might not be a solution with a good user experience to achieve what you want.
The safest solution would be the download button (as suggested by #HubertL).
If you want to work with the users' home directory you can get the path with file.path(Sys.getenv("HOME")) (at least on Windows it works). Now you can work with that path. Use OutputPath <- file.path(Sys.getenv("HOME"), fileName) to create the path %HOME%/fileName.
The third alternative (I can think of) is a simple textInput. Users can paste a string there that represents the path to the directory where they want the file to be stored. Check the string with dir.exists and use it if it is valid.