R shiny fileInput large files - r

Question

i have some problem with fileInput for R Shiny. Size limit is set to 5MB per default.
Since the files i have to work with are very large (>50GB), I only need the datapath and or name of the file. Unfortunatly fileInput wants to upload the complete file or at least it is loading the file somehow and tells me that the file is too big after i have reached the 5MB limit.
How can I only hand over the path to my app without uploading the file?
ui.R
library(shiny)
# Define UI ----
shinyUI(fluidPage(
h1("SAS Toolbox"),
tabsetPanel(
tabPanel("SASFat",
sidebarPanel(h2("Input:"),
actionButton("runSASFat","Run Job",width="100%",icon("paper-plane"),
style="color: #fff; background-color: #337ab7; border-color: #2e6da4"),
wellPanel(
#tags$style(".shiny-file-input-progress {display: none}"),
fileInput("FEInp","Pfad FE input Deck:"),
fileInput("FERes","Pfad FE Results:")
),
wellPanel(
checkboxGroupInput("options1","Auswertung:",c("Grundmaterial","Schweissnähte")),
conditionalPanel(condition="$.inArray('Schweissnähte',input.options1) > -1",
sliderInput("filter", "Filter:", 0.75, min = 0, max = 1))
),
wellPanel(
radioButtons("solver", "Solver:", c("Ansys","Abaqus", "Optistruct")),
conditionalPanel(condition="input.solver == 'Ansys'",selectInput("lic", "Lizenz",c("preppost","stba","meba")))
),
wellPanel(
checkboxGroupInput("options2","Optionen:",c("Schreibe LCFiles"))
)
),
mainPanel(br(),h2("Output:"),width="30%")
),
tabPanel("Nietauswertung"),
tabPanel("Spannungskonzept EN12663")
)
))
server.R
# Define server logic ----
shinyServer(function(input, output) {
observeEvent(input$runSASFat, {
FEInp <- input$FEInp
FERes <- input$FERes
opt1 <- input$options1
opt2 <- input$options2
filter <- input$filter
solver <- input$solver
lic <- input$lic
write(c(FEInp$datapath,FERes$datapath,opt1,opt2,filter,solver,lic),"ghhh.inp")
})
})
Thanks in advance
Michael

Answer 1

Thanks for the example #MichaelBird. I adapted your code to let users cancel the request without choosing a file (your app crashed after canceling):
This by the way only works on the PC hosting the shiny app.
library(shiny)
ui <- fluidPage(
titlePanel("Choosing a file example"),
sidebarLayout(
sidebarPanel(
actionButton("filechoose",label = "Pick a file")
),
mainPanel(
textOutput("filechosen")
)
)
)
server <- function(input, output) {
path <- reactiveVal(value = NULL)
observeEvent(input$filechoose, {
tryPath <- tryCatch(
file.choose()
, error = function(e){e}
)
if(inherits(tryPath, "error")){
path(NULL)
} else {
path(tryPath)
}
})
output$filechosen <- renderText({
if(is.null(path())){
"Nothing selected"
} else {
path()
}
})
}
shinyApp(ui = ui, server = server)
An alternative way would be to increase the maximum file size for uploads:
By default, Shiny limits file uploads to 5MB per file. You can modify
this limit by using the shiny.maxRequestSize option. For example,
adding options(shiny.maxRequestSize = 30*1024^2) to the top of app.R
would increase the limit to 30MB.
See this RStudio article.

Answer 2

Here is an example of using file.choose() in a shiny app to obtain the local path of the file (and hence the file name):
library(shiny)
ui <- fluidPage(
# Application title
titlePanel("Choosing a file example"),
sidebarLayout(
sidebarPanel(
actionButton("filechoose",label = "Pick a file")
),
mainPanel(
textOutput("filechosen")
)
)
)
server <- function(input, output) {
path <- reactiveValues(
pth=NULL
)
observeEvent(input$filechoose,{
path$pth <- file.choose()
})
output$filechosen <- renderText({
if(is.null(path$pth)){
"Nothing selected"
}else{
path$pth
}
})
}
# Run the application
shinyApp(ui = ui, server = server)
Is this what you're after?