Run a app from terminal and send a password - shiny

Question

I want to launch a shiny application from a terminal to avoid blocking the rstudio console.
My application uses the ssh package to connect to a remote machine.
When I launch the application from rstudio a small window opens to ask me for my password but when I launch the application from the terminal i get an error message.
$ "Rscript.exe" -e "shiny::runApp('app')"
Loading required package: shiny
Warning: package 'shiny' was built under R version 3.5.3
Warning: package 'ssh' was built under R version 3.5.3
Linking to libssh v0.8.6
Password callback did not return a string value
Erreur : Authentication with ssh server failed
Stopped
app.R
library(shiny)
library(ssh)
ssh.session <- ssh::ssh_connect(host = host)
cat("*** Logging in of the session ***")
# Define UI for application that draws a histogram
ui <- fluidPage()
server <- function(input, output) {
onStop(function() {
ssh_disconnect(ssh.session)
cat("*** Logging out of the session ***")
})
}
# Run the application
shinyApp(ui = ui, server = server)

Answer 1

I don't know about your security necessity in your use case...
What you could'd do (if its ok for you to specify a password while calling Rscript), is giving the password as an extra parameter when calling RScript and then forwarding it to ssh_connect(). You could also do the same with host variable. Im calling this R file via:
Rscript --vanilla home/user/R/app.R "password"
I'm not running shiny::runApp, because the line shinyApp(ui=ui, server=server) will automatically start up the shiny application, allowing us to connect to ssh beforehand.
In the app.R file we forward the arguments to ssh_connect.
app.R
library(shiny)
library(ssh)
args <- commandArgs(trailingOnly = TRUE)
host="host"
ssh.session <- ssh::ssh_connect(host = host,passwd = )
cat("*** Logging in of the session ***")
# Define UI for application that draws a histogram
ui <- fluidPage()
server <- function(input, output) {
onStop(function() {
ssh_disconnect(ssh.session)
cat("*** Logging out of the session ***")
})
}
# Run the application
shinyApp(ui = ui, server = server)