Run R interactively from Rscript - r

Question

I'm trying to start a shiny app or an interactive .Rmd document from an Rscript. However, all I get is a message
Listening on http://127.0.0.1:...
I believe this is because R is running in interactive mode (another post about this). How can I write the proper Rscript so that either of the following would work?
My script
#!/usr/bin/Rscript
## This
library(shiny)
runApp(appDir = "../app")
## Or this
## rmarkdown::run("Main.Rmd")

Answer 1

If I understand your question correctly, I was able to achieve this with littler, which I use in lieu of Rscript for scripting tasks that revolve around R. I'm running CentOS 7, and based on the code in your question it looks like you are on a Unix-like machine, so installing littler should not be an issue. For minimal reproducibility, I used the default shiny application and shiny-based Rmarkdown templates provided by RStudio, saving them as testapp (the project / application directory name) and testRMD.rmd, respectively. Then, I have the following scripts:
testapp.r
#!/usr/bin/env r
shiny::runApp(
"~/tmp/delete/testapp",
port = 7088,
launch.browser = TRUE,
host = "127.0.0.1")
testRMD.r
#!/usr/bin/env r
rmarkdown::run(
file = "testRMD.rmd",
dir = "~/tmp/delete",
shiny_args = list(
port = 7088,
launch.browser = TRUE,
host = "127.0.0.1"))
Set the permissions for these files so they can be executed -
[nathan#nrussell R]$ chmod +x testapp.r testRMD.r
(chmod +u ... should suffice, but regardless...), and you should be all set to run them from your terminal, etc...
[nathan#nrussell R]$ ./testapp.r
Loading required package: shiny
Listening on http://127.0.0.1:7088
[nathan#nrussell R]$ ./testRMD.r
Loading required package: shiny
Listening on http://127.0.0.1:7088
There is some additional command line output for the Rmd file that I omitted, but I'm sure this could be suppressed easily if desired. Anyhow, this seems to be working properly - both the shiny application and Rmarkdown application are interactive, just as when launched from RStudio - but if you had something else in mind please clarify.

Answer 2

Thanks #nrussell, your example helped me a lot!
Here is my solution for launching an interactive markdown doc on Windows 10.
REM Change to correct directory
cd "C:\Users\me\Documents\project_folder\"
REM Print files available (not required, but helpful)
dir
REM Point system to R's Pandoc with Rscript then launch
"C:\Program Files\R\R-4.0.3\bin\Rscript.exe" -e ^
"Sys.setenv(RSTUDIO_PANDOC='C:/Users/me/Documents/RStudio/bin/pandoc'); rmarkdown::run(file = 'myInteractiveMarkdown.Rmd', shiny_args = list(launch.browser = TRUE, host = '127.0.0.1'))"
I found I got two errors initially:
When I didn't point the system env to R's pandoc it gave the error message error pandoc version 1.12.3 or higher is required which I solved using the instructions here
When I set the port in the shiny_args, subsequent executions of the bat file would get an error that the port was already busy