install.packages("rstudioapi")

# install.packages("devtools")
devtools::install_github("rstudio/rstudioapi")

# Returns T/F
rstudioapi::isAvailable()
# Returns error if not available
rstudioapi::verifyAvailable()
# Optional argument allows you to specify version requirement
rstudioapi::isAvailable("0.99")
rstudioapi::verifyAvailable("0.99")
# Call an rstudio function
rstudioapi::callFun("viewer", "https://localhost:8080")
# This will raise an error if rstudio is not running, or the function
# is not found. To run a different function if it's not available,
# use exists
if (rstudioapi::hasFun("viewer")) {
  rstudioapi::callFun("viewer", "https://localhost:8080")
} else {
  browseURL("https://localhost:8080")
}
# You can use find to get the function. Throws an error if the function
# does not exist.
rstudioapi::findFun("viewer")
# You can also check version in exists and find
rstudioapi::findFun("viewer", 0.99)
rstudioapi::hasFun("viewer", 0.99)