onetime

Listen very carefully. I shall say this only once.

Michelle Dubois, ’Allo ’Allo

onetime provides convenience functions to run R code only once per user. For example, you can show a startup message only the first time (ever) that a package is loaded.

For more information, see the website.

Example

library(onetime)
ids  <- paste0("onetime-readme-", sample(1e9, 4))


for (i in 1:5) {
  cat("Loop ", i, " of 5\n")
  onetime_do(cat("This command will only be run once.\n"), id = ids[1])
  onetime_warning("This warning will only be shown once.", id = ids[2])
  onetime_message("This message will only be shown once.", id = ids[3])
}
#> Loop  1  of 5
#> This command will only be run once.
#> Warning: This warning will only be shown once.
#> This message will only be shown once.
#> Loop  2  of 5
#> Loop  3  of 5
#> Loop  4  of 5
#> Loop  5  of 5

# Meanwhile, in a separate process:
library(callr)
result <- callr::r(function (ids) {
  onetime::onetime_message("This message with an existing ID will not be shown.", id = ids[1])
  onetime::onetime_message("This message with a new ID will be shown.", id = ids[4])
}, show = TRUE, args = list(ids = ids))
#> This message with a new ID will be shown.

Installation

You can install the development version from GitHub with:

# install.packages("devtools")
devtools::install_github("hughjonesd/onetime")