Run code only once

Onetime allows package authors to run code only once (ever) for a given user. It does so by writing a file, typically to a folder in the user's configuration directory as given by rappdirs::user_config_dir(). The user can set an alternative filepath using options("onetime.dir").

Details

Core functions include:

• onetime_do() runs arbitrary code only once.

• onetime_warning() and friends print a warning or message only once.

• onetime_message_confirm() prints a message and asks "Show this message again?"

• onetime_rlang_warn() and onetime_rlang_inform() print messages using functions from the rlang package.

• onetime_only() returns a function that runs only once.

• check_ok_to_store() and set_ok_to_store() check for or grant permission to store lockfiles on the user's computer. It is package authors' responsibility to check for permission to store lockfiles. This may have been done already by another package if onetime was already installed. You can ask permission interactively on the command line by calling check_ok_to_store() with ask = TRUE.

For more information, see vignette("onetime").

Example

library(onetime)

ids  <- paste0("onetime-readme-", 1:3) 

for (i in 1:5) {
  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])
}

## This command will only be run once.

## Warning: This warning will only be shown once.

## This message will only be shown once.

See also

Useful links:

• https://github.com/hughjonesd/onetime

• https://hughjonesd.github.io/onetime/

• Report bugs at https://github.com/hughjonesd/onetime/issues

Author

Maintainer: David Hugh-Jones davidhughjones@gmail.com