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Show all the special environment variables available for customizing targets.


tar_envvars(unset = "")



Character of length 1, value to return for any environment variable that is not set.


A data frame with one row per environment variable and columns with the name and current value of each. An unset environment variable will have a value of ""

by default. (Customize with the unset argument).


You can customize the behavior of targets with special environment variables. The sections in this help file describe each environment variable, and the tar_envvars() function lists their current values.

If you modify environment variables, please set them in project-level .Renviron file so you do not lose your configuration when you restart your R session. Modify the project-level .Renviron file with usethis::edit_r_environ(scope = "project"). Restart your R session after you are done editing.

For targets that run on parallel workers created by tar_make_clustermq() or tar_make_future(), only the environment variables listed by tar_envvars() are specifically exported to the targets. For all other environment variables, you will have to set the values manually, e.g. a project-level .Renviron file (for workers that have access to the local file system).


The TAR_ASK environment variable accepts values "true" and "false". If TAR_ASK is not set, or if it is set to "true", then targets asks permission in a menu before overwriting certain files, such as the target script file (default: _targets.R) in tar_script(). If TAR_ASK is "false", then targets overwrites the old files with the new ones without asking. Once you are comfortable with tar_script(), tar_github_actions(), and similar functions, you can safely set TAR_ASK to "false" in either a project-level or user-level .Renviron file.


The TAR_CONFIG environment variable controls the file path to the optional YAML configuration file with project settings. See the help file of tar_config_set() for details.


The TAR_PROJECT environment variable sets the name of project to set and get settings when working with the YAML configuration file. See the help file of tar_config_set() for details.


The TAR_WARN environment variable accepts values "true" and "false". If TAR_WARN is not set, or if it is set to "true", then targets throws warnings in certain edge cases, such as target/global name conflicts and dangerous use of devtools::load_all(). If TAR_WARN is "false", then targets does not throw warnings in these cases. These warnings can detect potentially serious issues with your pipeline, so please do not set TAR_WARN unless your use case absolutely requires it.


#> # A tibble: 4 × 2
#>   name        value
#>   <chr>       <chr>
#> 1 TAR_ASK     ""   
#> 2 TAR_CONFIG  ""   
#> 3 TAR_PROJECT ""   
#> 4 TAR_WARN    ""