Question

In many (interpreted) programming languages, a variable is set when sourcing a file so that some code can determine the filename from where it is loaded. E.g. in ruby, the variable __FILE__ is set when loading a file.

Is there such a feature in R? Is there a way for R code to determine from where it is loaded?

Example:

main.R:

source("foo.R")

/home/bar/foo.R:

print(FULL_FILENAME)

What do I have to replace FULL_FILENAME with to make it print:

[1] "/home/bar/foo.R"

without hardcoding any filenames in the source?

Answer 1

You can use a hack provided by Gabor a while back by putting this on top of your file :

this.file <- parent.frame(2)$ofile

If you want to extract the name of the directory, you can do :

this.dir <- dirname(this.file)

From my understanding of things, sourcing a file creates two parent environments. The outer one (two steps up) contains the information about the file from where the code is sourced.