Why is R using system tar, not Rtools tar? [duplicate] - r

Question

This question already has answers here:
How to find correct executable with Sys.which on Windows
(2 answers)
Closed 2 years ago.
I'm trying to debug why I'm suddenly getting the error
tar.exe: Error exit delayed from previous errors.
on running install_github. Thinking there might be a problem with the tar program, I came across this oddity:
> Sys.getenv("PATH")
[1] "C:\\Program Files (x86)\\Microsoft SDKs\\Azure\\CLI2\\wbin;C:\\Rtools\\bin;C:\\Windows\\system32;[...]"
> Sys.which("tar")
tar
"C:\\WINDOWS\\SYSTEM32\\tar.exe"
> file.exists("C:\\Rtools\\bin\\tar.exe")
[1] TRUE
Why is R using the system tar, as opposed to the Rtools-supplied tar, when the Rtools directory is earlier in the path?
OS is Windows 10 2004 (build 19041.330), R 4.0.0.

Answer 1

This appears to be a known problem, for... several years now:
How to find correct executable with Sys.which on Windows
I tried to find documentation for this. I came across this:
https://cran.r-project.org/manuals.html
and in turn this:
https://cran.r-project.org/doc/manuals/r-release/fullrefman.pdf
but it turns out that PDF is specific to Unix, and omits Windows specific parts.
I am not sure of any official Windows PDF. So failing that, you can look at the
source directly:
The search path for command may be system-dependent: it will include the
bin directory, the working directory and the Windows system directories
before PATH.
https://github.com/wch/r-source/blob/92712b53/src/library/base/man/system.Rd#L77-L79
Note on the same page, I also see this:
This interface has become rather complicated over the years: see system2
for a more portable and flexible interface which is recommended for new code.
(If the Windows PDF is hosted in an official place, someone please let me know).