Install github fails in conda environment on Linux

In a conda installation of R on a Linux machine, devtools::install_github fails because it is unable to find the correct system commands:

$ docker run --rm -it condaforge/linux-anvil bash
conda install -y r-base r-devtools unzip
$ R -q -e 'devtools::install_github("r-lib/devtools")'
> devtools::install_github("r-lib/devtools")
Downloading GitHub repo r-lib/devtools@master
from URL https://api.github.com/repos/r-lib/devtools/zipball/master
Installation failed: error in running command

One work around would be to create a conda package and host it on Anaconda Cloud, but this can be a lot of work (especially if the package has many dependencies without corresponding conda packages). Often I want to test out the package prior to making the effort to create a conda package for it.

The problem can be solved by setting the environment variables to system commands correctly:

R -q
> getOption("unzip")
[1] ""
> Sys.getenv("TAR")
[1] "/bin/gtar"
> options(unzip = "/opt/conda/bin/unzip")
> Sys.setenv(TAR = "/bin/tar")
> devtools::install_github("r-lib/devtools")

Note in the example above, I installed unzip via conda. On a system that has unzip, I usually use options(unzip = “/usr/bin/unzip”).