[Rd] Evaluate values in `Sys.setenv`

[Jeff King]

Thanks for your explanation. The function `path.expand` is very helpful!

Best,
Jiefei

On Fri, Aug 28, 2020 at 8:34 AM peter dalgaard <pdalgd using gmail.com> wrote:

> It is the shell that does the ~ and $ expansions, and Sys.setenv() doesn't
> go via the shell, so you cannot expect it to understand the shell
> metacharacters.  Instead, you need to do the corresponding computations in
> R, e.g.
>
> > paste(path.expand("~/mypath"), Sys.getenv("PATH"), sep=":")
> [1]
> "/Users/pd/mypath:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/gfortran/bin:/usr/local/clang8/bin:/Library/TeX/texbin:/opt/X11/bin"
>
> which you can then pass to Sys.setenv().
>
> -pd
>
> > On 28 Aug 2020, at 11:00 , Jeff King <szwjf08 using gmail.com> wrote:
> >
> > Hi all,
> >
> > I would like to know if there is any way to evaluate the values in
> > `Sys.setenv` before setting the environment variables. For example, if we
> > want to add a path to the environment variable `PATH`, we can do this in
> a
> > terminal
> >
> > ```
> >> export PATH=~/mypath:$PATH
> >> echo $PATH
> > /Users/jeff/mypath:...
> > ```
> >
> > However, this style of assignment is not allowed in  `Sys.setenv`, it
> > treats its argument as a literal string, so
> >
> > ```
> >> Sys.setenv(PATH= " ~/mypath:$PATH")
> >> Sys.getenv("PATH")
> > [1] " ~/mypath:$PATH "
> > ```
> > Note that both the symbol `~` and the variable `$PATH` are not expanded.
> > While we can manually evaluate the home symbol `~`  and PATH using
> > `Sys.getenv`, the code seems not quite neat. I would like to suggest
> adding
> > a parameter in ` Sys.setenv` to make the function more convenient(e.g.
> > Sys.setenv(..., fixed = TRUE)) if no existing function in base R can do
> > them in one line.
> >
> > Best,
> > Jiefei
> >
> >       [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-devel using r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-devel
>
> --
> Peter Dalgaard, Professor,
> Center for Statistics, Copenhagen Business School
> Solbjerg Plads 3, 2000 Frederiksberg, Denmark
> Phone: (+45)38153501
> Office: A 4.23
> Email: pd.mes using cbs.dk  Priv: PDalgd using gmail.com
>
>
>
>
>
>
>
>
>
>

	[[alternative HTML version deleted]]