Evaluate values in `Sys.setenv`

paste(path.expand("~/mypath"), Sys.getenv("PATH"), sep=":")

On 28 Aug 2020, at 11:00 , Jeff King <szwjf08 at 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]]

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 at 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]]

--
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
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Phone: (+45)38153501
Office: A 4.23
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com