CODEWITHSUNDEEP
renvironment-variables
flodel
flodel

Reputation: 89057

setting environment variables programmatically

In R, I can set environment variables "manually", for example:

Sys.setenv(TODAY = "Friday")

But what if the environment variable name and value are stored in R objects?

var.name  <- "TODAY"
var.value <- "Friday"

I wrote this:

expr <- paste("Sys.setenv(", var.name, " = '", var.value, "')", sep = "")
expr
# [1] "Sys.setenv(TODAY = 'Friday')"
eval(parse(text = expr))

which does work:

Sys.getenv("TODAY")
# 1] "Friday"

but I find it quite ugly. Is there a better way? Thank you.

Upvotes: 22

Views: 12485

Answers (3)

arvi1000
arvi1000

Reputation: 9582

This is a variant of the accepted answer, but if you want to pack this into a single line, and/or avoid generating the intermediate args object, you can use setNames to get a named character vector, then coerce to list with as.list:

do.call(Sys.setenv, as.list(setNames(var.value, var.name)))

Upvotes: 2

G. Grothendieck
G. Grothendieck

Reputation: 269501

Try this:

.Internal(Sys.setenv(var.name, var.value))

Upvotes: 7

David Robinson
David Robinson

Reputation: 78600

You can use do.call to call the function with that named argument:

args = list(var.value)
names(args) = var.name
do.call(Sys.setenv, args)

Upvotes: 23

Related Questions