base (version 3.3)

Sys.setenv: Set or Unset Environment Variables

Description

Sys.setenv sets environment variables (for other processes called from within R or future calls to Sys.getenv from this R process).

Sys.unsetenv removes environment variables.

Usage

Sys.setenv(...)
Sys.unsetenv(x)

Arguments

...

named arguments with values coercible to a character string.

x

a character vector, or an object coercible to character.

Value

A logical vector, with elements being true if (un)setting the corresponding variable succeeded. (For Sys.unsetenv this includes attempting to remove a non-existent variable.)

Details

Non-standard R names must be quoted in Sys.setenv: see the examples. Most platforms (and POSIX) do not allow names containing "=". Windows does, but the facilities provided by R may not handle these correctly so they should be avoided. Most platforms allow setting an environment variable to "", but Windows does not, and there Sys.setenv(FOO = "") unsets FOO.

There may be system-specific limits on the maximum length of the values of individual environment variables or of all environment variables. windows Windows has a limit of 32,767 characters on the environment block, and cmd.exe has a limit of 2047 (Windows 2000) or 8192 characters (XP and later) for each value.

See Also

Sys.getenv, Startup for ways to set environment variables for the R session.

setwd for the working directory.

The help for ‘environment variables’ lists many of the environment variables used by R.

Examples

print(Sys.setenv(R_TEST = "testit", "A+C" = 123))  # `A+C` could also be used
Sys.getenv("R_TEST")
 windows
Sys.unsetenv("R_TEST")
 unix
Sys.unsetenv("R_TEST")  # may warn and not succeed
Sys.getenv("R_TEST", unset = NA)