Parse and Evaluate Expressions from a File
Description
Parses expressions in the given file, and then successively evaluates them in the specified environment.
Usage
sys.source(file, envir = baseenv(), chdir = FALSE,
keep.source = getOption("keep.source.pkgs"),
keep.parse.data = getOption("keep.parse.data.pkgs"),
toplevel.env = as.environment(envir))
Arguments
file
a character string naming the file to be read from.
envir
an R object specifying the environment in which the
expressions are to be evaluated. May also be a list or an integer.
The default baseenv() corresponds to evaluation in the base
environment. This is probably not what you want; you should
typically supply an explicit envir argument, see the
‘Note’.
chdir
logical; if TRUE, the R working directory is
changed to the directory containing file for evaluating.
keep.source
logical. If TRUE, functions keep
their source including comments, see
options(keep.source = *) for more details.
keep.parse.data
logical. If TRUE and keep.source is
also TRUE, functions keep parse data with their source, see
options(keep.parse.data = *) for more details.
toplevel.env
an R environment to be used as top level while evaluating the expressions. This argument is useful for frameworks running package tests; the default should be used in other cases.
Details
For large files, keep.source = FALSE may save quite a bit of
memory. Disabling only parse data via keep.parse.data = FALSE
can already save a lot.
Note on envir
In order for the code being evaluated to use the correct environment
(for example, in global assignments), source code in packages should
call topenv(), which will return the namespace, if any,
the environment set up by sys.source, or the global environment
if a saved image is being used.
See Also
source , and loadNamespace which
is called from library(.) and uses sys.source(.).
Examples
## a simple way to put some objects in an environment
## high on the search path
tmp <- tempfile()
writeLines("aaa <- pi", tmp)
env <- attach(NULL, name = "myenv")
sys.source(tmp, env)
unlink(tmp)
search()
aaa
detach("myenv")