R: Parse and Evaluate Expressions from a File

sys.source {base}

R Documentation

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"),
           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 value `NULL` corresponds to evaluation in the base environment. This is probably not what you want; you should typically supply an explicit `envir` argument.
`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.
`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. 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.

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")