R: Get 'FILE' Provided to R by a Shell

shFILE

R Documentation

Get 'FILE' Provided to R by a Shell

Description

Look through the command line arguments, extracting FILE from either of the following: -f FILE or --file=FILE

Usage

shFILE(original = FALSE, for.msg = FALSE, default, else.)

site.file(original = FALSE, for.msg = FALSE, default, else.)
init.file(original = FALSE, for.msg = FALSE, default, else.)

Arguments

`original`	`TRUE`, `FALSE`, or `NA`; should the original or the normalized path be returned? `NA` means the normalized path will be returned if it has already been forced, and the original path otherwise.
`for.msg`	`TRUE` or `FALSE`; do you want the path for the purpose of printing a diagnostic message / / warning / / error? `for.msg = TRUE` will ignore `original = FALSE`, and will use `original = NA` instead.
`default`	if FILE is not found, this value is returned.
`else.`	missing or a function to apply if FILE is found. See `tryCatch2()` for inspiration.

Value

character string, or default if FILE was not found.

Note

The original and the normalized path are saved; this makes them faster when called subsequent times.

On Windows, the normalized path will use / as the file separator.

Examples

FILE.R <- tempfile(fileext = ".R")
this.path:::.write.code({
    this.path:::.withAutoprint({
        shFILE(original = TRUE)
        shFILE()
        shFILE(default = {
            stop("since 'FILE.R' will be found, argument 'default'\n",
                " will not be evaluated, so this error will not be\n",
                " thrown! you can use this to your advantage in a\n",
                " similar manner, doing arbitrary things only if\n",
                " 'FILE.R' is not found")
        })
    }, spaced = TRUE, verbose = FALSE, width.cutoff = 60L)
}, FILE.R)
this.path:::.Rscript(
    c("--default-packages=this.path", "--vanilla", FILE.R)
)
unlink(FILE.R)


for (expr in c("shFILE(original = TRUE)",
               "shFILE(original = TRUE, default = NULL)",
               "shFILE()",
               "shFILE(default = NULL)"))
{
    cat("\n\n")
    this.path:::.Rscript(
        c("--default-packages=this.path", "--vanilla", "-e", expr)
    )
}