Determine path of the executing script

I have a script called foo.R that includes another script other.R, which is in the same directory:

#!/usr/bin/env Rscript
message("Hello")
source("other.R")

But I want R to find that other.R no matter what the current working directory.

In other words, foo.R needs to know its own path. How can I do that?

Here there is a simple solution for the problem. This command:

script.dir <- dirname(sys.frame(1)$ofile)

returns the path of the current script file. It works after the script was saved.

You can use the commandArgs function to get all the options that were passed by Rscript to the actual R interpreter and search them for --file=. If your script was launched from the path or if it was launched with a full path, the script.name below will start with a '/'. Otherwise, it must be relative to the cwd and you can concat the two paths to get the full path.

Edit: it sounds like you'd only need the script.name above and to strip off the final component of the path. I've removed the unneeded cwd() sample and cleaned up the main script and posted my other.R. Just save off this script and the other.R script into the same directory, chmod +x them, and run the main script.

main.R:

#!/usr/bin/env Rscript
initial.options <- commandArgs(trailingOnly = FALSE)
file.arg.name <- "--file="
script.name <- sub(file.arg.name, "", initial.options[grep(file.arg.name, initial.options)])
script.basename <- dirname(script.name)
other.name <- file.path(script.basename, "other.R")
print(paste("Sourcing",other.name,"from",script.name))
source(other.name)

other.R:

print("hello")

output:

burner@firefighter:~$ main.R
[1] "Sourcing /home/burner/bin/other.R from /home/burner/bin/main.R"
[1] "hello"
burner@firefighter:~$ bin/main.R
[1] "Sourcing bin/other.R from bin/main.R"
[1] "hello"
burner@firefighter:~$ cd bin
burner@firefighter:~/bin$ main.R
[1] "Sourcing ./other.R from ./main.R"
[1] "hello"

This is what I believe dehmann is looking for.

I couldn't get Suppressingfire's solution to work when 'source'ing from the R console.
I couldn't get hadley's solution to work when using Rscript.

Best of both worlds?

thisFile <- function() {
        cmdArgs <- commandArgs(trailingOnly = FALSE)
        needle <- "--file="
        match <- grep(needle, cmdArgs)
        if (length(match) > 0) {
                # Rscript
                return(normalizePath(sub(needle, "", cmdArgs[match])))
        } else {
                # 'source'd via R console
                return(normalizePath(sys.frames()[[1]]$ofile))
        }
}

frame_files <- lapply(sys.frames(), function(x) x$ofile)
frame_files <- Filter(Negate(is.null), frame_files)
PATH <- dirname(frame_files[[length(frame_files)]])

Don't ask me how it works though, because I've forgotten :/

This works for me

library(rstudioapi)    
rstudioapi::getActiveDocumentContext()$path

The answer of rakensi from https://stackoverflow.com/questions/3452086/getting-path-of-an-r-script is the most correct and really brilliant IMHO. Yet, it's still a hack incorporating a dummy function. I'm quoting it here, in order to have it easier found by others.

>sourceDir <- getSrcDirectory(function(dummy) {dummy})

This gives the directory of the file where the statement was placed (where the dummy function is defined). It can then be used to set the working direcory and use relative paths e.g.

setwd(sourceDir)
source("other.R")

or to create absolute paths

 source(paste(sourceDir, "/other.R", sep=""))

My all in one! (--01/09/2019 updated to deal with RStudio Console)

#' current script file (in full path)
#' @description current script file (in full path)
#' @examples
#' works with Rscript, source() or in RStudio Run selection, RStudio Console
#' @export
ez.csf <- function() {
    # http://stackoverflow.com/a/32016824/2292993
    cmdArgs = commandArgs(trailingOnly = FALSE)
    needle = "--file="
    match = grep(needle, cmdArgs)
    if (length(match) > 0) {
        # Rscript via command line
        return(normalizePath(sub(needle, "", cmdArgs[match])))
    } else {
        ls_vars = ls(sys.frames()[[1]])
        if ("fileName" %in% ls_vars) {
            # Source'd via RStudio
            return(normalizePath(sys.frames()[[1]]$fileName))
        } else {
            if (!is.null(sys.frames()[[1]]$ofile)) {
            # Source'd via R console
            return(normalizePath(sys.frames()[[1]]$ofile))
            } else {
                # RStudio Run Selection
                # http://stackoverflow.com/a/35842176/2292993
                pth = rstudioapi::getActiveDocumentContext()$path
                if (pth!='') {
                    return(normalizePath(pth))
                } else {
                    # RStudio Console
                    tryCatch({
                            pth = rstudioapi::getSourceEditorContext()$path
                            pth = normalizePath(pth)
                        }, error = function(e) {
                            # normalizePath('') issues warning/error
                            pth = ''
                        }
                    )
                    return(pth)
                }
            }
        }
    }
}

A slimmed down variant of Supressingfire's answer:

source_local <- function(fname){
    argv <- commandArgs(trailingOnly = FALSE)
    base_dir <- dirname(substring(argv[grep("--file=", argv)], 8))
    source(paste(base_dir, fname, sep="/"))
}

This works for me. Just greps it out of the command line arguments, strips off the unwanted text, does a dirname and finally gets the full path from that:

args <- commandArgs(trailingOnly = F)  
scriptPath <- normalizePath(dirname(sub("^--file=", "", args[grep("^--file=", args)])))

I've made a package for this, available on CRAN and GitHub, called "this.path". The current version is 0.7.0 published on 2022-04-24, you can find it here:

https://CRAN.R-project.org/package=this.path

https://github.com/ArcadeAntics/this.path

Install it with:

utils::install.packages("this.path")

or

utils::install.packages("https://raw.githubusercontent.com/ArcadeAntics/this.path/main/this.path_0.7.0.tar.gz")

and then use it by:

this.path::this.path()

or

library(this.path)

this.path()

The answer below is my original answer, kept just for reference, though it is quite a bit less functional than the most recent versions available above. Improvements include:

• handling filenames with spaces when running an R script from a shell under Unix-alikes
• handling both uses of running an R script from a shell (-f file and --file=file)
• correctly normalizes the path when using base::source with argument chdir = TRUE
• handling of file URLs with base::source (that is, "file://absolute or relative path" and "file:///absolute path")
• better handling of a connection instead of a character string within base::source
• this.path is compatible with URLs in source, that is:

source("https://host/path/to/file")

if this.path was used within the file, it would return "https://host/path/to/file". This also works for a URL beginning with "http://", "ftp://", and "ftps://". As an example, try:

source("https://raw.githubusercontent.com/ArcadeAntics/this.path/main/tests/this.path_w_URLs.R")

• compatibility with package testthat, particularly testthat::source_file
• introduces function here, similar to here::here, for specifying an absolute file path, relative to the executing script's directory
• on Windows, in Rgui, added support for all languages listed by list.dirs(system.file(package = "translations"), full.names = FALSE, recursive = FALSE)
• saving the normalized path within its appropriate environment the first time this.path is called within a script, making it faster to use subsequent times within the same script and being independent of working directory. This means that setwd will no longer break this.path when using relative paths within base::source or when running R from a shell (as long as setwd is used AFTER the first call to this.path within that script)

Original Answer:

My answer is an improvement upon Jerry T's answer. The issue I found is that they are guessing whether a source call was made by checking if variable ofile is found in the first frame on the stack. This will not work with nested source calls, nor source calls made from a non-global environment. Additionally, the order is wrong. We must look for source call BEFORE checking the shell arguments. Here is my solution:

this.path <- function (verbose = getOption("verbose"))
{
    where <- function(x) {
        if (verbose)
            cat("Source: ", x, "\n", sep = "")
    }


    # loop through functions that lead here from most recent to earliest looking
    #     for an appropriate source call (a call to function base::source or base::sys.source)
    # an appropriate source call is a source call in which
    #     argument 'file' has been evaluated (forced)
    # this means, for example, the following is an inappropriate source call:
    #     source(this.path())
    # the argument 'file' is stored as a promise
    #     containing the expression "this.path()"
    # when the value of 'file' is requested, it assigns the value
    #     returned by evaluating "this.path()" to variable 'file'
    # there are two functions on the calling stack at
    #     this point being 'source' and 'this.path'
    # clearly, you don't want to request the 'file' argument from that source
    #     call because the value of 'file' is under evaluation right now!
    # the trick is to ask if variable ('ofile' for base::source, 'exprs' for base::sys.source)
    #     exists in that function's evaluation environment. this is because that
    #     variable is created AFTER argument 'file' has been forced
    # if that variable does exist, then argument 'file' has been forced and the
    #     source call is deemed appropriate. For base::source, the filename we want
    #     is the variable 'ofile' from that function's evaluation environment. For
    #     base::sys.source, the filename we want is the variable 'file' from that
    #     function's evaluation environment.
    # if that variable does NOT exist, then argument 'file' hasn't been forced and
    #     the source call is deemed inappropriate. The 'for' loop moves to the next
    #     function up the calling stack (if available)
    #
    # unfortunately, there is no way to check the argument 'fileName' has been forced
    #     for 'debugSource' since all the work is done internally in C. Instead,
    #     we have to use a 'tryCatch' statement. When we ask for an object by name
    #     using 'get', R is capable of realizing if a variable is asking for its
    #     own definition (a recursive definition). The exact error is "promise already
    #     under evaluation" which indicates that the promise evaluation is requesting
    #     its own value. So we use the 'tryCatch' to get the argument 'fileName'
    #     from the evaluation environment of 'debugSource', and if it does not raise
    #     an error, then we are safe to return that value. If not, the condition
    #     returns false and the 'for' loop moves to the next function up the calling
    #     stack (if available)


    dbs <- if (.Platform$GUI == "RStudio")
        get("debugSource", "tools:rstudio", inherits = FALSE)
    for (n in seq.int(sys.nframe(), 1L)[-1L]) {
        if (identical(sys.function(n), base::source) &&
            exists("ofile", envir = sys.frame(n), inherits = FALSE)) {
            path <- get("ofile", envir = sys.frame(n), inherits = FALSE)
            if (!is.character(path))
                path <- summary.connection(path)$description
            where("call to function source")
            return(normalizePath(path, mustWork = TRUE))
        }
        else if (identical(sys.function(n), base::sys.source) &&
            exists("exprs", envir = sys.frame(n), inherits = FALSE)) {
            path <- get("file", envir = sys.frame(n), inherits = FALSE)
            where("call to function sys.source")
            return(normalizePath(path, mustWork = TRUE))
        }
        else if (identical(sys.function(n), dbs) &&
            tryCatch({
                path <- get("fileName", envir = sys.frame(n), inherits = FALSE)
                TRUE
            }, error = function(c) FALSE)) {
            where("call to function debugSource in RStudio")
            return(normalizePath(path, mustWork = TRUE))
        }
    }


    # if the for loop is passed, no appropriate
    #     source call was found up the calling stack
    # next, check if the user is running R from a shell
    #     on a Windows OS, the GUI is "RTerm"
    #     on a Unix    OS, the GUI is "X11"


    # if (running R from a shell)
    if (.Platform$OS.type == "windows" && .Platform$GUI == "RTerm" ||  # on Windows
        .Platform$OS.type == "unix"    && .Platform$GUI == "X11") {    # under Unix-alikes


        # get all shell arguments that start with "--file="
        # check the number of shell arguments starting with "--file="
        #     in case more or less than one were supplied


        path <- grep("^--file=", commandArgs(), value = TRUE)
        if (length(path) == 1L) {
            path <- sub("^--file=", "", path)
            where("shell argument 'FILE'")
            return(normalizePath(path, mustWork = TRUE))
        }
        else if (length(path)) {
            stop("'this.path' used in an inappropriate fashion\n",
                "* no appropriate source call was found up the calling stack\n",
                "* R is being run from a shell where formal argument 'FILE' matched by multiple actual arguments")
        }
        else stop("'this.path' used in an inappropriate fashion\n",
            "* no appropriate source call was found up the calling stack\n",
            "* R is being run from a shell where argument 'FILE' is missing")
    }


    # if (running R from RStudio)
    else if (.Platform$GUI == "RStudio") {


        # function ".rs.api.getActiveDocumentContext" from the environment "tools:rstudio"
        #     returns a list of information about the document where your cursor is located
        #
        # function ".rs.api.getSourceEditorContext" from the environment "tools:rstudio"
        #     returns a list of information about the document open in the current tab
        #
        # element 'id' is a character string, an identification for the document
        # element 'path' is a character string, the path of the document


        adc <- get(".rs.api.getActiveDocumentContext",
            "tools:rstudio", inherits = FALSE)()
        if (adc$id != "#console") {
            path <- adc$path
            if (nzchar(path)) {
                where("active document in RStudio")
                return(normalizePath(path, mustWork = TRUE))
            }
            else stop("'this.path' used in an inappropriate fashion\n",
                "* no appropriate source call was found up the calling stack\n",
                "* active document in RStudio does not exist")
        }


        sec <- get(".rs.api.getSourceEditorContext",
            "tools:rstudio", inherits = FALSE)()
        if (!is.null(sec)) {
            path <- sec$path
            if (nzchar(path)) {
                where("source document in RStudio")
                return(normalizePath(path, mustWork = TRUE))
            }
            else stop("'this.path' used in an inappropriate fashion\n",
                "* no appropriate source call was found up the calling stack\n",
                "* source document in RStudio does not exist")
        }
        else stop("'this.path' used in an inappropriate fashion\n",
            "* no appropriate source call was found up the calling stack\n",
            "* R is being run from RStudio with no documents open")
    }


    # if (running R from RGui on Windows)
    else if (.Platform$OS.type == "windows" && .Platform$GUI == "Rgui") {


        # on a Windows OS only, the function "getWindowsHandles" from the base
        # package "utils" returns a list of external pointers containing the windows
        # handles. The thing of interest are the names of this list, these should
        # be the names of the windows belonging to the current R process. Since
        # RGui can have files besides R scripts open (such as images), a regular
        # expression is used to subset only windows handles with names that exactly
        # match the string "R Console" or end with " - R Editor". I highly suggest
        # that you NEVER end a document's filename with " - R Editor". From there,
        # similar checks are done as in the above section for 'RStudio'


        wh <- names(utils::getWindowsHandles(pattern = "^R Console$| - R Editor$",
            minimized = TRUE))


        if (!length(wh))
            stop("no windows in RGui; should never happen, please report!")


        path <- wh[1L]
        if (path != "R Console") {
            path <- sub(" - R Editor$", "", path)
            if (path != "Untitled") {
                where("active document in RGui")
                return(normalizePath(path, mustWork = TRUE))
            }
            else stop("'this.path' used in an inappropriate fashion\n",
                "* no appropriate source call was found up the calling stack\n",
                "* active document in RGui does not exist")
        }


        path <- wh[2L]
        if (!is.na(path)) {
            path <- sub(" - R Editor$", "", path)
            if (path != "Untitled") {
                where("source document in RGui")
                return(normalizePath(path, mustWork = TRUE))
            }
            else stop("'this.path' used in an inappropriate fashion\n",
                "* no appropriate source call was found up the calling stack\n",
                "* source document in RGui does not exist")
        }
        else stop("'this.path' used in an inappropriate fashion\n",
            "* no appropriate source call was found up the calling stack\n",
            "* R is being run from RGui with no documents open")
    }


    # if (running R from RGui on macOS)
    else if (.Platform$OS.type == "unix" && .Platform$GUI == "AQUA") {
        stop("'this.path' used in an inappropriate fashion\n",
            "* no appropriate source call was found up the calling stack\n",
            "* R is being run from AQUA which requires a source call on the calling stack")
    }


    # otherwise
    else stop("'this.path' used in an inappropriate fashion\n",
        "* no appropriate source call was found up the calling stack\n",
        "* R is being run in an unrecognized manner")
}

I have wrapped up and extended the answers to this question into a new function thisfile() in rprojroot. Also works for knitting with knitr.

I tried almost everything from this question, Getting path of an R script, Get the path of current script, Find location of current .R file and R command for setting working directory to source file location in Rstudio, but at the end found myself manually browsing the CRAN table and found

scriptName library

which provides current_filename() function, which returns proper full path of the script when sourcing in RStudio and also when invoking via R or RScript executable.

I liked steamer25's solution as it seems the most robust for my purposes. However, when debugging in RStudio (in windows), the path would not get set properly. The reason being that if a breakpoint is set in RStudio, sourcing the file uses an alternate "debug source" command which sets the script path a little differently. Here is the final version which I am currently using which accounts for this alternate behavior within RStudio when debugging:

# @return full path to this script
get_script_path <- function() {
    cmdArgs = commandArgs(trailingOnly = FALSE)
    needle = "--file="
    match = grep(needle, cmdArgs)
    if (length(match) > 0) {
        # Rscript
        return(normalizePath(sub(needle, "", cmdArgs[match])))
    } else {
        ls_vars = ls(sys.frames()[[1]])
        if ("fileName" %in% ls_vars) {
            # Source'd via RStudio
            return(normalizePath(sys.frames()[[1]]$fileName)) 
        } else {
            # Source'd via R console
            return(normalizePath(sys.frames()[[1]]$ofile))
        }
    }
}

I also had this problem, and none of the above solutions worked for me. Maybe with the source or things like that, but it was not clear enough.

I found this, for me elegant, solution:

paste0(gsub("\\", "/", fileSnapshot()$path, fixed=TRUE),"/")

The important thing in that is the fileSnapshot() that gives you a lot of information about a file. It returns a list of 8 elements. When you pick path as the list element, the path is returned with \\ as separator, so the rest of the code is just to change that.

I hope this helps.

I just worked this out myself. To ensure portability of your script always begin it with:

wd <- setwd(".")
setwd(wd)

It works because "." translates like the Unix command $PWD. Assigning this string to a character object allows you to then insert that character object into setwd() and Presto your code will always run with its current directory as the working directory, no matter whose machine it is on or where in the file structure it is located. (Extra bonus: The wd object can be used with file.path() (ie. file.path(wd, "output_directory") to allow for the creation of a standard output directory regardless of the file path leading to your named directory. This does require you to make the new directory before referencing it this way but that, too, can be aided with the wd object.

Alternately, the following code performs the exact same thing:

wd <- getwd()
setwd(wd)

or, if you don't need the file path in an object you can simply:

setwd(".")

You can wrap the r script in a bash script and retrieve the script's path as a bash variable like so:

#!/bin/bash
     # [environment variables can be set here]
     path_to_script=$(dirname $0)
     
     R --slave<<EOF
        source("$path_to_script/other.R")
     
     EOF

I like this approach:

this.file <- sys.frame(tail(grep('source',sys.calls()),n=1))$ofile
this.dir <- dirname(this.file)

Note that the getopt package provides the get_Rscript_filename function, which just uses the same solution presented here, but is already written for you in a standard R module, so you don't have to copy and paste the "get script path" function into every script you write.

If rather than the script, foo.R, knowing its path location, if you can change your code to always reference all source'd paths from a common root then these may be a great help:

• https://github.com/r-lib/rprojroot or https://rprojroot.r-lib.org/
• https://here.r-lib.org/

Given

• /app/deeply/nested/foo.R
• /app/other.R

This will work

#!/usr/bin/env Rscript
library(here)
source(here("other.R"))

See https://rprojroot.r-lib.org/ for how to define project roots.

See findSourceTraceback() of the R.utils package, which

> Finds all 'srcfile' objects generated by source() in all call frames. > This makes it possible to find out which files are currently scripted by source().

I had issues with the implementations above as my script is operated from a symlinked directory, or at least that's why I think the above solutions didn't work for me. Along the lines of @ennuikiller's answer, I wrapped my Rscript in bash. I set the path variable using pwd -P, which resolves symlinked directory structures. Then pass the path into the Rscript.

Bash.sh

#!/bin/bash

# set path variable
path=`pwd -P`

#Run Rscript with path argument
Rscript foo.R $path

foo.R

args <- commandArgs(trailingOnly=TRUE)
setwd(args[1])
source(other.R)

I would use a variant of @steamer25 's approach. The point is that I prefer to obtain the last sourced script even when my session was started through Rscript. The following snippet, when included on a file, will provided a variable thisScript containing the normalized path of the script. I confess the (ab)use of source'ing, so sometimes I invoke Rscript and the script provided in the --file argument sources another script that sources another one... Someday I will invest in making my messy code turns into a package.

thisScript <- (function() {
  lastScriptSourced <- tail(unlist(lapply(sys.frames(), function(env) env$ofile)), 1)

  if (is.null(lastScriptSourced)) {
    # No script sourced, checking invocation through Rscript
    cmdArgs <- commandArgs(trailingOnly = FALSE)
    needle <- "--file="
    match <- grep(needle, cmdArgs)
    if (length(match) > 0) {
      return(normalizePath(sub(needle, "", cmdArgs[match]), winslash=.Platform$file.sep, mustWork=TRUE))
    }
  } else {
    # 'source'd via R console
    return(normalizePath(lastScriptSourced, winslash=.Platform$file.sep, mustWork=TRUE))
  }
})()

99% of the cases you might simply use:

sys.calls()[[1]] [[2]]

It will not work for crazy calls where the script is not the first argument, i.e., source(some args, file="myscript"). Use @hadley's in these fancy cases.

Steamer25's approach works, but only if there is no whitespace in the path. On macOS at least the cmdArgs[match] returns something like /base/some~+~dir~+~with~+~whitespace/ for /base/some\ dir\ with\ whitespace/.

I worked around this by replacing the "+" with a simple whitespace before returning it.

thisFile <- function() {
  cmdArgs <- commandArgs(trailingOnly = FALSE)
  needle <- "--file="
  match <- grep(needle, cmdArgs)
  if (length(match) > 0) {
    # Rscript
    path <- cmdArgs[match]
    path <- gsub("\\~\\+\\~", " ", path)
    return(normalizePath(sub(needle, "", path)))
  } else {
    # 'source'd via R console
    return(normalizePath(sys.frames()[[1]]$ofile))
  }
}

Obviously you can still extend the else block like aprstar did.

By looking at the call stack we can get the filepath of each script being executed, the two most useful will probably either be the currently executing script, or the first script to be sourced (entry).

script.dir.executing = (function() return( if(length(sys.parents())==1) getwd() else dirname( Filter(is.character,lapply(rev(sys.frames()),function(x) x$ofile))[[1]] ) ))()

script.dir.entry = (function() return( if(length(sys.parents())==1) getwd() else dirname(sys.frame(1)$ofile) ))()

#!/usr/bin/env Rscript
print("Hello")

# sad workaround but works :(
programDir <- dirname(sys.frame(1)$ofile)
source(paste(programDir,"other.R",sep='/'))
source(paste(programDir,"other-than-other.R",sep='/'))

Amazing there is no '$0' type structure in R! You can do it with a system() call to a bash script written in R:

write.table(c("readlink -e $0"), file="scriptpath.sh",col=F, row=F, quote=F)
thisscript <- system("sh scriptpath.sh", intern = TRUE)

Then just split out the scriptpath.sh name for other.R

splitstr <- rev(strsplit(thisscript, "\\/")[[1]])
otherscript <- paste0(paste(rev(splitstr[2:length(splitstr)]),collapse="/"),"/other.R")

I work in an HPC cluster environment. I develop my code in a different location from where I do my production runs. During development, I'm usually calling R interactively from the command line (not using RStudio). There is lots of source("foo.R") going on.

During production runs, I usually write a bash script that tries different parameters and runs each set of parameters in a separate directory. The bash script utilizes the workload manager (i.e. SLURM). In this environment, it is trivial to set an environmental variable. With this in mind, the below solution works best for me.

other.R

my_message <- function(){
return("R is awkward")
}

foo.R

srcpath = Sys.getenv("R_SRC")
# Check if runnning w/o setting R_SRC - presumably done in directory of development, i.e. /path/to/R/code
if(srcpath == ""){
    srcpath="./"
}
source(sprintf("%s/other.R", srcpath))
string = my_message()
print(string)

If running this from the R interactive shell and within /path/to/R/code, simply do

> source("foo.R")

If running not from the interactive shell and not running from /path/to/R/code, set the environmental variable R_SRC first, then call Rscript

$ export R_SRC=/path/to/R/code/
$ Rscript /path/to/R/code/foo.R

The solution arrived in 2016. Many thanks to the author, Sahil Seth!

The package funr on CRAN and github provides the function sys.script() which gets the full path to the current script. It even references a similar SO post.

Thus, the solution is:

myscript.R:

#!/usr/bin/env Rscript
f  <-  funr::sys.script()
show(f)

and then executing the command:

user@somewhere:/home$ Rscript myscript.R

at the command line will output, e.g.:

"/home/path/to/myscript.R"

to the console.

Just to build on the above answers, as a safety check, you could add a wrapper that asks the user to find the file if (for whatever reason) sys.frame(1) fails (as it might if interactive() == TRUE), or the sourced script is not where the main script expects it to be.

fun_path = tryCatch(expr = 
                      {file.path(dirname(sys.frame(1)$ofile), "foo.R")},
                    error = function(e){'foo.R'}
                    )
if(!file.exists(fun_path))
{
  msg = 'Please select "foo.R"'
  # ask user to find data
  if(Sys.info()[['sysname']] == 'Windows'){#choose.files is only available on Windows
    message('\n\n',msg,'\n\n')
    Sys.sleep(0.5)#goes too fast for the user to see the message on some computers
    fun_path  = choose.files(
      default = file.path(gsub('\\\\', '/', Sys.getenv('USERPROFILE')),#user
                          'Documents'),
      caption = msg
    )
  }else{
    message('\n\n',msg,'\n\n')
    Sys.sleep(0.5)#goes too fast for the user to see the message on some computers
    fun_path = file.choose(new=F)
  }
}
#source the function
source(file = fun_path, 
       encoding = 'UTF-8')