Get object names from a .R file

Question

I can get obj_name list from the environment, but how to get obj_name from a .r file?

I tried ls but is only get obj_name from the environment, but I need get from R file, eg:

# filename test.R
func_1=function(){...}
func_2=function(){...}
func_3=function(){...}
c_1=R6Class()
#page end

I want to get test.R's obj list name. Like this:

"func_1","func_2","func_3","c_1"

Good question, you can `source` `.R` file to a new environment and get object names from there - https://stackoverflow.com/questions/39620669/source-script-to-separate-environment-in-r-not-the-global-environment — pogibas, Dec 09 '19 at 08:46
@PoGibas I guess OP wants to retrieve the objects without sourcing the file — ThomasIsCoding, Dec 09 '19 at 08:57

Roland · Answer 1 · 2019-12-09T09:12:25.320

4

Sounds like an xy-problem. Anyway, you can parse the file and extract the first arguments of top-level calls to <- and =:

na.omit(
  sapply(
    as.list(
      parse(text = 
      "# filename test.R
       func_1=function(){...}
       func_2=function(){...}
       func_3=function(){...}
       c_1=R6Class()
       #page end")), 
    function(x) if (as.character(x[[1]]) %in% c("<-", "=")) as.character(x[[2]]) else NA))
#[1] "func_1" "func_2" "func_3" "c_1"

I'm assuming you don't use assign or more exotic forms of assignment. If you need assignments nested in other functions (such as if or for), you'll need to write a recursive function that crawls the parse tree.

edited Dec 09 '19 at 09:12

answered Dec 09 '19 at 09:04

Roland

127,288
10
191
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Maybe the assignment `->` can be taken into account as well? – ThomasIsCoding Dec 09 '19 at 09:06
@ThomasIsCoding You'll be amazed by what `as.list(parse(text = "3 -> a"))` returns. – Roland Dec 09 '19 at 09:07

score 2 · Accepted Answer · answered Dec 09 '19 at 09:49

2

thanks for @PoGibas's solution. that's what i want

my_env=new.env()
source("myfile.R",local=my_env)
ls(my_env)

answered Dec 09 '19 at 09:49

SummersKing

301
1
11

Get object names from a .R file

2 Answers2