What is the difference between list.files and dir?

Question

I tried using both list.files and dir; both commands returned the same output. What is the key difference between these two commands and what's their usage context?

Answer 1

They are identical in the sense that they take the same arguments, these arguments have identical defaults, and they use the same .Internal function to execute.

As pointed out by @RichScriven in the comments, a compact and accurate test that they are the same can be run using identical:

identical(list.files, dir)
[1] TRUE

We can also take a look at their source code.

dir
function (path = ".", pattern = NULL, all.files = FALSE, full.names = FALSE, 
    recursive = FALSE, ignore.case = FALSE, include.dirs = FALSE, 
    no.. = FALSE) 
.Internal(list.files(path, pattern, all.files, full.names, recursive, 
    ignore.case, include.dirs, no..))
<bytecode: 0x000000000fe1c388>
<environment: namespace:base>

and

list.files
function (path = ".", pattern = NULL, all.files = FALSE, full.names = FALSE, 
    recursive = FALSE, ignore.case = FALSE, include.dirs = FALSE, 
    no.. = FALSE) 
.Internal(list.files(path, pattern, all.files, full.names, recursive, 
    ignore.case, include.dirs, no..))
<bytecode: 0x0000000008811280>
<environment: namespace:base>

Note that

.Internal(list.files(path, pattern, all.files, full.names, recursive, 
        ignore.case, include.dirs, no..))

is executed in both functions.