Convert markdown italics and boldface to latex - windows

Question

I want to be able to convert markdown italics and boldface to latex versions on the fly (i.e., give a text string(s) return a text string(s)). I thought easy. Wrong! (Which it still may be). See the sill buisness and error I tried at the bottom.
What I have (note the starting asterisk that's been escaped as in markdown):
x <- "\\*note: I *like* chocolate **milk** too ***much***!"
What I would like:
"*note: I \\emph{like} chocolate \\textbf{milk} too \\textbf{\\emph{much}}!"
I'm not attached to regex but would prefer a base solution (though not essential).
Silly business:
helper <- function(ins, outs, x) {
gsub(paste0(ins[1], ".+?", ins[2]), paste0(outs[1], ".+?", outs[2]), x)
}
helper(rep("***", 2), c("\\textbf{\\emph{", "}}"), x)
Error in gsub(paste0(ins[1], ".+?", ins[2]), paste0(outs[1], ".+?", outs[2]), :
invalid regular expression '***.+?***', reason 'Invalid use of repetition operators'
I have this toy that Ananda Mahto helped me make if it's helpful. You could access it from reports via wheresPandoc <- reports:::wheresPandoc
EDIT Per Ben's comments I tried:
action <- paste0(" echo ", x, " | ", wheresPandoc(), " -t latex ")
system(action)
*note: I *like* chocolate **milk** too ***much***! | C:\PROGRA~2\Pandoc\bin\pandoc.exe -t latex
EDIT2 Per Dason's comments I tried:
out <- paste("echo", shQuote(x), "|", wheresPandoc(), " -t latex"); system(out)
system(out, intern = T)
> system(out, intern = T)
\*note: I *like* chocolate **milk** too ***much***! | C:\PROGRA~2\Pandoc\bin\pandoc.exe -t latex

Answer 1

The lack of pipes on Windows made this tricky, but you can get around it using input to provide the stdin:
> x = system("pandoc -t latex", intern=TRUE, input="\\*note: I *like* chocolate **milk** too ***much***!")
> x
[1] "*note: I \\emph{like} chocolate \\textbf{milk} too \\textbf{\\emph{much}}!"

Answer 2

Noting I am working on windows and from ?system
This means that redirection, pipes, DOS internal commands, ... cannot be used
and the note from ?system2
Note
system2 is a more portable and flexible interface than system,
introduced in R 2.12.0. It allows redirection of output without
needing to invoke a shell on Windows, a portable way to set
environment variables for the execution of command, and finer control
over the redirection of stdout and stderr. Conversely, system (and
shell on Windows) allows the invocation of arbitrary command lines.
Using system2
system2('pandoc', '-t latex', input = '**em**', stdout = TRUE)