R Markdown documents (with the filename extension .Rmd) are
re-compiled using knitr or rmarkdown when necessary (source files
are newer than output files), and the HTML pages will be automatically
refreshed in the web browser accordingly.
jekyll(
  dir = ".",
  input = c(".", "_source", "_posts"),
  output = c(".", "_posts", "_posts"),
  script = c("Makefile", "build.R"),
  serve = TRUE,
  command = "jekyll build",
  ...
)rmdv2(dir = ".", script = c("Makefile", "build.R"), in_session = FALSE, ...)
rmdv1(dir = ".", script = c("Makefile", "build.R"), in_session = FALSE, ...)
the root directory of the website
the input directories that contain R Markdown documents (the
directories must be relative instead of absolute; same for output
directories)
the output directories corresponding to input; for an
input document foo.Rmd under the directory input[i], its
output document foo.md (or foo.html) is generated under
output[i] if the output document is older than the input document
a Makefile (see make), or (if Makefile not found)
the name of an R script to re-build R Markdown documents, which will be
executed via command line of the form Rscript build.R arg1 arg2
where build.R is the script specified by this argument, arg1
is the input filename, and arg2 is the output filename; inside the R
script, you can use commandArgs(TRUE) to capture
c(arg1, arg2), e.g. knitr::knit(commandArgs(TRUE)[1],
commandArgs(TRUE)[2]); if this R script is not found, either, internal
compiling methods will be used, which are basically
knit(), knit2html(), or
render()
whether to serve the website; if FALSE, the R Markdown
documents and the website will be compiled but not served
a command to build the Jekyll website; by default, it is
jekyll build, and you can use alternative commands, such as
bundle exec jekyll build
Server configurations passed to server_config().
whether to render the R Markdown documents in the current R
session (TRUE) or in a separate new R session (FALSE); if the
former, the argument script can be a function with two arguments,
the filenames of the source document and the output document, respectively;
an internal function (basically rmarkdown::render() or
knitr::knit2html()) will be used if the script argument is
not a function and in_session = TRUE
The function jekyll() sets up a web server to serve a Jekyll-based
website. A connection is established between R and the HTML pages through
WebSockets so that R can notify the HTML pages to refresh themselves if any R
Markdown documents have been re-compiled.
The functions rmdv1() and rmdv2() are similar to
  jekyll(), and the only difference is the way to compile R Markdown
  documents: rmdv1() uses the markdown package (a.k.a R Markdown
  v1) via knit2html(), and rmdv2() calls
  render() in the rmarkdown package (a.k.a R
  Markdown v2).
R Markdown v1: https://cran.r-project.org/package=markdown. R
  Markdown v2: https://rmarkdown.rstudio.com. For Jekyll, see
  https://jekyllrb.com. The GitHub repository
  https://github.com/yihui/blogdown-jekyll is an example of serving Jekyll
  websites with servr::jekyll().
The blogdown package (based on Hugo and R Markdown v2) is a better alternative to Jekyll: https://github.com/rstudio/blogdown/. I strongly recommend you to try it.
if (interactive()) servr::rmdv1()  # serve the current dir with R Markdown v1
if (interactive()) servr::rmdv2()  # or R Markdown v2
# built-in examples
servr::serve_example("rmd", servr::rmdv1)
servr::serve_example("rmd", servr::rmdv2)
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