Package 'servr'

Generate Basic authentication strings

Description

Combine usernames with passwords with colons, and generate base64-encoded strings to be used for user authentication.

Usage

auth_basic(user, password)

Arguments

user	A vector of usernames.
password	A vector of passwords.

Value

A character vector of encoded credentials.

Examples

servr::auth_basic("foo", "B@R")

---

Reopen the last browsed page

Description

If you have launched a page in the browser via servr but closed it later, you may call this function to reopen it.

Usage

browse_last(open = TRUE)

Arguments

open	Whether to reopen the lastly browsed page. If FALSE, the URL of the previously browsed page will be returned.

Examples

servr::browse_last()

---

Create a server

Description

Create a server with a custom handler to handle the HTTP request.

Usage

create_server(..., handler, ws_open = function(ws) NULL)

Arguments

...	Arguments to be passed to server_config().
handler	A function that takes the HTTP request and returns a response.
ws_open	A function to be called back when a WebSocket connection is established (see httpuv::startServer()).

Examples

# always return 'Success:' followed by the requested path
s = servr::create_server(handler = function(req) {
    list(status = 200L, body = paste("Success:", req$PATH_INFO))
})
s$url

browseURL(paste0(s$url, "/hello"))
browseURL(paste0(s$url, "/world"))

s$stop_server()

---

Utilities for daemonized servers

Description

daemon_list() returns IDs of servers, which can be used to stop the daemonized servers.

Usage

daemon_stop(which = daemon_list())

daemon_list()

Arguments

which

A integer vector of the server IDs; by default, IDs of all existing servers in the current R session obtained from daemon_list(), i.e., all daemon servers will be stopped by default.

Value

The function daemon_list() returns a list of existing server IDs, and daemon_stop() returns an invisible NULL.

---

Serve static files under a directory

Description

If there is an ‘index.html’ under this directory, it will be displayed; otherwise the list of files is displayed, with links on their names. After we run this function, we can go to ‘⁠http://localhost:port⁠’ to browse the web pages either created from R or read from HTML files.

Usage

httd(dir = ".", ..., response = NULL)

httr(dir = ".", ...)

httw(
  dir = ".",
  watch = ".",
  pattern = NULL,
  all_files = FALSE,
  filter = NULL,
  handler = NULL,
  ...
)

Arguments

dir	The root directory to serve.
...	Server configurations passed to server_config().
response	A function of the form function(path, res, ...) that takes a file path and server response as input, and return a new response. This can be useful for post-processing the response (for experts only).
watch	A directory under which httw() is to watch for changes. If it is a relative path, it is relative to the dir argument.
pattern	A regular expression passed to list.files() to determine the files to watch.
all_files	Whether to watch all files including the hidden files.
filter	A function to filter the file paths returned from list.files() (e.g., you can exclude certain files from the watch list).
handler	A function to be called every time any files are changed or added under the directory; its argument is a character vector of the filenames of the files modified or added.

Details

httd() is a static file server by default (its response argument can turn it into a dynamic file server).

httr() is based on httd() with a custom response function that executes R files via xfun::record(), so that you will see the output of an R script as an HTML page. The page will be automatically updated when the R script is modified and saved.

httw() is similar to httd() but watches for changes under the directory: if an HTML file is being viewed in the browser, and any files are modified under the directory, the HTML page will be automatically refreshed.

References

https://github.com/yihui/servr

Examples

servr::httd()

---

Serve R Markdown based websites

Description

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.

Usage

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, ...)

Arguments

dir	the root directory of the website
input	the input directories that contain R Markdown documents (the directories must be relative instead of absolute; same for output directories)
output	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
script	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()
serve	whether to serve the website; if FALSE, the R Markdown documents and the website will be compiled but not served
command	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().
in_session	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

Details

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).

Note

Apparently jekyll() and rmdv1() require the knitr package, and rmdv2() requires rmarkdown. You have to install them before calling the server functions here.

All R Markdown documents are compiled in separate R sessions by default. If you have any R Markdown documents that should not be compiled as standalone documents (e.g. child documents), you can use different filename extensions, such as ‘.Rmarkdown’.

The baseurl argument does not work in jekyll(), and the base URL setting will be read from ‘_config.yml’ (the ‘⁠baseurl⁠’ field) of the website if present. You should not pass baseurl to the function jekyll() directly.

For the sake of reproducibility, you are recommended to compile each source document in a separate R session (i.e., use the default in_session = FALSE) to make sure they can compile on their own, otherwise the current workspace may affect the evaluation of the code chunks in these source documents. Sometimes it might be useful to compile a document in the current R session. For example, if reading data is time-consuming and it is not convenient to cache it (using the knitr chunk option cache = TRUE), you may read the data once, temporarily turn off the evaluation of that code chunk, and keep on working on the rest of code chunks so that data will not be read over and over again.

References

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().

See Also

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.

Examples

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)

---

Serve files under a directory based on GNU Make

Description

You can define how and when to rebuild files (such as R Markdown files) using Make rules, e.g. a rule _posts/%.md: _source/%.Rmd with a command to build ‘.Rmd’ to ‘.md’ will be executed if and only if ‘foo.Rmd’ is newer than ‘foo.md’. The exit status of the command make -q will decide whether to rebuild files: rebuilding occurs only when the exit code is not 0. When an HTML file has been rebuilt, it will be automatically refreshed in the web browser.

Usage

make(dir = ".", ...)

Arguments

dir	The root directory to serve.
...	Server configurations passed to server_config().

Note

You must have installed GNU Make to use this function. This is normally not a problem for Linux and OS X users (it should be available by default). For Windows users, you can either install GNU Make, or just install Rtools, which also contains GNU Make.

Examples

# some built-in examples (if you are not familiar with make, you can take a
# look at the Makefile of each example)
servr::serve_example("make1", servr::make)
servr::serve_example("make2", servr::make)

---

Find a random available TCP port

Description

Test a series of random TCP ports from 3000 to 8000 (excluding a few that are considered unsafe by Chrome) and return the first available one. A web server can be later started on this port.

Usage

random_port(
  port = 4321L,
  host = getOption("servr.host", "127.0.0.1"),
  n = 20,
  exclude = NULL
)

Arguments

port	The preferred port(s).
host	A string that is a valid IPv4 address that is owned by this server, or "0.0.0.0" to listen on all IP addresses.
n	The maximum number of random ports to be tested.
exclude	A vector of port numbers not to be considered.

Value

A port number, or an error if no ports are available.

---

Create a redirect response

Description

Create a response to redirect to a destination.

Usage

redirect(dest, status = 301L)

Arguments

dest	A destination path.
status	The status code (usually 301 or 302).

Examples

servr::redirect("https://www.r-project.org")

---

A convenience function to serve examples in this package

Description

Use server functions to serve built-in examples of this package.

Usage

serve_example(name, FUN, ..., run = interactive())

Arguments

name	the directory name of the example under the directory system.file('examples', package = 'servr')
FUN	a server function that takes the example path as its first argument, e.g. httd, or rmdv1
...	other arguments passed to FUN
run	whether to run the example (this is mainly for R CMD check purposes: the examples will not be really served when the R session is not interactive, so they will not block R CMD check)

Value

NULL if run = FALSE, otherwise the value returned from FUN().

Examples

# R Markdown v1 or v2
servr::serve_example("rmd", servr::rmdv1)
servr::serve_example("rmd", servr::rmdv2)

# GNU Make
servr::serve_example("make1", servr::make)
servr::serve_example("make2", servr::make)

---

Server configurations

Description

The server functions in this package are configured through this function.

Usage

server_config(
  dir = ".",
  host = getOption("servr.host", "127.0.0.1"),
  port,
  browser,
  daemon,
  interval = getOption("servr.interval", 1),
  baseurl = "",
  initpath = "",
  hosturl = identity,
  auth = getOption("servr.auth"),
  verbose = TRUE
)

Arguments

dir	The root directory to serve.
host	A string that is a valid IPv4 address that is owned by this server, or "0.0.0.0" to listen on all IP addresses.
port	The TCP port number. If it is not explicitly set, the default value will be looked up in this order: First, the command line argument of the form -pNNNN (N is a digit from 0 to 9). If it was passed to R when R was started, NNNN will be used as the port number. Second, the environment variable R_SERVR_PORT. Third, the global option servr.port (e.g., options(servr.port = 4322)). If none of these command-line arguments, variables, or options were set, the default port will be 4321. If this port is not available, a random available port will be used.
browser	Whether to launch the default web browser. By default, it is TRUE if the R session is interactive(), or when a command line argument -b was passed to R (see commandArgs()). N.B. the RStudio viewer is used as the web browser if available.
daemon	Whether to launch a daemonized server (the server does not block the current R session) or a blocking server. By default, it is the global option getOption('servr.daemon') (e.g., you can set options(servr.daemon = TRUE)); if this option was not set, daemon = TRUE if a command line argument -d was passed to R (through Rscript), or the server is running in an interactive R session. Note, however, that even though the server does not block the current R session, it is running in the same single-threaded process. Therefore, if a request is made from this same session, the client and server will block each other. If this is your use case, a better solution is to use a package such as callr to run a servr in a separate process, e.g, rx <- callr::r_bg(function() servr::httd(daemon = FALSE)); do_stuff(); rx$kill() (the do_stuff() function may want to wait a couple of seconds before making requests, to allow the server time to start).
interval	The time interval used to check if an HTML page needs to be rebuilt (by default, it is checked every second).
baseurl	The base URL (the full URL will be http://host:port/baseurl).
initpath	The initial path in the URL (e.g. you can open a specific HTML file initially).
hosturl	A function that takes the host address and returns a character string to be used in the URL, e.g., function(host) { if (host == '127.0.0.1') 'localhost' else host} to convert 127.0.0.1 to localhost in the URL.
auth	A list of the form list(scheme, creds) containing the authentication scheme and credentials. See https://developer.mozilla.org/en-US/docs/Web/HTTP/Authentication for more info. Please note that this argument is by no means intended for serious HTTP applications and there is no warranty on security. You should use other dedicated software packages or services if security is important. You have been warned.
verbose	Whether to print messages when launching the server.

Value

A list of configuration information of the form list(host, port, start_server = function(app) {}, ...).

Examples

# an example of authentication
servr::httd(auth = list(scheme = "Basic", creds = servr::auth_basic("john", "pa$s!")))

---

Serve R Markdown/HTML package vignettes

Description

Serve package vignettes under the ‘vignettes/’ directory. Because the HTML output files should not be included in the source package, this function renders R Markdown/HTML vignettes, displays them in the web browser, and deletes the HTML output files. You will see the HTML output when you click the links on the ‘.Rmd’ or ‘.Rhtml’ files (unlike the static HTTP server, the compiled output instead of the source document is displayed).

Usage

vign(dir = ".", ...)

Arguments

dir	The root directory to serve.
...	Server configurations passed to server_config().

Details

When developing R packages, you may want to preview your vignettes once in a while. You can certainly click the button in RStudio to do it, but that requires you to install the package and rebuild the vignettes. With this function, your vignette will be rebuilt automatically when you update the source document. Moreover, because the compilation takes place in the current R session, you can take advantage of devtools::load_all() (which has a keyboard shortcut in the RStudio IDE) to reload your package and see the updated vignette in the web browser.

Note

You are supposed to call this function from the root directory of your package. If that is not the case, you should provide the correct path to the ‘vignettes/’ directory of your package to the dir argument.

---