Middleware that calls a CGI script

You can use it as an unconditional middleware in app$use(), as a handler on app$get(), app$post(), etc., or you can call it from a handler. See examples below.

Usage

mw_cgi(command, args = character(), timeout = as.difftime(Inf, units = "secs"))

Arguments

command

External command to run.

args

Arguments to pass to the external command.

timeout

Timeout for the external command. If the command does not terminate in time, the web server kills it and returns an 500 response.

Value

A function with signature

function(req, res, env = character())

See RFC 3875 for details on the CGI protocol.

The request body (if any) is passed to the external command as standard intput. mw_cgi() sets CONTENT_LENGTH, CONTENT_TYPE, GATEWAY_INTERFACE, PATH_INFO, QUERY_STRING, REMOTE_ADDR, REMOTE_HOST, REMOTE_USER, REQUEST_METHOD, SERVER_NAME, SERVER_PORT, SERVER_PROTOCOL, SERVER_SOFTEWARE.

It does not currently set the AUTH_TYPE, PATH_TRANSLATED, REMOTE_IDENT, SCRIPT_NAME environment variables.

The standard output of the external command is used to set the response status code, the response headers and the response body. Example output from git's CGI:

Status: 200 OK
Expires: Fri, 01 Jan 1980 00:00:00 GMT
Pragma: no-cache
Cache-Control: no-cache, max-age=0, must-revalidate
Content-Type: application/x-git-upload-pack-advertisement

000eversion 2
0015agent=git/2.42.0
0013ls-refs=unborn
0020fetch=shallow wait-for-done
0012server-option
0017object-format=sha1
0010object-info
0000

See also

Other middleware: mw_cookie_parser(), mw_etag(), mw_json(), mw_log(), mw_multipart(), mw_range_parser(), mw_raw(), mw_static(), mw_text(), mw_urlencoded()

Examples

app <- new_app()
app$use(mw_cgi("echo", "Status: 200\n\nHello"))
app
#> <webfakes_app>
#> routes:
#>   use *
#> fields and methods:
#>   all(path, ...)         # add route for *all* HTTP methods
#>   delete(path, ...)      # add route for DELETE
#>   engine(ext, engine)    # add template engine for file extension
#>   head(path, ...)        # add route for HEAD
#>   listen(port)           # start web app on port
#>   patch(path, ...)       # add route for PATCH
#>   post(path, ...)        # add route for POST
#>   put(path, ...)         # add route for PUT
#>   use(...)               # add middleware
#>   locals                 # app-wide shared data
#> # see ?webfakes_app for all methods

app2 <- new_app()
app2$get("/greet", mw_cgi("echo", "Status: 200\n\nHello"))
app2
#> <webfakes_app>
#> routes:
#>   get /greet
#> fields and methods:
#>   all(path, ...)         # add route for *all* HTTP methods
#>   delete(path, ...)      # add route for DELETE
#>   engine(ext, engine)    # add template engine for file extension
#>   head(path, ...)        # add route for HEAD
#>   listen(port)           # start web app on port
#>   patch(path, ...)       # add route for PATCH
#>   post(path, ...)        # add route for POST
#>   put(path, ...)         # add route for PUT
#>   use(...)               # add middleware
#>   locals                 # app-wide shared data
#> # see ?webfakes_app for all methods

# Using `mw_cgi()` in a handler, you can pass extra environment variables
app3 <- new_app()
cgi <- mw_cgi("echo", "Status: 200\n\nHello")
app2$get("/greet", function(req, res) {
  cgi(req, res, env = c("EXTRA_VAR" = "EXTRA_VALUE"))
})
app3
#> <webfakes_app>
#> routes:
#> fields and methods:
#>   all(path, ...)         # add route for *all* HTTP methods
#>   delete(path, ...)      # add route for DELETE
#>   engine(ext, engine)    # add template engine for file extension
#>   head(path, ...)        # add route for HEAD
#>   listen(port)           # start web app on port
#>   patch(path, ...)       # add route for PATCH
#>   post(path, ...)        # add route for POST
#>   put(path, ...)         # add route for PUT
#>   use(...)               # add middleware
#>   locals                 # app-wide shared data
#> # see ?webfakes_app for all methods