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rmon

R’s equivalent of nodemon. Designed to make development easier by automatically reloading your R scripts and applications or executing arbitrary R expressions when files change.

can be used to:

  • auto-reload arbitrary R scripts
  • execute custom R expressions on file changes
  • auto-reload apps & apis:
    • shiny
    • ambiorix
    • plumber

rmon will monitor your source files for any changes and automatically restart/rerun your server or execute your custom R code. this allows you to focus on coding without manually restarting your server every time you make a change.

just like nodemon, rmon is perfect for development.

installation

to install the package from CRAN use:

install the dev version from GitHub:

remotes::install_github(repo = "kennedymwavu/rmon")

usage

monitoring R scripts 

rmon::monitor(
  dir = ".",
  file = "app.R"
)

executing R expressions 

rmon::monitor(dir = ".", expr = {
  cat('my custom expression at:', as.character(Sys.time()), '\n')
  # ... rest of your R code here
})

parameters:

  • dir: character vector. directory to monitor for changes
  • file: file to rerun when changes are detected (mutually exclusive with expr)
  • expr: R expression to execute when changes are detected (mutually exclusive with file)

monitoring multiple directories 

rmon::monitor(
  dir = c("path-to-first-dir", "path-to-another-dir"),
  file = "app.R"
)

if multiple directories are specified, file is assumed to be in the first directory.

specify extension watch list

by default, rmon monitors all files in dir for changes.

to watch only .R, .html, .css and .js files, set the ext parameter:

rmon::monitor(
  dir = ".",
  file = "app.R",
  ext = c("R", "html", "css", "js")
)

ignoring files

to ignore the file dev.R, do:

rmon::monitor(
  dir = ".",
  file = "app.R",
  exclude_files = "dev.R"
)

to ignore the directory test/:

rmon::monitor(
  dir = ".",
  file = "app.R",
  exclude_dirs = "test"
)

to ignore all files whose names match the pattern test:

rmon::monitor(
  dir = ".",
  file = "app.R",
  exclude_patterns = "test"
)

to ignore changes to hidden files, set monitor_hidden = FALSE:

rmon::monitor(
  dir = ".",
  file = "app.R",
  monitor_hidden = FALSE
)

delaying restarting

in some situations, you may want to delay restarting until multiple files have changed.

by default, rmon checks for file changes every second. if you’re uploading or modifying multiple files, this can lead to unnecessary multiple restarts of your application.

to delay restarting and avoid this issue, use the delay parameter:

rmon::monitor(
  dir = ".",
  file = "app.R",
  delay = 10
)
  • delay: a length one numeric. number of seconds to wait before checking for file changes again.

executing expressions

rmon now supports executing arbitrary R expressions when files change, providing more flexibility than just rerunning scripts.

basic expression execution 

rmon::monitor(dir = ".", expr = {
  cat("reading some csv file...\n")
  data <- read.csv("data.csv")
  cat("summarizing file contents...\n")
  summary(data)
})

advanced expression features

error handling 

rmon::monitor(
  dir = ".",
  expr = {
    tryCatch(
      {
        source("functions.R")
        cat("Functions reloaded successfully\n")
      },
      error = function(e) {
        cat("Error reloading functions:", e$message, "\n")
      }
    )
  },
  on_error = "continue" # or "stop"
)

output control 

# capture and display output (default)
rmon::monitor(
  dir = ".",
  expr = {
    result <- some_analysis()
    print(result)
  },
  capture_output = TRUE
)

# silent execution
rmon::monitor(
  dir = ".",
  expr = {
    log_entry <- paste(Sys.time(), "- Files changed")
    cat(log_entry, file = "changes.log", append = TRUE)
  },
  capture_output = FALSE
)

watch specific file types 

rmon::monitor(
  dir = ".",
  ext = c("R", "Rmd"),
  expr = {
    cat("R or Rmd file changed!\n")
    # rebuild documentation, run tests, etc.
  }
)