The hardware and bandwidth for this mirror is donated by dogado GmbH, the Webhosting and Full Service-Cloud Provider. Check out our Wordpress Tutorial.
If you wish to report a bug, or if you are interested in having us mirror your free-software or open-source project, please feel free to contact us at mirror[@]dogado.de.

watcher

Watch the File System for Changes

R binding for ‘libfswatch’, a file system monitoring library. This uses the optimal event-driven API for each platform:

• ReadDirectoryChangesW on Windows
• FSEvents on MacOS
• inotify on Linux
• kqueue on BSD
• File Events Notification on Solaris/Illumos

Watching is done asynchronously in the background, without blocking the session.

• Watch files, or directories recursively.
• Log activity, or run an R function every time a change event occurs.

Installation

Install the current development version of watcher using:

pak::pak("r-lib/watcher")

Installation from Source

watcher requires the ‘libfswatch’ library.

• On Linux / MacOS, an installed version will be used if found in the standard filesystem locations.
• On Windows, or if not found, the bundled version of ‘libfswatch’ 1.19.0-dev will be compiled from source.
• Source compilation of the library requires ‘cmake’.

Quick Start

Create a ‘Watcher’ using watcher::watcher().

By default this will watch the current working directory recursively and write events to stdout.

Set the callback argument to run an R function, or rlang-style formula, every time a file changes:

• Uses the ‘later’ package to execute the callback when R is idle at the top level, or whenever later::run_now() is called, for instance automatically in Shiny’s event loop.
• Function is called back with a character vector of the paths of all files which have changed.

library(watcher)
dir <- file.path(tempdir(), "watcher-example")
dir.create(dir)

w <- watcher(dir, callback = ~print(.x), latency = 0.5)
w
#> <Watcher>
#>   Public:
#>     initialize: function (path, callback, latency) 
#>     path: /tmp/RtmpcSO6DA/watcher-example
#>     running: FALSE
#>     start: function () 
#>     stop: function () 
#>   Private:
#>     watch: externalptr
w$start()

file.create(file.path(dir, "newfile"))
#> [1] TRUE
file.create(file.path(dir, "anotherfile"))
#> [1] TRUE
later::run_now(1)
#> [1] "/tmp/RtmpcSO6DA/watcher-example/newfile"    
#> [2] "/tmp/RtmpcSO6DA/watcher-example/anotherfile"

newfile <- file(file.path(dir, "newfile"), open = "r+")
cat("hello", file = newfile)
close(newfile)
later::run_now(1)
#> [1] "/tmp/RtmpcSO6DA/watcher-example/newfile"

file.remove(file.path(dir, "newfile"))
#> [1] TRUE
later::run_now(1)
#> [1] "/tmp/RtmpcSO6DA/watcher-example/newfile"

w$stop()
unlink(dir, recursive = TRUE, force = TRUE)

Acknowledgements

Thanks to the authors of ‘libfswatch’, upon which this package is based:

• Alan Dipert
• Enrico M. Crisostomo

These binaries (installable software) and packages are in development.
They may not be fully stable and should be used with caution. We make no claims about them.
Health stats visible at Monitor.