Use R to kill tasks on Windows

taskkill.R

# install (if applicable)
# install.packages(c("dplyr",
#                    "processx",
#                    "purrr",
#                    "readr"))

# libraries
suppressWarnings(suppressMessages(library("dplyr")))
suppressWarnings(suppressMessages(library("processx")))
suppressWarnings(suppressMessages(library("purrr")))
suppressWarnings(suppressMessages(library("readr")))


# list of applications to kill
kill_list <- c(
  "calc.exe",
  "notepad.exe"
)


# the below calls out to the operating system and runs
#   the command "tasklist /fo csv" on the Windows command line
# its standard output -- what is printed on the screen --
#   is captured and stored as a string within the list element named stdout
# stdout is then separated as a single character vector and piped into
#   the read_csv function from readr
# the final result is a dataframe with the output from the tasklist command


# %>% and %$% are from either dplyr or purrr
task_list <- processx::run(commandline = "tasklist /fo csv") %$%
  stdout %>%
  readr::read_csv()


# filter the dataframe to just those tasks in the list above
# note the need for backquotes (``) for the column name as it contains
#   and embedded space
tasks_to_kill <- task_list %>%
  dplyr::filter(`Image Name` %in% kill_list)


# function for printing out the commands that will be run
print_task <- function(x) {
  paste0("taskkill /f / pid ", x) %>% print()
}


# print out what is about to be performed
# extract out the PID column from the dataframe
#   and pass each value of PID into the print_task function
# walk is used for iteratively applying a function that has
#   side effects to each element in a list
tasks_to_kill %$%
  PID %>%
  purrr::walk(print_task)



# callback = simply echo the line back out
# using a callback is better than using the echo option within 
#   processx::run as it will not throw R errors but simply
#   print out the standard error to the console
cb <- function(line, proc) {
  cat(line, "\n")
}


# function to actually kill a task
kill_task <- function(x) {
  processx::run(commandline = paste0("taskkill /f /pid ", x),
                error_on_status = FALSE,
                stdout_line_callback = cb,
                stderr_line_callback = cb)
}


# iterate over all the tasks to kill, killing each one by one
tasks_to_kill %$%
  PID %>%
  purrr::walk(kill_task)