Killing Tasks on Windows with R
On my Windows machine, I oftentimes want to kill a set of applications that are running. This is especially true when I don’t have full control of my machine and am unable to adjust the applications that launch on startup.
Below are two examples — both accomplish the same feat — that use R to call down to the OS and kill a list of tasks / applications. One example is more readable while the other is more terse. An alternative impetus for writing the short scripts below was to experiment with the processx package. A more portable way to accomplish would be to simply use PowerShell. But this was a fun exercise.
Taskkill — Readable, Annotated
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| # 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) |
Taskkill — Terse, Single Pipeline
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| # for checking and installing packages | |
| # extracted from CRAmisc package | |
| # https://github.com/curtisalexander/CRAmisc/blob/master/R/install.R | |
| check_install <- function(pkgs, repos = NULL, ...) { | |
| installed_packages <- installed.packages()[ ,1] | |
| for (i in seq_along(pkgs)) { | |
| pkg <- pkgs[[i]] | |
| if (!pkg %in% installed_packages) { | |
| cat(paste0("Need to install: ", pkg, "\n")) | |
| if(is.null(repos)) install.packages(pkg, repos = "https://cran.rstudio.com") | |
| else install.packages(pkg, repos = repos, ...) | |
| } else cat(paste0(pkg, " already installed\n")) | |
| } | |
| invisible(pkgs) | |
| } | |
| req_pkgs <- list( | |
| "dplyr", | |
| "processx", | |
| "purrr", | |
| "readr" | |
| ) | |
| check_install(req_pkgs) | |
| # list of applications to kill | |
| kill_list <- c( | |
| "calc.exe", | |
| "notepad.exe" | |
| ) | |
| # callback | |
| cb <- function(line, proc) { | |
| cat(line, "\n") | |
| } | |
| # kill tasks using a single pipeline | |
| taskkill <- function(klist) { | |
| processx::run(commandline = "tasklist /fo csv") %$% | |
| stdout %>% | |
| readr::read_csv() %>% | |
| dplyr::filter(`Image Name` %in% klist) %$% | |
| PID %>% | |
| purrr::walk(~ processx::run(commandline = paste0("taskkill /f /pid ", .), | |
| error_on_status = FALSE, | |
| stdout_line_callback = cb, | |
| stderr_line_callback = cb)) | |
| } | |
| taskkill(kill_list) |
